Newsgroups: comp.robotics
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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: PWM DC motor control
Organization: The Armory
Date: Thu, 24 Mar 1994 10:18:44 GMT
Message-ID: <Cn5zB9.1Jn@armory.com>
References: <Mar18.181352.31507@acs.ucalgary.ca> <LXeHJc1w165w@sfrsa.com>
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In article <LXeHJc1w165w@sfrsa.com>, Ed Severinghaus <eds@sfrsa.com> wrote:
>morrow@cns8.cns.ucalgary.ca (Bill Morrow) writes:
>> 
>> Is anyone trying to actually vary the driving voltage to the motor,
>> using some feedback from shaft encoders? You know, just like they 
>> taught you in that control systems course. It seems to me that this
>> type of control system would be more efficient, responsive and cover
>> a wider range of motor speed.

>"... more efficient ..."  no way even if you used a variable output 
>switched mode power source.  PWM has the control (transistor) fully on or 
>fully off except for teh *very* brief switching times, "analog" control 
>would waste a ton or two of power in the control device.
>"... wider range ..."   why would you think that?
>Ed
-----------------
That's funny. I took Bill Morrow to mean to use the shaft encode output to
control the PWM pulse duty cycle or frequency or such. I don't think
anybody wants an old analog thingy, unless you just want to smooth the
motor activation with a cap. Did you, Bill?
-Steve Walz   rstevew@armory.com

