What you wanna do sense with it ?
Friedel

At 10:16 a.m. 15/11/01 +1100, you wrote:
>There are lots of cheap sensors available; photo transistors (MEL-12), photo
>diodes (even a standard red LED can be used), simple transistor or op amps
>can be used to boost the sensitivity to any reasonable level you require.
>But they all suffer from ambient problems.
>
>When mounted in a long tube (to block ambient light from the sides) they
>have a very limited view window.  When mounted at the focus of a parabolic
>reflector the angle is increased, but so is the ambient pick-up.  How can
>you get around this?
>
>Work out the geometry of your desired view zone and place a few sensors 'out
>in the open' to pick up the average ambient light.  Mount a few more in
>about the same positions, but blocked from the area of interest.  Mount a
>main detector in a parabolic reflector that fully covers your area of
>interest.  This gives you [+target +ambient], [-target +ambient] and
>[+target].
>
>A good choice is an old fashioned head light reflector with one pick up at
>the focus and another six (3 shielded) around the rim.  Real old ones have
>very wide pick up.  Sum the ambient sets with op amps and you get 3 signals
>to feed to a cheap PIC for logging (or processing and displaying in real
>time).
>
>Bye.
>
>
>-----Original Message-----
>From: Peter Grey [mailto:martech@OZEMAIL.COM.AU]
>Sent: Thursday, 15 November 2001 7:36
>To: PICLIST@MITVMA.MIT.EDU
>Subject: [EE]: Light Sensors
>
>
>I wish to measure light during the night. I am told that typical levels are
>around 0.1 lux. They want a wide range with good resolution. By the way it
>must be light and cheap! Has anyone got any suggestions? I am trying to
>measure a broad band of visible light that animals are exposed to. The moon
>is also a factor.
>
>TIA
>
>
>Peter
>
>--
>http://www.piclist.com hint: The list server can filter out subtopics
>(like ads or off topics) for you. See http://www.piclist.com/#topics
>
>--
>http://www.piclist.com hint: The list server can filter out subtopics
>(like ads or off topics) for you. See http://www.piclist.com/#topics

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics