Stepper motor gets really hot


I believe I have a problem with a stepper motor. I’m using this:
and drive it with a 8825 driver:
It’s connected according to the “Using the driver” diagram to a Raspberry pi. I set the current limiter in the driver to emit slightly less than 500mA, my external motor power supply provides 12V.

The motor works fine, it turns as expected. Different tested stepping modes work. But the motor gets rather hot. Quickly after providing power to the motor, it reaches 50°C measured on the outside. During operations, it easily reaches 65°C.

If I leave it idle for a while, temperature actually reaches close to 80°C.

The load it drives is really light, it just drives a sprocket wheel to transport film. Would this be within the expected parameters for the motor?



The data sheet gives the rated current as 500 mA/winding and the temperature rise as 80 degrees Celsius maximum with both windings on, so the motor is operating within specifications. Stepper motors can safely be run very hot, as long as the limitations given in the data sheet are observed.

With a light load, you should not need to run it at 500 mA, so reduce that. If motor speed is an issue, using a much higher power supply voltage will significantly increase the allowable step rate. See for more than you ever wanted to know.

Thanks Jim,

it seems, I missed/misinterpreted the 80° in the data sheet. I would have expected that the motor reaches 80 under heavy load but apparently it get’s there just idling/holding position with power on.

I’ll check whether I get the temperature down with lower current.

With a stepping motor, the load matters little. The current draw and heat dissipated is essentially the same regardless of load. Back EMF is developed only during a step, whereas in a brushed DC motor, back EMF is proportional to the rotational velocity.