Re: [CAD_CAM_EDM_DRO] small amp recommendation needed

Chris Stratton wrote:

> One of my co-workers needs a little amp to drive a DC brush servo
> motor (open loop) at up to about 2-3 amps, 30 volts or so. It needs to
> be moderately linear as he needs a sinusoidally varying velocity from
> the motor. (ie, he wants the shaft to osciallate)
>
> My gut feeling is that this is power op-amp territory, but we need to
> find something like an off-the-shelf module, as he simply doesn't have
> time to play with all the power-electronics gremlins like the ones I'm
> chasing in my prototype H bridge PWM/chopper.
>
> So far he's been using audio PA-system amplifiers, but keeps blowing
> the chips - the conclusion is that something designed and protected
> for motor drive use is needed.
>
> Any recommendations?

The most obvious is a Copley Controls DC servo amplifier. See
http://www.copleycontrols.com/
OR, he could build one of my velocity servo amps
http://pico-systems.com/servo.html
but, the Copley comes completed for about the same price as my
kit costs to build!

Or, you could search eBay for a DC servo amp for brush motors.

Audio amps are totally unsuited for this. I assume he is pulling out any
DC coupling capacitors, or any caps in the feedback that reduce gain
below a few Hz. Most amps have this to prevent shoving a lot of DC
through the speakers.

Jon