Any time the load can be easily back driven or is in a vertical orientation, an electromechanical fail-safe brake is highly recommended. Under no situation should a PLC or external controller be used to control a fail-safe brake on a servo. The response time will be diminished to the point of defeating protection. Instead, use the SmartMotor interrupt control features stated here:
Use the BRKG command in conjunction with the BRKTRJ or BRKSRV commands:
- BRKC 'Send automatic brake control signal to Port C
- BRKG 'Send automatic brake control signal to Port G
- BRKSRV 'Engage brake on any motor shaft fault, 'Position Error, Limit Switch Error,
'Continuous Over Current/Over Temp
- BRKTRJ 'Engage brake when not moving (Follows the Bt "busy trajectory" status bit)
In making use of selected commands from above, the brake will get a signal to engage (be de-energized) within 250 to 500 microseconds of its trip condition. Using the PLC will cause a delay of anywhere from 4 to 10 milliseconds due to scan time, process time and brake release time. By then, the current in the control could have already well exceeded limits.