Reverse the direction of the spindle using PCI 7344 motion controller

[Giridhar_Rajan]

I'm working on a machine tools application. I would like to know, how to reverse the direction of the spindle motor which is connected to the fourth axis of my PCI 7344 motion controller. Can I reverse the direction through software or should I have to enable some hardware bit for it. Also, when I use the "stop motion" VI provided in LV 7.1, the spindle keeps rotating at a slow speed instead of stopping completely. How to stop the motor.

Regards,

Giridhar Rajan

Automation Engineer

Cruiser Controls

Mumbai, India

[Buechsenschuetz]

If you just want your motor to turn in the opposite direction from time to time you have to enter negative values for a relative position mode.

If you want your motor just to turn the other way round as it actually does, there are several options:

- if you use a motor driver with differential inputs for step and dir signals plus a converter circuit to convert the single-ended motion controller signals to differential signals), just reverse the two lines of the DIR input of the motor driver. In case of a motor driver with single-ended DIR input you can also use a hardware inverter circuit for the DIR line.

- you can reverse the wires of one of the motor coils. When working with center-tapped coils, reverse the wires of the extreme ends of one motor coil

- you can swap the wires of the motor coils. For example, swap both wires of coil A with the both wires of coil B.

If you are using an incremental encoder as feedback device you will have to turn the direction of the encoder signals, too, I think in software version 6.1 and above there is a feature to reverse the encoder signals by software. Otherwise you have to swap the wire(s) of encoder phase A and phase B.

[Buechsenschuetz]

Concerning your second problem you should check with an oscilloscope whether the NI motion controller still sends step pulses to your motor driver when the motor is supposed to be stopped.

If there are no visible pulses but the motor still moves, it might be a problem with illegal signals detected by your motor driver, especially when the motor does not move evenly but with small irregular movements. Use shielded cables for the step and dir lines, and use differential signals whereever it is possible.