Mini Tesla Coil!

Ok so part of the reason why I’ve been procrastinating on the spectrum analyzer is cause of issues with free Eagle being unable to lay out a board large enough for the entire device, and that I’m waiting for supplies to etch PCBs. In the mean time, I’ve started work on a solid state tesla coil (SSTC)! It is based off of Steve Ward’s Mini SSTC.

I’ve been winding the secondary coil for the TC over the last day or so on a 4″ diameter PVC coilform with 30AWG magnet wire. The PVC tube was 10 feet long when purchased and I had it cut down, however the outer surface of the tube was too rough (would have damaged the insulation on the magnet wire, and made winding harder) so I set up a coil winding jig and started sanding the entire tube down (120 grit) followed by 220 grit and 400 grit to smooth the entire tube down. After a quick wipedown and cleaning, clear polyurethane varnish was applied to the tube while rotating (to prevent drips/runs).

Following the clearcoat drying, 4 L brackets were applied to give a mounting point for the secondary, and the winding began. Once the first few windings are laid down by hand, the motorized winding jig became extremely useful. Most of the coil was wound within an hour or 2 spread out over 2 days since the motor continually overheats when applying the level of torque required.

The secondary itself is 10″ long and 4″ wide. After I finish the winding, I’ll cut a piece of acrylic plastic to fit, glue and add a breakout point of a bolt. Beauty shots follow:

Spectrum Analyzer Update

Hi to all the folks from HackedGadgets, I have no idea why I got featured, but I suppose that’s enough to get me to stop being lazy and actually post an update. Here is the schematic for the most part, done in Eagle, but it throws a ton of ERC errors, so its not ready yet. I’m also waiting to try out some LM/NE5523/24 opamps to act as the preamp to the entire circuit since the LM358’s flat-out fail at giving a strong enough signal for the bandpass filters to work.

Below is the schematic, in rough form, at this point I’m mostly holding out to get the supplies to etch my own boards and figure out a decent preamp. Ontop of that I might replace the Vcc/2 stage (built from an opamp) with a separate regulator, I’m planning to power this thing from a 18V 1A brick power supply, so a 7809 would do just fine for a Vcc/2 without worrying about taking too much power, however for breadboarding purposes it seemed easier to make a Vcc/2 out of the unused opamp instead of an entire regulator.

Another excuse I have for not working on the spectrum analyzer was making a power supply out of an old UPS, I’ll get around to posting photos another day, right now though its 2am so this post may not be highly coherent.