control of 24VAC motor?

For that kind of application you would do far better using stepper motors.

Graham

If you can rip out the motors and replace them with DC motors your job will be easier. If the current motors are rated at 24VAC then you'll probably have to bite the bullet and generate 24VAC for them.

We need more detail. There are a lot of ways to build 'AC' motors. Posting pictures somewhere, or at least posting the make and model of the pan-tilt table, would be helpful.

The motors are probably 2-phase induction machines with a capacitor (or resistor) that gets switched to reverse the rotation. If this is the case then there really isn't a speed control (other than possibly resistively loading the motor to reduce the available torque). Control of such a motor could be as simple as using the current control head to building a variable-frequency drive connected directly to the motor.

The motors _could_ be series-wound commutated motors with provisions for switching the polarity of the field. This would be an odd way to do it, but it may be the case. In this case you could just run the thing off of DC, possibly even 12V.

Unless there's some mechanical reduction to the drive I doubt they are normal induction motors.

They might be some kind of brushless servo or synchronous motor though. A lot of the lines blur - you can argue that a permanent magnet synchronous motor *is* a stepper motor.

If they are induction motors with some kind of reduction drive then your variable frequency drive idea sounds good - really this isn't that far off from what the other drivers might look like, just likely lower power with the mechanical reduction in there than would be needed for even holding on a direct drive application.

We need to know what the motors are. What do the data plates say? Model number? Specs? On what basis did he decide they are 24v ac motors?

I really don't have the specs as I haven't bought the unit yet (need to know if it will do what I want first). Here's the unit I'm looking at:

I saw a similar item here that appears like it can have the speed varied:

Though this may have completely different motors, etc. They're all on Chinese New Year right now or I would try to ask them.

Do these sites give any more clues as to whether it can be speed controlled (and hopefully speeded up a bit since the rotation is a little slow for what I'm after)?

Thanks a bunch folks!

Joe

cs snipped-for-privacy@hotmail.com wrote:

The sites don't really give a clue. There's a bazillion ways to drive a motor with AC, so it's hard to say what one is used for these. You'd need to buy one and poke around to find out anything.

re camera pan/tilt motor control:

As a last resort, whatever type of motors they are you can speed control them by chopping the supply to them, so it can be done.

NT

I'm starting to wonder if this isn't a stepchild of TV antenna rotator technology. If that's the case it may be gearhead and might even by synchronous (ie, speed locked to frequency, and quite slow) as it seems that's how the feedback-less systems must work?

Directly from the spec sheet the pan/tilt is multi speed (means very likely a stepper inside) thus, it has some control electronics inside. If you want higher speed movement contact the factory or find an alternate vendor or three.

Most of these look like induction motor - worm gear drives. Hardly suitable to variable speed unless you want to rebuild the control electronics as well.