Post by thread:Motor control on-the-cheap

>I'm interested in controlling a 90-volt, 2.4 amp DC motor with a PIC >using PWM. This is not a servo application, just simple but precise >speed control in one direction with braking. >Unfortunately, all of the books I have seen on power supplies seem to >assume that any application over about 24 volts only requires current >in the milliamps range. Can anyone suggest a good AC to DC conversion >circuit, preferably without a transformer? I'm working on something similar, but at 12 volts. *However*, the technique may still be applicable. I'm using an audio power op-amp, made by SGS Thomson. TDA2040....I think. It's a 5-lead TO-220 package, grounded tab, good for about 3 amps continuous. They sell these things in a variety of current and voltage ratings. Hang an RC integrator on the front end and you've got a PWM-to-DC driver. It sources, it sinks, it's bulletproof and it's cheap! 90 volts is a little higher than I'd go with the 2040, but you might add a couple of power transistors on the output to beef up the voltage capability. Or, they make higher-voltage parts, though I'm not sure how *much* higher. Or, call Apex Microtechnology...they make POWER opamps up to kilovolts/kilowatts. Serious oomph, serious dollars. You may want to actively drive both leads, even though you want only one-direction rotation. Ya know how fast you can *stop* a motor by reversing the drive current? Yow! I've got sheared keys to prove it. spam_OUTforbesmTakeThisOuTpeak.org Mark G. Forbes "Never ascribe to malice that which can be blamed on the engineer."