Because the motor of the device is free to move after power failure, the device does not know the specific position of the motor after power-on. Therefore, after power-on, the software will send a motor homing command to let the device perform a motor homing.
Motor homing is generally when the motor runs to the end of the device. There is usually a limit switch at the end of the device. After the device reaches the end, the limit switch will be triggered. After the limit switch is triggered, the device will stop, and the motor homing process ends. The device also knows the current position of the motor. After the reset is completed, you can control your device.
NEJE control boards with hardware versions lower than v2.0.0 all use physical limit switches for end detection. When the device runs to the end, the limit switch should be triggered. If the limit switch is damaged or the limit switch is prevented from being triggered, you may find that the stepper motor continues to run at the end, making a "clicking" sound.
NEJE control boards with hardware versions higher than v2.0.0 do not use physical limit switches for end detection. Instead, they use current sensors for end detection. The embedded microprocessor samples the running current of the stepper motor 1000 times per second, and senses the arrival of the end by sensing the slight current changes between the normal operation of the stepper motor and the arrival of the end.
Using a current sensor to sense when the stepper motor reaches the end can solve the problem of limit switch damage and has higher reliability and almost unlimited service life.
Please refer to this document Motor Homing Troubleshooting