photodiode controller

[Paul Perry]

At 10:59 AM 1/03/99 +1100, Stewart Pye  wrote:
>I'm building a controller for CV and midi and thaught I'd try a photo diode
>recieving a 10kz signal being reflected by the hand from an led right next
>to the photodiode. This is then demodulated and filtered as in Elector
>march 1983 pg55.
>Elector says it will measure distance up to 6 or 8 inches. Does anyone have
>a better suggestion for sensing hand movement??? Longer range would be
>better. 

An australian mag (ETI?) some years ago showed an arrangement where both a 
light source and the pickup LDR were in the focal point of a parabolic car 
headlight reflector.
The LED points down to the parabola, the LDR is in a tube pointing away from
 the parabola from memory.
The LDR doesnt have any gain from the parabolic reflector, but the placing
of the tube means only collinear light is picked up.

That's how I remember it, anyhow!
Rember it isn't distance it is detecting, but reflection.. stay on beam!

paul perry Frostwave P/Lmelbourne australia

"Postmodernism is the cold fusion of the social sciences"