Build your own

Welding Arc Stabilizer

Under construction... Last updated on 05/28/02


 It was written:
>I saw this at a local pawn shop yesterday: Sears Hi Frequency
>Arc Stabilizer, prim volts: 115 VAC, Sec. volts: 3500.  He wants $150 
>for it. I have no use for it myself, plus don't have the $$. If 
>anybody wants it, let me know.

I "discovered" modern tesla coiling via some research into just this 
sort of device.  Basically what you will find inside is nearly an entire 
tesla primary circuit. Neon, cap, gap, and output coil ("primary"). 

This box still sells for something like $750 new out of the Sears 
Industrial catalog.  Not a bad markup for something your average coiler 
could scrounge for about $50. :) 

This device is designed to superimpose a High Frequency/High Voltage 
(generated by the gap/cap/primary) onto the welding current, supplied by 
the welder you'd attach the box to.  Weldors (folk who weld) like this 
since it eliminates having to manually "strike" the arc - the HF/HV does 
that for you (by ionizing the air) once the welding rod approaches the 
work.  To some extent, using this device will allow you to do a limited 
amount of TIG welding using a stick welder for a power supply.  Of 
course you still need an inert gas supply, etc for the TIG.

 I finally did discover what type of ferrite cores to use in my homemade 
coupling transformer.  The core is important not due to it's effective 
permeability (the core raises the primary inductance by a factor of only 
about 2).  However, the core greatly increases the coupling between the 
two coils by (?) causing more of the flux to link the output coil.  In a 
situation like this (I think) you want as high a coupling coefficient if 
possible.  Turns ratio is 1:1 and there is no use of any resonant rise 
phenomenon since output capacitance is variable and unknown.

 My TIG arcstarter runs on the live half of a half-dead 12000v 30 ma 
neon, using a 4-gap @ 0.028 RQ with fan, and only about 1500 pf of 
capacitance (doorknobs).  The output will pierce vinyl electrical tape, 
or jump over 1/2 inch under argon, which is more than sufficient for my 
purposes.

 If anyone has any questions feel free to contact me.  One of these days 
I'll get it all on the page, but don't look there just yet!

Here are three scanned pages - which started it all...






Here is MY setup:

My setup is rather similar to that of the book, with the following notable exceptions:
* Mine uses a ferrite-cored coupling transformer. Ferrite core available upon request.
* I have extra resistance (R2) in series with the spark gap for a couple of reasons:
    a) Decrease the intensity of the current to reduce power
b) Extend capacitor life
c) Extend spark gap life
* I have a small 500 pf HV cap (C2) across the output of the transformer to work as an LP filter. This will extend the life of the transformer.
* I have a 12.5K resistor (R1) in series with the secondary. Forms low-pass filtering to protect the transformer.
* Due to construction constraints I've used two separate spark gaps. One requirement is to use at least two gaps in series. A single gap spark gap won't work.


Additional description:
- T1 is a 120 volt input, 12KV at 30 ma output neon sign transformer.
- 0.0047 uf 20 KV "doorknob" capacitor.
- 10 ohm damping resistor. May be distributed.
- T2 primary is 10 turns of #18 magnet wire on a ferrite core.
- T2 secondary is 10 turns of #4 copper busbar on a PVC sleeve
- There are may approaches for the spark gap. The best approach is to use tungsten or tunsten carbide arc gap faces Alternately some have had luck using short (2 inch) lengths of copper piping, 3/4 diameter, 2 inches long,
epoxied to a ceramic tile in parallel. 0.028 airgap between each one.
- Poly metalized film capacitor, 0.47 uf 200 volt. RF bypass. Keeps HF out of your welder and routes it to the arc.

Pictures of specific internal details...
More to read about HF arcs stabilizers...
Experimental carbide spark gap photos...
See the movie of the arc stabilizer in action! (800K mpeg)

-Bill the arcstarter - experienced amateur weldor
"I'll try to weld anything!"
Starting arcs in Cinci, OH
http://www.geocities.com/CapeCanaveral/Hangar/6160

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