Hi all,

I have a need to detect an object passing by a phototransistor, 2=94 to 6=
=94 away.  Indoors is easy: I have an IR LED reflecting off the object.  (I=
 can not have the object break a light beam from the LED.  Everything must =
be contained in a single, small box.)  When the object passes by, I get an =
increase in voltage.  Outdoors, I expect the object to block ambient light =
and give me a lower voltage when it passes.  This works most of the time.  =
Sometimes I get a higher voltage (which is OK) but sometimes I get no or ve=
ry little change.  I have a narrow tube over the phototransistor about 2=94=
 long to make it more directional.  It has to work with the sun in any posi=
tion.  You would think it would work best when pointed in the direction of =
the sun (with the object blocking the sunlight), but this is actually one o=
f the worst conditions, especially in the afternoon.  Maybe extra IR is get=
ting in from hot surroundings?

Any idea why I don't always get a voltage change, and how I could possibly =
make this work?

Thanks much for any suggestions,

Dan
-- =

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