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Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
I set this up in about a day. I based my circuit on waverider's work. My coil resonates at about 4mhz and will produce about 1.5" of corona with 170vdc input. I am currently running from an isolation transformer so I can scope my gate and drain. I intend to make a simple wooden base for this coil and set it on my desk as a demo unit.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Cool! What do you use as the source for the oscillation? 4MHz crystal, VCO, external signal generator, or self-oscillating feedback from the TC resonator?
-Richie,
PS. You might need a heatsink on the bridge rectifier if you are running a few hundred watts of power from a 110V mains line!
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi,
Richie - if you looked at the video, it looks like he's using a sigle turn feedback winding under the coil - still resulting in 60V p-p at the gate. :O
cjk2 - how much power does the coil draw to produce that kind of spark? It's proably the largest spark I've seen so far from single-mosfet-and-feedback-winding coils. Also if you blew no mosfets while achieving this, I'm very impressed.
Still what I'm most surprised with is how are you getting away with primary made of such tiny wire. I would expect it to start smoking after 30s on that video.
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Cool! What do you use as the source for the oscillation? 4MHz crystal, VCO, external signal generator, or self-oscillating feedback from the TC resonator?
-Richie,
PS. You might need a heatsink on the bridge rectifier if you are running a few hundred watts of power from a 110V mains line!
I am using a flattened single turn feedback winding. I actually have not had any problems with the rectifier overheating. I estimate it is dissipating about 3W and it seems to be ok for short runs. I do have the space to add an aluminum fin to it if needed.
Richie - if you looked at the video, it looks like he's using a sigle turn feedback winding under the coil - still resulting in 60V p-p at the gate. :O
cjk2 - how much power does the coil draw to produce that kind of spark? It's proably the largest spark I've seen so far from single-mosfet-and-feedback-winding coils. Also if you blew no mosfets while achieving this, I'm very impressed.
Still what I'm most surprised with is how are you getting away with primary made of such tiny wire. I would expect it to start smoking after 30s on that video.
I destroyed the gate oxide on one FET during testing due to using a full turn for my feedback winding and causing a few hundred volts to appear on its gate. It looks like I am drawing about 2A at 120V RMS which implies 240W. I have no idea if this is at all accurate as power factor likely has an effect here. My primary does get hot and will be replaced with 18AWG wire when I get around to it. Still, with an average of 2A through it, the 23AWG only gets hot during extended runs.
Registered Member #3093
Joined: Mon Aug 09 2010, 11:40PM
Location:
Posts: 68
Crunchy Frog wrote ...
Very impressive for such a simple design! How does it self-start?
Looks to me like a pulse goes through the primary and resonant cap, which triggers the gate, and it keeps on cycling. also, what is the lowest voltage that you can achieve a breakout?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Crunchy Frog wrote ...
Very impressive for such a simple design! How does it self-start?
Looks like it starts by biasing the MOSFET on a little so it works as a linear amplifier. The circuit will start in Class A and ring its way up through B, C, D and E.
This is a nice little circuit, it's too bad we can't do it here in 230V land. :-<
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Class-E Tesla Coil working with direct mains power
