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Small Tesla coil power supply

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Arcstarter

Fri Apr 01 2011, 04:24AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

As off topic as it may be, if you have a scope i would really suggest Steve Ward's class E sstc. Class E switching is rather simple to understand.

I have gotten 7 inch sparks with a single IRFP460, and you could expect longer than that with an IGBT capable of higher voltage.

If you don't have a scope you can still pull off good efficiency, just play with the shunt capacitance until you get the best efficiency you can get at reduced voltage. A variable cap would be nice, and could be fairly small by using it in parallel with the main shunt caps.

Ash Small

Fri Apr 01 2011, 06:23AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

LittleVenture wrote ...

when i click the link i go to the web site with all of the computer types and click on windows icon and then a page comes up with a lot of blue links ? what do i download ?

I downloaded this one (for MS Windows)

I've tried it and it views the PCB file and the circuit diagram.

Josh

Fri Apr 01 2011, 06:25AM

Registered Member #938 Joined: Sat Aug 04 2007, 05:39AM
Location: Honokaa,HI,USA
Posts: 65

Thank you for showing that schematic for the SSTC.
I've been looking for something simplistic and should be a good first SSTC to build

ZakWolf

Fri Apr 01 2011, 02:30PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

does the input have to be exactly 25.2v at 2 amps ? i think i might build it thanks :)

James

Fri Apr 01 2011, 06:41PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

LittleVenture wrote ...

does the input have to be exactly 25.2v at 2 amps ? i think i might build it thanks :)

No, it looks like that's just the rating of the transformer he happened to use. The circuit should work over a reasonably wide range of input voltage, but I would aim for a transformer that puts out somewhere between 16-22VAC.

Arcstarter

Fri Apr 01 2011, 10:21PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

LittleVenture wrote ...

does the input have to be exactly 25.2v at 2 amps ? i think i might build it thanks :)

Well, what transformers do you have? The transformer for the driver power can be very low power, and 12vac and higher (up to around 30vac) would work with a 12v regulator, as the voltage after the rectifier will be nearly 17v, and most 12v regulators are pretty low drop-out so you only need maybe 2v headroom.

The 2 diodes and 2 caps just make a full-wave voltage doubler. It is not needed if you have a transformer with high enough voltage, just rectify and smooth. The power the class E sstc will draw depends on primary turns, and on time on the interrupter, it could draw as little as 1 watt if you had low on time and low breakrate, and it could draw a couple hundred watts or more with a high on time. So, be sure you pick the right main power supply for the duty cycle you'd like to be able to run. With a 50w transformer like Steve's you would have a rather limited duty cycle, but with the large 80v transformer i used, i could run CW all day.

For the record, i just happened to be remaking that class E coil, this time actually making a circuit board for it. If you want to know what parts i use or whatever you can PM me. The parts, values, and schematics i used differ greatly from what Steve's coil used, but i still use a typical gate driver IC and 555 which both serve the same purpose.

ZakWolf

Fri Apr 01 2011, 10:40PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

so it was looking at the schematic and i saw somethings i wasn't sure about.

1.) D3,D4 say 100v 4a min, what about speed? any that are recommended
2.) what does B+ mean on some of the outputs? ex. the output of the primary coil.
3.) is C6 a variable capacitor? what is the value for R5 ?
4.) could someone show an example of how the antenna is set up.

Thanks so much i really look forward to building this, Arcstarter said "you could expect longer than that with an IGBT capable of higher voltage." i have absolutely no experience IGBT's what would be a suitable IGBT for this circuit i would really like to maximize the output.

Dr. ISOTOP

Sat Apr 02 2011, 01:31AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

D3, D4 simply double the voltage from the AC transformer; they don't have to be fast.
B+ is the bridge power supply; its an input.
C6 is the tank capacitor, with a calculated value.
The coil really needs a MOSFET to work properly at the frequencies everyone uses; IGBT's just can't switch that quickly.

ZakWolf

Sat Apr 02 2011, 01:41AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

is C6 gonna be a small cap,like .01 of .1 uf, could i just use a variable cap an tune it to what works best.

ZakWolf

Sat Apr 02 2011, 09:02AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

What about Steve's sstc-5 mini? Is the output better than Class-E driver or would it be better to build this simpler one and make the other in the future. Here is the finished schematic for sstc-5

And here is the class E

Does the sstc mini require debugging with a scope? I am trying to get the best output for the least complexity.

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