L293D & stepper motors

Hi all
I'm still a newby at allof this so please be patient with me.
I've just bought myself a basic stamp starter package and I've got a
couple of stepper motors. I know how to interface the stamp with a L293D and a stewper motor but I've read on the net that you can use one L293D to control 2 steppers but I've yet to find out how to do that. So far I only know how to use control one motor per L293D. I'm tryimg to build a little application where I would need to control at least three steppers and I'd like to be able to use one L293D per every two steppers.
If somebody out there know how to interface/connect 2 steppers per L293D please let me know of just point me to some pages that will show me how to I'd really appreciate it. I'd like to get some diagrams please.
If possible mail it to me directly ( snipped-for-privacy@hotmail.com) or reply to the thread. Thanx a lot Fick
(This is really my name and not a prank on my part)
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Could you post a link to that information?
I don't see how you can use an L293 to control 2 steppers.
--
- Alan Kilian <kilian(at)timelogic.com>

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Well I got to thinking about it. Normally you can't control two stepper motors with one L293, you need two full h-bridges for a bipolar stepper motor. Thus one L293 per motor. This is true if you want bi-directional control of a bi-polar stepper motor.
But in thinking about it. If you only wanted a stepper to run in one direction only, not bi-directional, it would be possible. You are only using the lower half of a half bridge to do it. You could run two steppers off of one L293. To me it would be inefficient but it would work for running two bipolar steppers off of one L293. Basically you are connecting the upper end of the motor coil for each coil to V++, and the lower end of each coil to two outputs on the L293 (or vice-versa). Then when you pulse it (sinking) appropriately, it would turn the motor in one direction only. That would free up the other two half bridges to run a second bipolar stepper in the same manner.
A ULN2003 or other driver transistor array would make a much better solution though, or even using TIP125's, or MOSFET (IRF540's) drivers or 2n7000 fets as well. Depending on the stepper motor requirements.
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Thanx All
After doing a bit more research I found out that they were talking about standard DC motors and not stepper motors. I also inspected my existing circuits wich would prove the feasbility of my question.
Earl if you would could you please point me in the right direction to look a bit more into the other controlers that you've mentioned. I only knew about the L293D as I've just started this hobby, I used to be purely mechanical before - welding, building implements for my tractor, casting AL, etc, so I don't even know about these other components that are available. My main reason for the question was that I was worried that I'm going to run out of ports on my stamp.
By the way I'm building a little plotter, engraver, cutter for myself ... well I'm going to try.
Thanx again Fick
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Well. http://www.jameco.com is a good starting point. They sell the Motorla MC3479P stepper controller/driver IC which is fairly easy to use. They also sell the EDE1200 and EDE1204 and PIC-STEP controller IC's. I like the EDE1200 and EDE1204 chips. You simply pulse/clock the input pin and the IC chip controls the stepper coils for you. Putting a high or low on the direction pin changes the direction. Thus you are only using two I/O pins to control a stepper. With the EDE1200 a unipolar stepper controller, you typically use MJE3055 (2N3055) drivers, but smaller motors can use the ULN2003 array as well. The EDE1204 is for bipolar steppers, and you use H-Bridges with it. Thus the L293 or other driver chip would work well. They also sell the ULN2003 too, it is a simple transistor driver array. A easy way to use steppers is to use the BasicStamp chip from http://www.parallax.com , their manuals and guides are the best. They also have in the lab examples and a excellent tutorial for using a stepper motor as well. http://www.parallax.com/dl/docs/books/sw/exp/ComeON.pdf it uses a ULN2003 driver for the motor.
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I forgot to mention that http://www.allegromicro.com/ also sells many different kinds of stepper motor controllers as well. These tend to be more advanced in use, but they are pretty neat. Just do a search on "stepper" to get started. You can usually get the parts through www.digikey.com and other vendors. Allegro also sends out samples for many of the chips as well.

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