Re: What to do now... (partially completed Tesla coil)
sparky, Mon Mar 05 2007, 06:04AM

I'd go rotary SG, async or sync - doesn't matter. I'd go .04 uF for a "first light" capacitor - 3/8" copper tubing for the primary and 4" or wider PVC form for a secondary would also be strongly advised.

Re: What to do now... (partially completed Tesla coil)
Sam, Tue Mar 06 2007, 10:33PM

I've been having trouble with getting large white pvc pipe, any suggestions?

BTW I have started with the rotary, I got a 1/3 horse fan motor, and I'm using a lathe to build to disk holder...

And also with the secondary wire, i have some from the secondary of a MOT, but the wire is sort of crappy.
Where does everyone get their stuff?

Re: What to do now... (partially completed Tesla coil)
Mike, Tue Mar 06 2007, 11:04PM

i got loads of free white pvc by simply calling a local contractor/ builder and asking if i could browse their scrap pvc pile for parts for my science project .

Re: What to do now... (partially completed Tesla coil)
Sam, Wed Mar 07 2007, 04:30AM

Good Idea!!!!!!

RTSG parts





[Edit: Fixed double post, please have a look at the rules again.]

Re: What to do now... (partially completed Tesla coil)
ragnar, Wed Mar 07 2007, 11:20PM

Nice lathe work!

What are your electrodes made of?

Re: What to do now... (partially completed Tesla coil)
Sam, Thu Mar 08 2007, 03:55AM

hehe, fist semester on a lathe, thanks

I dont know what to make them out of yet... any ideas? what does everyone use?

Re: What to do now... (partially completed Tesla coil)
Sam, Sun Mar 18 2007, 04:48AM

I just finished building and testing my new bottle caps... Looks like I need some more... yummy pop.

Re: What to do now... (partially completed Tesla coil)
Sam, Sun Mar 18 2007, 11:35PM



Yumm, 4 more bottles, I have to piss alot now, I wonder why...

Re: What to do now... (partially completed Tesla coil)
sparky, Mon Mar 19 2007, 07:54AM

I'd call up CDE and ask for a few capacitors for a school project. They may just give you a few samples - 20 caps for free. Ask them about the 942 type caps, 1600 VDC - 0.68uF MMCs

Re: What to do now... (partially completed Tesla coil)
Sam, Tue Mar 20 2007, 04:17AM

will do, but these new caps work great, i got 8 going and the variac pulls like 3 less amps. cool!! bigger arcs and sparks.

My GF is really scared of it, she wont even go near it.

EDIT:

QUESTION??? I havn't yet fully calculated the voltage and current I am getting off the 2 MOTS. how would I go about doing this. I have a multi-meter but t only goes up to 750vAC.

I'm thinking like 9-12Kv?

Re: What to do now... (partially completed Tesla coil)
sparky, Tue Mar 20 2007, 07:27AM

sure... here is what I do. Run 120V into the secondaries of the MOTs. Measure the voltage off the primaries and you should get 3 VAC --- from 120V input on the secondaries. 120V divided by 3 V = 40 which is how many time the voltage will increase if you feed 120V reverse into the system. 120V x 40 = 4800 V .... tada!!

I can assure you that your voltage ratio will be 40:1 or 4800V at 120V input. With a voltage doubling circuit you will be running ~10 kVDC into the Tesla Coil. Current wise --- well I'd use a heavy duty current clamp meter and measure the input current first. But I'd be willing to wager that if you are using MO caps 0.9 -1.0 uF you'd probably be pulling 600mA + on a dead short. 3kVA total mains power draw... maybe a bit more.

I'd be really cautious with this circuit...

Re: What to do now... (partially completed Tesla coil)
Sam, Tue Mar 20 2007, 07:11PM

well at 12vac, I get 164.5 vac per MOT.

so I figure 164.3V * 10(thus 120v input) I get 1.645Kv with 120vac input

does that work right?

EDIT: tried the above method. I get 4500V on the dot when calculated(both MOTs)

and when my variac is at its max (161.7V) I can get 6080V.

Question, when going through the doubler is it just simply *2 or can it be complex?


