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oneTesla - a small single-board DRSSTC

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Dr. ISOTOP
Mon Jun 11 2012, 03:52AM Print View
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
12/28/2012:

Support our Kickstarter Campaign!
Our webstore (in progress) can be found here

*Coil specs*
*~220KHz Fres
*2.5x10" secondary, 36 AWG with 2x8" topload
*Peak current: 350A
*Max spark length (ground strikes): 23"
*400VDC doubled variac feeding a half-bridge of FGH60N60SMD's
*14AWG primary, 6 turns on 3.5" former, 68 nF 3KV CDE940 series tank cap

12/09/2012:

Better video footage, with a spun toroid:


For y'all people who are building this from eBay boards, I have a bit here about things you should and shouldn't do.

7/15/2012 UPDATES:

This project has grown a lot since it was first conceived. Performance is now up to about 2', from a 10" secondary, using FGH60N60SMD IGBT's.

pics:







There's a short run of professionally fabbed boards for sale here to help fund further development. Kramnik and I also have more complete accessories, a kit, and a polyphonic interrupter in the works.

Critical specs of the new coil:

*~220KHz Fres
*10" secondary, 36 AWG
*Peak current: 350A
*Max spark length (ground strikes): 23"
*400VDC doubled variac feeding a half-bridge of FGH60N60SMD's
*12AWG primary, 68 nF 3KV CDE940 series tank cap

If you want to assemble your own from an eBay board get the Eagle files here.

-----------------------OLD INFO BELOW----------------------------------------------
Inspired by EVR's microBrute, I decided to route a DRSSTC onto a 4"x6" board.

The result:



Half the credit for this project goes to Daniel Kramnik, who built the coil in the video above using his revision of my design (which includes an optical interrupter).

The driver:



Low-power (~50W) sparks:



Critical coil specs:

Driver: half-bridge of FGH60N60SMD IGBT's
Primary: 4.5 turns of 14 AWG on a 3.5" PVC former
Secondary: 2.5x7", 36 AWG with a 2x7" topload. Resonant frequency is ~320KHz
Tank cap: CDE940C30S68K-F, 0.068 uF@3KV

The video is running at 250A with 30uS on time and 340V bus voltage.

Power figures:

4"@30W, 5uS on
6"@80W, 20uS on
10"@140W, 30uS on

(all numbers at 200 bps)

Blog post about it here:

Board file for the (old) version of the coil:
Digikey BOM for everything except the transistors:
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Thomas W
Mon Jun 11 2012, 05:50AM
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location: UK, Dorset, Broadstone
Posts: 1276
Nice!
that is a really good idea, and design :D
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lightlinked
Tue Jun 12 2012, 06:06AM
Registered Member #2087
Joined: Tue Apr 21 2009, 08:32AM
Location:
Posts: 115
thats pretty awesome. how long of a streamer can you get in free air? what does the interrupter look like? is over current protection not needed in little coils?
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Dr. ISOTOP
Tue Jun 12 2012, 03:05PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
lightlinked wrote ...

thats pretty awesome. how long of a streamer can you get in free air? what does the interrupter look like? is over current protection not needed in little coils?


I can get 6-7" in free air; note that the entire coil floats, so this may be limiting my streamer performance.
The interrupter is microcontroller with optocoupled output.
I've yet to need OCD on this coil. The bridge seems to hold up fine during ground strikes.
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Josh Campbell
Tue Jun 12 2012, 07:09PM
Registered Member #5258
Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 117
Ha, great design. Good choice of song too, I like how the music's pitch affected the resonance and thus the output. Do you input unmodified (audible range) music or do you modify it to fall in a specific tonal range?
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Dr. ISOTOP
Tue Jun 12 2012, 07:14PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
2bytes wrote ...

Ha, great design. Good choice of song too, I like how the music's pitch affected the resonance and thus the output. Do you input unmodified (audible range) music or do you modify it to fall in a specific tonal range?


