Is it bad to use a DC gear motor to hold a position?

I would like to use a DC gear motor (something like this) in a mechanism that needs to be rotated to a Position A and held in Position A for 12+ hours at a time. A torsion spring will be providing a constant restoring torque on the motor in Position A. I would like to provide the motor with a current limited PWM signal to hold position. Provided that this current is under the motor stall current, is this acceptable practice?


You can use a brushed DC gearmotor like that as long as the load is appropriate for the motor (a general recommendation is 25% or less of the stall current). You will also need some kind of sensor feedback (e.g. an encoder) to implement closed-loop control.

However, given the 12+ hour interval you mentioned, it sounds like your application might have a long continuous operating lifetime requirement, and a brushed DC motor by itself might not be a great choice if that is the case. We do not have our motor or gearbox lifetimes well characterized, but for small brushed DC motors like ours you are generally looking at something in the range of a few dozen to a few hundred hours (depending on your operating conditions), so 12 hour intervals or full days of continuous operation can eat into that quickly. With that in mind, you might want to consider adding something to your system that would allow you to turn off the motor, like a brake or a locking mechanism, or you might consider a different type of motor designed for longer operating intervals, like a stepper motor or a brushless DC motor.

- Patrick