BTW here is hows its set up


ERROR IN THE PIC, T1&T2(C) 12.16Kv(161.7) should be T1&T2(C) 6 Kv(161.7)

[Edit: 400 pixels maximum]

Re: What to do now... (partially completed Tesla coil)
Marko, Tue Mar 20 2007, 11:11PM

What is your charging reactor? That transformer in behind?

Doubler will give you 2x peak voltage from the mot's. So if (for example) each mot gves 2000VAC your DC output will be 2*2*2000*1.414 ~ 11312V.

Re: What to do now... (partially completed Tesla coil)
Sam, Wed Mar 21 2007, 12:03AM

its a 5 amp choke. thanks for the math.

The Choke

Re: What to do now... (partially completed Tesla coil)
Marko, Wed Mar 21 2007, 12:10AM

If I figured it all right out, you have NO charging choke?

Voltage doubler alone, as it is, will not work in a tesla coil because the spark gap will dump all the energy from your filter caps with each firing, in a massive power arcing wich would blow your diodes right up.

If you are about for DC resonant charging then you need very large output choke (tens of H) and de-Qing diode in series with output.

Steve conner has great coil and info about it:

You could probably use big resistor to ballast the output of your doubler, but it would just waste large amount of power and it would probably be worse than if you ran the coil from 2 undoubled mot's.

Re: What to do now... (partially completed Tesla coil)
Sam, Wed Mar 21 2007, 12:15AM

http://hot-streamer.com/greg/motpic.htm

His works

"which ran at full throttle for months without popping any diodes"
http://hot-streamer.com/greg/frames.htm

Re: What to do now... (partially completed Tesla coil)
sparky, Wed Mar 21 2007, 01:17AM

Sure thing, Greg Hunter employed a straight DC rectified MOT PSU. Sure you'll get a fair output but you will loose power and performance without using chokes... I've tried both methods - with and without chokes, and the latter improves the Tesla coil performance considerably.

Re: What to do now... (partially completed Tesla coil)
Sam, Wed Mar 21 2007, 02:54AM

ARG, Well Ill just focus on my RSG for now. Figure the rest out later.

Re: What to do now... (partially completed Tesla coil)
sparky, Wed Mar 21 2007, 05:22AM

Its not a big deal... if you have spare MOT units hanging around these can be hooked up to act as chokes. Just short the primaries and run the high voltage through the secondaries.

Re: What to do now... (partially completed Tesla coil)
Steve Conner, Wed Mar 21 2007, 11:37AM

Like you guys just figured out, there are two ways to drive a Tesla coil with MOTs.

The way recommended by Greg Hunter uses a voltage multiplier circuit with no filter capacitors on the output, and undersized capacitors everywhere else. This makes it deliver pulsating DC at 60 or 120Hz, depending on how you wire it, and with a certain amount of inherent ballasting because of the reactance of the too-small capacitors, and the leakage inductance of the MOTs. The pulsating voltage that dips to zero 120 times a second, and the ballasting, both help the spark gap to quench, to the extent that this circuit can just about drive a static gap, especially if it's got forced air quenching from a shop vac or similar.

The other way, that was popularised by me with the Tesla-2, uses a multiplier with large capacitor and heavy filtering that produces a steady DC voltage. I then use a choke and de-Qing diode in series with the DC output. If it weren't for these, the large filter caps would discharge through the spark gap and blow everything. This requires a rotary spark gap or triggered gap: it's unstable with a static spark gap. It's also more expensive than Greg Hunter's system, because you need more and bigger capacitors. But it gives true DC resonant charging. In my Tesla-2 I started with a single MOT and ended up charging the tank capacitor to nearly 20kV.

If you put chokes on the output of a Greg Hunter style supply, that is like a cross between the two methods. I'm not sure what would happen, but I wouldn't be too surprised if it improved it like a previous poster said. You might be as well to just experiment with whatever components you have, and see what you can make that works well.

Re: What to do now... (partially completed Tesla coil)
Marko, Wed Mar 21 2007, 01:35PM

I apologize, I got confused with the upper schematic but now I figure you don't use any filter caps exactly as with greg's schematic.

