Motor control X Y Z

Hello everybody,
I'm searching a method to control a beamer with motors. The idea is to mount the projector to the ceiling, and create a system so that the
projector can turn around and move up/down. I want to control the movements with my own software. Because it will have to work in X, Y and Z, I know that I'll be needing two motors. I've read a lot about servo and stepper motors, and I think the last one will be easier to control by PC (?).
But how do you realise something like this? Can anybody give me some advice, an example, a tutorial?
I hope somebody can help me...
Thanks a lot in advance!!
Greetings, Tari
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Motor wrote:

"beamer"? I gather from context that you don't mean a BMW.

If you have three independent axes you need to control you need at least three independent actuators -- just like high-school algebra, where three unknowns required three equations. If you want to control direction as well as offset you'll need more motors.

As Windows gets more and more in the way between your software and the real world even stepper control gets harder and harder. I'd suggest you look at "Nuts & Volts", "Servo" and "Circuit Celler" magazines -- all of these have information and projects regarding the kind of basic stuff you want to do, and they should all have USB thingies for sale in the back to do what you want.

Stepper motors are easy to control, and they hold their position when you remove power. That's about the only good things I can say about them. They're big for their power output, they have limited accuracy*, they aren't forgiving if you ask more from them than they can deliver.
While there are applications for which steppers make good sense, you should make sure that this is one of them before you rule out using a DC motor in closed loop.
For this sort of thing you may be best served with some little motion-control modules that drive the axes to where you want them, controlled from an executive in the PC that just decides what the motor positions should be and transmits the data. If there isn't a USB-commanded servo controller out there, someone's working on it.
* unless you start microstepping them in which case they're less easy to control.
--

Tim Wescott
Wescott Design Services
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Here is one website to get some information from.:
http://www.galilmc.com/index.html
.... I'm not sure if these devices are cost effective, but they seem to have various capabilities.
Dave

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Rather than re-invent the wheel, you could always purchase a camera pan-tilt head on Ebay and mount the projector on that.. The higher-end ones come with either serial or Ethernet comms.
HTH, Cameron:-)
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