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GraemeJ

DC Motor Interference

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Is a low powered PWM controlled 12 VDC motor likely to cause interference with a DAQ board? The DAQ board, PWM controller and the motor will all be in close proximity in a small enclosure.

The hardware details are:

USB-6221 OEM (ie. no case)

PWM controller: not selected, but typically operating up to 30 KHz.

Motor 12 VDC 7 watt, geared brushed motor.

The application is for speed control of a motor driving a peristaltic pump. Control of the motor requires it to run at two speeds: one at 12 volt, with the resultant speed not important (this is for purging the pump); and the second speed range, say at six volt, requires close speed control under varying load, with software speed control by the user. The varying load is due to the pump rollers progressively squashing the pump tubing.

Any advice would be appreciated.

Regards,

GraemeJ

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I have worked with 'experimental' peristaltic pumps using every kind of motor drive (PWM, H-Bridge, Stepper, Servo) and never had a problem as long as you remember to

make sure that your analog and digital grounds stay as separate as possible.

If you need more isolation then send the PWM through an optocoupler which will break the ground connection entirely.

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Is a low powered PWM controlled 12 VDC motor likely to cause interference with a DAQ board? The DAQ board, PWM controller and the motor will all be in close proximity in a small enclosure.

Any motor and driver can generate a lot of electrical noise that can fry elctronics connected to them. I think sachsm is right about optoisolation. The PWM controller may have sufficient isolation on its own; it should be OK if it accepts TTL inputs, though a little paranoia is not a bad thing.

Otherwise, you'll want to be careful of your grounds, EMI and routing of cables. I've seen 12V solenoids create electrical noise on shielded twisted pair analog inputs when switching the solenoid.

Tim

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