Controlling stepper motor with DRV8833

Question

I’m trying to get a Nema8 stepper motor working with a DRV8833 controller. The stepper motor has 0.6 A specified on its label but no other data mentioned. Its the connections are A+, A-, B+ and B-.

I’m using an MSP430G2553 Microcontroller to generate a PWM waveform with 20 ms period on one pin. I’ve tried to test the motor with varying duty cycles from 5% to 20%. The stepper motor does not do anything, but when I touch the shaft of the stepper motor, it buzzes and seems to work against the force applied.

I’m using this board for the DRV8833. It has the following pins:

• The Pin Vmotor is connected to a power supply 5 V <700 mA PSU and Vmotor- to GND • PWM Input Pins: AIN1, AIN2, BIN1 and BIN2 • Output Signals: AOUT1, AOUT2, BOUT1 and BOUT2 • Other Pins: nSleep (connected to Supply Voltage High)

The problem is I’m not sure my connections are correct. How would one use the DRV8833 with a stepper motor and what would the PWM signals be?

How would the stepper motor need to be connected to the DRV8833 board?

• AOUT1 to A+, BOUT1 to B+, AOUT2 to A- BOUT2 to B-?
• AOUT1 connected to A+ and B+ and AOUT2 to A- and B-?

How would the PWM output send to the DRV?

• (only) AIN1 to PWM pin? Or
• AIN1 and BIN1 to PWM pin?

Since the behavior does not change with the above connections, I suspect that my power supply doesn’t give the needed current. Can someone advise on the connections for the DRV8833.

Answer 1

It seems you have a 4-wire 2-coil bipolar stepper motor, it is not controlled by a single PWM signal. You need to drive all four inputs (Ain1, Ain2, Bin1, Bin2) of the driver to obtain synchronized outputs for both coils.

The driver chip in the module you have is capable of operating both a standard DC motor and a stepper motor. In the data sheet disregard most of the data on the PWM mode until you understand the basic 4-signal stepper motor concept. Note that on figure 7.2 of the datasheet the connections are shown for both motor types, disregard the connections of the two DCM motors.

Here are a few tutorial pages on using stepper motors, these include other types of stepper motors and some more complex drive patterns, read more of the 4-wire bipolar examples first.

https://buildbotics.com/wiring-stepper-motors/

https://42bots.com/tutorials/stepper-motor-wiring-how-to/

https://forum.arduino.cc/t/simple-speed-control-for-bipolar-stepper-motor/301532