Re: Minibrute Construction Thread / FAQs
Ken M., Mon Dec 31 2007, 11:16AM

Well, if evr replies then he's your author, also with any medium to large and considerably powerful tc's they will still be loud, as for experience with Minibrute no I haven't had any, like I said tho, evr will be able to give u more info.

Re: Minibrute Construction Thread / FAQs
Reaching, Mon Dec 31 2007, 12:45PM

mh, if a sgtc is too noisy for you then i would suggest building a sstc instead .
a drsstc is really loud and screamy and from my own experience i would say a drsstc is much louder than a sgtc.

Re: Minibrute Construction Thread / FAQs
Dago, Mon Dec 31 2007, 07:52PM

Yes a DRSSTC will make even more noise than a SGTC.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Dec 31 2007, 09:30PM

i was talking more about the noise from a rotary spark gap itself. I didn't want to deal with that and not to mention the health hazards like x-rays, Uv light that come with a SGTC.

My main motive for building the DRSSTC was to add an external audio interrupter so it can play music.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Jan 01 2008, 02:49AM


The DRSSTC is definitely a challenging build, but you do have an enormous base of information (members) here with mucho DRSSTC experience.

Also, DRSSTCs are very loud as well . . . at least as loud as a SGTC. And contrary to popular belief, even though a spark gap does make some noise, the majority of the noise still comes from the high voltage arc itself, and not the spark gap.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Jan 01 2008, 08:34PM

My biggest concern will not be actually building the thing but all the fine tuning and testing prior to turning it on for the first time.

but I appreciate the support and I look forward to updating you guys once I start getting my hands dirty

Re: Minibrute Construction Thread / FAQs
Ultra7, Tue Jan 01 2008, 08:58PM

I just ordered the books myself!!!!
We thought you'd like to know that your Lulu order has shipped. (You can check out all the details below.)

Remember, you can always track the status of an order at our website:

Shipped on Tue, 01 Jan 2008 via USPS Media Mail
All items in your order have been shipped.


In This Shipment
===========================
1 of DRSSTC : Building the Modern Day Tesla Coil by Daniel McCauley (Printed)
1 of DRSSTC : Building the Modern Day Tesla Coil miniBrute Reference by Daniel McCauley (Printed)

Re: Minibrute Construction Thread / FAQs
Austin, Tue Jan 01 2008, 10:49PM

well maybe we can help each other out or something if we stuck on section. wait till you start ordering parts tho... kinda expensive.

Re: Minibrute Construction Thread / FAQs
Ultra7, Tue Jan 01 2008, 11:23PM

I built WilliamN.'s SSTC and I have built 90% of a SGTC (Pics to come) and I know by now that there is nothing inexpensive about this hobby.
I fooled myself into thinking that I could just buy one part this paycheck, or I could get this part cheaper, or that I could save a boatload buying this part in bulk. . .
you get the point.

I've spent a lot of my money, a lot of my time, and if I totaled it all up, I'd probably do it all over again.

But yes, I accept.
We can help each other in this project.

Ultra7

Re: Minibrute Construction Thread / FAQs
Austin, Wed Jan 02 2008, 12:02AM

sounds good! I am actually quite excited to started. Besides it wouldn't be a hobby otherwise if you didn't drop loads of cash into something that you will get no return on!

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jan 18 2008, 01:04AM

Hi guys. I recently completed my miniBrute based DRSSTC built using EVR’s book and boards. This was my first solid state coil (I’ve built 5 sgtc’s). I was waiting to post until I had a few pics, but I don’t have a camera right now and figure you may be able to benefit from my experience.

First off, let me say that it was not easy, and I have a large collection of dead silicon (not because of any design flaws, but because of my mistakes), but I finally have it working right and I have replicated Dan’s 48” sparklength. There were times when I did not know what was wrong, and I was very frustrated at blowing something up every single time I turned it on.

One of the stupid mistakes I made was forgetting the 4.7uF decoupling cap across the power supply rails (c101 in the schematic). I think I missed it because it is on the half-bridge section of the schematic, but it is not part of the half-bridge board. I blew up 8 IGBT’s and 16 TVS’s before I figured out that I had forgotten a crucial part! Of course, I had to wait a week for it to arrive from Digikey.

Another thing was at some point, I melted the relay. This caused me to blow many TVS’s before I was able to figure this one out by checking the voltage at the bridge instead of at the power supply caps. Again, I had to wait a week for parts from Digikey.

Also, because of the way I laid everything out inside the base, my cooling fan did not supply adequate airflow through the mmc. They get very hot very quickly with no airflow, and as a result, I burned several up. An interesting thing is that I managed to partially melt a cap without knowing it and before I cranked the current up all the way. I could only manage about 32” sparklength with this partially melted cap, even after I cranked it up all the way. I had no idea that this was limiting my output until it finally failed completely and I replaced it. Sparklength immediately increased to 44” consistently with an occasional (once every 5 or so seconds) 48”.

I now run 3 parallel strings of 4 series of the “normal” .15 CDE mmc caps (I had them on hand) so that they won’t get quite so hot so quickly due to my poor-airflow layout.

One final note about the testing/ fine tuning – I was able to build this coil and get great results with only a multimeter (Of course you should follow Dan’s testing/tuning instructions with freq. generator and oscilloscope if you can), and I didn’t even use the same secondary. I used wintesla and javatc to match the required resonant frequency and coupling (by adjusting # of turns and height) with a slightly smaller than specified secondary coilform, and this was accurate enough to allow me to use the original primary specifications with no additional tuning.

Hope this helps, and feel free to ask any questions.

-Freddie

p.s. I'd like to thank Daniel McCauley for taking the time to design excellent quality boards and publish professional quality books enabling a sstc n00b like me to build such an awesome coil on a first try!

Re: Minibrute Construction Thread / FAQs
Steve Ward, Fri Jan 18 2008, 03:33AM

I now run 3 parallel strings of 4 series of the “normal” .15 CDE mmc caps (I had them on hand) so that they won’t get quite so hot so quickly due to my poor-airflow layout.

No, id say Dan's design is over stressing the current capacity of the MMC, and adding more parallel strings was an appropriate upgrade. I could see problems if the MMC was enclosed and operating for hours, but if it needs a fan to cool film caps, that just sounds like too much dissipation in the capacitors for safe operation.

And from the description of the problems from missing the 4.7uF decoupling caps sounds like you have too much buss inductance with the electrolytics. My CM300 bridge actually doesnt use any film caps (nor does it require TVSs). Its just electrolytics, IGBTs, and lots of copper. This of course depends on having very high quality electrolytic caps for the bulk storage.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 18 2008, 05:25AM


Thanks for the heads up! I just took a look at c101 on the schematic, and even though its in the schematic (but not on the board) I can see why it would be easy to miss. before i'm done building this thing i'm going to systematically check every part and compare them to the parts list to make sure that everything is there. those IGBT's are like $33 a piece and blowing up 8 of them can get very expensive.

My DRSSTC is starting to really come together now, I just ordered my 4" x 13" toroid and it should be here very soon. I'm excited because spun toroids seem hard to come by these days.

Again thank you for your suggestions, I would like to avoid as many complications as possible.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 18 2008, 05:34AM


Wirenut what did you use for your high current bus bar? sheet of copper? wires? if so what gauge. Also i would love to see some pics once you get a working camera.

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jan 18 2008, 05:57AM

Wirenut what did you use for your high current bus bar? sheet of copper? wires? if so what gauge. Also i would love to see some pics once you get a working camera.

I used fine stranded 8ga. wire that I purchased from a local car stereo shop. One of the reasons I like this type of wire is because it is very flexible. Lead length from the power supply caps to the bridge is about 4" on one side and about 8" on the other, so I imagine it's not the lowest inductance design, but it seems to work. As Steve W. mentioned above, this high inductance design may be the reason I was blowing IGBTs when I was missing the snubber cap. I also used this wire for the connections from the bridge to the mmc and also for the leads to the primary. This wire gets warm, but not warm enough for me to want to change it.

Believe me, I would love to post some pics, and will as soon as possible. I'll try to borrow a camera from a friend this weekend.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 18 2008, 06:32AM


How much inductance is too much? Is that something i'm going to have to "tinker" with until things stop blowing up? I don't think McCauley actually mentions how he designed his bus bar. Is there an effective way to shield the wires from inducing currents in other components?

Re: Minibrute Construction Thread / FAQs
Bennem, Fri Jan 18 2008, 06:58AM

I used copper sheeting cut down in size, to connect
my bus to my bridge on my last DRSSTC.
I 'm not sure if my layout is as 'low inductance friendly'
as it should due to my copper sheets not close to one another,
but it seems to work fine, and no blown IGBT's yet (touch wood....lol)

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jan 18 2008, 12:18PM

How much inductance is too much? Is that something i'm going to have to "tinker" with until things stop blowing up?

I don't think so as long as you don't forget the snubber cap like I did. I think the rule of thumb is to try to keep the connections between the large electrolytics and the half-bridge as short as possible. I think to best way to do this is to put the caps and bridge head to head, but the caps I used were massive (nearly 1' long) so I had to put them sort of side by side with the bridge to get everything to fit inside the base.

Is there an effective way to shield the wires from inducing currents in other components?

I just used tightly twisted pair wires for the connections from the current transformers and to the gate transformer.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Jan 18 2008, 01:18PM


Actually, not correct on two points.

Firstly, the design of the MMCs in the miniBrute are not being overstressed during specified operational parameters. They are designed to be used with a cooling fan as described in the design. When used with the shown cooling arrangement, the temperature of the MMC capacitors are well within the temperature limits (derated) of the components.

Secondly, just because a fan is required doesn't mean the capacitors are being overstressed. Technically, the caps don't care whether a fan is used or not. All they care about is what temperature they are operating at.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 18 2008, 07:21PM


By snubber cap you are referring to the c101 capacitor correct? sorry I am not an electrical engineer. I think the most trouble I have with this forum is all the acronyms being used to describe things.

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jan 18 2008, 09:25PM

By snubber cap you are referring to the c101 capacitor correct?

Yes.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Jan 19 2008, 07:11AM

Ok, I have some pics:

Layout of my base:



The single white cap on the top left is the one I forgot...

48" sparks












Oh yeah, parts killed so far:

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jan 19 2008, 07:41AM

hrmmm some of the pics are not showing up... if you need hosting space or something let me know.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Jan 19 2008, 08:19AM

hrmmm some of the pics are not showing up... if you need hosting space or something let me know.

I think you get the image disabled tag if you're not logged in. Log in and try again. Also, the img disabled tag should be clickable even if you're not logged in.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jan 19 2008, 06:36PM

Very nice arcs! Looks sweet!!!!

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jan 19 2008, 08:06PM


its working now. looks very nice. few questions tho...

1. did you use the advance modulator described in the book or something different?
2. you MMC looks different as well. was this to relive some stress in the capacitors?
3.i noticed in the the pictures you the arcs were striking the ground and not targets, does that reduce the reliability of tesla?

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Jan 19 2008, 08:50PM

1. did you use the advance modulator described in the book or something different?

Yes, I used the advanced modulator. Here's a shot of the inside:

2. you MMC looks different as well. was this to relive some stress in the capacitors?

The specified mmc should work fine if you provide adequate cooling as per the design. My layout basically provided no airflow at all, so I overheated them. I should also point out that this was while running at maximum primary current without the current limiting circuit, which is obviously beyond the design specifications.

3.i noticed in the the pictures you the arcs were striking the ground and not targets, does that reduce the reliability of tesla?

I think if the coil was arcing continually to ground or a grounded target, then yes, that would push the limits of reliability, but what you see in the pics are only momentary strikes that last fractions of a second. I don't believe these kind momentary arcs are a problem, and I haven't had any failures since putting everything together correctly.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Jan 21 2008, 12:32AM

Here's some more pics from video capture with the lights on. The strike target is 45" in these shots.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Jan 21 2008, 12:41AM

beautiful arcs! did you not put a strike rail on your tesla?

you should try to modulate it with audio now. Thats what I wanna do with mine anyways.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Jan 21 2008, 12:51AM

beautiful arcs! did you not put a strike rail on your tesla?

Not yet, there has been multiple strikes to the primary, but nothing has died from it so far. Maybe after I pop some IGBTs, I'll be in a bigger hurry to get it done.

you should try to modulate it with audio now. Thats what I wanna do with mine anyways.

Yeah, I know, that would be awesome! I want to do that eventually too, but I haven't quite figured it all out yet. Maybe Dan will make a board kit for it one day?

Re: Minibrute Construction Thread / FAQs
Austin, Mon Jan 21 2008, 12:55AM

yes, audio modulation seems very hush hush. However maybe this will help you get started.



scroll down to audio interrupter. I also got some part numbers if you need them.

Re: Minibrute Construction Thread / FAQs
Bennem, Mon Jan 21 2008, 07:25AM

Wow...some great arcs you got there!
great perfomance and from only a half bridge too!

Have you got any video footage we can view?


Mel

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Jan 21 2008, 09:22AM

Have you got any video footage we can view?

Here's a short clip


]1200907294_141_FT36701_minibrute.wmv[/file]

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Jan 21 2008, 12:30PM

Very nice Wirenut!!! Looks great!

Re: Minibrute Construction Thread / FAQs
Bennem, Mon Jan 21 2008, 12:30PM

Hi Wirenut,
Thanks for posting your clip.

In the clip, is your overcurrent kicking in
or are you just turning on and off your interrupter?

What peak cuurent have you got your overcurrent
set to for that spark length?

once again....great coil!

Mel.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Jan 21 2008, 05:52PM

turning on and off your interrupter?

Yes.

What peak cuurent have you got your overcurrent
set to for that spark length?

It's all the way up (1000A).

once again....great coil!

Very nice Wirenut!!! Looks great!

Thanks guys!

Re: Minibrute Construction Thread / FAQs
Tom540, Tue Jan 22 2008, 05:18AM

Wow nice job! I like how when it stops you can hear it echo. Have you tried running it without a breakout point?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Jan 22 2008, 11:35AM


You don't want to do that. If you don't have a break-out point, the primary current ramps up extremely high and may possibly blow the IGBTs.

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Jan 22 2008, 07:15PM

I like how when it stops you can hear it echo.

Yeah, I thought that was cool too. Kinda gives you an idea of how loud it is, echoing off the neighbors house across the street.

Have you tried running it without a breakout point?

No, I haven't tried. As Dan mentioned, this is specifically advised against in the book. Too bad, I really like the look of an arc randomly floating around the toroid. I actually own one of your mini coils that doesn't use a breakout point and people love the little guy too.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Jan 22 2008, 09:15PM


what about adding a breakout point at the very top of the toroid? might look cool.

Wire I got another question, in one of your photo it shows an 8g wire going through your T21 and T1 (also known as primary current sense and primary current feed back). Is that 8g wire hooked up to the primary circuit or the secondary because in fig 2-8 it looks as if the copper wire coming from secondary should go through T21 and T1 and then grounded, not the primary. But then again why is it called primary feed back and current sense any insights?

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Jan 22 2008, 09:48PM

Is that 8g wire hooked up to the primary circuit or the secondary because in fig 2-8 it looks as if the copper wire coming from secondary should go through T21 and T1 and then grounded, not the primary.

Ah, yes, I remember being momentarily confused by this too. Fig 2-8 does appear to show the secondary wire going through the current transformers. This may be a relic from when Dan was using secondary feedback, I don't know. Anyway, it is primary feedback and as such, the primary lead goes through the CTs.

what about adding a breakout point at the very top of the toroid? might look cool.

I've tried this, looks kind of like a fountain type firework. Keeps the streamers away from the primary too.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Jan 22 2008, 11:11PM


Yeah, thats obviously an error. I'll add that to my list for the next edition corrections.
thanks

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Jan 22 2008, 11:23PM

Yeah, thats obviously an error. I'll add that to my list for the next edition corrections.
thanks

One other minor discrepancy I noticed is c32 is in the schematic, but not on the board.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Jan 23 2008, 01:06AM

I am glad I asked :)

Is c32 needed? should I follow the schematic or the board design?

Wire, are there any other obvious errors you found that you can remember? I just received my Digikey shipment today, so i'm sure i will run into some issues.

Re: Minibrute Construction Thread / FAQs
Wirenut, Wed Jan 23 2008, 01:21AM

Is c32 needed? should I follow the schematic or the board design?

I have to admit, although I know enough to be able to follow schematics, I do not understand enough about electronics to know what c32 is supposed to do or what would happen (if anything) if I'd included it. Since it was not on the actual board, I left it out and did not actually notice it until later. Seems to work fine without it, maybe someone else can elaborate on its function?

Wire, are there any other obvious errors you found that you can remember? I just received my Digikey shipment today, so i'm sure i will run into some issues.

No other errors that I can remember, but some of the digikey part numbers had changed. I was able to find the parts easy enough by just searching for the part name. The 220V TVSs were one of them. Since you've already rec'd your order, I assume you were able to figure this out too.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Jan 23 2008, 02:50AM

Off the top of my head, I think C32 is a 10pF capacitor on the input to one of the op-amps or comparators? If so, then it is recommended to add as a filter.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Jan 23 2008, 06:09AM


Some of the part #'s did change! thanks for the heads up wire. Also did you have any issues with the diodes not fitting through the holes of the PCB board? like CR3 and CR4. These two diodes in particular look different in the picture, but this might be because these are the lead free version?

Re: Minibrute Construction Thread / FAQs
Wirenut, Wed Jan 23 2008, 06:20AM

diodes not fitting through the holes of the PCB board? like CR3 and CR4.

Oh yeah, now that you mention it, I did have this exact problem. I just soldered some "posts" out of some of the scrap clipped leads from already-soldered in components, then soldered the leads of the diodes to the posts.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Jan 23 2008, 11:37AM

I vaguely remember these diodes not fitting. Easy fix is just cutting the leads short and mounting like surface mount, or using a small drill bit and widening the hole appropriately.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Jan 23 2008, 03:54PM


Thats exactly what I did.

This is great stuff Easternvoltage, I don't know how much feedback you get on your book but I promise if I can figure this out then anyone can.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Jan 23 2008, 09:37PM


Thanks! Great to get the feedback. My goal was to provide a complete set of plans to build a DRSSTC from the scratch up so it appears to be working!!!

Re: Minibrute Construction Thread / FAQs
keegan, Thu Jan 24 2008, 02:58AM

I'll jump in here with my first post. I just finished building the minibrute as my first tesla coil, it is currently producing 2-3 foot arcs with a 450A limit.

I am using a top mounted breakout (4" of 1/4-20 threaded rod, ground to a point) mainly to prevent arcs to the primary.

I have a question about the feedback transformers, does it matter if they are between the MMC and the primary coil or between the H bridge and the MMC? Does the MMC offset the phase of the current?

Thank you Dan for your books!

Re: Minibrute Construction Thread / FAQs
Steve Ward, Thu Jan 24 2008, 04:48AM

I have a question about the feedback transformers, does it matter if they are between the MMC and the primary coil or between the H bridge and the MMC? Does the MMC offset the phase of the current?

Review Kirchoff's current law, there *cant* be a phase shift in the current of a series circuit. It does in fact matter because the node connecting L to C has many kV on it. Review ohms law, V = I*Z where I is 450A and Z is the impedance of your MMC or primary at your operating frequency.

Final answer, put the CTs on the output of the H-bridge, not between the MMC and primary because there is HV present there, and you certainly wouldnt want a fault between the primary circuit and the CT!

Re: Minibrute Construction Thread / FAQs
Austin, Thu Jan 24 2008, 04:59AM

I was looking through the schematic and was wondering if C86 was on the Resonat Driver Board? It's in the schematic but it's not on the board that I can find. Another C32?

I also had another question, I couldn't find C7, C8, C62, C64, C66, C68, C81, C83 labeled on the circuit board. My friend had an idea that they were just all of the un-labeled boxes. Is this correct?

Thanks for the help.

Re: Minibrute Construction Thread / FAQs
Wirenut, Thu Jan 24 2008, 06:16AM

I was looking through the schematic and was wondering if C86 was on the Resonat Driver Board? It's in the schematic but it's not on the board that I can find. Another C32?

Looks like you caught another one - as with c32, I did not include this on mine and it works seemingly fine, but EVR will have to comment on its necessity.

I also had another question, I couldn't find C7, C8, C62, C64, C66, C68, C81, C83 labeled on the circuit board. My friend had an idea that they were just all of the un-labeled boxes. Is this correct?

Yes.

I just finished building the minibrute as my first tesla coil, it is currently producing 2-3 foot arcs with a 450A limit.

Welcome Keegan. Any pics?

Re: Minibrute Construction Thread / FAQs
Bennem, Thu Jan 24 2008, 07:00AM

Wirenut
I see from the layout of your base that
you connected your feedback CT on the HV side of
your MMC.
See Steve Wards post as to why he dosn't reccomend to
place the CT on the HV side.
Just a thought.

Mel.

Re: Minibrute Construction Thread / FAQs
Wirenut, Thu Jan 24 2008, 08:09AM

Wirenut
I see from your layout of your base that
you connected your feedback CT on the HV side of
your MMC.
See Steve Wards post as to why he dosn't reccomend to
place the CT on the HV side.

Yeah, I see how this could lead to a catastrophic failure. I didn't know there was a difference previously. Just out of curiosity, what is the approximate voltage on the primary? I don't know the primary impedance, but Fres is ~160kHz and pri current is ~1000A max.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Jan 24 2008, 09:26PM


-Just so I understand correctly, The placement of the CT should be placed where I drew the arrow in the image below?
http://4hv.org/e107_files/public/1201209653_1169_FT1630_1200725766_141_ft1630_img_0143.jpg

-Does the polarity matter for VR62, VR61, and VR107-VR110 (it says Bi-Directional)

-Are three wires being wrapped around T1?
Ie, Wire#1 is (S1/S2), Wire #2 is (G1/G2), Wire #3 is (twisted pair -> Gate DRV/RTN -> from the resonant board)?

Re: Minibrute Construction Thread / FAQs
Wirenut, Thu Jan 24 2008, 10:24PM

-Just so I understand correctly, The placement of the CT should be placed where I drew the arrow in the image below?

Yes, that is the recommended spot.

-Does the polarity matter for VR62, VR61, and VR107-VR110 (it says Bi-Directional)

Nope.

Are three wires being wrapped around T1?
Ie, Wire#1 is (S1/S2), Wire #2 is (G1/G2), Wire #3 is (twisted pair -> Gate DRV/RTN -> from the resonant board)?

Not quite. There are 3 wires, but wire 1 will be s1/g1 and wire 2 will be s2/g2. Wire 3 is correct. I had a hard time finding wire that was small enough to fit 20 turns on the ferrite. What I ended up using was wire from an old parallel cable. I took 2 strands (red and blue in my pic) and twisted them tightly together using a drill. I then wrapped 20 turns on the ferrite. Then I wrapped 10 turns over the top of the red and blue (yellow in my pic) with a third wire. I fed the leads of the 3rd wire through the holes in the board and then twisted them together, holding the ferrite to the board. I could then trim the red/blue wires to the correct length. I'm not sure if it matters, but I put both turn-1-wires to g and both turn-20-wires to s.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 25 2008, 03:41AM

Wire, what resistor did you use for R29? Its listed twice in the parts list with two different resistors. Also R28 says "open" on the schematic but I don't have a part for it.

