Technical FAQs

# Can I build a brake control circuit to control the brake on a Servo or Stepping motor?

Customers my have instances in which they need to control the release and setting of a holding brake of a servo motor or stepping motor independently.
This can be done but requires some additional circuitry to reduce the voltage to the brake when it is released so as not to overheat the motor.

Attached you will find a schematic diagram of a holding brake control circuit.

Circuit description is as follows:
When 24 volt is applied to the positive side of the junction of R1, D1 and C1, current will immediately flow through C1 because it is discharged, thereby releasing the brake.
As C1 charges the voltage is applied to the brake winding through R1 and it will maintain the brake in a released state.
This voltage will be reduced by R1 to maintain the brake in a released state without excess heating of the brake winding. .
When the 24 volts is removed, D1 serves to rectify the back EMF created by the brake coil magnetic field collapsing which will be discharged by C1 and R1
C1 will fully discharge due to R1 thereby preparing the circuit for the next brake release cycle.

Component values are provided below

For motors with brakes rated for 24 volts at approximately 8 watts
R1 = 24 ohms at 6 watts, C1 = 4700 uF at 35vdc, D1 = 1N4001 or equivalent.

For motors with brakes rated for 24 volts at approximately 20 watts
R1 = 18 ohms at 8 watts, C1 = 6800 uF at 35vdc, D1 = 1N4001 or equivalent

You can vary the value of C1 and R1 to meet the needs of motors with brakes that have other wattage ratings.

Rev 9-18-17