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Stepper Motor Basics

I have a stepper motor from Airpax, modle C82710 that has 6 wires connected to 2 windings with a center tap. It's rated at 12 volts, 36 ohms from center tap to the end of the winding, and 7.5 degrees per step.

I'm not too familiar with stepper motors, but understand the shaft can be moved in either direction one step at a time. I read some articles on Google but couldn't find any that showed the necessary signals and timing to rotate the motor continously in one direction.

I played around with it, and found I could move the motor shaft one step at a time by just alternating the connection to either side of one of the windings with the center tap common. But it only goes so far and stops, and the second winding was not being used.

So, the question is, what is a proper polarity and timing sequence on the various connections to continuously move the motor in the same direction?

-Bill

Reply to
Bill Bowden
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Look here:

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Cheers

Reply to
Varactor

Bill,

Here are a couple of links that may help. The first will show the drive sequence required for unipolar and bipolar operation (among other things); the second will show some methods of doing it.

Lots more on the web. Many manufacturers of driver IC's if you don't want to use transistors to drive the motors. Also, much good info about controlling these with microcontrollers or discrete logic.

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Have fun playing with these.

Richard

Reply to
Richard Seriani

Sounds like you have a uni-polar stepper there. The simplest way to drive it is just to use four transistors. Apply your 12 V to the common and setup the transistors to turn on to provide a ground path for the desired winding. Sequence them in the order A, B, ~A, ~B.

Once you have that part working, you can look into half-stepping (two phases on at once) and beefier drive circuits (choppers) that control the current through the windings for higher torque and speed.

Wikipedia has a pretty good article with additional links.

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--
Rich Webb     Norfolk, VA
Reply to
Rich Webb

Is there an echo in here?

Cheers

Reply to
Varactor

Or use 2 dpdt toggle switches as a quick visualization tool... switch them in the order 00 01 11 10 to go one way, reverse switch order to step the other way.

Reply to
BobG

links.http://en.wikipedia.org/wiki/Stepper_motor

Thanks, but I'm not sure of the sequence A,B,-A,-B. Suppose I have both center taps connected to +12 and the other 4 lines are connected to transistors. The problem is which side of which winding should I start with? And will the next transistor supply a ground to the other side of the same winding? An then there is a phase problem dealing with the second winding? How do I know which side of the second winding to ground next?

-Bill

Reply to
Bill Bowden

links.http://en.wikipedia.org/wiki/Stepper_motor

Playing with stepper motors I did the following: attach both centre taps to 5 volts, and attach a 10-15 cm piece of wood(I used a shaslik stick) to the stepper motor axis. Now ground one of the four wires,and mark the place pointed at by the stick. Use your hand to damp the motion, and in this way you get 4 marks close together. Now just check which wire belongs to one of those positions, and you know in which order you have to power them. I connected a 4 channel buffer IC to them, and connected the buffer to my computers printer port. I also put 4 leds on those outputs, to be able to see what my printerport did to those inputs. For medium force, just energise them 1-2-3-4-1-2-3-4 etc. For high force, use 12-23-34-41-12-23-34-41 etcetera.

Reply to
Sjouke Burry

links.http://en.wikipedia.org/wiki/Stepper_motor

Yes, I drew a little line on the shaft to watch the position and connected the 4 lines to push button switches so I could ground them in any order. After a few tries, I found a sequence that keeps moving the motor the same way. Haven't figured out how to reverse it yet, but it's a fun game pushing switches to see which way the motor moves.

-Bill

Reply to
Bill Bowden

On Sat, 12 Apr 2008 19:02:05 -0700 (PDT) in sci.electronics.basics, Bill Bowden wrote,

Still the best: Jones on Stepping Motors

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Reply to
David Harmon

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