Carbon Pile

isn't that kind of a poor way of throttling a motor?

Jamie

I thought carbon piles were almost a century out of date. You could always make one from the carbon rectangles in discarded 9v batteries. Surely there are easier ways to speed control a motor though.

If you must do it old school, a salt water dimmer is far quicker to make. Sometimes dubbed a scariac.

NT

Where are you getting 9V batteries made like that? All I've seen for years are made from six AAAA cells.

Look for sewing machine foot pedals. The old ones had carbon piles and the new ones might be an alternative to carbon piles.

those are the alkaline ones.

there's got to be a school in china still making dry cells.

Carbon-zinc super heavy duty, apparently. 6 lozenges stacked. Are those thick black plates carbon, or compacted battery gunk? Dunno. I'll take a stab at putting a pic on abse.

A series lampholder might do you, just pick a filament bulb to suit.

The ones I opened a few years ago were all stacked flat rectangle cells. No idea what types they were. I think usually they're whichever version you dont want.

NT

The OP said 200 (TWO HUNDRED) amps. Nothing mentioned so far comes anywhere near being capable of 200 AMPS. :-?

I don't think a carbon pile would be particularly stable, especially as it heats up. You could include it in a feedback loop and use an electromagnet to vary the pressure so as to keep it stable, but that would involve some way of monitoring its resistance.

For low resistance high current purposes, big wirewound resistors with multiple tappings are the cheapest and most stable answer. They are relatively easy to construct from slate bars and resistance wire, but the tapping switch is going to be the most difficult item to design and make.

If you want to go down this route, please ask for more information. I have made several 5 kW* units as replacements in motor-starting applications, so I may be able to help.