How did you mount the heat sinks to the board (did you use solder for adhesion) for U61, U62 etc...?

Thanks Wire, I could not do this without your help.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Jan 25 2008, 04:11AM


R28 should be open. All this sets is the gain on the op-amp. With it open, the op-amp acts simply as a buffer (gain=1)

Heat sinks (which probably aren't even required - i don't think U61 and U62 get hot) bolt to the board with a screw / nut through the TO-220 mounting hole.
They aren't soldered to the board.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 25 2008, 04:14AM

I'm not sure bolts came with those parts hrm maybe ill find some around the house.

what about R29?

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jan 25 2008, 05:24AM

what about R29?

I used the 10k.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jan 25 2008, 06:18PM

Are three wires being wrapped around T1?
Ie, Wire#1 is (S1/S2), Wire #2 is (G1/G2), Wire #3 is (twisted pair -> Gate DRV/RTN -> from the resonant board)?

Not quite. There are 3 wires, but wire 1 will be s1/g1 and wire 2 will be s2/g2. Wire 3 is correct. I had a hard time finding wire that was small enough to fit 20 turns on the ferrite. What I ended up using was wire from an old parallel cable. I took 2 strands (red and blue in my pic) and twisted them tightly together using a drill. I then wrapped 20 turns on the ferrite. Then I wrapped 10 turns over the top of the red and blue (yellow in my pic) with a third wire. I fed the leads of the 3rd wire through the holes in the board and then twisted them together, holding the ferrite to the board. I could then trim the red/blue wires to the correct length. I'm not sure if it matters, but I put both turn-1-wires to g and both turn-20-wires to s.
[/quote1201284778]

I have never done this before, so i want to twist together my s-wire and g-wire together before wrapping it around the the ferrite and then wrap the gate drv wire around the ferrite 10 times over the s,g wire... ill read up on this some more, i just finished my boards except for this ferrite business and then i'm on to building the primary. =P

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jan 25 2008, 08:03PM

Here's a close-up pic of my GDT




The red and blue wires are twisted together. There are 20 turns of the red/blue around the core. You can see the red wire is connected to s2 and g2 on the left side of the board. The blue wire is connected to s1 and g1 on the right, but is not visible.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jan 26 2008, 06:28AM

Wire I see what you mean when you say its hard to get 20 turns in, i'm using 18gauge wire to wrap around the ferrite I think I need something even smaller.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Jan 26 2008, 07:09AM

I need something even smaller.

Do you have an old computer parallel cable laying around? This is what I used. I couldn't even make the 24ga. wire from a cat-5 ethernet cable fit.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jan 26 2008, 07:34AM

I think I might, I just hope its long enough. did you use the same gauge wire for all 3 wire?

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Jan 26 2008, 08:03AM

I think I might, I just hope its long enough. did you use the same gauge wire for all 3 wire?

Yes, all three were from the parallel cable. I think it was about 5' long. I think they're about 26ga. - just barely smaller than 24ga. cat-5 wire.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jan 26 2008, 09:16PM


I believe i used 26AWG wire for my transformers. First I took all three wire (colored coded for easy identification), and then used a drill to twist the wires together. Then just wrapped say the 20 turns I needed. On the primary side where I needed 1/2 the number of turns on the secondary, I simply pulled an extra loop out at the 10th turn and continued winding all three wires the final 10 turns. Then i cut that pulled out loop, so now the primary wire is two separate equal length wires and wired that in parallel giving me 10 turns. (Just be sure phasing is correct)

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 12:53AM

Below are some images of the parts not included on the board but listed on the schematic. Please let me know if messed any of these up.




This is an image of C81,C83




This is an image of C32 (I soldered this cap between R25 and the ground for r28 <---- remember this is open/unused)




This is an image of C86 soldered in parallel with C85

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Jan 27 2008, 01:14AM

This is an image of my completed transformer. i twisted and wrapped the blue and white wire 20 times around the ferrite and the yellow wire on top 10 times around the ferrite

Sorry, but this is wrong. You have one wire going between s2 and s1 and the other wire between g1/g2. Take another look at my post above with the pic of the gdt.


*edit
hrm, the text I quoted seems to have been edited out.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 01:17AM


I know i realized this was wrong right as I was posting... I removed it thats probably why you were unable to quote. how about the other images tho?

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Jan 27 2008, 01:30AM

how about the other images tho?

C86 and C32 appear to be in accordance with the schematic. The first pic is confusing to me. There is a spot for C82 on the board so are those caps C81 and C83?

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 02:04AM

yes, my mistake its C81, C83. I will edit the previous post.

Do those look correct as well? if so then my resonant board is completly done.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Jan 27 2008, 02:17AM

Do those look correct as well?

Provided that they're the correct values, looks good.

if so then my resonant board is completly done.

Cool, but if you hook everything up and it doesn't work, you may want to insert the ICs into the sockets as well.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 02:48AM

obviously, I just left those out for now so they don't get ruined... I don't know how delicate they are.

I'm really excited the half bridge is done, along with everything else. Its now time to start working on the primary (shipment comes in Monday) so I can start hooking everything up! Wire and eastern you both have been a huge help. I'll continue to keep you up to date, I'm sure I will have more questions.

Thanks again

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 02:53AM

Speaking of questions, (I'm not sure that i need to know this now but what the hell) how did you go about tuning the potentiometers. Ie R23, R83, R30. Actually a better question is how do I tune them... I read the descriptions in the bottom of the pages but they are kinda veg. I think thats how you spell veg....

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Jan 27 2008, 03:23AM

I'm really excited the half bridge is done

I noticed in your (briefly) posted pic of your bridge, you were missing cr101&102.

how did you go about tuning the potentiometers

This is covered in the back of the book, but it took me some fiddling with to get right. I can help when you get there.

I think thats how you spell veg....

*Vague*

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 03:33AM

I have to order more of those CR's cause the book said I needed 11 when in reality I needed 12.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Jan 27 2008, 04:01AM

As long as you're ordering parts, you might want to order some of the 220V TVSs, I seemed to go through a lot of them before I got it sorted out, and they're relatively cheap. Also, it couldn't hurt to have some spare gate drivers on hand. And you do have some spare IGBTs, right?

Re: Minibrute Construction Thread / FAQs
Austin, Sun Jan 27 2008, 05:18AM

so expensive for those IGBTS.... i need extras? :(

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Jan 27 2008, 06:11AM

so expensive for those IGBTS

There's been some talk about using hgtg20n60a4d instead. They are TO-247 form factor so they do not dissipate heat as well as the hgt1n40n60a4d which are sot-227 package, but other than that they should work, and they're much cheaper at only $5 or so each. I recently purchased some, and I'm going to try them out, and I'll report back on how they work. Of course, the miniBrute half-bridge board was not made for these IGBTs so some modifications will be necessary, but I have a spare half-bridge board to play with.

i need extras? :(

Maybe learning from my (and others) mistakes will save you from blowing IGBTs, but if you ask most people on this forum who have built DRSSTCs, I think they will tell you that they've blown at least a few, and having at least 1 spare set is a good idea. I'd rather have a spare set and never need them than blow a couple and have to wait a week or so to fix it. But that's just me, $70 for spares that *might* not be needed is a lot.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Jan 27 2008, 03:03PM

if you keep the current limit way down low for the initial testing, you can drastically increase reliability of the IGBTs. And yes, the TO-247 package IGBTs work great. Just make sure you mount them to a good heatsink and properly with thermal grease etc...
Also, they need to be electrically insulated as well.

Regarding tuning of the potentiometers, you are merely setting the current limit here (table on schematic shows what the values are - start low), and i believe some others for setting the LEDs on the current meter which is non-functional anyways other than the display.

Just be sure to get a good understanding of HOW the circuits work. They are VERY simple (just simple comparators, digital logic, etc...) and once you understand them, than setting the values within each circuit is very simple.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Jan 28 2008, 02:52AM

since I don't see a heat sink on the parts list for the IGBT's what kind did you use Wirenut?

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Jan 28 2008, 03:04AM

since I don't see a heat sink on the parts list for the IGBT's what kind did you use Wirenut?

I bought mine from this guy on ebay
He'll cut it to any length you want (I had him cut a 4" and an 8") and the cuts are perfectly smooth. The heatsink is very beefy and probably overkill, but his price is fantastic, and he ships quickly in very good packaging. I mounted my bridge on the 4" section - fits very well.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Jan 28 2008, 03:22AM

4" x 8" correct? and how did you mount it? Did you drill some holes in the heatsink and screw it to the base? also the part list does not call for any screws, or screw mounts to attach the boards to the inside frame. any recommendations.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Jan 28 2008, 03:54AM

4" x 8" correct?

Actually it's 4" x 5 and 3/8". The heatsink is 5 and 3/8" wide and he sells it by the foot, but he'll cut the foot into any smaller lengths you want like 6"+6" or 8"+4" (like I did).

and how did you mount it? Did you drill some holes in the heatsink and screw it to the base?

It's attached to the rear wall with two countersunk screws from the outside going through two of the fins.

any screws, or screw mounts to attach the boards to the inside frame. any recommendations.

As far as mounting goes, the most difficult part was mounting the IGBTs to the heatsink. You can use the half-bridge board as a stencil for the mounting holes. As far as the boards go, I had tons of assorted hardware laying around, and I just used whatever worked. Home Depot and the like have assorted hardware. Also, I think that you should mount the main resonant board in a vertical position to minimize interference from the primary coil. I mounted mine to a slightly larger (than the resonant board) piece of polycarbonate and mounted the polycarbonate using cheap angle brackets from H.D.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Jan 28 2008, 04:00AM

Thanks again for the tip. I get most of my PVC in tomorrow so hopefully I'll start construction Monday or Tuesday. Until then theres not much I can do considering I am waiting on parts.

I really hope someone else stumbles upon this post like a month or two down the road and finds this information as valuable as I have.

Oh and one more comment about C81, I found out after reading the book a bit more in detail that it is in fact mentioned in the book (on a side note) and should be soldered in parallel with the U81 sensor. "C81 should be placed as close to U81 as possible directly across the lead of the device." Thought this was worth mentioning.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 01 2008, 01:46AM

its been a couple days since my last post. Here an update on the mechanical side of the project.




Picture of me cutting the PVC to proper length for the primary support




Drilling the holes for the primary supports




Threading the holes (The machine just melted the plastic, so I had to hand thread)




Squaring the piece to make sure everything is lined up correctly




Drilling holes in the base




Everything I have so far. believe it or not this is about 8 hours of work. I had no idea building the primary supports would take so long.

The biggest upcoming challenge will be bending the 1/4" O.D. Flexible Copper Tubing into a semi circle. Anyone have some suggestions on how I might be able to do this? Easternvoltage?

My goal will be to have the entire mechanical portion of this project done by Sunday. Then I will be able to start laying everything out inside the base. I'm sure I will have plenty of questions then.

Oh btw Wirenut, I ordered those heatsinks you suggested, they ship tomorrow and should be here sometime next week. Thanks for the tip, you have been a major help!

Until then cheerio.

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Feb 01 2008, 02:51AM

update on the mechanical side of the project.

Wow, your coil is going to look much nicer than mine! Looks like you have access to all the equipment to do everything right.

believe it or not this is about 8 hours of work. I had no idea building the primary supports would take so long.

I believe it! It took me and a friend a full day to build my base and primary, and it was all wood except the acrylic top.

The biggest upcoming challenge will be bending the 1/4" O.D. Flexible Copper Tubing into a semi circle. Anyone have some suggestions on how I might be able to do this?

The copper tubing comes pre-coiled, and I recommend leaving it in this pre coiled shape. I started threading the tubing through the holes from the top down, slightly bending the tubing into a tighter radius as needed. Because of slight imperfections in my primary support hole locations, threading the tubing through the holes became difficult about halfway through, and by the end, I had two other people helping me with each of us grabbing a third of the coils and pushing in unison to finish the job. I think it may be easier for you because the friction of your pvc supports should be lower, and my wood primary supports were thicker than specified.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Feb 01 2008, 03:31AM

You shouldn't have any problem winding your primary. The copper coils are prewound so just thread it through slowly. The only difficult part is actually the 1st turn on the 1st two primary supports. Once you make that, then the copper coil just follows its way up. Anytime the coil seems stuck, just make sure its going in straight at that first support its entering from your coil of copper as thats where it will usually snag.

Yes, wood is a bitch, especially if its thicker. Plastic goes smooth as butter.

Dan

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 01 2008, 03:34AM

I was referring to the strike rail (sorry ill be more clear next time), which is a straight 3' length x 1/4" diameter piece of metal =P

am I suppose to use a lath to try and wind it?

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Feb 01 2008, 03:46AM

I was referring to the strike rail

Strike rail should be a piece of cake compared to the primary. You could find something like a bucket or pot that is the approximate size to bend it around.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 01 2008, 04:24AM

Wire your a genius, I used a 9" diameter pot (figuring that the copper would expand some) and look what I got! Perfection.





I wonder how I should cut it...

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Feb 01 2008, 04:49AM

I wonder how I should cut it...

If you want it to look really pretty, then go buy a pipe cutter from home depot - they should only cost a couple bucks in the small size you need. As for me, I just used some linesman's pliers that of course flattened the end of the tubing, but I was able to get it semi-round again with the pliers and a steel punch.


*edit pic link added

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Feb 01 2008, 02:13PM


Actually, the strike rail should be made of 3/8" diameter tubing, not 1/4". Doesn't make a difference functionally other than the 3/8" looks better (IMHO for a strike rail), and a bit stronger since it only has 4 supports.

You can buy short lengths of 3/8" tubing at Lowes, etc...

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 01 2008, 05:32PM

yes your right i got my fractions mixed! 3/8th" is bigger than 1/4" =P

I am now ready to start wiring and mounting the resonant board, half bridge, MMC, feedback transformers, and etc to the base of the tesla. what type of screws or stand offs should I use for Type 1 PVC. I know Wirenut used wood so it was probably easier for him to just screw everything to the wood. My main concern is that i will have to drill all my holes and then put a machined screw though it which would be very time consuming. also do my stand offs need to be grounded as well?

When the schematic refers to "ground" I am assuming it is not referring to the 3rd prong in the outlet of my house. I heard this was bad because the tesla could induce currents in other devices around the house like my plasma TV . If the book truly means "earth ground" (3 foot steel stake in the ground) then how am I suppose to do all the fine tuning and etc? oh better yet operate in the house / garage if i wanted to?

and looking at Figure 2-8 it looks like everything is grounded through the Resonant board... am I correct?

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Feb 01 2008, 10:09PM

also do my stand offs need to be grounded as well?

no

and looking at Figure 2-8 it looks like everything is grounded through the Resonant board... am I correct?

The resonant board and center-tap of the low voltage transformer can be grounded to the house ground.

3 foot steel stake in the ground

A 3' steel stake would likely make a lousy ground. Ground rods are sold at home depot and are usually 8 feet long copper-clad steel. Please see pm.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Feb 02 2008, 02:05AM


Actually, i chose Type 1 PVC since it is very easy to machine and low cost as well. You can actually drill / tap it just like aluminum. I use standard steel hardware.


Not that time consuming. Its only 4 holes i think. You can get self-tapping screws too. The (4) corner holes on the resonant driver board are connected to the internal ground plane. You only need to have one ground going to the
control board.


Actually, i have never run a dedicated ground with my DRSSTCs, even the largest ones i've built. I always run earth ground to the 3rd prong on the outlet. Of course, anytime you hook up a Tesla coil to your power, you RISK damage to any other electronics wired on the same circuit. Its up to you to the way you ground your coil.

Just if you use a strike target, make sure to attach that directly to the ground where your secondary terminates. This helps maintain circular currents within that small loop during discharges. Otherwise, if your coil strikes the ceiling or other object nearby, it will find any path it can to make it back to the secondary and this means going through wiring in your house etc...


No. The only items grounded to earth are the secondary base, and the Resonant board. The resonant driver board is floating through the power transformer, so you need to ground the centertap for safety.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Feb 02 2008, 02:31AM

Actually, i have never run a dedicated ground with my DRSSTCs, even the largest ones i've built. I always run earth ground to the 3rd prong on the outlet.

It's funny you mentioned this EVR, I did the same thing with my coil, but did not want to bring it up on the forum for fear of criticism. I have not fried any electronics in my house and I have run my coil merely feet away from my tv and 15 feet from my computer. Of course, if you're really paranoid, all you have to do is unplug any electronics on the same circuit to protect them.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Feb 02 2008, 04:19AM

yes I got your PM Wire, Thanks for the tip even when faced with persecution . I Just finished my primary circuit today, and will begin the strike rail probably tomorrow.

Daniel what did you mean by "The resonant driver board is floating through the power transformer, so you need to ground the centertap for safety?" Also do you sell board for the basic modulator mentioned in "DRSSTC : Building the Modern Day Tesla Coil." I can't afford the advanced modulator.

Will the tesla even run without some kind of external modulation? Or will it just resonate at its natural frequency?

Oh and one more question. is the terminal block mentioned in figure 2-11 just a way of connecting the power cord to all the peripherals without actually soldering them to their perspective boards? I don't actually think its talked about in the book, probably because its common knowledge to some people.

I ask a lot of questions but I like to make sure... Building a tesla is not something I want to "guess" on. Besides someone than myself may find this useful one day.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Feb 02 2008, 04:43AM

[quote]
yes I got your PM Wire, Thanks for the tip even when faced with persecution . I Just finished my primary circuit today, and will begin the strike rail probably tomorrow.
[/quote]

Well, just remember, as with any tesla coil, there is always a risk in damaging electronic equipment. Best bet is to unplug anything sensitive.


The resonant driver board is powered via the small filament transformer which is isolated. If you don't ground the secondary side, no telling where the board is floating in reference to ground. So this is why we ground it - to ensure its tied to earth ground and safe to work on.

Don't sell the basic modulators. They are simple to build though. Just a 555 timer chip is needed and a few parts.


Without an external modulator, the tesla coil will not run. The input to the gate driver ICs are pulled low, so in the absenve of a modulator signal, they will be forever disabled.
Also, the modulator is necessary to ensure the system is "pulsed" and running a very low duty cycle. If you just pulled the external modulator up to high and run the coil CW (continuous), you'd most certainlky blow up quite
a number of components.


Yes

Re: Minibrute Construction Thread / FAQs
Austin, Sat Feb 02 2008, 07:09AM

Since I am on the subject of grounding things..... what prevents the user from being electrocuted while using an external modulator? Coax cables have conductive material in it, so what would happen if an arc struck the cable connected to the modulator?

-----> ?

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Feb 02 2008, 07:29AM

Coax cables have conductive material in it, so what would happen if an arc struck the cable connected to the modulator?

The co-ax cable has a grounded shield, so any arc connecting to it would be conducted to ground. Also, the modulator box is plastic. I also aim my breakout point to the side and no arcs have come close to hitting it. If an arc did hit it, I think it might kill the modulator - I've noticed that it is very sensitive to the rf or em field from the coil. If I'm closer than about 7 feet, the coil's output drops dramatically, especially if I hold the modulator in a manner that makes the board parallel to the coil. The advanced modulator design has 2 bnc jacks, and if I'm too close to the coil and I touch one of the bnc output jacks, I can feel a small shock from it. Nothing painful, but it's definitely there.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Feb 02 2008, 07:34AM

I was thinking about making my modulator out of something metallic for better shielding would this be a bad idea?

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Feb 02 2008, 07:41AM

I was thinking about making my modulator out of something metallic for better shielding would this be a bad idea?

Maybe some others here can share their experiences. On one hand, metallic objects near a running coil can have currents induced in them making touching them uncomfortable, on the other hand, yes the shielding should be better, and with my coil, the induced current problem goes away as long as I'm more than about 7 feet away. If you already have a metal enclosure planned, I'd say go ahead with it - it'll probably be ok, and you can change it later if it's not without too much trouble.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Feb 02 2008, 07:47PM


With a DRSSTC, you basically position a break-out point on the toroid to the side where you want arcs to propogate. Doing this, you can route the interrupter cable on the opposite side away from the arcs and shouldn't have any problem. However, you can never eliminate any electrical hazard risk with a Tesla coil so you need to proceed understanding the risks involved. When i run a DRSSTC, my interrupter is usually on the ground and i have minimal contact with it, also my cables are routed in such a way where the arcs never strike in the area where the cable runs.

However, even more dangerous would be the primary circuit coupling into resonant driver board and putting full DC bus voltage on the interrupter. Hence, the NEED to properly earth ground the floating modulator control board!!!

Re: Minibrute Construction Thread / FAQs
Austin, Sun Feb 03 2008, 02:42AM

The primary and base of the coil are done.... well almost, I ran into a snag. The books states that I only need 10-24 machined screws to bolt the primary and the strike rails into the board however the strike rail supports have an 8-32 tap dimension in the schematic. I'm assuming Daniel ment to say "8-32 falt head phillips machine screw, 1" length, stainless steel" instead of "10-24 flat head phillips machine screw, 1" length, stainless steel" in table 3-6. Any comments Daniel? Should I go ahead an order some of those screws?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Feb 03 2008, 04:06AM


Size of screw doesn't really make a difference here. Use whatever screws you have already. If you only have 10-24, then drill and tap for 10-24. I believe i meant for the screws to be 10-24 since they were already used for the primary supports.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Feb 03 2008, 04:15AM

I don't feel like machining everything again... id rather get some screws that fit I think.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Feb 04 2008, 02:39AM

what do you think about this layout? This is approximately where I want everything. I am missing a few items in the pictures, like the terminal block and display board etc. I also think I am going to leave the side walls off for a while till I figure out what material I wanna use for them. I was thinking about using all acrylic on the sides.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Feb 04 2008, 03:21AM

what do you think about this layout?

I would try to get the MMC board into the airflow a little more. The large DC electrolytic caps don't get hot so you can move them. Also the MMC should be .11uF - you need to remove one of the caps and replace it with a jumper wire. The primary and strike rail look good.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Feb 04 2008, 03:40AM

Putting the primary and strike rail was a major pain to say the least. It did turn out nice I agree. I have no idea how I am going put that 1/4" copper tube through the PVC to connect it to the MMC. Its so hard to bend.

[MODERATOR: Fixed Double Posting]


One of the many benifits to being an Engineer on a college Campus. I'm using the mechanical engineer shop! its very nice inside, ill try to get a better shot of the whole shop cause its huge. Steve Adams, the shop instructor almost didn't let me do this project because the equipment isn't suppose to be used outside of class projects and senior design, however he thought building a tesla coil was the coolest thing ever!

sorry for the double post, please don't kill me!

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Feb 04 2008, 03:52AM

I have no idea how I am going put that 1/4" copper tube through the PVC to connect it to the MMC. Its so hard to bend.

You don't have to put the copper tube through the pvc, you can solder the primary leads directly to the primary (you have to do this anyway) and run the flexible wire leads through the pvc. On my setup, I have the lower end of the primary sticking through my acrylic top. This was a major pain, as I had to first wind the primary, then remove all the primary support screws, then bend the first turn down, feed it through the acrylic, and finally re-attach all the primary supports.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Feb 04 2008, 03:53AM

Yes, you do want to make sure your MMC is in the cooling flow of the heatsink. The MMCs were designed to be cooled by air.

