Path: utzoo!attcan!uunet!wuarchive!cs.utexas.edu!asuvax!noao!lytle
From: lytle@noao.edu (Dyer Lytle  CCS)
Newsgroups: sci.electronics
Subject: selenium photo-electric cells?
Keywords: selenium photo-cell camera
Message-ID: <1990Jul13.223322.4820@noao.edu>
Date: 13 Jul 90 22:33:22 GMT
Organization: National Optical Astronomy Observatories, Tucson, AZ, USA
Lines: 27



    Does anyone here know much about selenium photo-electric cells of the
type found in *old* camera light meters?  I have an old camera whose light
meter has lost much of its accuracy and I would like to repair it.  I don't
think the parts are available anymore so I will have to substitute something.

    Is the selenium cell photo-voltaic?  Does it generate a voltage
proportional to the amount of light hitting it.  Does it generate a
proportional current?  The circuit has a 5600 ohm resistor and a meter
which I suspect is similar to a galvanometer.  I can play with the resistor
in an attempt to calibrate the circuit I suppose.

    Can I replace the selenium cell with a silicon solar cell such as those
I can buy at Radio Shack?  I've fooled around with these and the current
verses light curve seems to have a different shape than the selenium cell
although I can't be sure since I don't have a milliammeter.

    Otherwise, where can I get a selenium cell that I could cut to fit in
this camera?  Any information would be helpful.  Thanks.

 -Dyer                  lytle@noao.edu

-- 
Dyer Lytle, National Optical Astronomy Observatories, Tucson, AZ, 602-323-4136
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