The Dirty DRSSTC, part 2
I modified the PLL driver from the DW-SSTC to include an interrupter. I used a 4013 D-type flip-flop to synchronise the interrupt signal to the coil's resonant frequency. This means that the end of a burst will be "snapped" to the nearest primary current zero.
NOTE on June 3 2006: There has recently been some controversy on 4hv.org over whether this circuit is actually any good as a DRSSTC driver. Another forum member built it and found it to do some weird things that I had noticed too, but ignored because I had no idea what was going on at the time. In the light of this, I must admit that I'm not sure how well it works now, and I think if you're looking for a DRSSTC driver, it's better to try one of Steve Ward's circuits instead. Steve's driver has been built by dozens of people now, so it has a good track record.
I built this circuit into a metal shielding box, with a remote interrupter box connected by a screened cable. I then hooked it all to the Tesla-2 and the 300V DC power supply. It produced about 20" arcs when run at about 1 bps.
When fiddling with the tuning, I found several interesting things:
At first I used secondary base current feedback but I found it very unstable. Loading the secondary with ground arcs caused a large phase shift between primary and secondary current. I saw it shift up to 180'.
I tried primary feedback (using a CT cascade) and it worked a lot better. But I noticed that if I tuned the PLL for zero current switching (V and I exactly in phase) this was not the same setting that gave maximum current magnitude. By adding more inductance to the primary (in the pictures you can see odds and ends of wire wrapped round tea mugs) I was able to make the two points coincide. I assume this means the coil is in tune.
Previous page
Next- the great explosion
Return to Tesla page