Level shifter alone can't actually cause power arcing because it's 'ballasted' by secondary inductance of MOT's. There are 100W resistors in series with output wich are seemingly there just to protect the level shifter diodes when primary voltage rings under zero.

So, the circuit is more or less fine if you are happy with 100..200W of dissipated power in the resistors.


As steve already said, level shifter outputs only halfwave rectified voltage and thus I'm not sure if it is perfect for TC supply, but it is simple and cheap!

I imagine you could have trouble with synchronizing an ARSG to it, and maybe it will give somewhat less streamer growth because output is 'modulated' at 50/60Hz.

Re: What to do now... (partially completed Tesla coil)
sparky, Wed Mar 21 2007, 05:49PM



check out roger smiths' DC coil... might be worth the view :)

Re: What to do now... (partially completed Tesla coil)
Sam, Wed Mar 21 2007, 07:21PM

I have been working...

Got some cool stuff from school and built it all in class




Thanks for all Your help guys :D

And another Question: what kind of motors should be used for the RSG motor? I have one here, its 120AC but not variable, just on or off. I was told its only variable when changing the frequency.

Re: What to do now... (partially completed Tesla coil)
Steve Ward, Wed Mar 21 2007, 08:03PM

What is the plastic you are using for the disk? Might want to be careful about the hot spark gap electrodes and melting of the plastic. The electrodes will get as hot as a soldering iron (if not hotter), so keep this in mind. Most people use fiberglass/epoxy composites (garolite). G-10 is a really popular material for RSG uses. In any case, put a shield around your gap so you dont have accidental projectiles flying about the room if that plastic disk gets a little soft and lets go of the electrodes .

Re: What to do now... (partially completed Tesla coil)
Marko, Wed Mar 21 2007, 08:15PM

And another Question: what kind of motors should be used for the RSG motor? I have one here, its 120AC but not variable, just on or off. I was told its only variable when changing the frequency.

Universal motors are often picked for ASRG's because they are easily variable by most ordinary dimmer, and usually have very high max RPM. Such are motors from drills, angle grinders, vacuum cleaners and etc.

Guessing you have an asynchronous AC motor, it is pretty slow (3000..3600 rpm max) and you can't regulate it without a frequency converter. Such motors are, ofcourse, far more rugged than universals but I guess it just isn't needed in TC duty with short runs.


Regarding your setup using halfwave rectified input, I imagine your firing rate is going to be wierd.. but probably not much of a problem since it's still a DC coil.

Re: What to do now... (partially completed Tesla coil)
Sam, Wed Mar 21 2007, 09:35PM

I could have large aluminium bits with a tapped center to act kind of like a heat sink...?

maybe like 1" dia.

Edit: some pics

I'm getting sick of pop, but at least its not bear...



8 more bottles tonight, gets me to about 16nF

Re: What to do now... (partially completed Tesla coil)
Steve Conner, Thu Mar 22 2007, 10:21AM

Yea, like Steve Ward said, if that rotor is made of Lexan, you could be in for a nasty surprise.

Re: What to do now... (partially completed Tesla coil)
Marko, Thu Mar 22 2007, 11:52AM

Yes, and definitely be careful about your gap. You don't want it flying apart!

I would use some kind of good fibre impregnated plastic wich is resistant to heat and abuse.

in lack of imagination, I think that even few stacked dud PCB's would work! You can even leave the copper in an outside 'ring' to act as a conductor!

Re: What to do now... (partially completed Tesla coil)
Sam, Thu Mar 22 2007, 11:54AM

Im stuped. I cant really get ahold of any other material. I'm trying to think of a way to disipate the heat, like using larger bolts or...then if they let get its not very good. If I put two nuts to hold it in place on both sides...

any other ideas?

Re: What to do now... (partially completed Tesla coil)
Michael W., Thu Mar 22 2007, 03:10PM

How much does a jones soda go for? With the amount your buying you probably could have bought half an MMC...

