Newsgroups: comp.robotics
Path: brunix!news.Brown.EDU!agate!howland.reston.ans.net!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!mksol!strohm
From: strohm@mksol.dseg.ti.com (john r strohm)
Subject: Re: Motor noise locks up uController
Message-ID: <1993Dec1.162346.20069@mksol.dseg.ti.com>
Organization: Texas Instruments, Inc
References: <2cmqja$sga@usenet.rpi.edu> <loch-221193102549@137.79.107.113> <2ddpif$22b@skates.gsfc.nasa.gov>
Date: Wed, 1 Dec 1993 16:23:46 GMT
Lines: 24

In article <2ddpif$22b@skates.gsfc.nasa.gov> nstn@quercus.gsfc.nasa.gov (Nathan Stratton) writes:
>I have a problem with noise. I have 2 counters on my robot connected to
>encoders. When I move the motors I get something like this 1 2 3 6 7 9 10. I
>also get clicks on my drive counter when I move my steering motor and on the
>steering vounter when I move my drive motor. How do I fix this????

Most probable explanation is motor-induced noise getting into the counters.
If you don't have 0.01 uF capacitors directly across Vcc and GND at each
counter, try this first.  You might also dig out a Schmitt trigger input
gate package and use that to condition the encoder outputs into the counters.

>I also have a problem with PWM. When I PWM my motors at 50 Hz i.e. on for 8 ms
>off for 12 ms. The motor will spin slowly when the robot is off the ground,
>but when the robot is on the groung the it will not move until I pwm the motor
>to about %90. I am doing something wrong

Two possibilities: (1) your motors don't have enough torque at 50% duty cycle
PWM to haul your robot, or (2) for some reason you have a very high startup
drag problem.  The way to tell which is this: start the 'bot moving with
PWM at 90% or more, let it roll for a few seconds, then ramp the PWM duty
cycle down and see when the 'bot stops rolling and just sits there.  If you
can get your encoders working, this should be easy to detect.


