DC Voltage Control

Maybe a simple DC voltage regulator could accomplish this.

Thanks very much. A good power source is very cheap Au$ 70. I will try it out.

Hi,manufacturer of the tig brush cleaning system, Retropol, says below 10v dc. I have 2 tig machines, the frirst is too hot, it melts the carbon fibres. The second is ac/dc with almost all functions adustable, 9 control knobs, one of which allows me to turn off arc force. I haven't been able to test it yet as I have been in hospital. When able I will try it, as the hand piece allows me to contact the workpiece before turning on or off. Retropol thinks hf will be a problem. As I live in Ausrtalia and refuse to do any more business with USA, that option is out. I have ordered Power source 0-30v dc and 0-5 amps with very fine adjustments. I am an electronics novice but understand electrics very well, thanks for tour suggestions.

You originally asked :-

I need to limit DC volts from Tig welder neg.terminal to use carbon brush S/Steel cleaning system. Volts need to be 10 or less, Amps 0 to 20. can anyone help?

Things have changed completely it would seem.......!!!

A good TIG supply is a stable 'constant current' source whose 'open circuit' voltage is usually in the range of 50 < 80 volts, the current being controlled by the arc length....to limit the current for a 'touch' start, I use computer to sense 'open circuit' voltage and use a high current relay to switch in a resistance to limit the current on initial contact to less than 5A to avoid destroying the tungsten. As the arc is established and lengthened to where the arc voltage is > 10V the resistance is switched out and the current increased to the maintain the proper puddle. The switched resistor is 1/8" Nichrome wire, appx. 80 t on ceramic spacers, with an adjustable tap on one end so this minimal current can be adjusted depending on the supply. You could make a resistor like this to adjust your current for whatever supply you are using.

All true, but what an inefficient setup that would be, wasting power as heat in the resistors.....Not to be recommended....

A reasonably priced/secondhand efficient SMPS, would "earn its keep" in just a few days of intensive usage in comparison!!

As the old wise farmer, leaning on a gate, deep in the countryside, said to a tourist, who was asking the right direction for London.

"If I wanted to go to London, I would not start from here!!"

Hi Andy, I know efficiency is important, but this is on a 500 amp solid state switcher. with electronic controls...the supply adjusts down to 30amps (still too much current) and is non linear at this low setting (initial contact results in surge to 50+ amps before dropping back to 30 and destroys the tungsten tip). By switching in this series current limiter for a second or so to establish the arc I probably waste a couple of milliamphours and that's minor waste. The OP might waste a bit more power, but the series resistance might help stabilize the output....

Read the joke in post #6!!

That says it all.......remember, there is a big difference between what is theoretically possible and what is practicable.....

Especially since he is now buying what sounds like a lab power supply that supplies only up to 5 amps, max 30 volts, so the original request was seriously flawed alone from the need for 20 amps.....See post #7 and the original post!!

Problem therefore solved.....QED!!

Original speci was for 20 amps or LESS. Actualy 0-20. Retropol says 5 amps plenty

but not over 20 !

I have worked in specify designs many times in my life, the OP obviously hasn't a clue.

There is nothing more to learn/help with here, so I am leaving.

Bye