Re: What to do now... (partially completed Tesla coil)
Hazmatt_(The Underdog), Thu Mar 22 2007, 06:45PM

This is digging up a prehistoric thread, but here it goes:

You don't need any special tools to build my gap either with the exception of a drill press. I use set screws because they're almost the same mass on both sides, but you could use threaded rod too. It uses a sewing machine motor and arbor from Grainger. The rest is up to you.

Matt

Re: What to do now... (partially completed Tesla coil)
Sam, Thu Mar 22 2007, 08:52PM

I got some welding rods today, cut them into eight 1.75" bits. not sure how to mount them, maybe set screws? still havn't figured out the whole hear thing.

here is my next problem, I have been here and there and I cant figure out where to but the outer elecrodes, and how many...

I think in the link to the thread above its in the same configuration as the first pic below, and I see 4 electrodes.
should I go this way?

here is what I was thinking


EDIT, about the pop, its $1.50 CAN per, (hehe) can. But I like pop, and these caps You drink out of before You use, not like "perfessional" caps.

plus, they dont sell good caps at the 7-11 down the street.

Re: What to do now... (partially completed Tesla coil)
Electroholic, Thu Mar 22 2007, 10:47PM

for the design on the top left, you can just use a ring shaped conductor on the rotor instead of that U shaped connection. and move the hot stuff to the front, increase insulation distance.

as for the design on the right, i think TDU has a gap like that.

and the number of electrodes depends on what you wnat to build
sync or not, and rpm of the motor, bps....

Re: What to do now... (partially completed Tesla coil)
Sam, Thu Mar 22 2007, 11:37PM

maybe I shoule set it up so I can change it from the one on the left and the one on the right. the I have a huge range of frequency. plus the variac to controll RPM.

as for tonight, finishing 8 more bottle caps.

BTW spending nearly $30 on pop so far, I dont feel to bad about wasting money, i just have to start making my friends and family drink it too.

Re: What to do now... (partially completed Tesla coil)
Michael W., Fri Mar 23 2007, 12:13AM

Could you go to a recycling depot and buy 50 bottles for about $2.50?

Re: What to do now... (partially completed Tesla coil)
Sam, Fri Mar 23 2007, 01:21AM

Im kind f OCD, they all have to be the same kind of bottle...

Re: What to do now... (partially completed Tesla coil)
sparky, Fri Mar 23 2007, 01:38AM

Corona beer bottles, large tall clear glass wine bottles will work too. I think if memory serves me well a 700mL wine bottle could be 3-5 nF - I have some 1.5 L clear wine bottles that come in at 10nF each!!!

4 large 1.5L wine bottles - clear glass ones will be almost 40nF worth of capacitance , 1L maybe ~6-7nF guessing - 700mL maybe 3-5nF.

Re: What to do now... (partially completed Tesla coil)
Sam, Fri Mar 23 2007, 04:28AM

maybeI should get into the wine...

Re: What to do now... (partially completed Tesla coil)
Coronafix, Fri Mar 23 2007, 05:10AM


LOL... I'm kind of like that too!
It's not just scientific, there is a large artistic component to coil building.

Re: What to do now... (partially completed Tesla coil)
sparky, Fri Mar 23 2007, 07:25AM

no kidding... wine could enhance the whole tesla coiling experience too LOL

Re: What to do now... (partially completed Tesla coil)
Sam, Fri Mar 23 2007, 08:11PM

(in drunk tone) OHHHHHHHH PRETTY!!

so I scaped my crappy plasic disk the fun way(scrating it whileit was on a drill)

Here do get this new fanged "heat resistant" plastic...?

Re: What to do now... (partially completed Tesla coil)
Michael W., Sat Mar 24 2007, 12:13AM

Not sure the going value of it but heres the type of stuff your looking for...

Re: What to do now... (partially completed Tesla coil)
Sam, Sat Mar 24 2007, 04:30AM

PHENOLIC, I'll spend some time trying to say it aloud.

Once I get some cash in my new bank acount, then I get some cash in paypal, then I BUY stuff...

Re: What to do now... (partially completed Tesla coil)
Michael W., Sat Mar 24 2007, 05:50AM

You should look around more, I'm not sure if those ebay auctions give an accurate idea of what the material is actually worth...