The pitch affects the break rate, hence total power throughput and spark length.
I believe this is with unmodified music; the interrupter is Daniel Kramnik's design, so we shall wait for him to answer.
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Ben Solon
Tue Jun 12 2012, 08:34PM
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location: Holliston M.A., United States
Posts: 600
if you ground it you not only will get longer streamers, but the audio will stop crackling too. that's because the crackling is caused by the streamer having trouble breaking out. notice how you get perfect audio quality when you get "ground" strikes.

but on another note, very nice! i saw this somewhere a couple days ago, but good to see you have finalized it.
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Steve Ward
Sun Jun 17 2012, 06:55PM
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Excellent IGBT choice . I say this because i use that part for some other projects of mine and im very happy with them.

Have you reached a point of part failure? or have you simply limited the on-time and current to be "safe"? I suppose your single MMC cap can only take so much as well.

Maybe also consider using 2 separate heatsinks so that you can directly mount the IGBTs and avoid thermal resistance of an insulator. At least i'd look at that for maximizing the performance of those parts.

Very nice work, either way.
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Dr. ISOTOP
Sun Jun 17 2012, 10:22PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Steve Ward wrote ...

Excellent IGBT choice . I say this because i use that part for some other projects of mine and im very happy with them.

Have you reached a point of part failure? or have you simply limited the on-time and current to be "safe"? I suppose your single MMC cap can only take so much as well.

Maybe also consider using 2 separate heatsinks so that you can directly mount the IGBTs and avoid thermal resistance of an insulator. At least i'd look at that for maximizing the performance of those parts.

Very nice work, either way.


I've yet to reach IGBT failure on the 60N60's; on the old bridge (FGH40N60SMDF) it would silently die at about 300A. Been meaning to push the coil to the point of destruction, but I'm out of 60N60's for now a few transistors gave their lives due to human error.

Here's a new video with streamers; tying the secondary base to earth ground worked wonders. I also added a low-pass filter (R and C in parallel to ground) on the feedback pin on the 7414, which got rid of the static-ish noise in the first video.



Three coils are better than one, right?

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Daniel Kramnik
Fri Jul 13 2012, 02:26AM
Registered Member #3885
Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94
Update!

Bwang sent out a double-sided version of the board - all noise issues are long gone, and the performance is even better with longer on-times and looser coupling.

Specs. are ~2 feet spark length with 300 - 350A primary current at 400Vbus and a 2.5" x 10" secondary.





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lightlinked
Sat Jul 14 2012, 10:53PM
Registered Member #2087
Joined: Tue Apr 21 2009, 08:32AM
Location:
Posts: 115
would stuffing the secondary with caps like in steve's qcw tesla gun improve mini coil performance?
will a batch of boards be sold?
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kwinchee
Sun Jul 15 2012, 03:01AM
Registered Member #1287
Joined: Mon Feb 04 2008, 11:03AM
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Posts: 15
This is sweet! would also be interested in a board if you sell a batch :)
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Daniel Kramnik
Sun Jul 15 2012, 07:40AM
Registered Member #3885
Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94
Boards are on sale now! (link)

I'll admit they are a bit pricey, but you get free fast shipping, and profits go towards improving oneTesla =)
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Dr. ISOTOP
Sun Jul 15 2012, 06:10PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
lightlinked wrote ...

would stuffing the secondary with caps like in steve's qcw tesla gun improve mini coil performance?
will a batch of boards be sold?


Probably not by much. Steve's QCW is special in that it has an exceedingly low topload voltage, meaning the secondary MMC is feasible and the secondary does not flash over.
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Killa-X
Sun Jul 15 2012, 10:01PM
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1036
I'll buy a board off you from your eBay, nothing like helping someone out with a project...I got a s all coil, 3.5 x 12 at 150khz, let's see what it can do!!

*sighs* I guess i bought two :P
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Dr. ISOTOP
Mon Jul 16 2012, 12:23PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Killa-X pointed out to me it would be nice to have a full list of materials.

This one is nearly complete (when combined with the list on my blog):

1 UCC37321
1 UCC37322
1 74HC14
1 74HC74
3 16V electrolytics, I think 8mm spacing, preferably 1000uF
10 1uF ceramics
1 100 nF capacitor
1 330 pF capacitor
1 100k resistor
1 10k resistor
1 600ohm resistor
1 200ohm resistor
2 6.8ohm resistor
2 1N4148 diodes
2 MUR460 diodes (or some other 4A axial-package rectifier of at least 250V)
1 7815 regulator
1 7805 regulator
1 IF-D95 optical receiver
1 PJ-037B power jack (from Digikey)

It'll need a 19V wall adapter (such as a laptop adapter) to run. You'll also need to throw together an optocoupled interrupter of some sort (555/Arduino/whatever), but that's not terribly hard.
Note that at this point, the project isn't really production-ready, so if you buy a board, be ready to do some troubleshooting on your own. Kramnik and I will gladly help, but please do post your questions here (as opposed to PM's/e-mails) for all to see.

