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IR distance sensor?

hi,

im looking for a way to detect distance (around 4 feets) using IR.
basically a person will carry the IR transmitter and walk around until he comes across an IR receiver. the receiver is connected to a buzzer  where the buzzer will emit louder sound as the user getting near to the receiver. 
can this be done by using ir transmitter and receiver led?
any other better suggestion is welcome

thank you for your reply 

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It'll sort of work, but LEDs emit a cone of light, not a sphere. How will you point it ? Alternatively, a filament lamp, set to barely light might work ?
bhan1992 (author)  steveastrouk3 years ago
i will use a branch of IR transmitter together so that it produces enough IR light.
its ok for me that leds emit cone of light.
i just want to know which kind of IR sensor that has its output signal varies according to the intensity of the IR light it sensed.
Any IR photodiode's output is proportional to light intensity.
How is a single IR LED and a single receiver suppose to be used to determine distance so the micro controller can make the sound loader as the person gets closer?
Intensity will be somewhat proportional to distance, by inverse square law.

....-ish.....
rickharris3 years ago
A microprocessor project indeed.

http://www.techsupplies.co.uk/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.TechSupplies/Products/LED020

as an example.