Alternate Means of Controlling Amperage

Hi all, I just bounced some questions off an electrician and want to know what you think. Please feel free to fill me in where I lack knowledge, but...

A PWM is used mainly to control the amount of amperage flowing to the reactor in an HHO setup right? I know that there are other HHO applications too, but say I just want to focus on controlling amps for now.
Has anyone ever tried using a rheostat to control the amperage going to the reactor? It costs less than a PWM, and is designed to limit amperage flow, so why not use it in this application? I would greatly prefer having to use one of these, over messing with the electrolyte in order to dial in a certain amperage for my cell.
Am I missing something here?:confused:

Have seen no one answered so far...

Rheostat might not be cheap and depends on how much current you want to allow passing through it. Also, there usually is a mechanical wiper contact that can cause further resistance with wear and tear that could alter its stability.

A mosfet based current limiter seems a cheap alternative, solid-state and compact in size considering its current carrying capacity.

PWM can vary the power based on its "dutycycle". The below link gives a good circuit/schematic with description.

http://www3.telus.net/chemelec/Proje...-Limit-PWM.htm

RTJ Nair

A PWM controls average current by pulsing full voltage on and off very quickly to the generator.
A rheostat controls current by reducing the voltage to the generator.

A rheostat would work if you don't go too far below 2V per cell, but that doesn't give you a very wide range of adjustment.

A rheostat that handles 20A at 14V will set you back way more than a PWM of similar capacity.

A PWM power control is much more efficient than a rheostat based method and is an established fact. Also, a rheostat output is a "staircase" function and in certain load applications where power factor is lag/lead is not advisable except with power-factor corrective circuits.

RTJ_Nair

Thank you both for those insightful replies. The stuff I read didn't say that the voltage would be reduced -not something I want! It seems I'll have to scratch that one from the list then.
Hmm..a mosfet based current limiter is a better choice if I wanna keep costs down and control amperage? I'll have to check that out and see what I can come up with cost-wise.
Maybe I could build, or have a 'simple' PWM built that would satisfy my needs? I am sure I say some schematics during my google search.
It would be REALLY nice if a cost-effective alternative to a PWM could be found though. Any more ideas???

The Search Continues!

hey there fox, so I think dog hit the nail on the head with that one. Im a long time electrician and a rheostat will reduce the voltage as well, but them pwm's can be built at home for cheap with easy to find parts. now I havnt made my own yet butthe schematic looks simple enough.. good luck with that