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Help needed with "Dual voltage PSU" for Singing Tesla Coil

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Ash Small

Wed Jan 16 2013, 05:33PM

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

I'd try car headlight bulbs, 12V ones, maybe connect two in series for each circuit, to start with, and see what readings you get. (unless you can get some 24V truck headlight bulbs.

What is the rated power output of the two circuits? 12V headlight bulbs (here) are normally either ~60W or 100W. You may need to parallel more series pairs to load it sufficiently, but I wouldn't expect the logic circuit to draw a lot of current.

EDIT: I suspect that if you short the output of the 37V output, the other output will be nearer the voltage you require, but I'm not sure if it would be advisable to do that. You might damage something, so you probably shouldn't try it.

dingo27

Wed Jan 16 2013, 05:36PM

Registered Member #890 Joined: Tue Jul 10 2007, 10:06PM
Location: Slovakia
Posts: 180

Can i suggest simple measuring the voltage of naked transformer, or are you certainly sure you have right windings?

Maybe just use one output of transformer and use voltage regulator for 16V rail.

Fiddy

Tue Jan 29 2013, 09:16PM

Registered Member #8817 Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110

I built this kit too!

Im using a off the shelf 24VDC power supply @ 3.75A and it works a treat, The only extra thing i had to do was run a earth cable from the wall plug to the PCB.

my connections go like this:

Mains ground (connected straight to the secondary coil) RF Ground)

24VDC+ (Bridge level DC)

24VDC+ (Logic Level DC)

Power Supply Ground. (Circuit Ground)

The logic level DC goes straight into a 7812 voltage regulator, i haven't measure the current on the logic side or heat in the regulator as its going to be burning up the extra 12V's going in, but the fact you only need 24VDC makes it a lot simpler to use.

I also noticed a arc length increase by removing the secondary coil connection from that solder pad and putting it in the blue terminal connector with the mains ground.

Also added a 40x40x10mm fan for the heatsink of the IRFP450 and added another 22pF 3kV cap across the the Drain and source of the IRFP450 as said in the kit, experiment with the drain, source capacitance.

My breakout point i machined :D
Plasmaarcs Zps2267d779

Dark Horse

Thu Jan 31 2013, 02:43AM

Registered Member #2302 Joined: Sun Aug 16 2009, 04:38PM
Location: Seattle, Washington
Posts: 5

Very nice work! I love the breakout. It looks similar to the one on the prototype coil from the seller video, but nicer. My breakout poit was much more simple, but I plpan on making a better one soon.

On the RF ground wire, I am going to have to try that. It sounds like a good idea; and easy to take apart.

I did finally give up on making the original power supply work, as specified. I simply wired only one bridge across the whole secondary of the transformer, giving me 37V open circuit. I tapped into this rail with a lm317 adjustable regulator circuit, set to deliver 18V to the board. I reasoned that the regulator on the board could handle 37V, under ideal conditions and therefore would probably be ok with only the single voltage, but the gate drivers tap thier power before the on-board 12V regulator, so I wanted to play it safe. It works great.

I really like this little coil. Next, I need to house it complete with it's power supply. I would like it to have a "steam punk-ish" look.

Thanks so much. This is a great community

Mads Barnkob

Thu Jan 31 2013, 07:13AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Fiddy wrote ...

My breakout point i machined :D
Plasmaarcs Zps2267d779

This might not be a problem at these low power levels, but a toroid and for that matter the break outpoint should only have 1 sharp edge, where the break out is supposed to be. All those sharp edges you have along the rod will contribute to corona losses and lower the spark length of your coil.

Fiddy

Thu Jan 31 2013, 09:44PM

Registered Member #8817 Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110

Dark Horse wrote ...

Very nice work! I love the breakout. It looks similar to the one on the prototype coil from the seller video, but nicer. My breakout point was much more simple, but I plan on making a better one soon.

On the RF ground wire, I am going to have to try that. It sounds like a good idea; and easy to take apart.

I did finally give up on making the original power supply work, as specified. I simply wired only one bridge across the whole secondary of the transformer, giving me 37V open circuit. I tapped into this rail with a lm317 adjustable regulator circuit, set to deliver 18V to the board. I reasoned that the regulator on the board could handle 37V, under ideal conditions and therefore would probably be ok with only the single voltage, but the gate drivers tap thier power before the on-board 12V regulator, so I wanted to play it safe. It works great.

I really like this little coil. Next, I need to house it complete with it's power supply. I would like it to have a "steam punk-ish" look.

Thats fair enough, i haven't driven the bridge level at any higher than 28VDC, but i imagine you would get bigger arcs if that voltage was higher.

I noticed that the gate drivers tap off the logic level before the regulator, it hasn't been a problem yet for me.

The solder pad for the RF ground is annoying as! if you want to work on the PCB you have to desolder it each time, hence why i put it in the mains ground terminal and as a result i got a bigger arc too!

Mads Barnkob wrote ...

This might not be a problem at these low power levels, but a toroid and for that matter the break outpoint should only have 1 sharp edge, where the break out is supposed to be. All those sharp edges you have along the rod will contribute to corona losses and lower the spark length of your coil.

I know what you mean, i haven't seen it breakout from one of the machined steps yet and as you said it hasn't been a problem at this power, im getting a decent sized arc off the top with this breakout point too :)

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