Preceise positioning using stepper motors

[Wembley]

Hey folks...

I am starting on a project using BASIC Stamps (a type of micro-controller) and it got me to thinking... has anyone used precesion stepping motors to control parts of their puppets? For example- rolling eyes, hand grips etc?

A stepper mottor is a motor that is designed to move in very precise steps to provice very precise positioning. For example, stepper motors are used in the track-select mechanism in your disk drives in your computer, in robots to move arms and legs etc, and even in your VCR and DVD player to drive the heads/lasers.

The reason stepper motors would work well, is that they are ideally suited to control by computers and microcontrollers. Steppers work by swinging the inputs to the motor high and low in sequence. The speed and distance can be regulated by how fast the voltage changes go, and how many pulses the controller sends to the motor. If you send 10 pulses to the motor, it will move exactly the same amount each time you send a pulse. This would allow for very precise movement of eyes, for example. You can have a button you push, and it will make the eyes go back to the "look forward" position, or you can set a location, move the eyes, and the controller can count the distance and look back to the place it was looking before.

If anyone wants a prototype built, let me know. I'm going to be investigating this idea as part of my project, which uses aluminum reflectors to control radiation patterns of a 802.11b wi-fi antenna system. Instead of waveguides, I'll attach them to eyes! The linkage could get a little complex though...

Your thoughts?
-Rick
(oh, and if anyone wants, I'll also be documenting my experimentation with my waveguides, too. Let me know if you want a copy.)

 

[Buck-Beaver]

My question would be what is the advantage of using a stepper motor instead a servo? How heavy would the motor be? If it weighs more than a few ounces it's not that practical to use in puppet that would be held up by a puppeteer for a long time.

I know stepper motors are sometimes used in animatronics (mostly on theme park-type stuff I think) but I seem to recall someone telling me there are a number of disadvantages to them and I don't think they're used in most standard "Muppet" type puppets. I only have a basic layman's understanding of servos, motors, microcontrollers or whatnot so I may be wrong about this.

 

[thatonekid]

lol i never knew that puppetry could be so complex.
i didn't understand a word you guys just said.

 

[Iokitek]

I know this is an old post. But I was just wondering if anyone had any more info for me on where to get servo's, micro-controllers and the radars used to move all the parts. I actually need very small servo's. But most animatronics recources I find out there only deal with large powerfull servo's. There is a big difference between a $2, a $20 and a $200 servo. But I don't really see where those differences are exactly.

I want to build puppets who are only half the size of an actual human being. Only the head will be electronically operated though. And they should not be radio controlled but instead by a regular analog cable control. I have tried looking at motors taken from small household appliances. But I actually don't even really know how these things work so I'd rather get all the stuff I need from one source.

I would also like to know more about the difference between a stepper motor and a servo.

 

[FISH'N'WOLFE]

Well, I wouldn't be able to tell you the difference between the two. However if you want to save some cash, you can pull servos out of old turntables. I found a whole bunch of old Apple 8-inch floppy disc drives and pulled out stepper motors from them. If you look around you should be able to find what you're looking for without paying an arm and a leg.

 

[Iokitek]

I've already done alot of research in the mean time actually. Thanks for the reply though. Those motors may be helpfull. The biggest problem is making the driver and the controller and getting them to work properly. I'm looking into that right now.

Anyway I've got a long way to go. But atleast I'm on my way now.