Thursday, July 30, 2015

Project SSTC1 - Reviving my Tesla Coils and taking them further Southland Mini Maker Faire

I first saw instructions on building a Tesla Coil back in the early 1980's, in either Popular Science or Popular Electronics magazine, while at science camp over summer break during elementary school.  The design used a multiple gap spark gap (copper tubes inside a cylinder - which I now know is a Richard Quick Spark Gap) and capacitors made out of window panes and aluminum foil.  It looked Super Cool to me but the concepts were beyond my understanding and the idea of building it was a bit scary (I couldn't imagine who I could ask for help or even just address my questions),

The picture stuck in my mind - I just wanted to see one up close and in person. While on a road trip up the East Coast (early 90's) I saw a sign (it was somewhere either near or in Boston, MA) where they had some big coils that they used for a lightning display.  I remember going by the museum to find that the exhibit was closed.  Tesla Coils and man made lightning retreated in my mind.

Fast forward about 20 years - While working with my daughter on some basic electronics projects - make a simple electric motor using a magnet, magnet wire, a battery, paper clips and soda straws I thought why not make sparks!!!

I was really thinking about static electricity (I loved being able to shuffle across the carpet so I could reach out my finger to ZAP my brother or sister - they did the same to me of course).  So, I thought why not make a Van De Graff Generator.

After building a small one, that did work, just not very well I wanted a more impressive display.   A Tesla Coil seemed to be the answer, so I began my research (thinking it would only take a few weeks to build it). Well, it took a bit longer - more like 4 months research, trial and error, failures and finally success.


During my process of building the coil I was showing videos of Tesla Coils (on YouTube.com) to my daughter and we came across Tesla Coils that could play music.   That just seemed so amazing, I looked into how people were able to do it.  It appeared fairly complicated but I found something I might be able to do - an audio modulated Plasma Arc (or Plasma Speaker).  I did try building a basic Solid State Tesla Coil (Steve Wards Mini SSTC), but I just kept blowing MOSFET's and they were expensive and I had to get them by mail order.  So, I put the project on hold until I had more knowledge.

Now, I'm finally going for it and I thought exhibiting at the Southland Mini Maker Faire would be great motivation to finish it .  I re-built my half H-Bridge driver board (using my CNC to mill the board).  I connected everything up and it WORKED.



Well, for a few minutes at least and then a POP and some smoke.  The MOSFET's were quite hot and looking at my new board I saw...


Missing trace
A trace shorted and vaporized.  After desoldering all the components I determined that both MOSFET's were dead but all other components were fine.

I re-made the board on perfboard and added big heat sinks to the MOSFET's and a fan to help keep then cool.  No full test yet, ramping power up slower to make sure everything is OK.
New Half H-Bridge Board


Cut copper pads from around component connections to minimize arcing.