Also, Eagle is essential right now for assembly; the schematic really helps when putting things together/finding component values. There's a raw capture of the board attached for those who don't use Eagle.

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HB
Sat Jul 21 2012, 08:40AM
Registered Member #4146
Joined: Tue Oct 18 2011, 02:01AM
Location: Wisconsin, U.S.A
Posts: 56
I like this i'm planning to buy a couple at the beginning of this next month been wanting to play around with a DR and get the hang of things before i build something more complicated. This seems just what i need thanks alot.
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Mr Pink
Sun Jul 22 2012, 10:15AM
Registered Member #5174
Joined: Tue Jun 05 2012, 06:28PM
Location:
Posts: 4
Could you ship a board to Sweden?
If so I would be interested in buying one :)

The project looks great, I like it when things are kept as simple as possible but still are able to perform.
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Dr. ISOTOP
Sun Jul 22 2012, 10:06PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Mr Pink wrote ...

Could you ship a board to Sweden?
If so I would be interested in buying one :)

The project looks great, I like it when things are kept as simple as possible but still are able to perform.


You should PM Kramnik about that, since he's the one doing the shipping right now.
And thanks! This board was originally designed to be easy-to-etch, hence its minimalism.
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Killa-X
Thu Jul 26 2012, 12:51AM
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Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1036


I did a LOW power test, 100A, with IRFP260s (the 60N60 igbts are in the mail) seems to work well :) about 5" sparks.
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nixie
Sun Jul 29 2012, 03:06PM
Registered Member #3908
Joined: Tue May 24 2011, 09:40PM
Location: Gilbert, Arizona USA
Posts: 68
Hi There,
I bought one of the boards. And received the known items through Mouser/Digikey.

A few questions on materials and assembly. These may be common, and might help others wanting to build it.

(a) Heat Sink; Who is the supplier/Part number?

(b) GDT Core; a spec, or recommended supplier/part number?

(c) GDT windings; how many turns? I'm guessing 20 perhaps?

Thanks, Jeff




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Dr. ISOTOP
Sun Jul 29 2012, 09:20PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
nixie wrote ...

Hi There,
I bought one of the boards. And received the known items through Mouser/Digikey.

A few questions on materials and assembly. These may be common, and might help others wanting to build it.

(a) Heat Sink; Who is the supplier/Part number?

(b) GDT Core; a spec, or recommended supplier/part number?

(c) GDT windings; how many turns? I'm guessing 20 perhaps?

Thanks, Jeff







1) Mine are currently pulled from ATX power supplies; I'm still seeking a supplier that will do small quantities.
2) I used a Sanlin SL5 core about an inch in diameter
3) 15-20 turns seems about right.
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Ben Solon
Sun Jul 29 2012, 11:55PM
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location: Holliston M.A., United States
Posts: 600
Dr. ISOTOP wrote ...

nixie wrote ...

Hi There,
I bought one of the boards. And received the known items through Mouser/Digikey.

A few questions on materials and assembly. These may be common, and might help others wanting to build it.

(a) Heat Sink; Who is the supplier/Part number?

(b) GDT Core; a spec, or recommended supplier/part number?

(c) GDT windings; how many turns? I'm guessing 20 perhaps?

Thanks, Jeff







1) Mine are currently pulled from ATX power supplies; I'm still seeking a supplier that will do small quantities.
2) I used a Sanlin SL5 core about an inch in diameter
3) 15-20 turns seems about right.



Heatsink USA will sell relatively cheap heatsink by the inch^2, but I don't know if they do price breaks. They will also drill and tap for you(probably extra).

Really, any ferrite with a high permeability and good transfer at the desired frequency will work. Then just calculate the # of turns=(V*T)/(B*Ae).

I just may have to make/buy one of these myself after my big drsstc is done! Good work bwang and Kramnik, this is an interesting project you've got going here.
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Dr. ISOTOP
Mon Jul 30 2012, 03:06AM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
ben123324 wrote ...

