Tuesday, December 15, 2015

Project SSTC2 - Small tabletop coil

I've been at work on this coil for a while now (taking it slow and careful in an effort to limit my release of magic blue smoke as much as possible).  This coil design I credit to Gao Guangyan and his SSTC2 (Small Tabletop Coil) project - which is presented as a complete tutorial on SSTC design, very detailed and well written.  For anyone wanting to build an Solid State Tesla Coil - I encourage you to check out his site (besides the great information he has great photos and video of his coils in action).

I began this project just after the Barnes and Noble Mini Maker Faire, after my first SSTC failed to perform at a second Maker Faire (I had issues not long before at the Chicago Southland Mini Maker Faire). These failures motivated me to make a more robust and easier to transport coil for demonstrations and education.

Current project goals include:
  • solid modular design 
  • modules cleanly attach together (well marked and secure connections)
  • modular components well secured within case (secure but still accessible for repair/trouble shooting) 
  • Indicators and/or test points for each module accessible for inspection/troubleshooting
  • sturdy and clean looking case 
    • Grounded metal case (to shield from EMF generated by coil)
  • Better grounding of  HV side with bypass caps on AC supply to prevent/reduce interference
  • TVS Diodes across MOSFET's/IGBT's to clamp voltage at gates and prevent overloading gates
My first step, as it usually is with my Tesla Coils, is winding the secondary coil.  Not having and 34AWG magnet wire on hand I had to order it and wait for it to arrive (thankfully the company I order from is in Illinois, like me, and their order processing plus shipping time means I only need to wait 2-3 work days before it arrives).
Secondary PVC form cut down and winding just begun

Secondary after stopping to rest (slow going so far)
 This 34AWG wire is by far the thinnest wire I've used so far to wind a secondary (with the exception of a super mini 1.5inch secondary that I made but haven't used yet).  Winding at this point was very slow due to the wire spool rolling away as well as trying to keep winding's lined up (if they overlap I have to unwind and rewind them).
Finally keeping the wire spool stationary
 I finally did the smart thing and secured the wire spool, to speed up my coil winding.
 For such a small coil, it took a long time to wind (just about 3 hours - not including rest times).

Power and Control Electronics

Half Bridge

Half Bridge

Gate Drive Transformer

Power Supply for Low Voltage Side (5v and 12v)

Power Supply for Low Voltage Side (5v and 12v)

Bottom of etched pcb for Low Voltage Side PSU
 The pcb for the low voltage PSU - etching removed a portion of the trace on the left (bottom) side - repaired with solder bridge.
Controller Board (point to point soldering on perf board)

Feedback Transformer coil
I'm trying out Gao Guangyan's feedback (essentially using a step down transformer) instead of an external antenna.

My coil is not up and running yet (I'm taking my time and making certain that I test each portion before I connect sections together - I've fried enough silicon by rushing things so far).  I've gotten a bit further - so I'll be posting more updates to this project very soon.