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.

Finished

 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.

Barnes and Noble Mini Maker Faire - Joliet, Illinois

Coming up this weekend at Barnes and Nobles Bookstores, nationwide, are Mini-Maker Faire's.   Friday, Saturday and Sunday (11/6-11/8)

While I thought I didn't make the cut since I didn't hear anything by Oct. 9th... I got the call last week asking if I could exhibit on Saturday and Sunday at the Barnes and Noble in Joliet, IL.  Over the weekend I found they also had an open spot for Friday.  So, SURPRISE!!!, I'll be there all weekend (I said yes to all days - of course, see below for the Meet the Maker exhibit schedule).

Friday 11/6 (Meet the Maker)

• 5pm
• 7pm

Saturday 11/7 (Meet the Maker)

• 1pm
• 5pm
• 7pm

Sunday 11/8  (Meet the Maker)

• 1pm
• 5pm

Below is a brief summary of my entry for the Barnes and Noble Mini Maker Faire:

My Project Entry was my "Musical Lightning": A tabletop musical Tesla Coil. The electrical arcs produced by the coil are modulated to enable them to produce musical notes without speakers!
The first Tesla Coil that I built, about 4 years ago, was motivated by wanting to show my daughter a "Lightning Machine". Ever since building that first coil I've wanted to build a musical Tesla Coil. After a number of failed attempts at building a solid state Tesla Coil I shelved the project with the plan to go back after I've learned a bit more.  Finally, after building a home brew CNC Machine and 3D Printer I decided to go back and try again - even though I didn't feel I really understood enough yet. I knew it would be a struggle but I registered for the Chicago Southland Maker Faire knowing the deadline would motivate me to learn what I needed to know to build it. After lots of research and experimentation, both of which continue, I learned even more than I hoped I would - about electronics, music theory, micro-controllers and programming.

I put off repairing my coil when I didn't hear anything by Oct 9th and switched to other projects - mainly my daughters Halloween costume (we like to MAKE our costumes in this house), a File Shelving project, and online coursework on micro-controllers, C programming and electronics.

After working hard for the week leading up to the faire and getting very little sleep - I made it for Saturday and Sunday (to many issues Friday - trying to get everything to work).
 
Here are a few pics of the faire:

My Table

My exhibit was received well and I had the opportunity to talk to a lot of people in education, other Maker's, people in different tech fields, and my favorite - kids who love seeing tech stuff.

 

Lego's and Little Bits

 I missed getting pictures of other tables - forgot about taking them until Sunday near the end of the Faire.

There were a good number of last minute challenges that I faced for this Maker Faire:

• First was building the Geek Groups Audio Modulation board for SSTC - only to find after all my work that the software libraries needed to use it only worked on the Mapleleaf Board - based off Arduino but different pinout and library would need to be ported to the Arduino.
• Biggest was my exhibit coil failing 2 days before the Faire and I was unable to repair it.
• Old Faithful - my backup, battery operated, coil that always works - my Mazzilli Flyback driver died.  After waking up extra early on Friday I made a brand new Mazzilli driver on perf board with point to point wiring (took me a few hours) that died also.

Saturday night I again stayed up late and built a basic 555 based flyback driver and added audio modulation - just to have a nice demo piece - finally I had something that worked (and it continued to on Sunday).

For future Maker Faire's / exhibits I need to have better backup exhibits (less  fragile, in good solid enclosures).

This Maker Faire was great and I really hope Barnes and Noble continues their support of the movement.

Project SSTC1 update

Continuing work on improving my Musical SSTC.  Here is a newer video of the coil with an actual top load:

I've also added a fiber optic connection for the interrupter to reduce EMF interference - which solves a number of issues in testing.  Prior to adding the fiber optic connection - feeding interrupter signals to the coil using an Arduino controlled adjustable interrupter with a 16x2 LCD display (to enable me to see the frequency and duty cycle) did not work - as soon as the coil was powered interference would scramble the display.  I did try shielding the Arduino etc. but the direct wired connection to the MOSFET controllers carried too much interference back to the Arduino.

I 'have also done some experiments involving input to the MOSFET drivers - the UCC37321/2
chip enable pins are pulled HIGH (internally, according to the datasheet) so I was/am confused as to how to use them.  Other people have used the enable pin to turn on the enable pins (providing a HIGH - 5v logic signal).  Since the datasheet indicates that they are normally pulled HIGH I thought that possibly using a totem pole configuration (NPN and PNP transistors tied together) could keep the enable pin pulled LOW (off) when there was no HIGH (on) signal.  I tested this and it did not seem to change performance except that the coupling between the primary and secondary coils increased and the current levels through the primary coil increased to the level that the wires heated up and melted the polypropylene insulation I had between the primary and secondary coils.

As you can see, the polypropylene was effectively cut in half by the wire on the primary coil.

I have also built the audio modulation board from The Geek Group, with a few changes (which I will post soon).  I decided to put this together myself after I found that The Geek Group no longer had kits in stocks. In addition, the schematics they put up are missing the actual interface between the interrupter board and the driver board for the primary coil (not that hard to figure out, but is missing - I will also post this when I'm able).

A little side note - I'm trying to collect materials to build a DRSSTC, which requires high voltage/high current capacitors for the primary coil.  When I can find these I'll be able to build a coil of the same size that has a much greater output (more impressive display for the same size coil).

Project Signal Generator - ICL8038

The first chip I've had success in testing is the ICL8038 Precision Waveform Generator  (I have also tested the AD9850 DDS Synthesizer - but I'll post that separately).  This chip is fairly inexpensive off of eBay (just a couple of dollars a chip).  The ICL8030 only needs a few external components (resistors, potentiometer's and capacitors) to generate a sine, triangle or square wave.

Vary stable chip (I haven't accidentally fried even 1 of them).  I have not been able to test the frequency sweep function due to some issues with my bench PSU.  Using the test circuits presented in the datasheet I was able to produce sine, triangle and square waves.

Sine wave

Triangle Wave

Square wave

Datasheet Test Circuit

Formula for determining resistor and capacitor  values

Frequency range is ultimately determined by the capacitor value, so it would be necessary to be able to change  values for different ranges.  You are able to sweep through frequencies by varying input voltages across pins 7 and 8.

Current ranges at pins 4 and 5 are set by the resistor values Ra and Rb and need to fall within the range of 0.01mA to 1mA (so resistor values depend on supply voltage - I'm using 12v so my range is 2.6k to 260k).

Project SSTC1 - I've got Sound!!!

After reviewing datasheets, yet again, for the MOSFET drivers I'm using (TI's UCC37321/2) and re-reading some sources on interrupters for SSTCs and methods of audio modulation with SSTC's I finally had that Ah-Ha moment.

I've made Plasma Speakers / Singing Arc's just after building my first Spark Gap Tesla Coils.  These, generally took an audio signal (normally fed to a speaker or earphones) and put it through the driver for a Television Flyback Transformer.  The only method I used involved amplitude modulation (AM-like radio) and SSTC audio drivers seem more focused on frequency and pulse width modulation.  Correction, after re-reading datasheets for the LM555 timer chip I learned that pin 5 actually modulates the frequency (some descriptions I had read stated, incorrectly, that pin 5 adjusted the output amplitude.  I finally understood how you combine frequency and pulse width modulation (it's actually pretty simple and involves pretty simple calculations).

I'll get more into the difference later, for now here's the video: