My First SSTC

[sjsimmo]

Hello!

This post is just to provide some documentation of my old SSTC, which I completed about a year ago.


The SSTC was based on this coil: http://4hv.org/e107_plugins/forum/forum_viewtopic.php?172138
And the finalised circuit looks like this:


The driver circuit is a direct copy of the coil linked, except that the 555 interrupter has been replaced with a simple Audio one that I designed. Some minor faults include the fact that I used a comparator as an op amp (I believe this causes some oscillations, which reduce audio quality). And the current limiting circuit has a small fault, which means that higher input voltages reduce the operating current. This was later modified with a capacitor across the current sensing resistor, to allow more peak current (dodgy, but it works ).
The driver circuit was etched on a hand drawn PCB using a permanent marker, and ammonium persulfate etchant:


And the case was made from 1.5mm aluminium sheet, bent in a vice (with a rubber mallet). For the interrupter I drew the PCB design in MS paint (never could get used to PCB CAD programs... ), and used the toner transfer method to etch the PCB:


The secondary was wound on an automated winding jig (unfortunately I never took a photo of the robot, before it was disassembled), with wire from one of the brake mechanisms in a laser printer. The coil is 90x30mm and has approximately 600 turns.

The primary coil was originally allowed to touch the secondary, until I noticed the racing arcs between the 2 coils , at which point I made the small isolating blocks out of perspex.


The final result was a very small SSTC capable of low quality audia, and about 1-inch sparks with 50 VAC input (the faulty current limiter causes sparks to reduce in length above this voltage).



So that was my first SSTC... now back to the DRSSTC
Feel free to ask if you have any questions (I probably left some stuff out...)
- sjsimmo

[pentode]

I wonder why you enclosed your coil in a Faraday cage and did you earth it on the same earth line as the secondary coil ?

[sjsimmo]

I entered the tesla coil in a science competition, and so I made the cage to reduce EMI, and to come slightly closer to complying to regulations. Everything (including the cage) is on mains ground. Whilst this is not recommended for large coils, it's much more convenient for small ones

[Mads Barnkob]

Neat little coil with a good range of hacks and shortcuts to make it run, but nevertheless, getting sparks from your first coil is all that really matters. It is a jump pad into building something bigger and better once you get the craving for longer sparks

If you still struggle with finding a easy PCB cad tool, I have used https://www.expresspcb.com/ for many years, its simple and there is no complex libraries, settings etc. but also there is no gerber files, but if you only do toner transfer it is perfect for that. Else check out the recommandations in this thread for other programs: https://highvoltageforum.net/index.php?topic=354.0

[sjsimmo]

Thanks for the links,

I'll definitely have to look into expressPCB, by your description it sounds like it might be just what I've been looking for
Although I'm quite happy with some of the results I've managed with MS paint (the PCB file for my DRSSTC driver for example):

An upgrade could be particularly useful for reducing right angle traces, and speeding up the design process.

The step up to DRSSTC is quite large , I'd probably recommend to others to build a more complex SSTC before jumping to DRSSTC, but it's a bit late for that now... However the simple SSTC is a good way to learn the basics of how they work, along with some of the basic troubleshooting strategies required for larger coils, without costing too much (approx. 50AUD to make sparks, excluding the variac).