Boxing an SSTC

Boxing an SSTC

So After the success of playing with the SSTC, I decided to make a nice job of boxing it..

Using 5mm copper tube I wound a primary(5 T), and a Strike rail. Each turn is insulated from the next by a layer of varnish.

The gap around the rim is intentional to let a flow of air through the box. If I find a suitable set of brass fretwork or similar, I will cover this gap.

The single knob on a stick, is the feedback for the self resonant driver.

I have changed the circuit for the interrupter. I now use an LM339 PWM circuit to give me a variable on time and frequency, the circuit diagram is here

I'm not happy about the aluminium foil topload, and the pair of plastic control knobs for the frequency and duration controls, but these will have to stay until I find better looking replacements.

The Electronics is rather a tight fit into the box, All of the half bridge is fixed into the lid, (note heatsink) with the GDT. The HV stuff is on the LHS of the box and the driver is on the RHS.

Running the coil, does not quite give the same size of sparks that it used to in the bread-boarded version. This is probably due to the extra turn on the primsry (for reliability) and the looser coupling due to the primary beign spread over 40mm rather than 10mm.

A better view inside the base. Somewhere at the bottom is the fan..

I had HUGE problems with the driver, this close to the primary coil the analogue PWM circuit for the modulation was suffering from EMP, every time the coil struck the pulse would turn off the PWM and the on-time would end short, then on the next pulse it would let out one long burst and blow all the sillicon.

The driver is now contained in an aluminium box, to protect against RF and the circuit has decoupling caps EVERYWHERE. The problem has not gone away completly, but the pulse width control is at least usable now.

Running...