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From: mlipsky@powergrid.electriciti.com (Mark Lipsky)
Subject: MOTOR NOISE in my Transducer Circuits -- Please HELP!
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Date: Thu, 4 Aug 1994 22:17:23 GMT
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Organization: EFFECTive ENGINEERING

(This articale also posted to sci.electronics)

I'm a mechanical engineer and my project is paralyzed with electrical
noise;  can someone help me?

I have a ball screw actuator driven by a 130 vold DC brush type gear
motor (90:1 gearing).    The motor is being driven by a SCR (phase
chop) type controller.  The fixture also has a load cell (and signal
conditioner) and a pressure sender being read by a PC with a data
acquisition card.  This setup is being used for medical research.  

Currently, when I run the motor, I get horrible noise on my signal
lines going to the data acquisition system.  I've tried serious
grounding, RF shielding around the motor, EMI filters to the motor
controller & signal conditioning electronics, and I've tried a Minarik
PWM motor driver as a substitute for the phase chopped unit.  The
filtering helps some, but I'm still getting .2 volt spikes on my signal
lines.  I need to be down in the millivolts!  

What am I doing wrong?  Is there any hope of saving this setup or do I
need to go to a low voltage brushless DC motor and driver?   I would
greatly appreciate any help.   

Thanks in advance.  Mark.
