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Hi All,

This is for a simple home project i'm cooking up.
I need an optical component that signals high (or low..) as a beam it
emits is interrupted (basically, what the had in the old elevators to
open the door if somebody interrupted while it was closing). I'de
rather have a retroreflector on one side to keep all the wires together
so a trasmitter and receiver should be incorporated in one component
controlled by a microcontroller. The distance beteeen component and
retroreflector should be ~50cm-1m.

A cheap solution would be nice..


Re: OptoSwitch

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Take a 5mm IR LED and a matching photo-diode or transistor.  Put at
least the receiver in a tube so that it does not pick up light
directly from the LED. Drive the LED with a few kHz square wave.
If you use a low duty cycle you can often drive the LED with quite a
large current. Use a LM2907M or similar device to trigger on the
frequency that you use to drive the LED. This way you can AC couple
the Rx side amplifier, and use a high gain, since you are not
interested in amplitude info.

Hope this helps

   Anton Erasmus

Re: OptoSwitch
On Tuesday, in article

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Possibly even use a IrDA LED pair with this sorted already, including
IR pass optical filtering to only pass the light in the IR band and not
all light bands.
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Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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