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Class E SSTC

Project description

This very small SSTC was built along with my SSTC 1 – I don’t clearly remember which came first. It’s power section was designed to operate as a class E amplifier (though I’m not sure if it was ever tuned too well!). I’ll better not waste too much words onto explaining it into details, when Mr. Richie Burnett did it so well in his famous experiment. This is one of oldest Tesla coils I ever built. I couldn’t find any complete schematics of the circuit, and am somewhat dubious that they even ever existed! However, I managed to find the original 4hv thread and a crude block diagram showing the outline of the circuit:

The class E Tesla coil "plan"

The class E Tesla coil “plan”

The whole coil is pretty obviously hacked together from other people’s work –  I’m pretty certain it attempts to merge Steve Conner’s original PLL driver, Richie Burnett’s theory and Steve Ward’s implementation, plus the buck-boost supply voltage regulator for which I have no idea why on earth I used it. There are also some now-obvious blunders such as failing to realize the 90-degree phase shift that XOR phase detector exhibits in locked state, and the fact that the heat sink used was way too tiny to dissipate the required power. And regardless of all this, the coil worked, albeit not too efficiently, but it sparked and I had tons of fun with it!

On the other hand, I feel much more proud when I look at the construction pictures:

The test setup

The test setup

I wish I had time today to build circuits on perfboard as dense and pretty as this!

I wish I had time today to build circuits on the “perfboard” as dense and pretty as this!

The underside of the PCB

The underside of the PCB

The whole coil

The whole coil

And it made some 10cm+ sparks!

And it made some 10cm+ sparks!

This long exposure spark picture turned out unexpectedly nice looking

This long exposure spark picture turned out unexpectedly nice looking

And I even used it to demonstrate wireless power back then!

And I even used it to demonstrate wireless power back then!

I’ve even found a video of the coil in operation – taken with early 2000’s era digital camera, but better than nothing I guess!

Conclusion

While the coil worked well for the short bursts of power, it tended to overheat quickly in continuous runs. One day I decided to see whether I could see a larger spark from this little secondary, and wired it up to a powerful half bridge driver. I got carried away, resulting in the secondary flashing over to the primary and turning into a fireball. Despite I had a spare secondary, I never repaired the coil, as I was quite satisfied with the amount of fun I had with it and went on to other projects. However the coil is still sitting on my shelf, waiting for the day I might become nostalgic and put it back into action!

The result of a greedy experiment

The result of a greedy experiment

Links and references

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