Alt-BEAM Archive
Message #02797
To: westy civic83@execulink.com
From: "Jesse D." smokin@n-link.com
Date: Fri, 30 Apr 1999 00:29:58 -0500
Subject: [alt-beam] Re: fled photovore
westy wrote:
> My problem is the circuit dosn't work, is the resistance of these ldr's
> too high?, should I run a 2.2k resistor in parallel with the ldr? what
> about using photodiodes?
>
> Also, what is the difference between a photodiode and a phototransistor?
>
Photodiodes are the way to go in a photovore, you can order them from
Digi-Key or rip them out of an old PC mouse (theres 2 inside [sometimes
Phototransistors] along with 2 IR LEDs)
As for PhotoTransistors. You can use them instead of diodes BUT they
MUST be the 3-lead type (with base) all you do is use one half of it,
I.E. The base (center pin) and one of the other pins, doesnt matter
which.. the Transistor has a light sensitive PNP junction. all you need
is one of the PN junctions (a diode)
Although I do believe I have seen some schematics for using
photoresistors. Just make sure they are both the same value...
--
__ __ Jesse C. Druehl __ __
/ `-' / ,,, AKA (Smoke) ,,, \ `-' \
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