Does the stepper motor need to add an encoder?

There is no encoder for the stepper motor. If you want to add an encoder to the stepper motor, you can step the motor with a double shaft extension and add an encoder to the rear shaft.


The stepper motor is the original, the encoder belongs to the feedback system, the encoder is used with the stepper motor, and the PLC is used to control its operation. According to the principle, the PLC sends a pulse command to the stepper driver. The driver supplies the stepper motor with corresponding current to run. When the encoder detects that the stepper motor runs to the position that needs to be reached, it will feed back the signal to the PLC. The feedback signal stops sending the pulse signal to the stepper driver. When the stepper motor does not have the electric original supply current, it will stop running immediately. (The servo motor is such a device). In fact, the encoder will continuously feed back the current position to the PLC. The PLC compares the feedback value with the target value to adjust the angle of the rotor rotation.


Of course, it will not stop. After stopping, is it the position you want? This depends on whether the motor has a brake device. Of course, if the speed is running at a low speed, the general feed accuracy can be satisfied.


Another is to calculate the number of pulses required for the stepper motor feed in advance, and then use PLC programming, run so many pulse numbers, the stepper motor stops, the encoder feedbacks the motor position at this time, forming a semi-closed loop control. In addition to the high-speed positioning, the PLC program can set the motor to decelerate and feed when it is approaching the position, which can meet the positioning accuracy.


How to add encoder to stepper motor


The resolution of the encoder is roughly the same as the resolution of your stepper motor. If the subdivision on the drive is very high, and you only want to detect whether it is lost, the resolution of the encoder can be equal to or slightly higher than the resolution before the subdivision.


Although the stepping motor is a device that can be precisely controlled, it is open-loop, and an encoder is required to implement closed-loop feedback control. The stepping motor can be measured for out-of-step and rotation or moving speed for dynamic speed control. For this statement, Xiao Bian feels that the first open-loop control requires the encoder to achieve closed-loop feedback. It is understandable, because Xiaobian himself is in use, and occasionally the stepping motor's line connection is not good, resulting in stepping. The motor did not work properly. For the second point stepper motor speed control is not necessary, because by controlling the pulse frequency of the stepper motor can already achieve speed regulation, it is really not necessary to use external feedback.


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