Manual Control of a Stepper?

[tobybirch007]

I'm building a remote camera pan/tilt rig and want to use steppers, but I don't want to use a PC to control them. I don't need alot of speed, and don't need to know where the stepper rotor is. All I need to be able to do is precisely position the camera. From what I understand of steppers, they are basically controled by a cyclic series of on/off for certain electromagnets. Is it possible to make a hand cranked device that switches these poles on and off (or +/-) in the right order connected to a power supply? I'm not sure why, but the term commutator is popping in and out of my head as I write this. I have some bipolar steppers that would be perfect for my device, but I don't seem to be able to understand how they work well enough to come up with a design on my own.

Any help would be greatly appreciated, even if it's "I don't think this will work"

[mxtras]

I am sure this can be done, but I am not one to tell you how - not without a PC anyway. Accomplishing this with a PC would be pretty easy.

Scott

[pminmo]

Most drives are of the step/direction type. That is they have two control signals to accomplish the motor movement. Simplest control for direction is a switch, and the simplest control for step is a simple adjustable frequency source like a 555 timer. You can use rotary encoders to do what you want by decoding the output of the encoder to get direction. Bottom line is it isn't a real difficult task if you have some electronics savvy.

[High Seas]

If you don't mind a kit:
http://www.allelectronics.com/cgi-bi...LLER_KIT_.html
Might be what you are looking for.
Jim

[tobybirch007]

How far can the motor be from the driver board? I need 40 to 50 feet. So far this is what i have in mind. Sorry for the crappy drawing, computer crashed a few weeks ago and havn't reinstalled CAD. The black is a positive signal, red is negative. The wheel is spun and as the brushes move from one pole to the other, the motor turns. Possible? to much work? For 25 bucks that kit is looking pretty good. Thanks for the link.

[Horsedorf]

There are a lot of ways to do this. I think, the mechanically simpler you go, the better off you'll be. for example, if you use some slide potentiometers and a pic, you could read the positional changes of the pot's and send step and direction data to the camera via a differential signal for long distance and good noise immunity. How many axis? pan and scan? that's 8 wires for the four differential signals of step and direction. If you really REALLY want a wheel, then use one of those cheap encoders for quaddrature and a pic again to determine direction of the wheel and again, send step and direction to the camera. Use something like a PMDX board or PMINMO's controller to convert the step and direction into stepper motor signals.

That would require power at the camera, but I'm assuming you have that available there.

[tobybirch007]

I'm guessing you're talking about programming a microcontroller? I've done a little work with basic stamps, and actually controlled and R/c servo with it. I guess I don't understand the "send step and direction data" part. What does the code look like to do this? Also, how do I get the higher voltages to the motor without frying the microcontroller?

[Horsedorf]

Mkay, a basic stamp would work..

Here's what I had in mind.. the 'system' would be two parts.. the camera with the stepper motors and the stepper motor control hardware and it's own power supply for teh steppers and the controllers. The controllers require two signals , a "direction" signal which is used to control which direction the stepper motor will move , and a "Step" signal which is used to tell the stepper motor to take a step in the indicated direction.

Your controller box could be a basic stamp, that has two pins assigned as inputs, to which you put variable resistors on (Slider type). And it would have, say, four output pins.. two for direction, and two for step. One pair of step and direction pins would be wired to the step and direction pins on the controller for the panning, the other pair would be connected to the step and direction pins on the controller for scanning.

You code would do something like....

Measure the potentiometer for scanning.
If the potentiometer has moved, make the scanner controller take n number of steps to match the new scanning position.
Measure the potentiometer for panning.
If the potentiometer has move, make the panner controller take n number of steps to match the new panning position.
Repeat forever.

That, in a nutshell, would be it.

The devil, as they say, is allways in the details.

The controller with the sliders, by teh way, would use it's own five volt power supply or so, and the grounds between the two systems would be in common if they are close together. or you'd have to use a differential sender/receiver without any common ground between them if they are farther away.

Good luck!

[High Seas]

More than one way to solve the question -- Is it camera control or the stepper control?
Here is a shortcut (again under 50 bucks delivered) for camera control and its wireless:
http://cgi.ebay.com/X10-Ninja-Pan-Ti...QQcmdZViewItem

I might like to weatherproof that one! Pirate Watch! Jim

[tobybirch007]

Thanks for the link on that one, I bought it. The main question was controlling a camera about 50 feet away from any control equipment, not so much about the stepper control. I just figured I could build a controller cheaper than the $99 price tag those are usually at. Somehow i forgot to ebay that specific controller... I think I'll still try to rig up a manual stepper controller though, I'll keep it updated if i ever get it working.

[High Seas]

Yeah - kinda like when I am draining the swamp -- all those gators - I miss the objective!
Hope that all works out - I've used (BSR) X-10 gear for years - first pc link was in 1983 -- oops thats age talking.
Jim
If you do go the kit route --keep us posted like to see how it goes

[rickharris]

You can control a stepper with nothing more than a set of DPDT switches. Seems to do what you want.