bought myself an inexpensive TIG/stick welder. it is a lightweight inverter type and has no provision for a pedal to control the output. It has, instead, a knob on the box. This works great for controlling the output while using it as a stick welder (set and forget), but while using as a TIG power supply, I want more convenient control.

So, I propose to install a control pedal from a sewing machine (cheap and available). However, these pedals use a 2 wire variable resistor and the control on the inverter is a 3 wire potentiometer.

So, the question is: can the variable resistor be used, and how?

are these two circuits functionally equivalent?



The potentiometer is a 10k, low watt device.

I am proposing to put a 10k fixed resistor between the red and green leads and wire the variable resistor of the pedal between the red and blue leads.

does this make sense and, more importantly, will it work?

If not, any suggestions?

dave

I wouldn't imagine it will last long if it's for a domestic machine. They aren't exactly heavy duty. The wife's worn 2 out just sewing so if they are carrying welding current they will arc as well as wearing out.edit:- The ones we have are a rheostat, not a variable resistor although I don't claim to know the difference. Rheostat controls current and variable resistor controls voltage.
http://www.kpsec.freeuk.com/symbol.htm

[Edited on 1/4/05 by Peteff]

Fraid that almost certainly won't work. Swop the blue & red in your diag. & change the resistor to a 1k and you'll get something that will control up to 90%, so might be a goer.
good luck
Bob

I have recently been considering the exact same modification, I have a 150 amp inverter and scratch start torch and would like a bit more control over it .I was going to try and make a pedal using a heavy duty potentiometer and a lever linkage and spring set up. I also considered looking at car throttle pots as used on the drive by wire systems .
The current rating is unimportant as it is only a signal device , not actually controlling ther weld current.
Paul