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Re: Automatic flushers



Thanks, Michael. As my old daddy used to say, that's slick as snot.

Paul O. Johnson

----- Original Message -----
From: "Michael Edmiston" <edmiston@BLUFFTON.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, October 19, 2001 4:12 PM
Subject: Re: Automatic flushers


* * * * with regard to diaphragm valves * * * *

I have made a drawing and have included some text to show how a diaphragm
valve works. There are several variations of this, but my drawing and
explanation should get the idea across.

My drawing and text are in an Adobe Acrobat PDF file. Since we're not
supposed to put attachments on e-mails to the list, I put this file on my
root directory of our Internet server. I am way behind times getting a
personal web page set up... I just don't have the time. But you can get
in
your browser and get this PDF file by using the following URL.

www.bluffton.edu/~edmistonm/diaphragm.valve.pdf


* * * * with regard to IR actuators * * * *

William Beaty's description of smart sensors using a microprocessor unit
was
interesting. I am not sure that any smart units are available powered by
batteries; I would guess perhaps not because battery life could be short.

The units we installed in a new building on campus are indeed battery
operated, and I would guess they are not very "smart." It does not
require
a microprocessor to avoid random flushing by passers-by, or by changes in
ambient light, etc. There are a variety of ways to do this. By using
some
combination of integration or differentiation of the photo-detector signal
via simple operational-amplifier circuitry followed by simple digital
logic,
the unit can be made immune to drifting light levels (ambient light
changes)
and immune to quick changes (passers-by). A sustained significant
increase
in detector signal (for a second or two), followed by a sustained
significant decrease in detector signal can actuate the valve. This can
be
done with very low-power op-amps and logic circuits that could easily run
several months on a battery.

This new building also uses key-cards with magnetic strips like those used
in hotels. These also operate from batteries, and battery life is said to
be about a year.



Michael D. Edmiston, Ph.D. Phone/voice-mail:
419-358-3270
Professor of Chemistry & Physics FAX:
419-358-3323
Chairman, Science Department E-Mail
edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817