Step Motor Controller with hand knob

[htekin42]

Dear All,

We have a plastic film cutting machine and blades are controlled with stepper motor. Motor moves blades with ball screw but on the other side of screw there is an hand knob. Microcontroller send the pulses to motor for required blade position. At the movement time, operator may use hand knob and we need to detect that operator trying to operate with hand knob and disable the stepper motor. We are using NEMA 23 motor with 4A current and MA880 driver. It has enable pins. How can we detect that the user trying to operate with hand knob? current sense or etc.

 

[KlausST]

Hi,

If possible don't use the existing hand knob and replace it by an electrical hand knob.

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Otherwise install a rotation encoder to detect if someone moves the knob. Then disable the motor driver.

Klaus

 

[danadakk]

You could use capacitive touch to detect operator touching knob. Many
processors these days have that capability. Very cost effective.

https://www.cypress.com/file/219726/download

In fact these parts have A/D on them so touch could light an alarm, actual
knob movement using A/D to detect V or I change to stop stepper.....

Same processor by the way can handle stepper control as well....

PSoC 3 Stepper Motor Control with Precision Microstepping

Stepper motors are ideally suited for many measurement and control applications. However, their advantages can only be realized through careful circuit design built around an appropriate MCU.

www.digikey.com

Regards, Dana.