Alt-BEAM Archive
Message #02360
To: beam beam@corp.sgi.com
From: "Ben Hitchcock" beh01@uow.edu.au
Date: Thu, 15 Apr 1999 18:53:35 +0000
Subject: [alt-beam] IR photodiodes in Mouses (Mice?)
I pulled apart an amiga mouse and tried to get the photodiodes to work.
Here's what I found:
The transmitter is coloured pink, has two leads, and operates above 0.5 mA.
The receiver is clear, has three leads, and consumes about 5 mA at 5 volts.
The receiver is pretty special: it appears as if there is a bit of logic
inside it: It outputs a clear high/low signal depending on whether the
transmitter is in range or not. There is no analog levels, just a digital
high/low.
Connections:
Hold the transimitter (pink) with the bubble facing towards you, and the
leads hanging down.
The lead on the left is negative, and the lead on the right is positive.
Hold the receiver (Clear) with the bubble facing towards you, and the leads
hanging down. The lead on the left is negative, the lead in the middle is
signal, and the lead on the right is positive.
The transmitter is just like a LED: Connect a 500 ohm resistor in series
with it, connect it up to a 5 v supply, and the thing will transmit.
The receiver is even easier to wire up: Connect the negative lead 0 Volts,
and the positive lead to 5 volts. Then just use the signal lead as an input
to your microcore, however you wish to wire that part up. It will output
High when it sees IR, low when there's no IR visible.
The receiver starts operating at about 2.7 volts, so I guess it's meant for
5 volt operation.
I got a range of about 5 cm facing one another, and 1 cm range detection
(bouncing the IR light off a wall). So you aren't going to be able to use
this as a wall detector, but it would work well as a cliff sensor, mounted
close to the ground.
In the case of using a calculator, you will probably have to use a
transistor or similar to switch the 'equals' pad when the beam is made or
broken.
See http://wollongong.apana.org.au/~ben/info/
for more information on
transistors.
Ben
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