Also, if you follow the design in my book, you want (3) capacitors, not (4) as you have it. Add a shorting bus on the 4th position.

And more than likely you will also need to shield the control electronics since they are so close to the primary coil. (Use copper)

Re: Minibrute Construction Thread / FAQs
Austin, Mon Feb 04 2008, 06:38PM

Yup, I certainly messed up the 4th Cap on the MMC good catch guys. The final stages of my Tesla are now coming into play. All I need is the secondary, and all my boards attached and wired.

Few questions

What is exactly the External 0-140VAC Variac?

Is K121:A just part of the Relay switch? the image denoted in the book makes me think I need to wrap another ferrite or somthing.

Will my MMC fail without airflow if so should I redesign it so it is not as stressed?

Does it matter which way the IGBTS are mounted, Ie Polarity?

Does Polarity matter for 10uF, 1uF, caps as denoted in the diagram?

For JMP41 what is the diffrence between Dot mode and Graph mode?

Thats all I can think of for now! Also another note, I have midterms this week so I will probably be MIA till this weekend. I say this just incase you guys miss me.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Feb 04 2008, 07:34PM

What is exactly the External 0-140VAC Variac?

A variac is an autotransformer that allows you to vary the input voltage to the bridge. I bought mine from Fry's electronics new for about $75. It is only rated at 500W, but it works fine for short runs with a new larger fuse. Similar ones are available on ebay.

Is K121:A just part of the Relay switch? the image denoted in the book makes me think I need to wrap another ferrite or somthing.

Yes, it's part of the relay. One half of the relay switches on/off the fan, and the other half of the relay switches a bleeder resistor in/out for the big electrolytics.

Will my MMC fail without airflow

Yes

should I redesign it so it is not as stressed?

If you decide to do this, use these caps:

If you put them in a 4 series X 3 parallel array, you will get the necessary capacitance of .11uF.

Does it matter which way the IGBTS are mounted, Ie Polarity?

Yes.
The side without the notch is the emitters.

Does Polarity matter for 10uF, 1uF, caps as denoted in the diagram?

You mean on the resonant driver board? If so, then yes for the 10uF tantalum caps, no for the ceramic.

For JMP41 what is the diffrence between Dot mode and Graph mode?

Dot mode will light up only two of the LEDs up to the current level, bar mode will light up all the LEDs below those two also.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Feb 05 2008, 01:11AM

50 bux for those Cap... jeez. Maybe ill stick with the current design, I'm just afraid of melting my current caps. I rearranged some stuff, let me know what you think. I still have to take off that 4th cap.

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Feb 05 2008, 01:33AM

50 bux for those Cap... jeez. Maybe ill stick with the current design, I'm just afraid of melting my current caps.
Wirenut

Yeah, they are expensive caps. I had 20 of them on hand from previous spark-gap coils. Dan's MMC design really should work fine as long as you cool them properly. I honestly would focus most of the airflow through the caps and worry about the bridge second. The super-beefy heatsinks from barredboss don't even get warm, and I don't think any of the IGBTs I've killed were from overheating.

*edit* I just saw the pics. The heatsink has fins running the other direction, so you may want to turn the bridge 90 degrees.

Re: Minibrute Construction Thread / FAQs
kwinchee, Tue Feb 05 2008, 12:18PM

Not to sound cheap or if its an embarrassing quention
What has it cost you so for to build the coil

With and without factoring in the book and PCBs

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Feb 05 2008, 04:59PM

What has it cost you so for to build the coil

It's hard to say exactly, as I bought parts from so many different sources. I am pretty sure it was more than 1k.

Re: Minibrute Construction Thread / FAQs
Reaching, Tue Feb 05 2008, 05:42PM

yup. nice work has its costs :P

i wouldnt worry much about the caps. i dont think you want to run that thing for hours, and all my drsstcs had mmcs without forced air through them and i never wracked an mmc due to overheating.
the cornell dublier caps are not much better than wima fkp1 caps you get here in germany. for a mmc like yours with wima caps you pay around 10 to 15€ around 20bucks. 50 bucks are way too much for this small sized mmc..

but i dont know, i have no experience with cornell dublier caps, cause they are hard to get here and i have no need for them. wima caps are high tech compared to this selfmade looking roll cde caps.(sorry, but here in germany you wont find any cap manufacturer who declares rolled caps for pulse applications)

for the price of cde caps you can buy wima snubbers with fat leads and mashine screw terminals, rated for extreme pulse applications.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Feb 05 2008, 10:06PM


I have prob put about 1k into this whole thing, thats including the boards and books tho...

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Feb 15 2008, 02:28PM

Okay, Austin, I'm getting worried about ya bro.
I haven't heard any progress on the Minibrute in a while.

Just got my tax return and am ordering up all the machine hardware from McMaster-Carr, and I plan on getting the Digikey components once my Local electronics supplier can give me a quote to see if they can beat them.

Hey EVR, I noticed that the parts list in the books might be off a bit, do you have an updated list?

Also, here is a list of prices of Toroids from Ross Engineering, cliped from my email.

Mike from Houston , Texas here.
Building some gadgets down here, and was wondering, what are the prices of the following toroids with both satin and polished finishes?

PER SET OF 2 UNWELDED HALVES-SATIN FINISH ONLY

T126 2.36/12" $167
T201 3"/21" $255
T220 4"/"12 $268
T251 5"/15" $308
T290 6"/18 $362
T301 6"/24" $418
IN STOCK TO 6 WEEKS

Egad, thats expensive.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Feb 15 2008, 08:28PM

I'd avoid Ross Engineering. They are way overpriced, even for a commercial outfit.

Try to see if John Freau has any toroids or make your own. Making your own doesn't look as nice, but it works just as good.

Dan

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Feb 15 2008, 08:38PM

Yeah, the one for my SGCT is 2 Stainless steel pie pans with Al drier duct. Works like a charm.

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Feb 15 2008, 10:40PM

Try to see if John Freau has any toroids or make your own.

John F. is futuret at aol.com - I bought my toroid from him - highly recommended. There are some decent looking 3x12 toroids on ebay

Okay, Austin, I'm getting worried about ya bro.
I haven't heard any progress on the Minibrute in a while.

Don't worry, he hasn't given up - he had mid-terms last week and was busy. I believe he's working on the secondary and interrupter.

I'm going to a friend's house tonight with my coil - will try to get some better and longer video footage and some new pics to post tomorrow!

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 15 2008, 10:43PM

Sorry Ultra, The reason I haven't posted any updates is simply because I don't have any.

I am all out of money to finish my tesla. I still need a 0-140 variac and an external modulator. I was going to buy Chris Mile's Audio Modulated box, however $800 is a bit out of my price range. I will probably end up getting EVR's Advanced Modulator but again I am still running into that whole money issue.

Last week was crazy also, I had 3 midterms and I was violently ill.

I sent Wirenut a little PM telling him that I wasn’t dead, cause I was trying to avoid double posts.

As far as your toroid issue goes.... good luck getting a hold of John Freau, he has falling off the face of the planet. I got my toroid for $268 on e-bay. That’s the best deal I have found so far.

Good luck, keep me up to date!

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 15 2008, 10:45PM


Wirenut, Ur the MAN!

Re: Minibrute Construction Thread / FAQs
kg7bz, Sun Feb 17 2008, 05:16PM

I've built lots of older coils, spark gap, Vacuum tube, now I'm gathering the parts for a DRSSTC using the Mini-Brute design. The one part I'm wondering where to get is the Fair-Rite core for the IGBT grive transformer. It doesn't look like Fair-Rite sells direct from their web site, what's a distributer that sells them?

Thanks for any information,

August

Re: Minibrute Construction Thread / FAQs
Bennem, Sun Feb 17 2008, 06:38PM

I got my Fair-Rite cores from 'bytemark'
just do a google search under type 77 or 78 ferrite cores.
They do small orders too!

Mel

Re: Minibrute Construction Thread / FAQs
kg7bz, Sun Feb 17 2008, 09:05PM

Thanks very much! My mind just needed jogging, I've bought from them before. Looks like Amidon also carries them for the same price. Let the fun begin!

August

Re: Minibrute Construction Thread / FAQs
Austin, Sun Feb 17 2008, 09:10PM

would this make a good variac for the minibrute or should I get something with a bit more amperage?
link

Re: Minibrute Construction Thread / FAQs
Ultra7, Mon Feb 18 2008, 01:52AM

I Just bought one of those for my SGTC!!!!
No BS!
Though, I paid 86.55 total for it.
I guess you got a better deal than I did.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Feb 18 2008, 04:17AM

I didnt buy the variac cause I thought 3amps was a bit low, anyone willing to give some input? how many amps should my variac be able to pump out?

Also does the polarity matter for the mmc board? Ie does it matter which end I hook the output from the half bridge to mmc?

Also does the polarity matter for the current sense transformers? Ie does it matter which way the 8awg cord goes through the hole of those two transformers that hook up to the resonant board?

I had one last question about the "physics of induction". I remember learning about the right hand rule in physics 213 and how that applies to magnetic fields. if your thumb points in the direction of the current and you curve the end of you finger tips, that points the directions of the magnetic field. ......... if this is true than two wires that are "perpendicular" to each other will have a harder time inducing current on one another than if those wires were parallel. if that assumption is correct it will help me lay out my wires in the base of my tesla. Let me know what you guys think.

Re: Minibrute Construction Thread / FAQs
Wirenut, Mon Feb 18 2008, 06:01AM

I didnt buy the variac cause I thought 3amps was a bit low, anyone willing to give some input? how many amps should my variac be able to pump out?

That was probably a good idea (not buying). The variac I use is a small 5 amp one that I put a 20A fuse into. I think this is at the minimum limit of what will work, as it gets hot after about a minute of use.

Also does the polarity matter for the mmc board? Ie does it matter which end I hook the output from the half bridge to mmc?

No.

two wires that are "perpendicular" to each other will have a harder time inducing current on one another than if those wires were parallel.

This is correct.

ps... sorry no new pics or vid yet. I am having a problem with my coil that I haven't figured out yet. Output arcs have dropped down to 3 feet initially, and rapidly shrink to two feet. Wall current draw seems excessive. MMC caps seem ok, I think I may have a half-blown IGBT - is that possible?

Re: Minibrute Construction Thread / FAQs
Austin, Mon Feb 18 2008, 06:32AM


apparently, I did some quick research and found that your not the only one with a "half blown" IGBT... one instance can be found here linky ... its not the exact part, however operating principles may still apply. you should really invest in a strike rail =P

so would a 0-140 volt / 10-20 amp variac work?

Re: Minibrute Construction Thread / FAQs
Wolfram, Mon Feb 18 2008, 06:48AM

The guy in the forum you linked to is talking about bricks with two IGBTs in each, presumably halfbridge bricks. As I understand it, "half-blown" means that only one of the two IGBTs in the brick is blown.

Re: Minibrute Construction Thread / FAQs
Bennem, Mon Feb 18 2008, 07:52AM


Correct feedback phasing is important.
When you come to apply buss volts and nothing seems to oscillate,
try reversing your CT connections or reversing the direction of your wire into the CT hole,
either will give you the required 180 degree shift in feedback phasing.


Mel.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Feb 19 2008, 08:01AM

I don't suppose anyone has an "advanced modulator board" laying around that they want to sell me? Dan is fresh out and wont have them for another 8 weeks or so.... If this is true than I may be stuck for a while unless I follow the schematic and solder up my own PCB board.

This sucks too because I just ordered all the parts from digikey.com and the total was over $100

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Feb 19 2008, 02:26PM

You could build the basic version of the interrupter - much easier until you get the adv. mod. board

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Feb 19 2008, 03:01PM

Regarding toroids, Science First of NY also sells toroids. I believe they have an 8x2 and a 12x3 which are pretty inexpensive. They don't list them in their catalog, but if you call them, they will place the order for you.

Search GOOGLE for their website and give them a call.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Feb 20 2008, 03:17AM

Anders. M has an extra modulator board laying around that he is willing to sell so I am back in business! See kids, when in doubt it never hurts to ask.

I really want a professionally spun secondary, does anyone on this form or anyone you guys know do custom secondaries? perhaps you or your friend would like some extra cash? If so let me know via private message or other means.

he are some updated pictures




I hope these are well insulated. I had trouble finding nylon stand offs so I used this type of plastic that separates the two screws (one on top/one on bottom) from touching each other.




I am starting to regret this layout just because I don't like how the capacitors are facing the MMC... I just have so little space tho.

Re: Minibrute Construction Thread / FAQs
Wirenut, Wed Feb 20 2008, 04:01AM

I really want a professionally spun secondary,

Really? Why? I like winding secondary coils. It's really not that difficult to get a good looking secondary. I wound mine in less than half an hour with only minor prep. and a friend's help to pull the trigger on the drill to spin the form. Besides, don't you want to be able to show off your coil and tell people that you built all of it including winding the coils?

I just have so little space tho.

Ahh, the rat's nest inside my base should make a little more sense now...
Just wait until you wire the fan, add the relay, CT's, LV transformer, bridge and control power wires, etc.

Re: Minibrute Construction Thread / FAQs
teravolt, Wed Feb 20 2008, 05:33AM

another place for spun toroids is information unlimited

Re: Minibrute Construction Thread / FAQs
CT2, Wed Feb 20 2008, 06:27AM

As to spinning the secondary, if you want it to look professional, just take your time. I wound this coil today sitting in front of my computer watching south park... it only took like 4 epeidodes. I wound it by hand, and it was 36 awg wire... it's a PITA, but for other coils I have built a winding jig and that really helps. It isn't too hard to get a great looking secondary and you can say you made it.

Re: Minibrute Construction Thread / FAQs
Bennem, Wed Feb 20 2008, 07:09AM


I personally wouldn't recommend buying toroids from Information Unlimited IMHO.
I ordered two (a 12x3 inch and a 8x2) and both
arrived dented,knicked and scratched, one had a small extra hole at the side of it
and both halves of the toroids were not a good fit.
I have had one of John F toroids and they are excellent!... second to none in comparison!

Mel.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Feb 21 2008, 07:30AM

More pictures. I'm a bit concerned about the designed layout but I feel its a bit to late to change it. Let me know if you guys think this layout might cause any foreseeable problems with induction etc. my biggest concern right now is how close the MMC and big caps are to each other.

Re: Minibrute Construction Thread / FAQs
Bennem, Tue Feb 26 2008, 05:58AM

Hi Austin,

Its looking good!!!

Any more progress/updates?

Mel

Re: Minibrute Construction Thread / FAQs
Austin, Tue Feb 26 2008, 07:34AM

I turned on the Tesla for the first time last week. I tested the resonant boards voltages and everything is looking great! I did fry one of the ICs while check the voltages however, and now the over temp light wont turn off. I thought U1 was the culprit however a closer look at the schematic shows that removing U1 actually cuts all power to the IC. Instead of testing EACH IC I just ordered a bunch from digikey. hopefully that will fix the problem.

Note to self! do not test board with ICs in them. I did read the disclaimer posted by Daniel in the book however since my ICs were already in the board I didn't want to take the risk of damaging the leads by removing them from the board. oh the irony....

here are some new pictures!

















I talked with some electrical engineer kids at my school, and one of them saw a picture of my wrapped ferrite. he said from the looks of it, it was wrapped incorrectly. Could i get a second opinion from one of you guys. I twisted the blue and white together then wrapped them around the ferrite 20 times. I then took the yellow wire and wrapped it 10 times around the ferrite. there is some overlapping but they are evenly spaced around the ferrite. One of the students said for the best results, I should divide the ferrite into 3 sections and wrap each wire individually around the ferrite in their own sections without overlapping. Any comments would be great.

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Feb 26 2008, 02:25PM

One of the students said for the best results, I should divide the ferrite into 3 sections and wrap each wire individually around the ferrite in their own sections without overlapping

I'm not an EE so I can't tell you if this would work better, but I can tell you that your GDT looks exactly like mine, and it seems to work.

Looks like your coil is coming together! What size is the toroid? What size is the secondary? Have you figured out the details (# of turns, winding length, etc.) of the secondary?

Re: Minibrute Construction Thread / FAQs
Austin, Tue Feb 26 2008, 04:04PM

my toroid is 4" x 13 and my secondary is 4.5" OD x 18". Exactly what the book specifies. I am just waiting for the board from Anders and then i can start the advanced modulator.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Feb 26 2008, 05:45PM


No, thats not quite right. Actually, the students are wrong, and the way you wound it doesn't seem correct as well.

One of the most important parameters of this transformer is the coupling factor, which determines what the leakage inductance of the windings are.

To maximize coupling, and minimize leakage inductance, the windings need to be wound trifillar and as tightly as possible.

If you wound as the students said, the leakage inductance would be extremely high (very poor coupling), and your method of winding the secondaries separate and then putting the primary on top of them is also not very good.

I would suggest starting over. Begin by taking three wires, and putting the one end (three wires knotted together) in a cordless drill. Then use the drill to spin and twist the three wires tightly together. Then, wind 20 turns around the core.

For the primary, that needs 10 turns, you would first wind this bundle of three wires 10 turns. Then pull out a loop at the 10th turn and twist this loop together. Then continue winding the rest of the 10 turns. Then cut the pulled out loop, and make a parallel winding with it.

But defintitely start over.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Feb 26 2008, 09:08PM


So should it look something like this? I didn't understand the last part of your reply when you said "Then pull out a loop at the 10th turn and twist this loop together. Then continue winding the rest of the 10 turns. Then cut the pulled out loop, and make a parallel winding with it".




Please note that each of the 4 sections represent 5 turns for a total of 20

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Feb 27 2008, 03:27AM

Not sure what you are trying to show there.

Anyways, here is what the winding should look like. Blue and Red are the secondary windings. Green is the parallel primary winding. The center of the green primary is where you would have pulled the loop out and then cut it to split the winding.

Re: Minibrute Construction Thread / FAQs
teravolt, Wed Feb 27 2008, 05:29AM

eastvolt fogive me if i am out of place but why do need to twist 3 wires for primary and 3 for sec when your book sais there are 2 paralell primary windings of 10 turns and 2 secondary turns of 20 turns. Does your students know about the phasing dots and there importance.

Re: Minibrute Construction Thread / FAQs
EDY19, Wed Feb 27 2008, 06:10AM

You don't need 3 primary and 3 secondary, but you do need to twist 3 wires together. These three wires will eventually serve as the primary and two secondaries. After twisting, wind however many turns you need for the secondary. Count in from either side to find the center of the winding, and pull out one of the wires- you want to divide one wire into two separate windings with 1.2 the turns (all you need to do is cut one wire). Now you will have two windings with 20 turns each, and two windings with 10 turns each. Make sure the phase is correct on the 10 turn windings, and put the two in parallel to create the primary coil.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Feb 27 2008, 06:34AM

I think I got it now... Here are some pictures to show what I did. Please let me know if this correct before I install the ferrite to the board.

Re: Minibrute Construction Thread / FAQs
Wirenut, Wed Feb 27 2008, 02:25PM

You have two different colored wires labeled as S1/G1. One wire goes between S1/G1 and the other secondary winding goes from S2 to G2. You can also double check that the primary winding is paralleled (instead of two separate primaries) by checking for continuity between primary gate and gate return.

Re: Minibrute Construction Thread / FAQs
vasil, Wed Feb 27 2008, 07:05PM

It's very simple. I used 10 twisted insulated wires to wind 12-16 turns on the ferite core. Making all the windings together helps a lot identifying the phases. Check each winding for the continuity, mark it, then put two in series for each IGBT to get the 1:2 coeficient. i used two paralleled primaries for more current too.

LINK

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Feb 27 2008, 07:10PM

Just a note on that black secondary.
Do you know what kind of material that is? Usually dark plastic (if its not type i PVC) is usually somewhat conductive which is bad.

Before you wind your secondary, i'd be sure you know what material is being used.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Feb 28 2008, 01:16AM

other than miss labeling the blue and white wire (S1/G1) does it look correctly wound?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Feb 28 2008, 01:35AM


Its hard to tell from the photo, but just use common sense. If the winding looks like the one i made an image of, then its correct.
Just be careful when you hook it up to ensure proper phasing is in order.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Feb 28 2008, 04:25AM


I'm pretty sure its Type 1 Pvc I bought it next to the "white" PVC in the plumbing department at Home Depot.

Re: Minibrute Construction Thread / FAQs
Bennem, Thu Feb 28 2008, 06:56AM

Yeah....phasing is important, you don't want both igbts on at the same time.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Feb 28 2008, 07:53PM


I am like 90% sure the phasing and the primary winding are all correct now. But then again I guess one can never be too sure until he looks at it under an oscilloscope. Wirenut and I had an extensive discussion on this last night just to be absolutely sure. All that remains to this project is finishing the secondary and Advanced Modulator. I am waiting on parts so I will keep you guys update when I have made some more progress.

Until then I might be MIA for while, finals and term projects are coming up so the next two weeks I will be extremely busy.

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Feb 29 2008, 01:38PM


Hello Mike,

I am sorry, but we no longer manufacture toroids. They were just not popular enough to sustain production. Good luck in your hunt.

Thank you,
Joe Welsh

Customer Service Team
Science First
95 Botsford Place
Buffalo, NY 14216
T: (716) 874-0133
F: (716) 874-9853
Email: **link**

Re: Minibrute Construction Thread / FAQs
Austin, Fri Feb 29 2008, 11:41PM

I'm looking at oscilloscopes and I was wondering about this one for testing the minibrute.

Link

Re: Minibrute Construction Thread / FAQs
teravolt, Sat Mar 01 2008, 05:37AM

if you can get a tektronix 2440 storage scope. storage abilities are helpful and can be used for other things like pulse work

Re: Minibrute Construction Thread / FAQs
Austin, Sat Mar 01 2008, 08:01AM

I'm really trying to keep it under $100. Not to sure how realistic that is.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Mar 01 2008, 01:24PM

Austin,

Any cheapo 20mhz scope will do fine for testing out any solid state tesla coil. Sure it may not have the bells and whistles as other scopes, but there are plenty of scopes on EBAY for less than $100.00 that will do the job.

The only one requirement you will want is the capabiliity for 2 channels where you can add them together. This is VERY important as it allows differential measurements. Basically, you'll hook one probe on CH1, the other probe on CH2, and then set function to ADD and INVERT CH2. This way you can measure signals which are not referenced to ground.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Mar 01 2008, 07:12PM


any 2 channel scope should be able to take a differential correct?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Mar 01 2008, 10:23PM


Not necessarily. It needs to have the ADD function and an INVERT function on one of the channels. At least if you don't want to do the math in your head.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Mar 01 2008, 10:34PM

What about this one EVR? i'm trying to download a manual / specifications however im not finding anything... probably because it is so old.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Mar 02 2008, 03:21AM

EVR, I hit a snag while trying to properly tune the meter on the display board. After talking extensively with Wirenut I found out that he too had the same issue while trying to adjust the meter to display the correct number of LED's.

