New Member & Can RPi Zero Control Stepper Motors Query

Looking at the project and assuming it is working, there is nothing to stop you replicating this pretty much exactly on the PI Zero. The GPIO is completely compatible so it should work without alteration. Just make sure the power for the motor controller is not coming from the PI

I agree with Peter.

The main thing you have to keep in mind is that the IO pins on the PI Zero can only source so much current.

So to properly drive stepper motors you want to put either a motor controller between them or add driver transistors on a separate power buss to ensure that you do not overtax the PI Zero, or any other processor, IO capabilities.

The devil is in the details, so you need to look at the current drive requirements of the motors, and the control card.

As long as you do not violate those limits, you can drive a lot of different devices with any MCU, but you need to take care or you release the magic smoke.

DAB

Thanks for the pointer.

Cheers.

A further suggestion would be to look into using an L297 & L298 combo board, the L297 is a dedicated stepper motor controller which can simplify the task. Rather than having to drive all 4 connections in the correct sequence patterns, the L297 takes just 2 inputs, 1 for direction and 1 for speed (which you pulse, the faster you pulse it the faster the stepper turns). I think they only work in full step and half step mode though so if you are going to want to use wave control you'll probably have to do that yourself.

DAB

Understood, thanks for the info, However I can't find the stepper motor (OKI EM-546 12V with 48 steps per revolution) datasheet so any suggestion regards measuring the motor drive current?

Cheers,

Niel.

Yes, I noticed the L298 data sheet flags use of the L297 so currently trying to tack down a boards with both on.

Cheers,

Niel

I think you will find that most stepper motors can support multiples of 48 steps/ revolution.

You just might have to do more steps.

The motor you select will provide you with the drive requirements depending upon the amount of load the motor has to drive.

DAB

Use Ohms law V=IR (voltage = current x resistance). The sum can be reconfigured to I=V/R (Current = Voltage divided by Resistance).

You know the voltage is 12V right so you have 1 piece of information, the next part is to find the resistance of the coils. Bipolar stepper motors have 4 wires, you'll find that they are connected in pairs to a coil within the stepper motor. Measure each pair with a multimeter on Ohm's or resistance setting (each pairs result should be the same) and apply the sum above to your value so Current=12/ohm's

(another useful piece of information is that stepper motors can be used at a greater voltage by reducing the current proportionally, this helps with overcoming back emf and energising each coil phase faster resulting in increased performance but is probably getting out of the scope of somebody just approaching stepper motors).

Hope this helps and good luck!!

You also need to assess the coil reactance, not just the wire resistance.

You get different effects with frequency and stray capacitance in the leads.

DAB

Agree