Homing Operation Basics

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om_tech_support_JT
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Homing Operation Basics

Postby om_tech_support_JT » Tue Oct 30, 2012 1:56 pm

Q: Any advice on how to account for when there's a power failure while the stepper motor is running? In other words, how do you make the motor go back to STEP 0 when this occurs.? Thank you.

A: What you are describing is a homing operation function that would be present on your controller, pulse generator, or PLC. There are 2 main types of homing operations: electrical homing and mechanical homing. We have products that do both as well as some select products that can even do sensorless homing. Please ask if you're interested. Electrical homing means that we're commanding the motor to go to a position where the pulse counter (in the controller) is zero. The zero position is wherever the motor shaft is positioned during power up. As the motor is commanded to move, the controller tracks an internal count of the pulses, or steps. The number of steps means how far you are from your electrical home position. The controller will just execute a move using the same number of pulses from the internal counter, but in the reverse direction in order for the motor to reach its electrical home position. You can understand how unreliable this could be if power fails often. Mechanical homing is the more reliable method of the two. When you're doing a mechanical homing routine, you are commanding the motor to rotate in a specific direction until a physical home sensor is triggered. Of course, the home sensor will need to be placed at your specific home position and connected to the controller. The pulse counter will also reset itself to zero after the mechanical homing operation to reflect the fact that your motor is at its home position. You will need to do a mechanical home seeking routine whenever the power fails during the middle of a move to ensure the same starting/home position everytime your operation starts. For any more details regarding homing operations, please ask our knowledgeable technical support group or post your question here.

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