# Motor torque limiting

Hi everyone, so I'm controlling a small geared motor with a h-bridge via pwm and am wanting to decrease the torque by half (I know this sounds weird but I just want too for "experimentations sake" )
There are two methods I can think of, one is to gear down the motor with a 3d printed gearbox and the second is to put a current limiting resistor in line with the motor. My question is, is there a difference on which method I use. Gearing down the motor and limiting motor current should both result in the motor stalling early right? So does it matter which I do or is there a difference?

Also I know a bit about motors and pwm control but I want to learn a bit more on pwm control and the effect of motor voltage and current variation on performance, if you could drop a link or reference for somewhere for me to start, that would be great

Thanks, any advice and insight is appreciated.

Gearing down the motor and limiting motor current should both result in the motor stalling early right?

No, "gearing down" increases torque at the expense of rotational speed.

A resistor reduces the voltage to the motor, depending on the motor current.

Torque is proportional to motor current, which in turns depend on the applied voltage and speed of motor rotation.

Since you have an H-bridge, presumably connected to an Arduino PWM pin, then you can change the torque by analogWrite()ing a different value to the pin. It may take some experimentation to find exactly half as the response is not linear.

Normally in motor control you would control torque by using a current sensor on the motor lead(s) and
then implement a PID loop to control the motor current. This allows programatic setting of the torque.

For simple max torque control you can use simple current limiting on the supply, but this then drops the
voltage to the H-bridge when it limits and some H-bridge's don't like that.