The book says to apply a variable DC voltage of 0-12 volts to the Isense terminal. while measuring the voltage on pin5 of the U41 (the Display chip). I did everything the book said however when I started turning up the voltage on my variac R21 started to smoke at 5volts. I turned everything Off and started troubleshooting the situation with wirenut.

I set my variac to exactly 12volts and hooked up the leads to the Isense terminal again and measured the voltage. It only read 3 volts. I then measured the voltage at Pin5 on U41 (referenced to ground) and only measured 2 volts.

I told Wirenut what happened and he explained that the same thing happened to him while he was testing his display board. He currently operates without it.

Do you have any suggestions? below are some photos of my voltmeter.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Mar 02 2008, 04:19AM

R21 is a 3W, 1.6 ohm resistor. Using Ohm's laws, I just did a couple quick calcs and...
The formula for power is E^2 / R sooo
12V^2 = 144 / 1.6 ohms = 90 watts!!! How is that 5W resistor supposed to handle that? I must be missing something or something is wrong.

Re: Minibrute Construction Thread / FAQs
teravolt, Sun Mar 02 2008, 04:30AM

R21 is 2.7 ohms and you may have to lift one of the legs to give the board a referance. mesure R21 to see if is still 2.7 ohms then repeat. make shure the current transformer is also disconnected

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Mar 02 2008, 04:47AM

My book lists R21 as 1.6 ohms. A 2.7 ohm resistor would still be over 50W.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Mar 02 2008, 02:45PM


Just ask the seller. If he can't answer it, then at least have him to take a close-up of the controls so you can determine if it has what you want.

Also, be careful of double posts.


Yes, something is definitely wrong. The test procedure that is. You simply need to insert a variable DC voltage source across capacitor C31 (i.e. 12V) which is the input to the LM3914 display IC. This will allow you to set the display chip to full scale.

Also, the 1.6 ohm resistor is sized properly.

But instead of telling why, i'll you guys figure that out - so put your thinking hats on!!!

Dan

Re: Minibrute Construction Thread / FAQs
Austin, Sun Mar 02 2008, 06:29PM

I am not an electrical engineer but does it have something to do with setting the Overcurrent potentiometer to a low voltage (ie 2.95v = 300amps) for initial tests?

Re: Minibrute Construction Thread / FAQs
Wirenut, Sun Mar 02 2008, 07:18PM

Is it because the voltage from the CT is actually low-duty-cycle AC?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Mar 03 2008, 02:40AM


Yes.

Re: Minibrute Construction Thread / FAQs
Ultra7, Wed Mar 05 2008, 11:36PM

Okay, in looking for the IGBT's, I noticed that you guys bought them all up.
No one has any left unless I want to pay $40+ apiece for them.

Sooooooooo. . . . .

I was looking at these.
HGT1N30N60A4D


I noticed that they are not all that different, accept that the 40 is rated for 200A with a 55 fall time and the 30 is rated at 150A with a 58 fall time.

With the active current limiting board, wouldn't I be able to use them safely or would need a complete overhaul of the system?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Mar 06 2008, 12:26AM

yes, those are fine.

Re: Minibrute Construction Thread / FAQs
Ultra7, Thu Mar 06 2008, 01:26AM

Cool, I just bought 6 of them then, that leaves me 2 spares to blow up.
At 10 bux a pop, i figure I'll be able to save some money at least. . . .

Re: Minibrute Construction Thread / FAQs
Austin, Fri Mar 07 2008, 10:26PM

The secondary is just about done, just need to add a few more coats of the minwax.

This was my first attempt at making a secondary. It turned out alright however leaving it outside over night to dry must have caused the wires to bunch up and overlap just a little. It was very tightly wound and the bumps were not there the night night before.

Has anyone ever experienced this before? Also will these bumps cause a major problem? Below are some pictures of the secondary.

I would also like to thank Anders M. For sending me an extra modulator board. Without the help and support from you guys the construction of this DRSSSTC may not be possible.





Taken after I left it outside to dry





Taken before I put it outside!

Re: Minibrute Construction Thread / FAQs
..., Fri Mar 07 2008, 11:24PM

The windings loosened up when you let it sit outside because pvc shinks when cooled, but copper doesn't (or at least to a much lesser degree). I wouldn't worrry about them, it is mostly a cosmetic defect.

In the future, it is best to wind the secondary when it is nice and cool (like leave the former out overnight) and paint it after it has warmed up so that the pvc will expand a little and help tighten up all of the windings

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Mar 07 2008, 11:49PM

Looks fine to me. I don't think it will be a problem. In fact, i can't really see any problems that you describe anyways in your pics.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Mar 09 2008, 10:54PM

Finished up the modulator board, just need to wire up the switches, which has kinda confused atm. I am having a hard time telling where the 10k ohm resistor goes and the 1meg ohm resistor goes.

Here are some pics. Its not very pretty but it should work. My dremel ate part of the board on the top left hand corner.

Re: Minibrute Construction Thread / FAQs
Ultra7, Thu Mar 13 2008, 03:40PM

Okay Austin, I just bought my boards from EVR.
I've spent since December acquiring parts, so I am about to start my build finally.

The advanced modulator looks like just a bunch of 555's so I'm going to perf that one by myself, but the rest have been officially ordered.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Mar 13 2008, 11:08PM


Nice Ultra! keep us up to date...

Look what i got today









My very first brand new pre-owned Tenma oscilloscope. Ah... its like buying your first car all over again. Now I just have to figure out how it works.

I will be MIA for about a week or two due to finals! So ill see yall in a week or so.

Oh did i mention it only set me back 35 buxs!

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Mar 14 2008, 02:53AM

Excellent. That scope will definitely do exactly what you need it to do. Differential included with ADD 1 and 2 and INVERT 2nd channel.

As with any scope, especially with differential and hv measurements, make sure you don't exceed the voltage ratings of your probes etc...

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Mar 14 2008, 12:48PM


Thats a nice scope for $35.00.
Were you able to find a manual for it?

Re: Minibrute Construction Thread / FAQs
ragnar, Sat Mar 15 2008, 12:12AM

That's funny... I had a 'LABTECH' brand oscilloscope that looked exactly the same, and I believe Marko has a 'HUNG CHANG' oscilloscope, also exactly the same... which one is the real deal? =P

Re: Minibrute Construction Thread / FAQs
Austin, Mon Mar 31 2008, 01:13PM

Two Words...... It's Alive!

My very first Coil is finally up and running, Well sort of. I am still unable to reproduce Daniel's 4' Arcs. Later this week I am going to fine tune it and see if that makes a huge difference.

Special Thanks to Wirenut for hours of troubleshooting and Daniel for the wonderful book! without the support from this community my coil would not be here today!

check it out at (you tube)

Re: Minibrute Construction Thread / FAQs
Dr. Drone, Mon Mar 31 2008, 03:20PM

Re: Minibrute Construction Thread / FAQs
Ultra7, Mon Mar 31 2008, 04:16PM

Congo Rats, Austin!

Re: Minibrute Construction Thread / FAQs
Reaching, Mon Mar 31 2008, 05:24PM

mh, did you say "it blew" at the end of the video? oh man, i recognise my first attempts to build a drsstc. man was that a huge amount of dead igbts and other stuff. but great work and keep on it, its really worth it. try tuning it for best sparklenght without turning the on time too high (i could hear that on the end of the video. you turned up the on time until it blew)
my drsstcs are working with on times around 80 to 150µS . everything above that i stress to the igbts and other parts. you will soon find a point where the sparklenght stays the same, even if you turn up the on time, the sparks wont grow.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Mar 31 2008, 06:06PM

Nice job! Glad its working for you.


4' Arcs is a definitely challenge. 3' should be relatively easy once you get through fine tuning. Getting 4' is all a compromise between reliability and performance. I typically run my current limit so that 3' is the maximum arc length. This keeps it at a good reliability.

Dan

Re: Minibrute Construction Thread / FAQs
Wirenut, Tue Apr 01 2008, 12:25AM

Austin wrote...

Two Words...... It's Alive!

Great to see some sparks! What blew at the end of the vid? Another fuse or...

Reaching wrote...

I see that Wirenut has his current limiter set to full 1000 amp peak before it cuts off
to get his 48 inch spark length....may be out of the safe operating area of the IGBT's
and IGBT's may not last long that way especially with some ground arcs.

Dan wrote...

4' Arcs is a definitely challenge. 3' should be relatively easy once you get through fine tuning. Getting 4' is all a compromise between reliability and performance. I typically run my current limit so that 3' is the maximum arc length. This keeps it at a good reliability.

Yeah, I definitely like to push the limits for performance. I am well aware of the risks and I keep a spare set of IGBTs on hand because of this. So far, so good, though!

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Apr 01 2008, 02:42AM

Wow 1000A current limit? I only run my DRSSTC to about 500A peak. Thats really pushing it!!! Good to see its really working for you.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Apr 01 2008, 03:03AM


Believe it or not I blew one of the wires connected to mmc where the 4th cap would go. since then i have put a "bigger wire" there but i have yet had a chance to tune the coil. I have been so busy with my new job.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Apr 01 2008, 07:31PM

Yeah, you need a good thick piece of bus wire there.

Re: Minibrute Construction Thread / FAQs
Bennem, Wed Apr 02 2008, 05:33AM

Well done Austin!!

Bet it feels great to get your coil working?...

As Reaching said, best keep your on times to a safe limit
for less stress on your components.

What is your current limiter set to?

Just play around with your tuning now.

Mel.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Apr 02 2008, 02:19PM

Also, note if your PRF is low, current increases per pulse (as voltage droop on the DC bus caps is less), so ideally you want to stay at least 100Hz for less stress.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Apr 02 2008, 07:08PM


It feels great Mel, I cried a bit once it made its first light. Just kidding

There is not current limit set at the moment. I was going to set it to aprox 500A when I tune my coil but I just have not had the time due to my new job.

The current meter is not currently working either, so I have to figure out whats wrong with that as well. I remeber the test procedures for the meter was somewhat confusing. The bottom lights work on the meter but thats it about it. They don't go higher or lower. Its probably another fine tuning issue with the POTS.

Re: Minibrute Construction Thread / FAQs
Bennem, Sun Apr 06 2008, 07:05PM




I haven't read Dan's miniBrute book, just read his first book on the ISSTC 2,
but with my coil which uses his current meter circuit,
i tested out its function by inputing a variable supply to the bargraph and adjusting the pot
to read 1 volt = 1 LED on, 2 volts = 2 LED's on etc..
With my current transformer and burden resister combination (1000:1 and 10 ohm)
100 amp peak = 1 volt = 1 LED on

Mel

Re: Minibrute Construction Thread / FAQs
Ultra7, Thu Apr 10 2008, 10:39PM


Hey guys. . .
How critical are the values of this cap?
I.E. the voltage rating / Cap value?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Apr 11 2008, 02:42AM


Not too critical. 2.2uF to 6uF should fine. Rated at least 450VDC. Polypropylene or similar.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Apr 15 2008, 01:40PM

Austin wrote ...

quick question... where did you ground your strike rail and secondary? the ground that plugs into the control or high voltage portion of your tesla? My secondary is grounded through the 3rd prong that is hooked up to the variac, I'm wondering if this is a bad idea.

Anonymous wrote..,

I think mine is the same way - I never touch the variac when the coil is running anyway, but I think you're right, it would be better to connect the secondary to the "control" ground and ground the xfrmr and res board to the "power" ground.

End quote

Can I get a confirmaton on which is better? Also I am aware of the possible risks associated with grounding a tesla through a house ground instead of earth ground. However I know most of u guys probably don't have an 8 foot pole sticking out of your lawn.

Re: Minibrute Construction Thread / FAQs
Ultra7, Tue Apr 15 2008, 05:03PM

I have an 8 foot ground rod in my yard, but only about 6 inches of it is sticking up.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Apr 15 2008, 05:41PM



I've never had any problems grounding to the 3rd prong on the outlet with my miniBrute. And i've run CD players, Synthesizers, Amplifiers, LCD TV, etc... off the same outlet with no problems. However, as stated before, anytime you share a circuit with any Tesla coil, there is always a risk.

Re: Minibrute Construction Thread / FAQs
Austin, Tue Apr 15 2008, 09:09PM


which prong? the one that goes to the controls or to the high voltage portion of the minibrute. Because when i start cranking up the voltage my variac starts making a ticking noise and im just wondering if its because my coil is grounded to the 3rd prog that runs to the variac then to the wall. or perhaps it doesnt matter at all.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Apr 15 2008, 09:59PM

The EARTH GND prong of course.

Your variac is ticking because a DRSSTC is a pulsed system. Your seeing big chunks of current being passed through. What is the PRF frequency when you hear the ticking?

Re: Minibrute Construction Thread / FAQs
Austin, Tue Apr 15 2008, 10:56PM


Perhaps I was not clear... There are two earth (3rd) prongs to choose from, the one that powers the controls, and the one that goes to the high voltage protion of the tesla. I am currently using the 3rd prong on the cable that goes from the tesla through the variac and then into the wall socket. I was just wondering if it was harmful to have high voltage going through the 3rd prong connected to the variac. My other option is to just use the 3rd prong on the cable that supplys power to the controls, that way its a direct path to the wall and does not have to go through the variac to ground.

I hope this makes more sense.

I wasnt sure what my PRF was set to once it started ticking, I'll have to watch for it once I fire it up again.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Apr 16 2008, 01:06AM

I have all grounds inside my miniBrute enclosure tied together and with both 3rd prongs on both outlets.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Apr 16 2008, 02:39AM

k thanks for the clarification

Re: Minibrute Construction Thread / FAQs
EdwinWise, Sun Apr 20 2008, 04:11PM

Hey fine sparky people,

I finally got my miniBrute up and running, with some pictures on my site, Simreal.com

It's a pretty decent little coil! Right now, I can't run it at its full potential since the fuse in my variac has a tendency to vaporise, which is fairly exciting. Good stuff.


Edwin!

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Apr 20 2008, 05:19PM

Very nice!
How long is your maximum output arcs?
You should be able to easily tune for about 36" at only about 120VAC input.

Re: Minibrute Construction Thread / FAQs
EdwinWise, Sun Apr 20 2008, 07:16PM

Right now I'm getting about two-foot arcs (guestimate) with about half of that input. When I kick it up more I explode the fuse in my variac. I'm tempted to just plug it into the wall and see what happens...

It's an impressive little runt of a coil!

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Apr 20 2008, 07:30PM

What size fuse are you using? I typically use a 10A variac, but run a 20A fuse for short durations run time.

Re: Minibrute Construction Thread / FAQs
EdwinWise, Mon Apr 21 2008, 10:36PM

My variac is lame -- a 5A version from Fry's -- and I dropped a 10A fuse into it. The massive coil of wire inductor might be worth trying, or something, or I could try to find a decent variac. From what I've seen, though, they are pretty spendy, even on eBay.

Re: Minibrute Construction Thread / FAQs
EdwinWise, Tue Apr 22 2008, 07:14PM

Ooo, never mind, found a 3kVA variac on eBay, $150 shipped. Not bad.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Apr 24 2008, 02:44PM

Just a comment on increasing reliability for the miniBrute (or any DRSSTC really)

I have found recently through some demonstrations that simply using a long 50ft extension cord in series with your bridge power for the miniBrute greatly improves reliability without sacrificing performance. It doesn't really act like a resistive ballast but rather an inductive ballast. A spool of wire would likely have the same effect.

Re: Minibrute Construction Thread / FAQs
Ultra7, Thu Apr 24 2008, 05:00PM

So what you are saying is. . .
Hook the variac up with the 50Ft extension cord instead of just straight from the wall?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Apr 24 2008, 06:13PM

Yep, this definitely will help.
I can run my electrodes 1 foot apart from each other at maximum PW and maximum PRF with super hot white arcs with no problems at full voltage this way. The extension cord acts as a poor man's inductive ballast to limit peak current.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Apr 25 2008, 12:07AM

Great tip thank you! Daniel, I just got all my parts in for the modulator. I start construction this weekend if everything goes well.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Apr 26 2008, 09:35PM

Sorry for the double post.

Daniel, I'm working on the Xenosonic Audio Interface and i noticed that R56 is listed twice in the parts list. is R56 suppose to be 100k or 1M

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Apr 26 2008, 10:41PM

Look at the schematic. Use the value specified in there.

Re: Minibrute Construction Thread / FAQs
Wirenut, Sat Apr 26 2008, 11:48PM

The link on your site for the schematic goes instead to the block diagram. BTW, I'm ordering my xenosonic board and parts this week.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Apr 27 2008, 03:21AM

digikey mailed me the wrong cap for c12. I went to fry's electronics and bought a .47uF mylar film cap 100v this should work just fine right?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Apr 27 2008, 04:21AM

R56 should be 100k. This is the hysteresis on the comparator to prevent chattering.

C12 will work if its a 100V cap, but can't say it will fit in the 0.200" spaced holes.

Re: Minibrute Construction Thread / FAQs
Dr. Shark, Sun Apr 27 2008, 12:11PM

Well, does it?
You are coiling both the live and the ground return around the same path, so effectively you have two coils wound in opposite directions. The magnetic fields should pretty much cancel.
Or are you just running the cable in a straight line and relying on the distance between the live and neutral conductor to provide the inductance? In that case I suppose a small air core coil on the input of the power board could provide the same inductance and would do the job much more efficiently.

Re: Minibrute Construction Thread / FAQs
..., Sun Apr 27 2008, 03:42PM

I am also a little skeptical about that, since there is probably much more than 50f of wire between the outlet and the main breaker panel... The only thing I can think of would be that you are using a cheep (small sized wire) extension cord which does have a significant resistance. 100ft of 16awg wire is .5oh, 100ft of 14awg wire is .25ohm.

Re: Minibrute Construction Thread / FAQs
Dr. Drone, Sun Apr 27 2008, 05:04PM

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Apr 27 2008, 07:30PM


Turning down the variac would reduce current, but at the expense of performance. During normal operation (no ground strikes), the DC bus charges up nominally between pulses. However, during a ground strike, a lot of energy is discharged from
DC bus and hence the ballasting effect limits DC bus recharge and acts like an active ballast.

And yes, i agree based on the little inductance in the power cord that it is likely more resistive based ballasting.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Apr 27 2008, 08:10PM

will TC7662ACPA work instead of ICL7662CPA-ND for U5. Because Digikey no longer sells ICL7662CPA-ND.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Apr 27 2008, 09:55PM

Get the ICL7662 via free samples from MAXIM.

Re: Minibrute Construction Thread / FAQs
Austin, Sun Apr 27 2008, 10:12PM

Im trying to get this working today, TC7662ACPA should work correct?

grrr and also for some reason my dot graph is not working at all, i checked all the LEDS for polarity. Ill keep yah up to date.

Re: Minibrute Construction Thread / FAQs
Austin, Mon Apr 28 2008, 01:43AM

ok Daniel im officially stuck. I get no output of U53 or U4. Both of which i have changed twice. However i get a signal out of U3. I got the VU meter working great and it seems to be blinking to the music, however when I hook up J2 to the Tesla i get nothing. =(

Again sorry for the double posting.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Apr 28 2008, 02:14AM

Check your voltage at pin 5 of U4. You should be getting a voltage level there greater than 6V i think. R10 is open right? If not, then increase gain of ENV amp R3. Check all stages with oscilloscope etc...

Re: Minibrute Construction Thread / FAQs
Austin, Mon Apr 28 2008, 02:17AM


pin 5 shows +5 volts and r10 is open, jmp1 is also at the "B end" of the jumper if that helps any. I currently am not near a scope. Any other ideas?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Apr 28 2008, 11:44AM

Austin,

Please keep thread on topic. This thread is for the discussion of the miniBrute DRSSTC.

If you have questions regarding Xenosonic, then create a new thread.

Thanks
Dan

Re: Minibrute Construction Thread / FAQs
Ultra7, Sun May 04 2008, 07:26PM



Heya guys, quick question.
Just about to connect the Windings of the GDT to the Half-bridge.
Lemme see if I gets this straight.

The side I started winding from will be turn 1 and the side I ended on is turn 20.

If I used red= G1=S1, blue= G2+S2 and green as the 10//10.
Will turn 1 red =S1 and turn 20 red =G1, and turn 20 blue =S2 and turn 1 =G2?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun May 04 2008, 08:41PM

I sent a PM. Yes, this sounds correct. Both secondaries are out of phase from each other. Anyways, you'll find out if its right when you do your scoping at the gates (no bridge power)
Just make sure everything looks right before applying DC bridge power, otherwise, you'll blow both them IGBTs like a drunk miner with a box of old dynamite.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Thu Jun 12 2008, 04:05AM

I want to build a miniBrute. I have reviewed the parts list and with a few exceptions it looks like all the parts should be easy enough to get. The project has been completed by others and it looks like there is an amazing amount of experience on this forum, and even real nice PCB's.

However this project is well over my head. I have the basic theory and process down but how that is being done in the circuits is flexing my mind a bit. With that said I have come across a few parts issues and there potential substitutes. I have simply made my best guess. If anyone can spare some time to look over these numbers they are all from Digikey except the IGBT's witch it looks like the HGTG20N60A4D will work in the place of the HGT1N60A4D but the heat sink will need to electrically isolate the IGBT's from one another, ground and remove the heat better.

miniBrute DRSSTC parts list

1.5KE7V5CADICT-ND to 1.5KE7.5CALFCT-ND or a 1.5KE9.1CAMSCT-ND

1.5KE18CADICT-ND to 1.5KE22CALFCT-ND

1.5KE220CADICT-ND to 1.5KE250CALFCT-ND

3295W-502LF-ND to 3296W-502LF-ND

Advanced Modulator parts list.

339-1360-ND to 339-4605-ND

Ill order the miniBrute book and the boards now, and wait on the parts. I want to add the XenoSonic Audio Interface as well but I think it best to make an operation DRSSTC first.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Thu Jun 12 2008, 04:45AM


Sems now us two will build this project in same time. I ordered book yesterday and now i will order boards

Re: Minibrute Construction Thread / FAQs
Ultra7, Thu Jun 12 2008, 11:09PM

There is an Unknown tantalum Capacitor on page 81 in the upper left corner.



I have not found an image online that shows this capacitor, but rest assured, the book shows that there is a capacitor here.
What capacitor is this in the parts list, or is it not in the parts list.

If I need to include it, what value should it be?

the same as C15?

Austin, Wirenut, did you guys include this cap?

Thanks for any help. . .

Ultra7

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jun 13 2008, 02:49AM

If I need to include it, what value should it be?

the same as C15?

Austin, Wirenut, did you guys include this cap?

I threw a 10uF tantalum cap in there (same as c15) and it works fine - I'm not sure if it's needed as it's not on the schematic or parts list though.

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jun 13 2008, 05:08AM

I would not use the images listed in the book as any indication of where parts should go because some of them are outdated. Following the schematic would be your best bet. I don't have the book in front of me however if Wirenut says its not listed in the schematic, chances are I did not include it.

