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Subject: Re: Wanted: comparator circuit design
Organization: The Armory
X-Newsreader: trn 4.0-test69 (20 September 1998)
From: email@example.com (Richard Steven Walz)
Date: 29 Oct 2002 07:26:01 GMT
In article ,
>I have a linear actuator which incorporates a 1Kohm potentiometer
>which indicates the relative position of the arm. Fully retracted it
>reads about 900 ohms and fully extended it reads about 200 ohms.
>I want to wire up some comparators and logic to automate the shut-off
>of the motors which extend and retract the arm.
>There is a separate power lead on the motor for each direction (120V
>I would like to incorporate the following:
>1) An "extend limit" potentiometer; this sets the upper limit at which
>the motor stops when extending (example: set for 890 ohms).
>2) A "retract limit" potentiometer; this sets the lower limit at which
>the motor stops when retracting (example: set for 210 ohms).
>3) A momentary "extend" pushbutton, which when pressed, will apply
>power to the extend motor, until the actuator potentiometer reaches
>the limit set in 1) above.
>4) A momentary "retract" pushbutton, which when pressed, will apply
>power to the retract motor, until the actuator potentiometer reaches
>the limit set in 2) above.
>5) A momentary "stop" pushbutton which will disable either the extend
>or retract motor, if running, prior to hitting the above limits.
>6) Pressing "extend" while already retracting or "retract" while
>already extending would cancel the current movement and begin movement
>in the chosen direction.
>I know this can be accomplished with a few comparators, some logic
>gates, and some latches.
>The motors draw under 1 amp; it would suffice to switch them via a
>relay driven by the logic output, although a solution using a triac or
>similar would be all the better.
>Any ideas greatly appreciated!
Also, you can use LM339 open-collector single-supply comparators to
run an NOR gate RS-latch to an H-bridge to do the same thing.
-Steve Walz firstname.lastname@example.org ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
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