IR beam proximity sensor

Discussion in 'The Projects Forum' started by optimus9, Oct 18, 2009.

  1. optimus9

    Thread Starter New Member

    Sep 15, 2009
    4
    0
    Here's my problem:

    I want to make a simple IR beam barrier proximity sensor with a range of about 15cm.
    I've bought the TIL78 IR receiver (phototransistor) & TIL32 IR emitter (IR LED), but the problem is that ambient light (& probably CFLs as well) interferes with it.
    I've also tried to cover the phototransistor & protect it with IR filters (floppy disk magnetic disk), but it doesn't help a lot.

    One possible solution is to modulate the IR LED at 38Khz & use an infra-red receiver module to decode the signal. Unfortunately, these IR modules aren't sold in my country.
    So, can anyone suggest a simple circuit whereby I can encode a signal with the IR LED & decode it with phototransistor? For the encoding, I've found circuits using 555 timers, but no decoding circuit.
    :)

    Btw, I'm using these sensors with an automated curtain system which is activated using an LDR & timer. Motor is controlled via an H-bridge I designed because I couldn't find any on-chip H-bridges. (That's the simulation circuit, contains redundant parts because some of them weren't available for sale.)
     
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