A4988 / Stepper Motor Troubleshooting

I am having some trouble getting a stepper motor working with the A4988 stepper driver. I have been trying to figure out where the setup is failing. I have isolated the stepper driver for troubleshooting purposes and made connections as shown in the diagram below.

To keep everything as simple as possible, MS1,MS2,MS3, and EN are not used.

The current limiter has been set to 0.6V for the reference voltage (previously working with same motor)
When pin7 STEP is supplied with +5V, pins 11-14 all show +12V
When pin7 STEP is disconnected , pins 11-14 all show 0V

This seems logical and correct. If its not somebody please tell me what I’m doing wrong.

Standard bipolar stepper motor. I have identified the coil pairs by connecting the pairs and observing the motor torque. I have connected the pairs to the 1A/1B and 2A/2B pins respectively. I have measured the voltage as it enters the motor to ensure proper connections and still all 4 pins show +12V.

It is my understanding that with this setup I can intermittently apply +5V to pin7 STEP and I should see/hear/feel something from the motor. However, nothing happens. It is also my understanding that there should be some holding torque present in the motor when pin7 STEP is disconnected. Again, this is not the case.

I’m am out of troubleshooting ideas at this point. I do not know how to further test the motor and I am not positive I have tested the A4988 correctly. Any advice would be much appreciated.

( please note the diagram is missing a 100uF decoupling capacitor on the +12V net )


Can you post some pictures of your setup and tell me how you are powering your stepper motor driver? Could you also post a datasheet for your stepper motor or a link to where you got it?

- Patrick

I have wired it all via a breadboard as shown in my previous post exactly to the diagram. I am unable to take pictures at this time.

Voltage has been checked along the entire circuit, both 12V net and 5V logic net. Power going into the A4988 is as expected for for driving the motor and for the A4988 logic. I guess what I really need to know is assuming the STEP pin is HIGH with 5V, what should I expect the voltage to be at 1A,1B,2A, and 2B? If I am getting the appropriate output voltage, I would be more inclined to assume the motor is dead and replace it.

Thankfully I purchased the A4988s in a lot of 5, so I have been able to swap them out just in case. Sadly, I am down to my last available stepper motor so I am unable to swap that out to troubleshoot. Im open to other means of testing a stepper motor, I just dont know any.

I would not expect all of the motor outputs to ever be high at the same time. Are you sure you have A4988 carriers we made? There are a lot of knockoffs of our stepper motor driver carriers out there. Can you post some pictures of your drivers and your setup?

- Patrick