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Jonathan Allison
02-24-2005, 09:24 AM
Ok I've been doing a bit of research on bipolar motors and most of the post here seem to be somewhat inconclusive. Although in one post I read you can use 8 bs2 pins and a darlington array to control them or alternativley some other chip. I'm interesting in using 8 of the bs2 pins, does anyone have any schematics of this or know of any good resources pertaining to the bs2 / bi-polar steppers?

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Johnny

Post Edited (Jonathan Allison) : 2/24/2005 4:28:03 PM GMT

Ray Steers
02-25-2005, 02:27 PM
Johnny-

As I have done this before and it works very well and is SO much easier that what you are thinking of trying I will tell you:

Go find some old floppy drives. 5 1/4" or 3 1/2" work fine. the larger ones have bigger motors. They already have all the driver circuit boards built and require only 2 signals. one for direction and one for step.

check out this link for better info.

http://jewel.morgan.edu/~tmalone/dskdrv/dskdrv.html

or better yet this:

http://www.doc.ic.ac.uk/~ih/doc/stepper/tm100/

I have used this information to built 2 very accurate coil winding machines for next to nothing. ($5.00 a piece for old floppy drives at goodwill or salvation army)

You can send the signals from the PC parallel port or a basic stamp. I use Winbatch http://winbatch.com and win95 (better access to the port than on an NT kernal like XP which uses a HAL)

works great.

good luck,

-Steers

David B
02-26-2005, 01:32 AM
There is nothing mystical about bipolar steppers, but they are harder to drive with discrete parts than a unipolar.

With a unipolar, you just need to send current through 1 or 2 of 4 windings in the right sequence, and the motor runs. The current either passes in the same direction through any coil, or no current flows.

With a bipolar, you need to pull one wire low while pulling the other wire high to send current through in one direction, then pull the low end high and the high end low to send current through in the other direction. So the driving circuitry is more complicated. Since each wire needs both a high-pulling switch and a low-pulling switch, the driver circuit looks like an H, where the coil is the bar of the H, so drivers are sometimes called H-bridges.

Sure, your stamp could run the motor, but you need to know what you're doing with controlling the power switches - if you accidently turn on both the high and the low switch, things would not go smoothly in your circuit!

You can buy H-bridge drivers for not too much, if you just want to run your motor for some project.

David

agentile
02-26-2005, 08:48 AM
I would recommend using the L6219 bipolar stepper driver (from mouser for about $2.25). It can provide 750mA per winding, and it can be controlled with 2 (or 4) bs2 pins. The datasheet for the L6219, which is also available at Mouser, has a good wiring diagram. If you use 4 pins, you can control the current level to the windings in four settings, off, low, med, and max. If you go this route, send me a note and I'll send you some code to run the motor.



AG

Jonathan Allison
02-26-2005, 11:19 AM
I think I'll look into the L6219, I've got yet another list of parts so I'll add this.

Thanks AG, I'll let you know.

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Johnny