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From: "Thomas C. Sefranek"
Subject: Re: Wanted: comparator circuit design
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
Date: Mon, 28 Oct 2002 22:38:17 GMT
NNTP-Posting-Date: Mon, 28 Oct 2002 14:38:17 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
I'd use a single Microchip PIC with analog inputs.
| __O Thomas C. Sefranek WA1RHP@ARRL.net
|_-\<,_ Amateur Radio Operator: WA1RHP
(*)/ (*) Bicycle mobile on 145.41, 448.625 MHz
Mike wrote in message
> 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
> AC motors).
> 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!
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