Basic Stamp Stepper Controller

Pat Alonzi

Hi everyone

I am currently working on a project to automate a piece of industrial equipment. (A common topic around this forum). I was planning on driving a ball screw with either a stepper motor or servo motor.·The final goal is to have a Visual Basic application output a signal (the position requested) to a stamp and then have the machine home itself to the requested position. Does anyone have any suggestions on the best way to do this?

I am leaning towards using·this stepper motor: http://www.kelinginc.net/KL34H280_55_4A.pdf

Thank you for your help.

-Pat

Pat Alonzi

Also I forgot, I was planning on using Upper and lower limit control switches to make sure the shuttle does not move past the end of the rails

Mike Green

1) A stepper motor will need some kind of motor driver because of the currents involved. Parallax does sell several and you can build your own. Look at their offerings and search the forum for discussions. The particular motor you're planning to use will draw up to about 5A at low voltage (2.5V) which is quite different from what the Parallax-sold drivers are designed for (higher voltage and lower current), so you'll probably have to do your own.

2) Stepper motors do slip. You will want to recalibrate your position on power up and occasionally if you leave the device powered up for a long time. You can use the limit switches for this if they're accurate enough.

Post Edited (Mike Green) : 5/27/2007 7:59:49 PM GMT

Pat Alonzi

Thanks Mike

Would I be better off with a servo motor and a rotary encoder?

Mike Green

If you use a real servo motor, you will only have 90 to 180 degrees of motion.
The continuous motion servos won't give you the kind of control you would want.

You could use a dc motor and rotary encoder or the stepper motor. The dc motor
would also need an external driver that you could buy or build.

Stepper motor drivers are not hard to build (www.aaroncake.net/circuits/stepper.asp)
and (www.elabinc.com/ede1204.pdf).

stamptrol

Depending on the power requirements, the DC motor and encoder will give you a lot of flexibility in terms of power and speed. The encoder really works well at high speed if it drives a dedicated counter so that the processor doesn't miss any pulses. Also, it doesn't have to be an encoder. Lots of high performance positioners use linear pots or cable pots.

If the power requirements are small, steppers (within their capabilities of speed and torque) are easiest to use.

Cheers,

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Tom Sisk

http://www.siskconsult.com
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