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Jun 13 2008, 04:02PM


I suppose I'll do the same thing.
I guess it's better to have it, and not need it, than to need it and not have it. . .
Kind of like toilet paper.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Jun 13 2008, 05:29PM


Yes, this was kind of an optional capacitor. Just as an energy storage reservoir. Not really needed, but if you put it in there, its not going to hurt anything. Just helps supply energy to any bypass caps during switching.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Fri Jun 13 2008, 08:15PM



What was original value of it ?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jun 14 2008, 06:57PM

these capacitors are typically rated at least 10x the combined bypass capacitance on the board.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Fri Jun 20 2008, 12:52PM

Hello,

i hope i can jump in this thread and ask few questions :

Fairrite does not have a toroid core 5978006401
Digikey was out of stock on 18 and 220 TVS, can anybody sell me some ?

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Jun 20 2008, 04:08PM


Check Mouser.
18V

220V


As far as the toroidal core. . .
Kreger has plenty of them.

Might ask to sample one from them.

Or, I used Steve Wards source for toroidal cores.

Package of 5 for a dollar.

We'll see how well these work when I fire it up.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Fri Jun 20 2008, 04:38PM


Thanks, i will try to see in these shops. Problem is that evrytime i order something it calls for 50-100 $ of shipping

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Jun 20 2008, 06:25PM


EEEK!
I see your issue now.

I'm kind of lazy, with a really difficult work schedule, but I guess if you needed someone to ship gear to you, I'd be happy to try and help.

Looking at US Postal, overseas to Croatia, with a flat rate envelope and a 6-10 day delivery . . .
Is $11.95 USD.

A first class international package with weight at 3 pounds is $23.00 USD.
The weight is over rated, I figure a 1 pound package should work.
A 1 pound package is $10.30USD. The issue here, is that it says delivery time "Varies". What does that mean to you and me? I don't know, maybe a week, maybe a month.

Add that to what it would take to ship any of those to me in Texas, and that might end up cheaper than supplier shipping rates.
I guess the only issue would be the shipping times.
the
If you want to try to work this out, PM me.

I'll post a topic in the general discussion and see if anyone else has gone this route before, and see if they can give us pointers.
Has anyone else used the US Mail to ship gear to guys and gals overseas before?

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Jun 20 2008, 06:45PM

hey guys, on the advanced modulator, how did you go about wiring SW2?
I'm kind of having a hard time figuring it out.

See, There are only 4 contacts on the switch, but the schematic shows a common point J1:pos that contacts to either c or d and 9 V that contacts to either LED2 or LED3.

Should this have been a DPDT instead of DPST, or am I just not getting it?

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Fri Jun 20 2008, 07:00PM



We will continue on PM. Waiting is not problem

Re: Minibrute Construction Thread / FAQs
Wirenut, Fri Jun 20 2008, 10:09PM

Should this have been a DPDT instead of DPST

Yes.

When I realized that I had the wrong switch, I just temporarily hard-wired the "Auto" mode so I could at least try it out until I could buy the correct switch.

Re: Minibrute Construction Thread / FAQs
Ultra7, Sat Jun 21 2008, 01:40AM


Darn it!
I guess I'll just have to go to EPO tomorrow. . .
While I'm there I can pick up another 1.63 ohm 3W resistor to replace the one I nuked today setting up the current meter.
I guess he really meant it when he said the positive goes to the square terminal.

I can never get out of EPO without spending $100 bucks tho. . .

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jun 21 2008, 02:45AM


When setting the current meter, you need to disconnect one lead of the 1.6 ohm resistor. This is an error in the instructions.
The 3W value is sized for low duty cycles during normal operation, not CW as if you were to test the meter with an external source.

Re: Minibrute Construction Thread / FAQs
Ultra7, Sat Jun 21 2008, 02:52AM


Bummer . . .
Oh well, if this is the only part I fry getting this baby up and running, I guess I'll count myself lucky.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Sat Jun 21 2008, 09:48AM

Dr. Shock do you have a list of errors in schematics, parts list and book?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jun 21 2008, 01:03PM


If you send me your address, i'll be happy to send you a new 1.6 ohm resistor.


Most of all the errors, including the 1.6 ohm error has been discussed in this thread. Please take time to read through all the comments and you'll pick up on any errors / concerns / etc...

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jun 21 2008, 03:41PM

yup as Daniel stated, you will save a lot of time and headaches if you kinda thumb through this thread. I've pretty much asked all the same questions so far.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Sat Jun 21 2008, 03:47PM



I read complete thread and aware of mentioned here. I just wanted to ask is there anymore that is not discussed here.

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jun 21 2008, 04:38PM

well everything discussed here was enough for me (does not know much about electronics) to finished building my version of the minibrute. And just look how it turned out! =)

this of course does not imply that you wont stumble upon any other difficulties but thats why this form exists. To help people!

youtube link

Re: Minibrute Construction Thread / FAQs
Dr. Drone, Sat Jun 21 2008, 06:08PM

Re: Minibrute Construction Thread / FAQs
Austin, Sat Jun 21 2008, 06:18PM

Yes i was kind of wondering about that! It has moved since that video. =P

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Sat Jun 21 2008, 08:10PM


Well i know something in electronics but anyway double check of everything is needed.

Your coil works very good. Just a question, what is the current limit there?


As for your coils they are inspiration how beautiful you make it. Usually personal projects i just lash-up, rarely make it pretty. And now i will try to make something similar to your coils :)

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Sun Jun 22 2008, 01:11PM


Is it possible for me to buy one Fairrite 5978006401 from you? Shipping&handling included on my cost. I almost found all parts but fairrite does not have this part number and i dont want to pay company shipping and custom tax from company for 1 core. Ultra will stock me with TVS and im ready to go

Second i did list of errors mentioned in this thread. All builders can help to fix what i mistaken, and help Dr. Shock in next revisions.

Collection of errors found within
parts list, schematics and book.

1. C101 decoupling capacitor

This capacitor is not located on bridge board, however oprating
without it will blow the IGBT-s. You will need to add it "manually"

2. c32 exists in schematics but not on the board. Its needed to solder this
capacitor on board

3. Note: put the current transformers on the output of the H-bridge,
not between the MMC. This is not an error, just a reminder

4. c32 not on board. Add manually

5. r28 needs to be OPEN - reminder

6. C81 should be soldered directly on the temperature sensor

7. Unamrked capacitor in top left of board. By EVR:

Yes, this was kind of an optional capacitor. Just as an energy storage reservoir.
Not really needed, but if you put it in there, its not going to hurt anything.
Just helps supply energy to any bypass caps during switching. these capacitors
are typically rated at least 10x the combined bypass capacitance on the board.

8.Swithces on advanced modulator DPDT instead of DPST

9. When setting the current meter, you need to disconnect one lead of the 1.6 ohm resistor.
This is an error in the instructions.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Tue Jul 01 2008, 06:25AM

Can I get some opinions on this layout. Linked page

Re: Minibrute Construction Thread / FAQs
Ultra7, Tue Jul 01 2008, 08:10AM


Wow, thats cool!
Everyone has plexiglass things going on nowadays, I guess I should start learning to build with it as well.

I want to see how you wire up your relay with that layout.
Also, the heatsink is huge!

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Tue Jul 01 2008, 09:08AM


Looking good i agree. Only thing i would suggest is to put the display board in front logic board. Why have such distance over these ?

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Wed Jul 02 2008, 12:37AM

My goal is too keep all the wiring at the bottom of the base. under the heat sink. Keeping it in place with aluminum tape. As for the display board, I ordered a 36" ribbon cable for the connections. I wanted to have access to the pots on the control board.

Re: Minibrute Construction Thread / FAQs
Wirenut, Wed Jul 02 2008, 12:42AM

Can I get some opinions on this layout.

Looks good, but like Ultra7 said, wow, that is definitely overkill on the heatsink.

I wanted to have access to the pots on the control board.

Aha! Good idea!

Collection of errors found within
parts list, schematics and book.

Thanks for doing this Kreso. I plan on eventually building another one, and this makes it a lot easier. I've been meaning to do this for a while, but this thread is really long. This list really sums up the key points in this thread.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Wed Jul 02 2008, 05:14AM


No problem, we all need it. Feel free to correct it if see anything more & wrong

Re: Minibrute Construction Thread / FAQs
Ultra7, Wed Jul 02 2008, 12:25PM

I don't know if I was just out of it, or if The silkscreen was wrong, but the power led's on the display board for the +5 and +15 volt were completely backwards.
There was a little line on the silkscreen of the LED's that I thought was supposed to line up with the flat side of the actual LED on the display board.
This was causing my +5 volt regulator to overheat and my power lights weren't coming on.

On a whim I reversed the LED and my lights came on.

So I guess pay attention to what is going with the actual components on the board, as well as looking at the silkscreen.

I have an odd feeling that this might be why my current display board isn't lighting up as well. . .


We'll test this when I get home today, I want to have the coil up for 4'th of July.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Jul 02 2008, 09:15PM


I did the exact same thing... I don't remember if it was the silkscreen that was backwards or if it was just me =P

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Thu Jul 03 2008, 05:50AM

I followed the square solder point, as the anode. I haven't tested the board yet but I'll bet mine is wrong too. I just assumed the square was the anode.

on the solder side:
5v--a,k
15v-a,k
HV-k,a
OC-k,a
R---a,k

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Jul 04 2008, 04:06AM

The silkscreen on the board explicitly states in bold white lettering, "NOTE: SQUARE PAD IS LED ANODE"

There should not be any confusion.

The silkscreen LED was a default silkscreen. I've seen LEDs with notches on either side of the diode indicating cathode, so i wouldn't rely on that.
Hence the reason i added the note.

Plus if you see the + side of C42 connected to the square pad of the LEDs, then obviously the square must be the anode.

Re: Minibrute Construction Thread / FAQs
, Fri Jul 04 2008, 05:21AM

I have gotten to the point where I need to check the phasing of the GDT and the waveforms from Gate to Emitter on the IGBT's. The instructions say to connect the Advanced Modulator but I haven't received it in the mail yet. Can I apply 5v to the External Modulator and check the phasing and waveforms on the IGBT's at 100% duty cycle.

Or would that short out the secondaries for too long on the GDT and mess things up?

Re: Minibrute Construction Thread / FAQs
Ultra7, Fri Jul 04 2008, 01:30PM


Soft, Dan, no one blamed you for anything. . .
In fact, I clearly stated that "I was out of it." and that I should have paid attention.
No need to get jumpy,

Clearly at least 2 of us made the mistake, so I figured I'd post it, just to make sure everyone else doesn't have to un-solder their display boards.
Not all of us are super I.Q. masters that can look at a capacitor on a board from 4 feet away and instantly know that the silkscreen might be wrong.

I was just trying to get the thing built.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Fri Jul 04 2008, 04:52PM


Be sure to find anything that you could find to be in error or just need more attention. It will help many people here im sure. Here is updated list:

Collection of errors found within
parts list, schematics and book.

1. C101 decoupling capacitor

This capacitor is not located on bridge board, however oprating
without it will blow the IGBT-s. You will need to add it "manually"

2. c32 exists in schematics but not on the board. Its needed to solder this
capacitor on board

3. Note: put the current transformers on the output of the H-bridge,
not between the MMC. This is not an error, just a reminder

4. c32 not on board. Add manually

5. r28 needs to be OPEN - reminder

6. C81 should be soldered directly on the temperature sensor

7. Unamrked capacitor in top left of board. By EVR:

Yes, this was kind of an optional capacitor. Just as an energy storage reservoir.
Not really needed, but if you put it in there, its not going to hurt anything.
Just helps supply energy to any bypass caps during switching. these capacitors
are typically rated at least 10x the combined bypass capacitance on the board.

8.Swithces on advanced modulator DPDT instead of DPST

9. When setting the current meter, you need to disconnect one lead of the 1.6 ohm resistor and the current transformer.
This is an error in the instructions.

10. The square pad on display boards is led anode. Be careful and dont trust the notch on your LED.
Its not board error but simply error that coem constructers made, and helped others not to repeat it :)

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jul 05 2008, 03:05AM


No one is getting jumpy here. I'm merely stating a given fact.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Mon Jul 07 2008, 02:52AM

Hello, well i'm testing my control and display. Im stuck on the HV charging indicator. I'm applying 15vdc to pins 1 and 2 of the tlp372 photocoupler 1 is +, I have a solid ground on the 4 pin but the device isn't activating and applying a - to pin 5.

FIrst I assumed I had the led installed incorrectly but I have since removed it and I'm just testing for voltage.

I have also replaced the tlp372 Photocoupler and installed a new one.

Anyone able to point out some obvious mistake I may have made?

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sat Jul 12 2008, 12:12AM

I think I have simply smoked the led in the tlp372 as I connected 15vdc to it as discribed in the book directly to the board connections and not through both r124 and r126. Does that sound about right? R124 and R126 are 25k 5w and I expect the working voltage of the TLP372 led is around 1.5v.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Jul 13 2008, 07:43PM


Yeah, that sounds about right.
Remember, the diode (input) on the optocoupler is a CURRENT device, not a voltage device. It requires a specified current to operate (usually a few mA) If you simply put 15V across it, you'll get a short circuit and blow the diode. You need a limiting resistor.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Wed Jul 16 2008, 11:12AM

Well i came to my first problem.

All works, except my enable pins are all time pulled down. I apply + 5V to the external modulator input and it is present on PIN 5 of HC14, PIN 9 of HC08 and PIIN 11 of HC74 but it does not propagate to the gate drivers. Any suggestions ?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Jul 16 2008, 04:56PM


What is the shutdown pin enable look like?

Also, you may need to have an input drive signal (from primary current feedback) to toggle the flip-flop. I forget since its been awhile since i've looked at the logic. Just do a simple truth table if you have trouble tracing the logic. This will also give you a better understanding on how the synchronized logic operates.

Re: Minibrute Construction Thread / FAQs
KresoLiubov, Thu Jul 17 2008, 04:29AM

I solved the problem. The U21 (LM311) was constantly in "high" over current state. The problem was solved by simply putting a new one in there. I don't know why it was dead (it was new from Digikey). Anyway replaced it and everything works good. All functions of the board work perfectly and i already placed it in the coil.

Thanks for help

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Thu Jul 17 2008, 06:12AM

Im rethinking my dc power conductors. To go through and do everything in a flat buss. Having not even lit this thing off for the first time, how much peak amperage can I expect between c121,c122 and the half-bridge board, and onto the primary. Will .015 copper 1/4-3/8 wide handle the load with cooling?

I think the "Monster Cable" I have on here now may lead to trouble.
Link

Re: Minibrute Construction Thread / FAQs
Tom540, Thu Jul 17 2008, 02:41PM

Monster cable will be fine for powering the bridge but might not be too good for the primary or leading to the primary.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Jul 17 2008, 06:57PM


Stranded 8 AWG wire is more than enough for both the DC bus and primary connections.

Re: Minibrute Construction Thread / FAQs
Austin, Thu Jul 17 2008, 07:09PM

yup thats what i used... however u might have some issues finding some good wired to put on MMC where there is no cap.

Re: Minibrute Construction Thread / FAQs
Ultra7, Thu Jul 17 2008, 10:40PM


I used a paper clip.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Jul 18 2008, 02:25AM


Don't use a paper clip. These are made of steel which is not very good. It will get very hot, and fail open.

Use a piece of copper busswire, or solid core wire.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sat Jul 19 2008, 08:06PM

I'm testing the operation of my 1/2 bridge. testing up to this point has been correct. I have channel 1 on the out put of the 1/2 bridge and channel 2 on the dc neutral connection. Both channel 1 and channel 2 grounding leads are connected to one another and nothing else. Im using a 555 time on the current feed back input. and an advanced modulator on the ext mod input at 250us pw and 100khz pf.


On the scope I only see positive output no negative swing at all.

I expected to see a positive swing with an opposing wave of the same magnitude.

Does this indicate a blown igbt on the negative side?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Jul 19 2008, 08:48PM

I think you might have some things set up incorrectly.
Your 555 time on the current feedback should be set for the resonance frequency (i.e. 100kHz, 50% duty), and the modulator should be set for 100Hz, not 100kHz.

The modulator pulse (250us) should bracket a bunch of the 555 pulses. If the 555 is running at 100kHz, then you should have 25 pulses (10us period) for each burst which occurs every 10ms.

I think this is your problem, as im only seeing a single pulse here.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sat Jul 19 2008, 08:58PM

Im not very skilled with an O scope yet maybe I was zoomed in to fare.

Here is a shot of a sample take with channel 1 on the pos igbt gate terminal and channel 2 on the neg igbt gate terminal.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sun Jul 20 2008, 02:16AM

As much as I hate to smoke things due to simple lack of knowledge of the components I am using, I assembled the rest of the miniBruts and lit it off.

Time to look into the tuning section of Mr. McCauley's book.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Jul 20 2008, 02:26AM


The polarity is definitely correct. The waveforms look a bit funky, but that could be just an artifact of the oscilloscope - not sure.

Anyways, it looks like you got output, so that means its working. Now the fun part and doing all the fine tuning!

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sun Jul 20 2008, 03:47AM

Im not real impressed with the output. I have experimented with the primary tap and it occurs to me that the impedance of the primary is greatly influenced by the cable being used to make the tap and the tap onto the primary it's self. Is it advisable so rewind the primary so that it contains only the optimal number of turns on it. This would be a little difficult to re bend the copper and another hole through the deck would be required.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Jul 20 2008, 05:29PM

Without actually seeing the coil in operation, i can't say for sure if the output is what you would expect given the input conditions (voltage, etc...)

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sun Jul 20 2008, 07:52PM

Currently my input voltage is limited 114 vac. I'm using copper foil strap to tap the primary at exactly 5 turns. Any wire simply diminishes performance. Advanced modulator at the largest pulse width from the stock build and the highest pulse freq. the output arcs to a RF grounded object are 19 1/2 inches. and the current on the primary is right at 400 amps.

The in put voltage is below spec of 140 vac. Maybe that is the next place to tune.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Jul 20 2008, 08:18PM


Not sure why wire would diminish performance much. Thats sounds weird.

For Adv Mod, i wouldn't push longest pulsewidth. Keep it as short as pulsewidth possible. There should be a point when you increase pulsewidth where the arc doesn't get any longer. This should be your "sweet" spot. Any additional pulsewidth just makes the arc fatter and consume more power which you don't really want at this point. Also, PRF should be kept around 100Hz. I wouldn't go above that.

Tuning is definteily the next step. 19 inches is an excellent starting point. Remember, DRSSTCs are like finely tuned automobiles. They take a lot of work to get properly tuned (playing with coupling, tuning, etc...) until you find the sweet spot.

With tuning, its going to be a trade-off between maximum arc and maximum current. (See my paper on tuning or in the book on advanced tuning)

My minibrute puts out up to 48" arcs easily. But it took a long time to get the right tuning point. The tuning point in the book was my sweet spot, but unfortunately, no secondary / tororoid / etc... is exactly the same so there is always variacnes and the need to fine tune.

But you're on your way. Just take your time, tune at low power, and proceed slowly.

Remember, using an extension cord from your wall outlet to the variac will definitely improve reliability without sacrificing performance. Acts as a ballast somewhat and protects the coil from power arcs to ground (limits peak currents during these conditions)

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Mon Jul 21 2008, 03:16AM

I found that my grounded strike rail was getting hot during my testing and tuning. I happened to look at the book and there is a section missing in the original builds strike rail. after removing this 3 inches of 3/8 tubing the output of my coil gained 3 inches in arc. Can anyone explain the effect on output that the solid loop strike rail had?

Re: Minibrute Construction Thread / FAQs
Andyman, Mon Jul 21 2008, 03:25AM

In a coil, if the strike ring is continuous, the coil "sees" it as a shorted turn and performance drastically decreases.

Re: Minibrute Construction Thread / FAQs
ragnar, Mon Jul 21 2008, 09:10AM


Unlikely to be artefacts on the scope; looks like a Fluke PM3092 or PM3094.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Tue Jul 22 2008, 12:05AM

Here are 4 scope shots:
1. corona just starting to form at full bridge voltage and PW at min.
2. max spark length same power level not sure about the PW about 250us I expect
3. no change in spark output more power through the primary PW about 300-325us
4. no change in spark output even more power at the primary, PW 400us

Is there any direction in tuning that can be gathered from this information?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Jul 22 2008, 01:21AM

What exactly am i looking at here?

Is this primary current?

If it is, then it looks like what i would expect to see.

Tuning will be a compromise between longest arc and maximum current.

If you have my book, read the section on advanced tuning and pay special attention to the tuning graphs. You'll see the graph of arc vs. current in which you want to shoot for.

Basically, you sort of detune it at low power (i.e. it requires much more current to begin arcing), but as you increase power (increased arc length), the system becomes "more" tuned and you get more output with little current increase.

If you tune where current is lowest when arcs first initiate, thats basically a tuned system at no load and what will happen, the arc will detune the system and limit output.

Of course, the trade-off is that you don't want too much current or you'll blow the system.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Tue Jul 22 2008, 05:14AM

The samples are taken with one probe leads ground connected to a large metal table under the tesla coil and the probe not connected to anything.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Jul 22 2008, 11:58AM

Okay, that still looks like the profile you would get.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Tue Jul 22 2008, 11:51PM

looks like all the tuning is within one turn, so some place in this turn should be a taping point where spark length will double and I will need to limit duty cycle and even voltage to keep the current under control in the 350-400 amp range.

I just want thank you all for answering my noob questions.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Fri Aug 08 2008, 05:44AM

My variable transformer does not out put over input, but it has 2 transformers on one shaft. My house voltage is only 119 and so I get about 300vdc on the buss.

Would it be ok to use my 240 connection and pass each leg through its own variable transformer to get the dc buss voltage to 400 vdc?

Secondly, should the capacitor board be connected directly to the top turn of the primary or to the bottom turn of the primary and tapping with the neutral jumper. Does it even make any difference in polarity and/or primary to secondary relationship physically.
Link

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Aug 08 2008, 11:53AM

Not sure about the variable transformer. Not something i would personally recommend.

The capacitor board can be on either side - doesn't really matter. I would tap with the upper jumper though. Also, once you find an optimum tapping point and are confident you won't be changing it, you can simply cut off the extra primary at the top. This will help reduce arcs as the voltage there will exceed what is present at the upper tap point.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sat Aug 09 2008, 05:06AM

Using a modulator on the miniBrute what component is at risk running using a PRF higher then 120-300 hz?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Aug 09 2008, 03:44PM


The problem is primarily your switching power circuit (i.e. the IGBTs)

What happens is as you increase PRF, but keep pulsewidth constant, you are increasing duty cycle which increases power draw and power dissipation in the IGBTs. This is the 1st order effect. There are 2nd order effects as well.

For the Xenosonic where you do run at PRFs greater than 300Hz - actually almost up to 2kHz, there is a duty cycle foldback circuit. As frequency increases, the pulsewidth starts folding back to maintain constant duty cycle.

But for regular DRSSTC operation, there really isn't much reason to above 300Hz. In fact, i never really run mine above 150Hz.

Also, note that running low PRFs (especially without overcurrent protection) is typically stressing as well. This because the steadystate voltage of the DC bus capacitors is much higher (has much more time to recharge between bursts) and current will tend to increase for the same variac setting than at say 100Hz.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Nov 16 2008, 02:51PM


Could be triggering of the scope.


Not sure what you mean by whole cycle.


