New Member & Can RPi Zero Control Stepper Motors Query

Question

Just joined, hello all.

I joined to help learn about controlling stepper motors for a few little projects I'm working on. One query is whether or not the RPi Zero can also be used to run stepper motors as out lined for example in TUTORIAL - How to control a bipoloar 4 wire stepper motor? I've not come across anything about the zero doing so. If there is info out there I would appreciate a pointer or two

Cheers,

Niel

drmac · Accepted Answer

Thanks for the pointer. Cheers.

e14 Contributor · Answer

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!!

e14 Contributor · Answer

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.

Robert Peter Oakes · Answer

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

DAB · Answer

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

DAB · Answer

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

Robert Peter Oakes · Answer

In answer to if the PI Zero can run stepper motors is simple YES BUT, you will need a driver to convert STEP and DIRECTION pulses to coil rotation signals strong enough to drive the stepper, or you will need a driver that can directly control what is called a DUAL HBRIDGE that can directly control the stepper, basically an H Bridge is made up from 4 transistors and is able to reverse the voltage on the windings of the motor coil. If your plan is to drive a stepper fast then using a driver that takes step and direction pulses is an easier way to go, this also simplifies the code. If you're playing with steppers and learning how to drive them then building or getting a basic HBRIDGE based driver will teach you more. The Driver (HBRIDGE with 4 wires or a controller with Step and Direction) can typically be easily driven by pretty much any microcontroller or embedded CPU, this includes all of the Raspberry PI range, Arduinos, Launch pads etc. PI driven Stepper Controller HAT :- https://www.adafruit.com/product/2348 Alternat and far more powerful stepper controller that can be driven by a PI (Great for Robots and the like) Stepper Motor Drivers | Farnell element14 more expensive yes but much more applicable for industrial and heavier duty use, also much more robust.