Variable Pot for Testing Brushed Motors, or????

[wrenwright]

I'm interested in some sort of swithc/pot for turning brushed motors on/off while doing bench testing. Of course it's possible to use an esc, but that means I have to have a dedicated esc for bench testing and also have to have a servo tester to run it in addition to a Rx battery to power the tester.

What I would like to have is a pot that I could use to power up the motors that wouldn't lose any power when it was all the way on. A simple on/off switch would work except I don't know any way to have a "soft" start with a simple switch.

I run all sorts of brushed motors all the way up to 36 cells at 60A.

Any ideas?

[slipstick]

Are you trying to CONTROL the motors from zero to WOT with a pot or is a soft start switch all you're looking for ?

A variable resistor to handle 40+V and 60A is completely impractical. Anyone trying to do it would use MOSFETs controlled with PWM.....in other words most of an ESC.

Similarly you could build a soft start switch but it would need to have the same type of MOSFETs in that are in an ESC and because you're building it as a one-off it probably would cost more than an equivalent ESC.

Steve

[nihil]

I'm not sure about that cost estimate. An AVR Tiny2313 is only a few bucks, and digikey has some MOSFETS that'll do 60V at 80A for a buck a piece with a $3 H-Bridge to drive them. Another couple bucks for a max232, a 10k potentiometer, and misc parts. You could do a nice one for less than $20 that can be controlled by any of PWM from typical RC receiver, a knob (potentiometer), or your PC/PDA via serial port.

[wrenwright]

Are you trying to CONTROL the motors from zero to WOT with a pot or is a soft start switch all you're looking for ?

A variable resistor to handle 40+V and 60A is completely impractical. Anyone trying to do it would use MOSFETs controlled with PWM.....in other words most of an ESC.

Similarly you could build a soft start switch but it would need to have the same type of MOSFETs in that are in an ESC and because you're building it as a one-off it probably would cost more than an equivalent ESC.

Steve

I'm really just looking for something that will give a sort start as to not damage any of the gear or belt drive reductions I use. I'm only going to be testing for WOT amps/watts.

[AndyKunz]

An ESC is the way to go. It will be much cheaper than a rheostat to handle the current.

Andy