Heatsink USA will sell relatively cheap heatsink by the inch^2, but I don't know if they do price breaks. They will also drill and tap for you(probably extra).


It needs to be the right shape of extrusion (for board-mounting).
Really, the cheapest way might just be getting surplus Dell PSU's off eBay and gutting them
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Killa-X
Mon Jul 30 2012, 05:01AM
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1036
I got my heatsinks off ebay, had to really hack them up to fit.
I use the ferrites electronic goldmine USE to sell.
I'm using 8 turns, which is my typical DRSSTC setup.

Seems to work great, may do a 120V test with IGBTs today, get more sparks you know? :D
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Dr. ISOTOP
Tue Jul 31 2012, 10:36PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
So Killa-X told me via PM that the IGBT's died at 300A doing burst mode operation. Kramnik also killed a bridge doing music with really long pulsewidths, so I guess the conclusion to be drawn here is that the coil doesn't like super-high duty cycles.
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Ben Solon
Tue Jul 31 2012, 10:54PM
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Joined: Thu May 19 2011, 08:28PM
Location: Holliston M.A., United States
Posts: 600
Raise be impedence of the system a couple times. I would like to see the results of that. It might not increase spark length or primary current, but the longer on-times might make it a bit more user friendly for people who buy one without the knowledge of exactly how they work.

What exactly have the limits been? 300A by Kramnik, has anyone else blown a bridge and measured the conditions? The irg4pc50Ud might be a decent upgrade...
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Killa-X
Tue Jul 31 2012, 11:08PM
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Location:
Posts: 1036
I had to been running 50 primary current cycles...quiet a bit heh...plus i was burst-mode.



Once i replace the bridge later on i will leave everything the same and attempt to count the cycles..and measure the on vs off time, of when my coil went pop..

Most DRSSTC bridges have a snubber capacitor on them, is it not required on yours for some reason..?


not to mention i had 1 flash over before the video, i lifted the coil up by an inch, fixed the issues.
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Dr. ISOTOP
Tue Jul 31 2012, 11:16PM
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
ben123324 wrote ...

Raise be impedence of the system a couple times. I would like to see the results of that. It might not increase spark length or primary current, but the longer on-times might make it a bit more user friendly for people who buy one without the knowledge of exactly how they work.

What exactly have the limits been? 300A by Kramnik, has anyone else blown a bridge and measured the conditions? The irg4pc50Ud might be a decent upgrade...


IMO high-impedance primaries are actually less user-friendly - they require long on-times and run the transistors hotter.
I haven't tried the IRG4PC50UD yet...they seem roughly equivalent to the 60N60's I've been using and have a higher thermal impedance, plus they are a bit slower.


Killa-X wrote ...

I had to been running 50 primary current cycles...quiet a bit heh...plus i was burst-mode.



Once i replace the bridge later on i will leave everything the same and attempt to count the cycles..and measure the on vs off time, of when my coil went pop..

Most DRSSTC bridges have a snubber capacitor on them, is it not required on yours for some reason..?


not to mention i had 1 flash over before the video, i lifted the coil up by an inch, fixed the issues.


Wow, nice work. 50 cycles is a lot...that's a couple hundred microseconds at your resonant frequency right? If you were variac'ing the bridge while keeping pulsewidths and such constant, have you tried holding the bridge at a constant voltage and raising pulsewidth until you find performance satisfactory?
My original excuse for not using a snubber was that i didn't have the board space for one (back when the board was etched on to 4x6" PCB stock from eBay). The current design uses a super-low-inductance laminated bus, so I haven't really found a need for a film cap yet. A film cap will most likely improve performance a bit - you can try soldering one directly to the capacitor terminals if you want.
As an FYI for everyone who has bought a board so far: the bleeders are meant to be soldered directly to the buscap terminals on the bottom of the board! Use bleeders!
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Killa-X
Tue Jul 31 2012, 11:53PM
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Posts: 1036
I can see, i have a few caps but they maybe too small for snubber use. Its a 400V 1uF capacitor, 0.007ohm ESR.

I only messed with the duty cycle for making the arcs have some meat to them, and not be thin strains of hair, and its roughly around that 200Khz zone.
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