Yes. Do not connect the grounds. (You can connect grounds of probes together) And also, be sure the voltage you are measuring DOES NOT exceed the voltage ratings of each probe.


Each IGBT should be in opposite phase of one another. When on is ON, the other is OFF.


Yes, this is correct. However, you make sure to have power on the control before putting on adv. modulator. I don't believe it wil hurt anything though.

Re: Minibrute Construction Thread / FAQs
nelsonic, Mon Nov 17 2008, 06:17AM

Thanks Dan

I realized that my sig. gen set at 50kHz not 100kHz. Sorry about that.

Dave Nelson

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Tue Nov 18 2008, 07:33PM


I still don't know what you are referring to? Is this the output pulses of the bridge, the interrupter signal, etc... ? ? ?

Interrupter signal should be on the order of Hz, not kHz. Output pulses of the bridge should approximate the Fres of your system. (i.e. 100kHz, 200kHz, etc...)

Re: Minibrute Construction Thread / FAQs
nelsonic, Wed Nov 19 2008, 01:58PM

Ah yes, yes. Signal generator (going to current FB) was originally wrongly set to 50kHz - my mistake. Interupter was approx. 100Hz. Output of half bridge is correct frequency but not at all square like the diagram in the book. Should it be square or rounded off a bit? However, I have now successfully run my minibrute. First run achieved 18inch sparks. I have tested for resonant frequency of secondary to find 185kHz. Reduced primary by one turn and now getting 28inch sparks at current of 400A.

It all seems to be working ok but sparks seem thin.

Setting the overcurrent point has proved difficult. Adjusting R23, I can't get a voltage greater than 5V at U21 pin2. Also current limit cuts in at about 400A, rather than at 500A as predicted. I will keep checking. Any suggestions?

Will increasing the current create fatter sparks?

Also, I have completed the Xenosonic interface. After a long testing/adjusting phase and not seeing any output signal I decided to plug it in and see what happens. It worked! With a signal generator at least. My crappy casio keyboard seems too quiet for the interface.

Thanks again for your support.

Re: Minibrute Construction Thread / FAQs
d20180, Sat Nov 29 2008, 03:51PM

Hello, I am starting the build. I built 2 TC's but this is my first solid state. This thread has very helpfull. Does my T1 appear correct? On the resonant driver board, the unmarked positions, have I identified them correctly? Where can you get the IGBT's or is there a good substitute? I have 2 of the HGT1n40n60a4d's, can the HGTG20N60A4D-ND be used? See any mistakes? Please excuse me if I posted the Photos wrong, and let me know how to do it properly.

Thanks

Re: Minibrute Construction Thread / FAQs
d20180, Sun Dec 07 2008, 10:40PM

So far, so good, or it seemed like a good idea at the time

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Dec 07 2008, 11:10PM

Wow! That looks great. Very nice work.
Yep, your transformer looks right as far as i can tell. Just remember to have the phasing right when paralleling the primary. Easy enough though.
Not sure about the 20N60's, but i use 30N60s with no problem.

There is also a IXYS equivalent IGBT everyone has been using. See SALE board for more information on this.

Re: Minibrute Construction Thread / FAQs
d20180, Mon Dec 08 2008, 04:44PM



"Yep, your transformer looks right as far as i can tell. Just remember to have the phasing right when paralleling the primary. Easy enough though."

Can you explain?

Thanks

Re: Minibrute Construction Thread / FAQs
Tom540, Mon Dec 08 2008, 05:18PM

That looks awesome. I like those copper inserts you have. It amazes me how you guys make your primary supports like that and manage to push that copper through those holes. Ive never tried it with plastic supports but on wood its impossible. I always have to cut the holes out and snap the copper in instead.

Re: Minibrute Construction Thread / FAQs
d20180, Mon Dec 08 2008, 08:05PM

Thanks

Windex really helps feeding the copper

Re: Minibrute Construction Thread / FAQs
d20180, Mon Dec 08 2008, 08:54PM

Is telephone wire ok for the T1,T21, Temp, and HVSAMPLE connections?

Re: Minibrute Construction Thread / FAQs
lbenson, Mon Feb 23 2009, 05:04AM

Would making an oil filled secondary coil for my MiniBRUTE have any ill effects?

also. would there be anything wrong with insulating the primary winding with some plastic tubing, like from lowes?

finally, what would be the best way to power the leds for the supports. i know dan suggested a battery, but i would to be able to leave the lights on even when its not running, for aesthetics. And what would be the best wiring topology of these 2? A or B and would it be better in series or parallel? or would a star topology be better?

Re: Minibrute Construction Thread / FAQs
lbenson, Mon Feb 23 2009, 05:07AM

Heres the A and B i was referring to

Re: Minibrute Construction Thread / FAQs
Tribologist, Sat Apr 11 2009, 03:42AM

My Minibrute is messing with my mind. First time I put it together it ran like charm, took minor tuning to make it resonance just fine.

I had it apart for some time and just put it back together and I cant make teh controller board behave.

I checked the tuning of the primary and sec and I tuned it with the scope and a signal gen to about 240kHz.

When I am running it it lock in at about 470Khz, then the bridge turn of it rings out at 1.6MHz.

The green trace is the output voltage of the half bridge and the yellow is from a 1:100 CT with a 1Ohm load.

Any idea why it does not lock in at the240kHz?

Ulf

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Apr 13 2009, 03:35PM

something definitely doesn't look right there.

Re: Minibrute Construction Thread / FAQs
lhl_henrylui, Fri Apr 17 2009, 02:21PM

what's a minibrute?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Apr 20 2009, 11:41AM


Its a mini-sized DRSSTC solid state Tesla coil that packs a huge punch!

See

Re: Minibrute Construction Thread / FAQs
Austin, Wed Apr 22 2009, 03:52AM

glad to see this thread as a sticky! I think Daniel is doing a great job keeping up with all the new questions. =)

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sat Jun 20 2009, 06:32PM

I'm looking at the CCM1235-ND 15 amp EMI filter (from digikey)as a power entry for both the 0-120 vac and the control section of my mini brute. Are these a good choice to protect my house and everyone else for that matter.

[MOD EDIT: Image deleted - size too big - read the rules]

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Jun 24 2009, 04:54PM


When building a Tesla coil, always assume there will be risk to your house / electronics regardless of what filters you use etc... So to answer your question, they might help reduce the hash spit back on the line from the DRSSTC, however, i myself personally don't use any type of filtering.

The most important thing you can do is to have a ground target for the DRSSTC to arc to and to connect the grounded target back to the EARTH ground point of the secondary. This ensures circulating discharge currents stay within the coil. Otherwise, if you arc to the wall in your house or ceiling etc... (or even floor), the circulating discharge currents will travel all over your house wiring trying to find its way back to the coil. Not good.

Re: Minibrute Construction Thread / FAQs
Austin, Wed Jun 24 2009, 08:39PM

Daniel do have a full/half bridge schematic for CM600 IGBTs? I want to build the MEGABRUTE mentioned on your site. I am assuming I can use the resonate board from the minibrute. I'll make the appropriate changes to the secondary, primary, and MMC.

Also instead of pulling from a single 240 line can you just use two 120 volt lines from two separate breakers?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Jun 24 2009, 10:33PM


Steve Ward should have some CM600 based DRSSTC schematics.

Re: Minibrute Construction Thread / FAQs
lhl_henrylui, Fri Jul 10 2009, 05:35AM

I've just received the Minibrute reference book and I really don't understand a part in the schematics.As I'm not a EE so I'm not sure whether that is a mistake.Please look at p.29 in the book(figure2-8).The current transformers are connected to the secondary but not primary.However,the previous chapter said that this DRSSTC uses primary feedback,isn't it? Also,the ground of the secondary should not be earth ground but RF ground,right?

Re: Minibrute Construction Thread / FAQs
Austin.Weil, Fri Jul 10 2009, 06:10AM

yes this is a mistake in the text. make sure to read this thread fully, this question has already been answered here.

Re: Minibrute Construction Thread / FAQs
lhl_henrylui, Fri Jul 10 2009, 06:15AM

Sorry,I have just found them.
Another question: If the currents are reconnected to the primary,are they also connected to the RF ground?

Re: Minibrute Construction Thread / FAQs
Austin, Fri Jul 10 2009, 04:11PM


I'm not sure that i understand your questions. But i will give a stab at it anyways...

in figure 2-8, the current transformers are wrapped around the secondary wire which is connected to RF ground, this however this has since been changed. instead the current transformers are now wrapped around the primary wire. if you read the the this thread it will show you exactly where to put the current transformers. Also the primary is not connected to ground.

Re: Minibrute Construction Thread / FAQs
lhl_henrylui, Sat Jul 11 2009, 12:53AM

Are the current transformers possible to be homemade?I don't want to order them on internet because the shipping bill is very expensive.

Re: Minibrute Construction Thread / FAQs
Austin.Weil, Sat Jul 11 2009, 08:39PM


I'm not a EE but as far as i understand it, a current transformer is basically coiled up magnetic wire that has a current induced upon. that induced current is the feedback signal that gets sent to the resonance board which helps drive the IGBTS.

^--- I could be totally wrong tho

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Jul 13 2009, 06:52PM

Yes, you can build your own current transformer. A ferrite core with say 100 turns around it should be okay for the feedback. I think Steve Ward used 1:33 and another 1:33 to give 1000:1 ? Check Steve Ward's website for "homemade" current transformers. I always buy commercial since i'm too lazy to design or wind my own.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Mon Aug 17 2009, 03:09AM

Building the MiniBrute was really lots of fun, I want to build another one. I was thinking of selling the one I built to fund the next one. I don't see anyone selling completed tesla coils of any type on the internet, Is there some legal reason for this or is there simply no market?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Aug 26 2009, 11:30AM

[MOD NOT]
Please keep responses in this thread on the subject of the miniBrute construction / issues / problems / questions.

Discussion of why i like tesla coils and what i'm build next is not permitted.

Re: Minibrute Construction Thread / FAQs
audio:deviant, Fri Aug 28 2009, 04:10PM

got a question about the voltage going into the optocoupler (U42) the HV sample input. how high should this be?

also, im running off 240v uk.. do i need the relay (k121) what does this do exactly? the mechanical side of this is drsstc II but im using all the mini brute boards, have a bigger MMC, and one big 3500uf 450v cap.

cheers gang

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Aug 31 2009, 05:38PM


The input to the HV sample input can be up to 400VDC. HOWEVER! It must be in series with the 25K resistors as shown in the schematic. If you don't run through those power resistors, then you will blow up the optocoupler.

The relay controls the safety bleeders for the DC bus power. When power is removed, the relay turns off and puts the resistors across the caps which bleed them down.

Re: Minibrute Construction Thread / FAQs
lhl_henrylui, Thu Sept 10 2009, 10:44AM

What measures should be taken when running the DRSSTC in order to lengthen the DRSSTC's life?
The measures mentioned in the book are too few.

Re: Minibrute Construction Thread / FAQs
audio:deviant, Sat Sept 12 2009, 10:40AM

ohhh right cool, thats a good idea! was just looking over the schematics for the mini brute, on the primary coil it says comes from the MMC and then to neutral, is this neutral on the DC power? sorry if that sounds stupid just doing some reseach into the half bridge system.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sat Sept 12 2009, 07:36PM

Thats the neutral from your AC line.

Re: Minibrute Construction Thread / FAQs
audio:deviant, Sat Sept 12 2009, 11:00PM

from the variac? would that not feedback?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Sept 14 2009, 11:12AM

The neutral on the DC power is the same "node" as the neutral from your line AC.
However, the tie point would be at the centerpoint of your doubler caps in your DC supply.

Re: Minibrute Construction Thread / FAQs
audio:deviant, Thu Sept 17 2009, 06:15PM

okay cool that makes sense. right i think ive done everything. put some power thought the self resonant driverboard everything seems to be in order so far! very exciting. i have a question about the testing and tuning. how different is the mini brute testing to the DRSSTC II? i only have the book with building plans for this is it very different? im also using an ardiuno for the controller which im hoping will do the job.

cheersfor the replies, just want to get the thing running now!

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Sept 21 2009, 12:28AM

The testing would be the same, although the minibrute book has the process much more detailed.

Re: Minibrute Construction Thread / FAQs
Brandon, Mon Sept 21 2009, 03:10PM

One question in the testing of the Mini Brute. I constructed the 555 circuit as described in the Mini Brute book. I also completed the Advance Modulator Board. If I understand this correctly the Advance Modulator Board will operate the output @ 100hz. What size scope will work for this purpose??

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Sept 23 2009, 10:43AM


The Advanced Mod board is a low frequency modulator which will operate around 50-300Hz. Any low cost oscilloscope will work for this application.

Re: Minibrute Construction Thread / FAQs
Brandon, Sat Sept 26 2009, 06:00PM

Has anyone had a problem with noise in the square wave from the output on the Resonant Board. I check Pin one on U1:A and I have a nice square wave on the output from pin 2 U1:A and I have a square wave but, on the top on the top of every 4-5 square wave i am getting a half wave hump. I assumed that this is not normal and this could be the noise that I am seeing on the output. The Resonant board is grounded... Has anyone had any problems like this ???

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Sept 28 2009, 10:01PM

maybe your getting noise coupled into your oscilloscope? It could be 60Hz noise.

Re: Minibrute Construction Thread / FAQs
Brandon, Wed Sept 30 2009, 02:36AM

I have located the noise it is caused when I put a 10uf cap in series with T10 or T102. What type of cap should be used here?? (tantalum, film??? When testing the phasing on the transformers how should the scope be set up (invert channel 2 and ADD)???. I think no... but, not sure.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Sept 30 2009, 11:58AM

I used Tantalums.

Re: Minibrute Construction Thread / FAQs
audio:deviant, Fri Oct 02 2009, 07:44PM

Right I bought the other book, made sence to get it. Have a quick question, when I apply power to the self resonant board I get a current fb light turn on on the display board should I be worried?

Also has anyone used an arduino as an external modulator?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Oct 04 2009, 01:37PM

If you haven't set your thresholds yet for current sensing, than that is probably likely if its set real low.

Re: Minibrute Construction Thread / FAQs
audio:deviant, Sun Oct 04 2009, 08:43PM

Sorry been a right fool found a short on the top of the board making it show the overcurrent! I still don't seem to be getting any pulse just 5 volts on the pin 2 of u4 and u5, I'm using 2 arduinos to produce the current feedback and ext mod but there about 3v output. Is this too low for it to be working? I thought there should at least be a weak signal

Re: Minibrute Construction Thread / FAQs
tritium, Sat Jan 02 2010, 01:12PM

an question about the gdt,
I have a core FERROXCUBE - TN32/19/13-3E25 with has an Al of 6950nH

in the drawings I see that the primary is 250 uH, so when L=Al x n2 then I come to 6 turns for the primary on this core, am I right or do I have to order the core from the minibrute part-list?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Jan 10 2010, 12:53AM


You want the cores on the parts lists, or ones that are very similar. Any deviation of these parts, and you are on your own for determing number of turns, etc...

Re: Minibrute Construction Thread / FAQs
UnionTesla, Tue Feb 23 2010, 03:45PM

Hi, I have noticed that throughout this forum, people have been mentioning undeeded components that are listed in the miniBrute book, andI was wondering if there is a list of corrections that I should take into account when building one.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Feb 26 2010, 01:08PM


Hi. We are relaunching our company in April 2010 with a complete new product listing including COMPLETE kits for SSTCs and DRSSTCs. All the parts corrections which have been mentioned will be updated in this new website. Stay tuned . . .

Re: Minibrute Construction Thread / FAQs
AmonRa, Wed Mar 24 2010, 05:06AM

I successfully completed this coil last week. Great design EVR and a well put together book. Thanks to your input in this thread and all of the great info from the other builders, I assembled the coil, completed the testing, turned it on, and had streamers on the first try. A week later, after tuning, it is still going strong without ever having blown up a single component (knock on wood).

I did find one thing in the schematics that has been mentioned here but was not answered. The initial setting for the overcurrent setpoint has you set the voltage at u21-2 to 2.59v via r23. After first light, per the instructions in the book, I went back to r23 to adjust the setpoint up to 500A. I found that I was only able to get 5vdc max at u21-2 with the 10K pot r23 turned down to near 0 resistance.

After checking the input voltage to r23, I found that there was only 5vdc going into the pot. The schematic shows 15v as the input. Taking a look at the pcb, I followed the trace from the r23 input to where it connects to the top of r85. The schematic figure 2-4 shows that the input to r85 is 5vdc which is correct in the book and on the pcb. The schematic figure 2-2 shows that the input to r23 is 15vdc, which is incorrect in the book. It's only getting the 5vdc from top of r85.

I have absolutely no intention of running my coil above 500A, so really, no change needs to be made. However, I though it was still worth pointing out in this thread.
Also, as stated several times in the thread and in the book, running above 500A drastically reduces system reliability; doing so is at your own risk.

If a builder does wish to be able to adjust the overcurrent setpoint throughout the entire range up to 1000A, cut the pcb trace between pot r23 and r25 and run a trace wire on the back of the pcb from u21-8 to the input side of pot r23. Now you will be able to set the voltage at u21-2 from 0 - 15vdc allowing you to run over 500A current limiting.

Once again, great design EVR. This coil is a whole lot of fun.

Re: Minibrute Construction Thread / FAQs
UnionTesla, Wed Apr 14 2010, 09:29PM

So, I am currently in the process of making the minibrute, and I am wondering how people who have successfully built it bent the strike rail. Did you have to anneal the copper?

Re: Minibrute Construction Thread / FAQs
AmonRa, Wed Apr 14 2010, 11:42PM

I bent the copper strike rail around a pot i had in the kitchen thanks to the nice tip found earlier in this thread. It wasnt exactly the same diameter, but close enough and the rail expanded a bit naturally when pressure was released. Find a pot or 5 gallon bucket or something similar in diameter and slowly bend the rail around while holding one end in place.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Apr 29 2010, 05:11PM

Beautiful coil AmonRa! Excellent craftsmanship and a very nice output arc!

Re: Minibrute Construction Thread / FAQs
Austin, Fri Apr 30 2010, 08:05AM


indeed

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Fri Apr 30 2010, 04:59PM

Thanks to everyone for their comments and errors you pointed out, i have summed them up into a single document.

You can access the PDF addendum here:

http://www.easternvoltageresearch.com/drsstc_minibrute.html

Re: Minibrute Construction Thread / FAQs
raysf, Mon May 03 2010, 06:54AM

Hi Just joined the forum and am working on building a Minibrute kit, which is my first Tesla coil. Just got it soldered together and it passed the smoke test. I have a question about the enclosure: The coil is going on a piece of metal artwork, and it would be much more optimal as far as aesthetics and construction if the housing at the base was metal. Assuming good precautions against shorting the electronics to the housing were taken, maybe even with some plexiglass under the high voltage boards, could there be any other issues with this?

Edit: One other issue I thought of might be the primary causing inductance in the metal housing and heating it up/wasting power, so I guess i'd just cut a gap(like a very thin pie slice) into the housing from the center to the outside and fill it with something nonconductive.

Re: Minibrute Construction Thread / FAQs
UnionTesla, Wed May 05 2010, 09:19PM

Because I am building the minibrute through a University, safety is a very important aspect. I can see the different types of grounding equipment people use, but I am wondering what exactly they consist of and how they are constructed. Can anyone help?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu May 13 2010, 02:27PM


Not sure exactly what you mean by this question. What do you mean by "grounding equipment?"

Re: Minibrute Construction Thread / FAQs
raysf, Sun Jun 06 2010, 05:36PM

Hi,
I'm wondering about the maximum frequency for doing audio modulation. Further back, I saw evr say that the xenosonic goes up to about 2 khz. Assuming duty cycle is held to a fixed percentage, what kind of bad things could happen if you go above that?
I made a microcontroller based audio modulator that seems happy up to about 6 or 7 khz and keeps a set duty cycle, but for now I limited it in software to 2 khz. We've got to have the tesla coils going for a show in 3 weeks, so i cant afford to blow too much up before then!
Cheers
Ray

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Mon Jun 14 2010, 05:25AM

Hello,
After almost a year in storage I got my miniBrute back out and to my delight It still works just like it did when I put it up. Less one minor issue with a modulator power switch.

I was never able to get the desired out put so I thought I would revisit the fine tuning. After looking through the advanced tuning section of Dr. McCauley's book on the miniBrute I have come to the realization that I have no idea what I'm doing here.

So as I commonly do I just fiddled with the primary tap at first moving it 1/4" at a time and documenting the output with markers. until I found no improvement in spark length to primary current. The best length of arc to a grounded object is 21".

I built my toroid with mandrel bent 3.5" 90 degree tubes welded them together and polished them up. this is out of the build spec a little so I threw a 3" sphere on to for good measure. Today I went to the hardware store and picket up a 4" aluminum duct to make the correct dimension of toroid 4" x 13". I performed the same primary tap adjustments and ended up a little short at only 20".
Back to the original 3.5 x 13" toroid and a final best primary tap location of 5.5 turns.

video of coil at 318hz prf and 150us pw

Also my variac is only capable of direct output so my input voltage is limited to 121 vac. Other then that I believe every other part of my build is within spec.

I also found the breakout point or its total distance from the toroid has a little bit to offer in regards to adjustments.

Are there any other areas I can address to try and achieve greater performance with out putting the system at risk?

Re: Minibrute Construction Thread / FAQs
Martin King, Tue Jul 27 2010, 04:32PM

Hi, I've just joined the forum after receiving the miniBrute reference design book. I've already ordered up all the plastic and copper stock. I'm going to try and spin the top toroid myself but have a local spinner preparing a quote as a back up but I suspect a one-off will cost far too much . I'm going to wade through all the previous posts at some point but to answer some recent questions (sorry if they have been answered in previous posts) When bending copper tube if you fill it with dry sand or molten wax and then seal the ends it helps prevent crushing while you bend it although you still need to bend it carefully a little at a time. The "proper" but expensive way to do it is to fill the tube with a very low melting point alloy such as "woods" metal WARNING contains cadmium=nasty, although I think there are safer versions around.

Re: Minibrute Construction Thread / FAQs
Martin King, Tue Aug 10 2010, 07:26PM

OK so I've started building the mechanical bits of the miniBrute, I'm a bit annoyed that the addendum doesn't mention a couple of mistakes in the mechanical drawings/items list, although luckily none of them are major problems, also I feel it would have been better to have the 0 datum either at the edge of the plate or reference everything from the centre line, Having the datum 0.75" in from the edge is a pain for marking out and a calculator error meant I had two holes in the wrong place but luckily they were only small pilot holes and are covered by the primary coil supports. Now to my main question, there is a central hole shown in both the mounting plate and the coil base that doesn't appear to be used for anything? Of course I drilled the holes before I noticed they're not used and I was wondering if I could use it as a plug/socket connection between the secondary and the base to make the coil easier to dismantle for transport/storage are there likely to be any issues with doing this e.g. arcing in the connection? Another option would be to use a brass bolt and make the ground connection with a solder tag and brass nut, again are there likely to be any issues with this?

Cheers.Martin.

