> will hit the aluminum foil reflector and bounce back to the IR transistor
> and signal the device that the door is closed. Will this work? I've never
> done any IR work, so I don't really know what power LED is required,
> what the distances are, etc

It will work, it's the basis of some shop door beepers. I've got a friend's
here right now. It's not very well. The reflector is faceted, presumably to
bounce signal back to whence it came at whatever angle it whenced. Not
as good as the one they left on the moon probably. It's a similar effect to
the retroreflective coating on road signs

Overall LED power doesn't need to be much. Just ping it every second
with a quick burst. At 5V the current limiting resistor can be quite small,
10 ohms or less, if the pulses are kept fairly short, eg 1ms. Most IR LEDs
will take several amps for short periods. If you notice the LED getting
warm you're probably close to too much

Joe
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