A4983 weird grounding issue

Hi, I’m getting strange behaviour from my A4983 Stepper Motor Driver Carrier which is driving a 12v bipolar stepper motor.

I’m current running at 9v off a power supply and regulated 5v logic and 50Hz stepping signal from a micro-controller for testing.
When switched on, the motor just shudders without rotating. However, when I touch my finger to the metal casing of the motor, the motor starts rotating. It stops as soon as I stop making contact with the motor casing. The motor also stops when I ground myself by touching the metal casing of my computer wile touching the motor casing.

How can I fix this? Any help in solving this problem would be greatly appreciated.


Do your stepper motor driver and microcontroller have a common ground? Can you be more specific about how everything is connected and what your power supply is? What have you set the driver’s current limit to?

- Ben

The power supply is generic mains input, 9v 2A max DC output. The micro-controller and the driver is commonly grounded as its power is tapped from the same regulated 5v that powers the driver. The 50hz signal is fed into the step pin of the driver while the direction pin is grounded. all MS pins are grounded for full step. enable pin is grounded with reset and sleep is pulled high via a 2k resistor. the current limiting resistor hasn’t been adjusted due to using motor voltage lower than the 12v rated for the motor.


It sounds like you are saying that both enable and reset are grounded while sleep is pulled high, which could at least partially explain your problems. For the driver to run, the reset pin needs to be pulled high. You can do this by connecting it to the neighboring sleep pin, which is pulled high internally (so you do not need the external pull-up). The enable pin is grounded by default, so you don’t need to externally ground it.

Given that touching the circuit made the behavior change, suspect something is not grounded the way you think it is and recommend you double-check your ground connections. I also recommend you check your solder joints to make sure that you have good electrical connections between all of your header pins and the board.

Also, using a lower voltage than your stepper motor is rated for does not mean you can ignore the current limit. If the limit is set too low, your stepper motor won’t get enough current to turn.

If you still have trouble, could you post some pictures of your setup and a diagram of how everything is connected?

- Ben