Re: Minibrute Construction Thread / FAQs
Martin King, Tue Aug 10 2010, 09:23PM

BTW is there anyone else here (particularly UK based) building or looking to build a miniBrute? If so I have a list of useful UK suppliers that I've found so far. Also I will very likely have some surplus parts that I can post in the sales forum if anyone's interested, particularly (as it stands at the moment) Metric screws and inserts, PVC offcuts, imperial drill bits (for the primary and strike rail support holes) and copper bar for the strike rail post. I'll probably post what I have left over in the sales forum as one big post anyway at the end of the project but if anyone has any particular needs now them PM me.

Cheers.
Martin.

Re: Minibrute Construction Thread / FAQs
Martin King, Thu Aug 12 2010, 12:26AM

Hm, wound the primary coil tonight, does it normally take four hours ?!?!?! Everything was as per the book, PVC supports, hole sizes, copper diameter etc. I even chamfered the end of the tube with a file to reduce the chance of it sticking in a hole and lubricated the tube/holes. After the first turn I had to take out one screw from each support and loosen the other so they could float a bit, this improved things a bit but not much and after I'd eventually finished it was a real bitch to get the supports back into alignment and get the screws back in

Martin.

Re: Minibrute Construction Thread / FAQs
Xplorer, Thu Aug 12 2010, 03:52AM

Just ordered your book EVR. It seem like a great project.

-Tony

Re: Minibrute Construction Thread / FAQs
rjdel, Sun Sept 19 2010, 02:57PM

I have begun construction of the miniBrute via kit from EVR!

I am just finishing up soldering up all the boards, and I have a few pretty elementary questions.

Capacitor identification:
I still have yet to install the following 7 caps:

C2 - (line 22) part # BC1089CT-ND : 1000pf,50v
C21 / C82 / C85 (line 24) part # 445-2647-ND : 1uf,50V
C22 / C32 (line 25) part # BC1013CT-ND : 100pf,50v
C30 (line 26) part # BC1001CT-ND : 10pf,50v

And I am currently left with the following 7 caps but am having a hard time determining which is which:

3 "dipped blob" style ceramics with the markings "105 ESM" on one side and "818 RAT" on the other.
Based on conventional markings I am thinking these are the three 1uf (line item 24) for C21,C82,C85.

However, I am also left with:
3 capacitors that are in the small rectilinear block style package.
2 of these have the marking "M390 14/01 1219" on one side and "JAVX 9524 014(or B14)" on the other.
1 of these has the marking "M390 14/01 1317" on one side and "JK 0705 C" on the other.

Additionally I have one tiny blob-style cap with the marking "BC 10J" or "8C 10J" ...hard to read.
I suspect this is the 10pf for C30 (line item 26).

Can anyone help me confirm/identify these caps?

IC Sockets:
Also...my parts via EVR came with only 2 IC sockets. These are 8 pin sockets.
Based on posts in this thread, it seems I should use these for gate drivers U4/U5 as these seem to be IC other have blown. Anyone have any thoughts on this?

IGBT orientation.
I am using the IXYS IXGN... IGBT
One mounting hole is circular, and the other is a u-shaped notch.
I read elsewhere in this thread the notched side is the emitter side.
Can someone confirm this?

Thanks.
-Rob

Re: Minibrute Construction Thread / FAQs
GORT, Sun Sept 19 2010, 10:04PM

Regarding the fan on the film caps... Honestly, caps are not designed for heat dissipation via air flow. Blowing on them doesn't really accomplish much due to the fact that heat dissipation within the cap is not going to be affected by airflow on the outer shell.. sorry, that's just physics... design for the rms (always best practice).

Re: Minibrute Construction Thread / FAQs
raysf, Thu Sept 23 2010, 02:57AM

I was confused about all the diodes and diode looking parts, but had pretty good luck just entering the numbers on them into google to figure out what they were(and learned lots about diodes and voltage suppressors in the process). I think doing the same with the capacitors would probably help you figure that part out. Wish I remembered more specifically which caps were which, but i dont right now.
Cheers
Ray

Re: Minibrute Construction Thread / FAQs
william L, Sat Sept 25 2010, 03:48AM

Just got my minibrute books and board kit! I have a question: With a non modified copy of the design, and the primary circuit be tuned to around 190Khz?
(I have a coil and toroid)
also, Is anyone else building one at this time?

Re: Minibrute Construction Thread / FAQs
rjdel, Sat Sept 25 2010, 12:25PM

Hi WilliamL,
I am currently building mine too.
I have about 70% of the mechanical done (hope to pretty much complete it this weekend), and about 80% of the electronic complete.
Have you completed the soldering of your components?
If so, maybe you can help me identify those last 7 caps I mentioned in my previous post, and also regarding the IGBT orientation.

Also..did your kit come with IC sockets for all the ICs, or just two 8 pin?

Re: Minibrute Construction Thread / FAQs
william L, Sat Sept 25 2010, 07:34PM

Hi WilliamL,
I am currently building mine too.
I have about 70% of the mechanical done (hope to pretty much complete it this weekend), and about 80% of the electronic complete.
Have you complete the soldering of your components?
If so, maybe you can help me identify those last 7 caps I mentioned in my previous post, and also regarding the IGBT orientation.

Also..did your kit come with IC sockets for all the ICs, or just two 8 pin?

I only just ordered mine.
Hopefully it comes soon so I can get building though!
good luck.

But again, with a non modified copy of the design, can the primary circuit be tuned to around 190Khz?

(I have a coil and toroid)

Re: Minibrute Construction Thread / FAQs
johncohn, Thu Oct 14 2010, 01:23PM

Folks..
I'm working through a minibrute build and have a couple of questions. Hopefully Dan or others can comment:
- I'm fashioning the screen for the self-resonator board .. The book calls out using copper foil as the shield. Can I use copper screen instead ? Is this for electrostatic or magnetic shielding.
- what do folks suggest I use for a clamp to use for tuning the primary ? Do people use an alligator clamp of some sort ?
- is it really necessary to bring the top of the primary down through the base ? I have done so.. but the bends in the Cu tubing are not that beautiful. Would I be electrically OK to cut the Cu at the top of the primary ?
Thanks !
-jc

Re: Minibrute Construction Thread / FAQs
william L, Fri Oct 15 2010, 03:48AM

Just got my kit!
One question: on the advanced modulator, which PW is the 1Meg pot supposed to go to?
(R15) EDIT: resolved that, but now a new question: my boards arrived as one big pcb separated by many plated holes. any suggestions as to how to cut them apart? EDIT:Also resolved.
Anyway, to anyone who has built (or designed) the advance modulator, can anyone help me with wiring up the switches and fire button?

Re: Minibrute Construction Thread / FAQs
william L, Tue Oct 19 2010, 05:55AM

Almost done! just need to wire it up and finish that darned modulator.....

EDIT:sorry about the double post.

Re: Minibrute Construction Thread / FAQs
raysf, Wed Nov 03 2010, 11:13PM

Update from something awhile ago:

A few months ago, I and someone else were both having trouble with coils that were working, but not that great. Well, I found my trouble, so figured i'd share incase anyone else has the same problem! I was glad I have the luxury of having three of the same units to swap parts between, which made isolating the problem easier. It turns out I had a diode (CR1) backwards in the current feedback area. So the circuit must have been seeing only half of the feedback and only working half the time! Probably wasn't too good for the IGBTs, but it did run for hours straight at a few shows before quitting!

Edit: and also a question: Does anyone know where to get the 5X20 mm fuse size that fits in the power sockets recommended in the kit instructions? I can't seem to find high enough amperage ones, and I've had such headaches with those that I've taken to bypassing them and using the variac fuse only.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Nov 04 2010, 06:50PM


Great questions. The 5x20mm fuses are standard and should be available at most electronics distributors. I've gotten mine from Digikey, Newark, Allied. I usually use 15A, but have 20A as well.

But during testing, I think i've bypassed mine as well as just use the fuse in the variac which is rated for 20A.

But glad to hear everything is working good for you!

Re: Minibrute Construction Thread / FAQs
raysf, Mon Nov 08 2010, 04:05AM

Will check Newark-I had no luck at Mouser or Allied. I ordered some "25A" fuses at Mouser, but it turns out they goofed and they were actually 2.5A! And the coils are 12 feet up when installed in the sculpture and the fuses take ninja hands to reach in and change, so blowing all 3 at once didn't make me too happy! Luckily, somebody had a burrito, so I wrapped them in aluminum foil and no fuse troubles after that!

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Nov 10 2010, 06:01PM


Aluminum wrapped burittos work great!

Re: Minibrute Construction Thread / FAQs
william L, Thu Nov 11 2010, 01:26AM

I got my coil working! http://www.youtube.com/watch?v=7GRHkAaQC6A , but I had forgot to check the current limit. (my display sorta broke on my faulty soldering) So, I fixed that to 300 amps limit, and now the coil won't work any more. I investigated the cause, but I have only found out that the 5 volt regulator is getting hot and the d flip-flop is working, but running hot. Anyone have any Idea as to the problem?
Everything seems to be working up until the input of the gate drivers.

Re: Minibrute Construction Thread / FAQs
johncohn, Tue Nov 23 2010, 10:08PM

I'm just about finished with the final wiring in my minibrute and have come across a question. I'm looking at the relay k!21 in Fig 2-7 of Dan's book. one side of the relay is being used ot switch in R123 as a safety bleeder. Here's where I'm confused,.

1) looks like C121 and C122 already have pretty good bleeders in R121 and R122.... That looks like a time constant of about 12 seconds.. is R123 really necessary ?

2) If so, I was planning on using short thick 8 gauge wired to connect C121 and C122 to the half-bridge.. Both side of K121:C are labeled 'DC_Supply+' do I

(a) wire the non-switched side (ie. the left) to the half bridge and just switch the bleeder in and out with K121... or

(b) am I supposed to wire K121:C in series with that connection. (I.e. wire from the plus end of C121 to the center pole on one side of K121, then wire the Normally open contact of that same contact pair in K121 to the half-bridge ? . It seems like a lot of current to stick through that tiny relay..

Any guidance much appreciated.

Also.. I just want to confirm.. the schematic on fig 2-8 shows the current sense in the secondary. I believe this is a throwback to when Dan was doing secondary current sensing.. I'm supposed to put the sense in the grounded side of the primary.. Right ?

Once get this figured out, I'm ready to begin testing.. Wish me luck !
-jc

Re: Minibrute Construction Thread / FAQs
johncohn, Tue Nov 23 2010, 10:13PM

Re: Minibrute Construction Thread / FAQs
SunWind, Sun Dec 05 2010, 11:13AM

I got my MiniBrute Coil working somehow, yet i have to build a new controller and tune it. Here's a vid from my toy in somewhat of an action:
Youtube:

Here is my 230V power supply schematic for those wondering, should work great when the load is symmetric

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Thu Dec 09 2010, 04:40PM


Hi Gort.
Actually, that is not a true statement. Forced air cooling works extremely well for these types of capacitors. It is done all the time even in well designed military applications such as pulse power supplies. Anything you can do to remove heat from the surface of the capacitor, whether its forced air cooling, direct interface (through thermal interface material) with a cold plate, etc... will allow the internal structure of the capacitor to run at a cooler operational temperature.

Also, simply designing a capacitor to meet an RMS spec doesn't necessarily mean you are operating the capacitor within its proper operational envelope. For example, the 942C 0.15uF capacitor has an IRMS spec of about 13A at 70degC. If the capacitor is operating above 70degC, you would need to derate accordingly, or if its operating at less than 70degC, the IRMS maximum current actually increases. Most capacitor vendors, including CDE, can provide you with test data and specification curves for their capacitors on request.

Re: Minibrute Construction Thread / FAQs
BryanD, Sun Dec 19 2010, 01:19AM

Hello everyone. I'm an Electrical Engineering Technology student of Canada here. I'm Building the miniBrute and hoping to take a crack at designing an audio-modulation circuit for it as a technical report project in order to graduate. This is my very first Tesla coil build, so there's been lots of learning.

I'd like to thank Dan for all you've done and everything you've made available, it's greatly appreciated. This site was also very helpful. There's only a couple questions I have before completing the build:

1) In the addendum it states that the thermal sensor (LM35) is no longer suggested. What is the reasoning behind that?

2) Also, concerning the caps on the PVC pipe for the secondary support, the CAD drawings show them to have a diameter of 4.5" which would put them resting on the pipe. However, the picture diagrams all show the caps to be inserted inside the pipe. I'm figuring that the extra 1/4" added to the secondary support would make a big difference in it's position in relation to the primary. I'm not sure which way to go with that, to put them on the outside or inside the PVC pipe.

If anybody could clear those things up for me, it would be greatly appreciated.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Sun Dec 19 2010, 02:30PM


Great questions. Anyways, the thermal sensor isn't needed because in actual practice, the sensing point (provided you use a good heatsink with fan cooling), the heatsink is never going to get warm. It was sort of a nice to have in the beginning intitially, but ended up never using it.

Also, another great catch! I'll have to add that to the addendum. That is just a misprint. The diameter of the end cap should fit INSIDE the PVC pipe.

Re: Minibrute Construction Thread / FAQs
BryanD, Sun Dec 19 2010, 08:46PM

Thanks for your timely response, and clearing that up for me. I had a personal goal set to have first spark by the new year, but it's looking like it may be a week or two later. I'm trying to learn EVERYTHING as I go along so it's taking a little longer than it should. I figure that considering what I'm working with, I don't want to be guessing on anything, and it will make my design process for the audio modulation a bit easier.

If you didn't mind clearing one more little thing up for me. I went ahead and constructed my own torroid, using two pie plates, a length of dryer duct, and aluminium tape. Since I couldn't find a smaller size pie plate, the total diameter is a few inches bigger than your design calls for. However, from what I understand, the torroid is basically acting as a sort of capacitor, and the size of it would just determine how fast it charges and discharges, making a difference of only milliseconds. Am I out in left field on this one, or am I on the right track?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Mon Dec 20 2010, 01:10PM


The extra few inches could affect the tuning somewhat, as yes the topload does act as a capacitor which affects the resonant frequency.

As long as you retune everything with the slightly larger topload you should be fine, just keeping in mind the tuning point shown in the design will not be optimum anymore.

For toploads, I simply use 4" corrugated heating duct with a plywood center. Makes the perfect size.

Re: Minibrute Construction Thread / FAQs
Ruben, Tue Dec 21 2010, 04:11AM

Here is my 230V power supply schematic for those wondering, should work great when the load is symmetric

I'm in Australia, so I definitely was! however this thread:

seems to suggest another configuration (connecting the primary return to the DC bus negative rail and a single bus capacitor). I'm confused as to how this would work for a half bridge.

Can anyone clarify, and/or provide consensus as to the best practice for those on 240V.

Re: Minibrute Construction Thread / FAQs
johncohn, Mon Dec 27 2010, 08:55PM

Hi friends
I finally had time this holiday to finish up my minibrute build and got to testing. I had first light last night.. Looked very good and strong !. I was beginning to tune this morning at low power (~200 A) when the discharge failed. I heard a sizzle of sorts and smelled burning plastic.. I immediately shut down and did a search for heat. The only thing hot was the middle cap in the primary cap stack. I did a cautious re-power.. got no discharge on my breakout point, but , heard the same sizzle and backed down immediately. Again the cap (c104 0.33uF, 2kv ) was getting hot. I ohmmeter tested the bridge and it seemed fine. as did everything else I spot checked. I used a cap bridge in circuit and found the middle cap was indeed not measuring like it's brothers c103 and c105. I unsoldered one lead form all three and measured them. c103 and c105 were within 5% of the 0.33uf spec. C104 has a resistive short (about 22k). I was doing the test without the fan on.. as suggested.. but only was doing bursts of a few second. I don't think that was the reason for the heating. Is it possible that the cap was just bad ?

Has this happened to anyone else ? Any suggestions on other things I should check that could have lead to that cap's failing.. or could have been taken out when the cap failed ? Any suggestions appreciated !
-jc

ps. Hope everyone's having a happy holiday !

Re: Minibrute Construction Thread / FAQs
SunWind, Tue Dec 28 2010, 10:26AM

Can anyone clarify, and/or provide consensus as to the best practice for those on 240V.

I can't say is my circuit the best way to do it but it clearly works! It has a same principle than the original in the book but it doesn't double the voltage. It also takes less current so 10A fuse can be used. I made my half-bridge as described in the book using FGH50N6S2 IGBT's and replaced VR105 and 106 with 20V TVS diodes, havent blown any components so far ;)

Re: Minibrute Construction Thread / FAQs
BryanD, Fri Jan 14 2011, 09:38PM

I was wondering about a couple things. I know that contrary to the schematics, the feedback CTs should be sampling the current from the primary rather than the secondary, but not sure where they should be ideally placed. There's this picture from Austin, is that a good place for them?


Also, c101 calls for a 4.7uF cap, but I was sent a 4.0uF. Could this be used in place, or should I order a 4.7uF?

Edit: Sorry, I should have done more research before posting. I found my own answers :P

Thanks again!

Re: Minibrute Construction Thread / FAQs
johncohn, Sun Jan 16 2011, 12:43PM

Folks,
Making progress !. I'm now about to commence tuning. I have a good strong 10" discharge .. but I'm a little scared to take it above about 40% on my variac before I have my fine tuning done. . I'm a little confused as to what would make a good tuning procedure. I chose the primary tap point by first finding the series resonance frequency of the secondary and toroid, then took that frequency and found the parallel resonance point for the primary in parallel with the primary cap. I've never tried to fine tune a SSTC like this before. if it were a disruptive coil I'd just start walking the tap point left and right by 1/4 inch increments and find the paint of maximum spark would that work here ? How do people usually tune these things ?

Thanks again for any help !
-jc

Re: Minibrute Construction Thread / FAQs
BryanD, Thu Jan 27 2011, 05:18AM

So I got everything put together and wired. It made my heart warm seeing it all pieced together for the first time. I'm now going over everything with a fine tooth comb to make sure EVERYTHING is correct. Once I'm done that I'll be ready to start testing. I read the testing chapter, and it made another question arise.

Although it may seem common sense to some, I'm a bit unsure. The question is about the primary tap for tuning. Right now I have both ends of the primary going trough the base, and my two leads soldered to them. I'm assuming I need to desolder the lead going to the top of the primary, and tap off the at the appropriate place on the coil itself using something like a grounding clamp or something. Or can I just jumper from my soldered lead to the tap point?

Again I'm sure this is common knowledge, since it hasn't been asked before, I just want to make sure. It's down to the wire now, I got 2 months to get it completed and have my audio modulation circuit designed. Hoping for smooth sailing. :P

Thanks again, in advance.

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Feb 02 2011, 12:32PM


Hi Bryan,

Thats an excellent question. If you have built everything exactly to the dimensions provided including secondary winding (height, diameter, winding length), primary winding, toroid, size, etc..., there should be no need to tune the coil. The only reason to tune to the coil would be if you used something different, like different toroid size, etc...

Also, with regards to the capacitor part number question. Some of the capacitors we use are MIL-SPEC M39014 type capacitors. If you download any of our other instruction manuals (i.e. Class-E, SSTC 1.0, etc...) the last two pages of the manual includes an M39014 capacitor cross-reference.

I hope this helps! Good luck with your project!

Re: Minibrute Construction Thread / FAQs
BryanD, Wed Feb 02 2011, 01:04PM

Thanks for the reply Dan,

I believe I'll end up having to tune it, as My torroid isn't quite to spec. Besides the torroid I believe everything else is bang on the money. I'm actually at a standstill right now. I'm trying to track down the fuses I need locally, I figured they would be standard physical dimensions, but apparently not. I think I may end up having to order some online.

Once, I get the fuses I'll start testing, and if the results are good enough to present the project, I won't bother about fine tuning until after I'm out of school.

Thanks again

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Feb 02 2011, 04:27PM

BryanD,

The fuses are standard 5x20mm. BTW, if you are using an external variac with a built in fuse, you can simply short out the fuse connection on the power outlet cord. Or you could use an external fuse using a standard BUSS fuse. I think most people just short out the built-in outlet fuse and use an external fuse. Just make sure you use a fuse.

Re: Minibrute Construction Thread / FAQs
BryanD, Wed Feb 02 2011, 09:46PM

Well turns out nowhere in town carries them. I'll have to be ordering them online I suppose. Yet another shipping fee :P
Thanks for the advice about the variac fuse. Since I'm ordering fuses, I'll order a dew the proper dimension for it, however I'll keep that in mind if I end up blowing a few.

While we're on the business of fuses. There's a fuse on the variac (20 A) and a fuse just down the line on the input of the coil (20A). Should I synchronize them at all, meaning make one slightly larger, one with longer inverse-time characteristics, or it doesn't matter.

BTW I'm using a variac rated for 10A with a 20A fuse in it, aas this seems to be common practice to save a few pennies. However, it should be only used in short intervals. What is considered short intervals? Guess it depends on the specific variac eh?

Re: Minibrute Construction Thread / FAQs
HV Enthusiast, Wed Feb 02 2011, 10:40PM



BryanD, Just contact me via my website email and let me know what you need. I'll send you some new fuses out free of charge. Not sure if i have 20A, but i definitely have 15A in stock - at least i think i do.

But if you're using a variac with a fuse in it, you should be fine. Just make sure the control 3A fuse is in place. Also, running a 10A variac at 20A is okay. Just keep in mind that if you do have a short circuit event, you may get some "pitting" in the variac core as peak current could get pretty high until the fuse blows.

Hope this answers your questions.

Re: Minibrute Construction Thread / FAQs
BryanD, Fri Feb 11 2011, 03:13AM

So I got the fuses, thanks Dan. I started testing, but ran into a little problem, or I guess more of a misunderstand. When I checked the voltages coming off the low voltage transformer LP-575 I got 12V on either lead in reference to ground, but 24V from lead to lead. Is this right? If so, once I connect it to the driver board I get double the voltages I'm supposed to get everywhere. I'm wondering if I wired the xformer wrong or something.

I tried connecting the primary in series rather than parallel to get half the voltage on the secondary, thinking I'd get the right voltage levels on driver. Instead I got the same voltage levels as when I was applying 12V.

No matter what I seem to do I'm always getting about 36 V on pin 1 of LM7805 and LM7815 which is above the maximum rating for their input.

I attached a drawing of how I got the xformer wired. Can somebody clue me in on what's happening here please.





EDIT: Wow, I really wish I could delete this post, but since I can't I guess I'll explain what I did in case someone else does the same thing :P I was using my bench meter rather than my meter I typically use which auto differentiates between AC/DC. I checked the voltage level off the xformer which is AC, but then forgot to switch my meter to DC when measuring on the board after the diodes. The reading I was getting was the metering error, which worked out to be 2.2 times larger.

I woke up this morning and with a fresh head rechecked the voltages and everything was fine. I was baffled for a while, untill I realised what I must have done.

Note to self :P

Re: Minibrute Construction Thread / FAQs
BryanD, Sat Feb 12 2011, 06:27AM

I hope this isn't considered a double post, since it's a different topic. I made a bit of progress today on testing, however once I came to check the signal coming from E1 & E2 I got stuck. I had no idea how to take a differential measurement, so I researched it. What I came up with was, I needed to take the two probes and attach one to E1 and the other to E2 without connecting the grounds to anything. I then need to set the scope to add and invert CH2. So that's what I did. I got the driver board completely isolated, the only thing connected is the power, 5V to the ext Mod, and 100kHZ to the current FB. What I'm getting is this funny wave.





