Driving bipolar stepper motor using piface

hi All,

I bought Piface recently and want to drive 12V bipolar stepper motor(four wire). i did found some tutorial on internet around driving unipolar motor, but there is nothing on bipolar motor.

I am from software background, and have very little electronic knowledge, so if someone can guide me on circuit arrangement that will be helpful.

thanks in advance for your help,

D_Hersey over 11 years ago

Both unipolar and bipolar motors are intended to set up a magnetic flux in order to turn the rotor. The unipolar has four coils, two in opposition magnetically speaking. The bipolar has two coils which must be driven both ways. If you have a 6 or more (8) wire unipolar motor, it can be run in bipolar mode at twice the potential through connecting it appropriately.

You need either a split supply with push-pull drivers, or a single supply and H drivers.
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rew over 11 years ago in reply to D_Hersey

Yes, but he has a 4-wire motor, so hooking it up as an unipolar one is not possible.

My suggestion: Buy an A4988 stepper driver. (I have a few, more are in the mail. :-) ). If you configure most of the inputs statically, you need only two GPIOsignals to drive the module: "direction" and "step"....
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Former Member over 11 years ago in reply to D_Hersey

Thanks Don,
At a moment I have only bipolar four wire motor, I had drived this motor previously with Arduino using Arduino motor shield, so interfacing was straight forward, but how do interface/connect my four wire motor with Piface ? can it be done without using any additional components/drivers ? if not then which driver is recommended on top of PiFace ?
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Former Member over 11 years ago in reply to rew

I like A4988 drivers, I will order couple of them to experiment with.
but for now can drive motor with simple H-bridge or ULN ? and how circuit will look like ?
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rew over 11 years ago in reply to Former Member

I checked the specifications for the "piface". PiFace – PiFace Digital and it lists: 8 Open-Collector Outputs, which is good for driving two unipolar stepper motors, but doesn't help you a bit in driving a bipolar one like you have.
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Former Member over 11 years ago in reply to rew

hi Roger, I got my A4988 driver, I am trying to setup circuit using PiFace. In A4988 connection diagram logic power supply is going to VDD pin, now I am not sure which pin on PiFace is VDD ?
also I am assuming "logical power" is actually power coming out of PiFace (output pin 5V and GND on input pins) ?

it will be helpful if you can show me complete circuit arrangement.
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shabaz over 11 years ago in reply to Former Member

Hi Sharique,

As I understand (I don't have a PiFaceDigital or a A4988) the PFD has a 5V supply rail derived from the raspberry pi. There are screw terminals on the PFD for that, marked 5V and 0V. You can confirm that 5V is present with a multimeter. It could in theory be used to power the logic of the A4988.
You need a separate supply for the motors of course.
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Former Member over 11 years ago in reply to shabaz

thanks Shabaz, on PiFace there is 5V pin within output pins and I guess your referring to GND pin by 0V, there is a GND pin within input pins.
and to confirm is it ok to use 5V pin as VDD ?
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shabaz over 11 years ago in reply to Former Member

Hi, that's correct.
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Former Member over 11 years ago in reply to shabaz

thanks it works.
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