control of 24VAC motor?

[[email protected]]

I'm pretty new to electronics and was wondering what it would take to
control two 24AC motors on a pan/tilt head with 12V DC and have a
variable speed setting? Is this very tough? I'm not sure how 24VAC
motors are controlled.

The head is just a cheap commercially available one.

I'm thinking something like a joystick for pan/tilt and then a slider
switch for the speed setting. It needs to run off 12VDC (auto) though.
I'm trying to make a remote video camera pointer.

Thanks.

Joe

 

[Pooh Bear]

I'm pretty new to electronics and was wondering what it would take to
control two 24AC motors on a pan/tilt head with 12V DC and have a
variable speed setting? Is this very tough? I'm not sure how 24VAC
motors are controlled.

The head is just a cheap commercially available one.

I'm thinking something like a joystick for pan/tilt and then a slider
switch for the speed setting. It needs to run off 12VDC (auto) though.
I'm trying to make a remote video camera pointer.

For that kind of application you would do far better using stepper motors.
http://en.wikipedia.org/wiki/Stepper_motor

Graham

 

[Tim Wescott]

I'm pretty new to electronics and was wondering what it would take to
control two 24AC motors on a pan/tilt head with 12V DC and have a
variable speed setting? Is this very tough? I'm not sure how 24VAC
motors are controlled.

The head is just a cheap commercially available one.

I'm thinking something like a joystick for pan/tilt and then a slider
switch for the speed setting. It needs to run off 12VDC (auto) though.
I'm trying to make a remote video camera pointer.

Thanks.

Joe

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.

 

[[email protected]]

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.

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?

 

[[email protected]]

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:

http://www.21best.com/21_best/electronic/security/video/pan_tilt/for_sale_.html#Weatherproof

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

http://www.minkingcctv.com/en/product/products_tk15.htm

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

 

[Tim Wescott]

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:

http://www.21best.com/21_best/electronic/security/video/pan_tilt/for_sale_.html#Weatherproof

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

http://www.minkingcctv.com/en/product/products_tk15.htm

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

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.

 

[[email protected]]

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

 

[[email protected]]

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:
http://www.21best.com/21_best/electronic/security/video/pan_tilt/for_sale_.html#Weatherproof

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?

 

[Joseph2k]

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:

http://www.21best.com/21_best/electronic/security/video/pan_tilt/for_sale_.html#Weatherproof

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

http://www.minkingcctv.com/en/product/products_tk15.htm

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

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.

 

[Joseph2k]

http://www.21best.com/21_best/electronic/security/video/pan_tilt/for_sale_.html#Weatherproof

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?

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.