I hope it's not something like my last problem. I know I'm asking for lots of help, but please remember that I am a student after all and have no real experience :P

EDIT: So I get the proper input to U4 & U5, however I keep getting that on the on the outputs or E! & E2 rather. I'm wondering, could the ICs be fried, or am I just taking the reading wrong?

Re: Minibrute Construction Thread / FAQs
Ruben, Thu Feb 24 2011, 10:14AM

The MiniBrute secondary is specified as 12" winding length, 1140 turns (=95TPI)

using AWG30, single build insulation (0.01009), javaTC is reckoning only 1017 turns @84.75 TPI. Simple math would suggest 1189 turns are possible in 12" so obviously some factor is being included to account for imperfect winding.

What are the turn counts and winding lengths you guys have actually built? Both seem to effect Fres.

which is more important, what should i shoot for?

Re: Minibrute Construction Thread / FAQs
BryanD, Sat Feb 26 2011, 04:35PM

Hello Ruben,

Since your not getting a definite answer, I'll tell you what I did :P
Now mine isn't up and running yet, so no idea on performance. However, I just wrapped it at exactly 12".

Re: Minibrute Construction Thread / FAQs
johncohn, Sun Mar 06 2011, 10:07PM

Good news / Bad news...
First the good news.. I got my minibrute all tuned and boxed in the other day... With current limit set to 400A I was able to get a good hot 26-30" spark.. It was beautiful.. (see low quality attached vid)

Now the bad news.. I say was because it failed the very first time I took the coil out of my lab to show folks at work.. . I set the thing up in my office and arraigned for a nice unplugged wall lamp with a ground as a target.. The thing worked fine for a few multi-second bursts.. then on one of the strikes to the lamp I hear a loud pop and the thing went dead.... . So much for first public demo. All I can assume is that the arc jumped form the lamp back to the primary.. . though I never saw it.

I took the coil home and pulled it apart and found both IGBT's were shorted between gate, emitter and collector (grrrrr) and the 20A fuse in the bridge supply plug was blown. .. I plugged in the control supply and turned on the advanced modulator and noticed that I could not hear the self resonator board buzzing the pulse transformer. So.. I replaced the IGBT's with spares I'd ordered just in case. I also spot checked all the components on the bridge port with a DVM.. everything seems OK. I put on the control supply and the modulator and was pleased to hear the resonator buzzing. I cautiously turned on the HV supply and slowly began turning up the voltage. I noticed at low setting that the florescent tube in the room started glowing... a little more juice and I stared to hear a corona at the breakout point.. but.. as I turned the variac up to 40% I still got no appreciable breakout, even though I noticed the LED ammeter registering about 200A. Before the thing failed 40 % would have generated a lout, hot 25" spark...

So.. I'm a bit stumped.. the bridge seems fine.. the pulse transformer is
buzzing merrily, but no good spark. One clue is that I put a scope on both IGBT's gate and saw a pulse train, but I measure nothing on the emitter of either device. Is it possible that I fried one of the U4/U5 gate drivers ? I originally thought not since I could hear the resonator board buzzing the transformer.. Any clues ?!?
One other question I have since I'm at it.. When the coil was working well, I noticed it was very sensitive to where I placed the advanced modulator.. and where my hands were in relation to it. For example.. just reaching my hand down to change the modulator frequency would cause the coil output to drop almost to nothing.. I'd turn the pot... then withdraw my hand.. as soon as my hand was clear the thing coil would go back to full output.. I noticed the same thing when I tried to do the demo in my office before the coil failed. Does anyone know why the output would be so sensitive to my hands proximity to the modulator ? Is there anything I can do to make this more robust ?

Thanks for any feedback !
-jc


Here's a lousy cellphone recording of a recent test ]tesla2.wmv[/file]

Re: Minibrute Construction Thread / FAQs
BryanD, Fri Mar 11 2011, 10:32PM

Hello guys,

Sorry to hear that Johncohn, wish I could help you out there.

I'm about to ask one of those simple questions again. I'm having an issue with my DC power supply. I have everything the same as the diagrams, the only difference is that I'm using a bridge rectifier rather than CR121 and CR122. No matter what I try the circuit is not amplifying the voltage. Whatever comes out of the rectifier is what I get off the output of the Dc supply. I'm using the same values as in the schematics (2800uF caps and 6k resistors), I also have them connected the same as in the schematics. I don't understand what's going wrong here.

I tried simulating it using a Multisims type program, but got no results.

I have one week left before I need to have it complete it. I was hoping to have it audio modulated, but since time won't allow for that, I was hoping to at least have a working coil to present. Any help would be greatly appreciated.

EDIT: I included a picture showing how I wired it, and how I'm testing it in case that helps

Re: Minibrute Construction Thread / FAQs
johncohn, Sat Mar 12 2011, 07:17PM

BryanD,
Are you using the bridge as a full wave or a half wave bridge.. I'm pretty sure you want the halfwave. picture your bridge as it's component 4 diodes and wire them the way the discrete diodes would have been wired.. that means you'll only be using 3 of the tabs on the bridge.. not all four.. Get what I mean.. If not.. I can draw it for you.
-jc

Re: Minibrute Construction Thread / FAQs
johncohn, Sat Mar 12 2011, 07:22PM

Folks,
Here's an update.. I checked out the advanced modulator.. it's working fine.. I've started to work through the resonator board with a scope . It seems the strike zorched at least U1 (a lowly 74HC14) and U5 the UCCC3731 negative going gate drive. Can anyone see how a primary strike (which is what I assumed happened) .. could take out U1.. or U5.. I can imagine.. I guess that a catastrophic failure of the IGBT's could have sent a nasty HV pulse back through the gate pulse transformer.. but I'm baffled how that would have propagated back trough to U1.. Any clues ?
-jc

Re: Minibrute Construction Thread / FAQs
BryanD, Sat Mar 12 2011, 07:55PM

Hey Johncohn,

I tried your recommendation, and everything is working A ok now. Thank you very much! Now on to the rest of the testing :)

Re: Minibrute Construction Thread / FAQs
BryanD, Tue Mar 15 2011, 11:52PM

Hello again,

I've ran into a problem with testing the IGBTs, and was wondering how others went about it. I tried measuring the Vge (step 6 on page 90). I tried researching how to do it properly, but came up empty once again. I've connected one probe to the gate of one IGBT and one of the emitter screws of the same IGBT. I left the ground clips of both probes disconnected from everything. I added the two inputs and inverted one. All I get when I do this is a bunch of noise. I also have all the proper inputs, modulator and signal generator. Do you have any idea what I've done wrong here? I seem to have problems with these differential measurements :P

Whats really weird is the first time I measured the first IGBT there was lots of noise but I was able to make out the appropriate signal, and was even able to measure the rise and fall times, which were ok. I moved on to the second IGBT in the same fashion, but got nothing but noise. So I moved back to the first IGBT to see if I can catch the differences, I ended up getting nothing but noise on that IGBT now. Since then I haven't been able to get anything out of either one.

Could it be something wrong with my CT or am I just measuring wrong again?

Thanks in advance,

Bryan

Re: Minibrute Construction Thread / FAQs
johncohn, Sun Apr 03 2011, 08:45PM

Just an update.. the primary strike I had seems to have taken nearly out every piece of silicon on y resonator board.. the 74hc14's, the opto-isolator on the HV sense, both gate drivers,.. and it's still not working. I have a mysterious problem with the current feedback circuit.. the signal from the current sense circuit... or the signal generator I'm using for test.. is not propagating completely through the U1 74hc14 hex schmidt trigger.. I have a nice square wave on pins 1.. it's inverse on pins 2 and pin 3, but only a low swing noisy mess pin 4 .. ugh.. I have had to patch many broken tracks caused by desoldering. . my one recommendation to everyone starting their project now is to to SOCKET EVERY CHIP !!!
-jc

Re: Minibrute Construction Thread / FAQs
UnionTesla, Mon May 02 2011, 01:41PM

Hi, I am curently constructing the minibrute and was wondering if there was a specific gauge of wire you used for the high current bus labeled in the schematic?

Re: Minibrute Construction Thread / FAQs
UnionTesla, Mon May 02 2011, 03:39PM

Hi, I am curently constructing the minibrute and was wondering if there was a specific gauge of wire you used for the high current bus labeled in the schematic?

Re: Minibrute Construction Thread / FAQs
raysf, Tue May 24 2011, 01:27AM

The high current wire wants to be something like 8ga or thicker

Re: Minibrute Construction Thread / FAQs
rjdel, Tue Jun 28 2011, 03:03AM

Ok..been away from this project for a while, but I am glad t be back at it.

Mechanical is pretty much done, and electronic in 95% done...just a few things left!

I have a few question about the addendum for the Mini-brute:

1. Item 1 in the REV-A section refers to the manually placed C32 as 10pF, while the schematic and parts list refer to it as a 100pF. ??

2. In the REV-A section, item 4 states that C81 and C82 are correct in the schematic but that they are not on the PCB. My PCB actually does have C82. Just curious if this is a typo in the addendum, or if I am somehow mistaken (very likely!)


thx.

Re: Minibrute Construction Thread / FAQs
Uspring, Thu Jul 07 2011, 04:17PM

Hi guys,

I'm new to this forum and recently got my minibrute kit. I've a couple of
questions, you may be able to answer.

1.) I'm using a different secondary, than the one Dan describes. It has the same
diameter but a higher resonant fequency (about 240 kHz). Instead of decreasing
primary inductance, I thought of decreasing primary capacitance by adding a 4th
set of caps in series to the standard 3.
I've done a simulation, which tells me, that for a given current limit, it is better
to decrease capacitance instaed of inductance. Right?

The secondary I want to use has its connecting leads on the inside of the
tube. I was wandering if there might be a problem of discharges inside
the secondary. Can I use some plastic foam or other to avoid this. Anyway I'm
wondering, why the standard minibrute doesn't discharge right down into the
strike rail. That seems to be the shortest way.

2. Instead of threading the primary through the holes of its support,
wouldn't it be easier to make slits?
I'm aware that there might be magnetic forces due to the high current.
IMHO they would tend to lengthen the primary and make it contract so slits,
open to the outside, should work.

Thank you for your thoughts.

Re: Minibrute Construction Thread / FAQs
UnionTesla, Wed Jul 13 2011, 05:21PM

I have ever so cleverly lost page 25 of the construction book which is making completing the addendum difficult. What do C 81 and C82 connect to in the diagram on page 25?

Re: Minibrute Construction Thread / FAQs
Uspring, Thu Jul 14 2011, 12:18PM

C81 is between the 5V supply (Pin 1 of U81) and ground.
C82 is between Vout of U81 (pin 3) and ground.

Re: Minibrute Construction Thread / FAQs
UnionTesla, Wed Jul 27 2011, 02:10PM

I am currently in the testing phase, and we have the Self resonant control board working, but when I test the display board, instead of the LEDs for power and 5V lighting up, the 5V and overcurrent LEDs light up, and I cannot seem to figure out what the problem is. Any suggestions?

Re: Minibrute Construction Thread / FAQs
Uspring, Thu Jul 28 2011, 03:56PM

Possibly it's the cable. If you put on the
connectors wrong, you might interchange
pin 1 with 2, pin 3 with 4 etc.

Re: Minibrute Construction Thread / FAQs
Ruben, Mon Oct 03 2011, 01:06AM

Hi all,

I've got my minibrute up and running at last!

First light saw me get about 12" discharges to air -- unfortunately my MMC failed after a 30s run (fan was not connected, I cursed my own stupidity).

MMC is now 5x12 0.047uf polypropylene caps to give 112.6nf (measured) at 7.5kv.

I'd be very great full if anyone could help with the following questions:

1) My LED bar graph works under testing, but not when running. i.e. when I lift one end of R21 and apply a voltage, everything works as it should. When I run the coil with R21 in place, I can scope the primary current waveform, but I get no bar graph led's lighting. The rest of the display board LEDs work as they should.

2) OCD operation: When my OCD activates, I should see the pulse train length decrease, right? (when viewing primary current) this is what I observe.

3) My OCD is set to ~550 A, and it seems to kick in when the signal I scope is ~8 V peak (ie ~5 A across a 1.6 ohm burden resistor) -- unless I'm mistaken this all makes sense. HOWEVER, I'm at this point with just 16" sparks to ground, and 203 V on the DC bus -- is this normal?

Any suggestions warmly welcomed.

Re: Minibrute Construction Thread / FAQs
Uspring, Sat Oct 08 2011, 09:33AM

Hi Ruben,

Try testing the led bar without the secondary. I've seen
its high voltage field (or ground current) interfere with
the electronics.

Re: Minibrute Construction Thread / FAQs
Ruben, Sun Oct 09 2011, 12:11AM

Thanks for the suggestion,

In the meanwhile I've made some progress:

*Started plotting primary current vs arc length, and increased my tap point from 4.5 to 5.0 turns -- now able to get 16" arcs at just 174VDC, ~275A

*31" arcs to grounded target with 310V on the bus, and ~375A (increases during ground strike).

After watching a video I captured, I realise that my first graph LED is lighting (Whole board is installed upside down), but it's as if the set point is WAY too high:



I'm still quite confused, as I was quite careful in setting the full scale with R21 lifted.

********************

HOWEVER - after attempting to run the coil at 500A I experienced a semi-catastrophic failure. I've created a separate thread, and would much appreciate any help in troubleshooting!

*********************

Re: Minibrute Construction Thread / FAQs
johncohn, Sun Nov 06 2011, 03:56PM

Folks,
A short update after a long silence. Earlier in the year I reported that my MiniBrute self destructed after its first public demo. A primary strike managed to destroy every piece of silicon in the unit. Thank to massive help from my good friend and tesla guru Scot F I've now got it working again. (thanks so much Scott !!!!) We rebuilt the resonator board with new PCB and new components (and sockets !) .. and Scott who's a much cleaner fabricator, helped me re-layout and robustify the HV wiring. The thing came back up fine.. but managed to eat the bottom IGBT (IXGN60N60C2D1-ND's) in the bridge two more times during medium power testing.. We now have the current limit set back to 300A and it seems stable (knock on wood) The disappointing thing is that at the 300A set point I'm getting about an 18" spark instead of the 30+ I was getting when I had it set to 500A.
I'm now interested in making this device work *reliably* at the 500 A set point to get the advertised spark .. Is anyone out there reliably running their device above 300A ? and/or is anyone getting 30"" spark (or so) .. ?

Friend Scott was also wondering if the replacement IXGN60N60C2D1-ND IGBT s were just a little less robust than the original HGT1N40N60's in Dan's kit. . I'm eager to hear if anyone anyone out there experimented with replacing the bridge with more robust devices ?

Very eagre to hear wHat are other people getting out of their Minibrutes !
-jc

ps. One spot of good news is that this morning I rigged up a simple audio circuit in the advanced modulator and now have the coil singing the Jeopardy theme song albet wiht an 18" max spark. Still cool, though

Re: Minibrute Construction Thread / FAQs
Uspring, Tue Nov 08 2011, 02:20PM

I'm getting about 30" sparks from mine at a 650A setting. I am using a different secondary coil from what Dan is describing and I don't believe my coil is properly tuned to this one yet. I burned up 2 IGBTs from a ground spark. At 500A the coil worked reliably, ground arcs or not.

Apart from using a long extension cord for the variac power (Dan recommends this in the addendum), I have separated the control power ground from the secondary bottom ground. The secondary ground is connected only to the spark rail and then firmly grounded elsewhere. I have also grounded the heatsink to the control ground. I really don't know if that makes sense but my experience is not as bad as yours.

Re: Minibrute Construction Thread / FAQs
johncohn, Sun Nov 13 2011, 08:01PM

@uspring... Thanks for the suggestion.. the idea of separating the grounds sounds reasonable as does grounding the heat sink. I'd been wondering about leaving it floating.
Anyone else out there using their coil reliably (eg ground strikes OK) at 500A setting ?
-jc

Re: Minibrute Construction Thread / FAQs
UnionTesla, Wed Apr 25 2012, 07:19PM

Hello, I am testing the self resonant control board, and I have replaced all of the ICs at this point, but I am still not getting the first 0V-5V square wave in the testing procedure to come through. Instead I am getting a 500mV peak to peak square wave. Has anyone else had this problem?

Re: Minibrute Construction Thread / FAQs
BubeeMike, Tue Jun 12 2012, 11:29AM

I didn't think it appropriate to start a thread over this, but just wondering if anyone has found a place to buy a PDF version of both these books? I too have the DRSSTC, but I hate paper, and have been contemplating buying the Mini-brute book, but I don't want another paper book. Just curious?

Re: Minibrute Construction Thread / FAQs
Daniel Kramnik, Tue Jul 10 2012, 09:11PM


Sounds suspiciously like a scope probe x1/x10 mistake...

Re: Minibrute Construction Thread / FAQs
Graham Armitage, Tue Aug 14 2012, 08:01PM

UnionTesla
I had the same problem on my controller board with really low voltages. Thought I had blown the ICs too. Turns out there was a break in the of the solder points that prevented the 74HC14 from getting a ground connection and so was not outputting the correct signal from pin 4. Took me a long time to find the problem and kept second guessing myself. Not saying this is your issue, but maybe it can help.

Re: Minibrute Construction Thread / FAQs
Rollingblackout, Sat Oct 26 2013, 05:09AM

A few years ago when I built my miniBrute one of my main low performance issues was due to making a complete loop or ring with the strike rail. Back to the book found the part I missed and performance was reestablished. I put it away for a few months then found that the over current protection circuit was incorrectly powered. Following a posted repair I gained even more power and put it away. Today I'm playing again and after a few hours of making my neighbors look over the fence I noticed my secondary is leaning. It turns out I made another loop with the grounding. I stuck copper tape in a nice ring around the bottom 3/4" of the form. Well it heated up and the clear plastic started to melt. Now that is also fixed and I have a question. Does the toroid make a loop? I am using a aluminum duct 3" and I covered that with wall smoothing compound then covered that with aluminum tape. I found small blue sparks in the surface of the smooth finish where tape corners are. When I disassemble the thing I think the toroid is warmer then when I started. Is this another place where I could be loosing performance?

Re: Minibrute Construction Thread / FAQs
Polishedball, Sat Oct 03 2015, 12:22AM

I am currently building this coil, I am trying to get a better idea of how where to connect the RF ground. I have read and saw the pictures connecting the bottom of the secondary to a piece of copper strap on the side , but have either missed or it isn't there where to connect RF ground. Does this coil require a stake in the ground for it?

Edit: c101 is sorted heard back from Dan, just as FYI for future the 4.7 isn't used and the .1 goest from negative DC rail to earth ground. So still looking for info on how to ground and what points this coil.

/Also C101 does anyone know if it was changed I do not have a 4.7uF @600V but seem to have a poly cap that is .1 @ 2000V that seems to have no home? Thoughts /

Thanks

Re: Minibrute Construction Thread / FAQs
Mads Barnkob, Mon Oct 05 2015, 09:05AM


Did you read through this topic? Did you search for ground in this topic? I do not think you did any of those simple routines.

It is covered already at page 4:

Re: Minibrute Construction Thread / FAQs
Polishedball, Tue Oct 06 2015, 12:44AM

Thanks you are correct. I only skimmed it, I did Google the topic prior and seems to be lots of opinions. That was why I came here and asked.
I have now read the 16 pages. Thanks again for the link back.

I'll add build pics in my next post.


.

Re: Minibrute Construction Thread / FAQs
Polishedball, Sun Oct 11 2015, 09:22PM

Anyone spot any issue with this layout? Just wanted to ask before I wire it up. Thanks

Also can you tell me is there a way to test the phase of the gates, without the advanced modulator. That book has you using it. (I will own it shortly, but would like to test before it arrives.)

Re: Minibrute Construction Thread / FAQs
Polishedball, Sat Oct 24 2015, 10:57PM

Complete and worked the first power on. Thankful for the information here and the excellent responses from EasternVoltage.

Re: Minibrute Construction Thread / FAQs
Bud, Wed Jun 22 2016, 02:32PM


I have built this as my third coil. I am also studying electronics in my spare time.
Not sure of your abilities but it did tax my knowledge in electronics. I did finish it and got it working. Had to write to Dan several times but be did give me enough help to finish it. Mechanical it was easy for me but my background is in tool and die making and engineering. This is a nice table top coil but not a real strong performer. Great for teaching aid. If you want a coil that performs 3-4 foot arcs continuously.....this may not be your pick. I use mine as a teaching aid and very happy that I built and tested it. demonstrates Tesla's ideas very well in a public setting while maintaining a very safe environment. Here are some pics.

s1243.photobucket.com/user/ForrestMohrman/ slideshow/tesla%20coil/minibrute

Good luck.

Bud

Re: Minibrute Construction Thread / FAQs
Jim_VE7UV, Tue Aug 30 2016, 01:47PM

Hi all,

I have finished building all of the miniBrute circuit boards, and had a local plastics supply shop that had some new old stock PVC 1/2" thick plate cut up all of the miniBrute case pieces. I was also able to obtain some very nice grained birch 1/2" thick plywood to make up the 4 wood case pieces. When I originally bought my miniBrute kit from Dan at EVR I tried to also buy the 2 piece panel kit he sold for $59.99 but they were all gone. In the color miniBrute reference design construction book I bought also from EVR there are not-to-full-size scale images of these two panel templates, and I could probably fool around with my laser printer's built-in enlarging capable photocopier to make my own full size panel templates, but thought I'd check first on the forum if another user could please email me them, or email me a weblink to where there may be one.

Thanks, Jim VE7UV
BC, Canada

Re: Minibrute Construction Thread / FAQs
Polonium210, Sun Nov 20 2016, 06:01PM

I'm just finishing up the last few driver board components and have an issue with the 10uf caps.
I have 9 - 10uf caps left to place. 7 electrolytic and 2 Tantalum. The problem is the schematic that was sent with the kit says C4,C5 and C6 are all Tantalum but the kit was only supplied with 2.
C6 is a DC blocking cap so I cannot use an electrolytic...
Also the photo in the book shows all the 10uf caps as Tantalum..

Re: Minibrute Construction Thread / FAQs
Alex Yuan, Tue Sept 05 2017, 07:06PM

Just recently got my 'minibrute' working again. Apart from the primary and secondary parameters, the thing is hardly a minibrute anymore. A while back the minibloc IGBTs shorted, dumping the energy from the bus caps into the GDT thus making it explode. Took out the original driver too.

So I threw in a CM200 and redid all of the electronics:


[/link]

Re: Minibrute Construction Thread / FAQs
Alex Yuan, Tue Sept 05 2017, 07:13PM

Oops sorry for the double post :(

Just recently got my 'minibrute' working again. Apart from the primary and secondary parameters, the thing is hardly a minibrute anymore. A while back the minibloc IGBTs shorted, dumping the energy from the bus caps into the GDT thus making it explode. Took out the original driver too.

So I threw in a CM200 and redid all of the electronics:


3.6 feet: