Very noobie question so apologies in advanced. I didnt see anything on this forum, or in several google using various search terms, related to this
I have a raspberry pi 3, a polulu drv8835 dual motor driver kit for raspberry pi (assembled and tested with two small toy motors), and two stepper motors (a Nema 17 and a small PM25L-024-BRW6). The raspberry pi 3 has its own separate power supply.
I have two questions:
- I dont know how to connect steppers to a drv8835 to stepper motors in general. Basically where do the four stepper wires connect to on the drv8835?
- can the drv8835 drive a nema 17? If so, what do I need to do (if anything) to the drv8835 (I think there is a need to connect the the two channels but not sure how)?
if there is a diagram or pic of the setup, it would be really appreciated.
the nema 17: JK42HS34-0404, 12V, 0.4A
the PM25L: cant tell if 12V or 24V, 3A
many thanks in advance
Our DRV8835 Dual Motor Driver Kit for Raspberry Pi is meant to drive a pair of brushed DC motors. It is not possible to drive two bipolar stepper motors independently using that board and we generally recommend using an indexing driver like our A4988 carrier boards with stepper motors since they have a simpler interface.
The product page for the A4988 board has general instructions for the using the driver like a minimum wiring diagram and a video that discusses how to set a current limit for your motors. You might look around for general instructions about how to connect a stepper driver that uses step and direction pins (like the A4988) to the GPIO pins on the Raspberry Pi. If you post a wiring diagram for your system here, we would be happy to look at it.
Thanks for the reply.
One of the reasons I bought the drv8835 was because the Polulu website specifically mentions “Dual-H-bridge motor driver: can drive two DC motors or one bipolar stepper motor” (https://www.pololu.com/product/2135). That said, I thought it might be able to drive the one PM25L (which is a small stepper) OR the Nema. I can still use it for some small motors I have but the website should be corrected
It is possible to use two H-Bridges like those on the DRV8835 Dual Motor Driver Kit for Raspberry Pi to control a single bipolar stepper motor like the ones you mentioned. If you want to use your DRV8835 board, you can look at this post on our forum for more information about how to connect the two coils and how to control the H-bridges. You also might be able to find other tutorials on the web that provide more explanation about how to use a pair of H-bridges with a bipolar stepper motor.
The maximum coil currents for the two motors you listed are below the maximum continuous rating for our DRV8835 board (1.2A), so it should be capable of driving either of those two motors. You should be aware that the NEMA 17 motor you mentioned requires a 12V supply to reach that current and the maximum supply voltage of the DRV8835 is 11V, so you would need to use a lower voltage supply and the coil current (and therefore, the motor torque) would be lower than the specified maximum. The 12V and 24V ratings for the other motor you listed seem to be supply voltages when used with a current limiting stepper driver like the A4988 I mentioned in my last post. To use the DRV8835, you would need to determine the voltage at which the motor’s coils will draw their rated current and use a supply voltage that does not exceed that.