Hi Roman, et all,

You are in deed correct. I put the photodiode on a breadboard,
and attached my DMM to it. I read 500K when no IR light was present.
I shined the IR light from my digital camera on the photohdiode
and the resistance dropped to practically nothing. Thanks !

P.S. I changed my reply to address to the piclist

>Kevin A. Benedict wrote:
>>
>> >From David Duffy
>> >The 3 pin IR detector may be 2 IR detectors with a common lead?
>> >Does the encoder have 2 sections - one 2 pin and the other 3 pin?
>> >I'd think that it'd have to otherwise it couldn't detect the direction.

>>
>> I got a nice Infrared Picture of the phototransistor,
>> and three other pictures of the mouse circuit, about
>> 200kb all together.
>> http://www.members.dca.net/kben/misc/mouse.html
>
>> Any comments on interfacing the ir led and phototransistor
>> to a PIC are welcome.
>
>
>Hi Kevin, that IR sensor is a dual IR photodiode.
>It has one common pin and two pins for the outputs
>of the 2 separate IR diodes.
>
>These are easy to interface to the PIC, you can run
>the LED with a few mA, normally about 5mA, and connect
>the IR diode(s) via a high value resistor to +5v.
>Try about 56k to start. The IR diode is REVERSED.
>
>When NOT illuminated the IR diodes have little leakage
>and will act open circuit, so the voltage to the PIC
>is a logic HI.
>
>When illuminated with IR, the diode resistance drops
>to a few k ohms, and the voltage to the PIC goes to
>a logic LO.
>
>Like this:
>              a   k
> 0v (gnd)------->|-------*----R1------- +5v
>              IR diode   |    56k
>                         |
>                         |
>                   output to PIC
>
>-Roman
>PS. Can you FIX your reply-to address!!!!
>
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>
>
>

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