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Infrared emitter detector

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I have a question about a circuit that I looking design & build to solve a problem that I have. I haven't dabbled in electronics for a few years so please excuse any mistakes I make.

I'm looking to design a simple infrared emitter / receiver circuit. So simple that it won't be used to transmit data, but only to actually detect that the infrared signal exists. The only design requirement that I have is that the receiver circuit will be stationary while the emitter circuit will be traveling at speed of up to 70km/hr and at a maximum distance of up to 10m away from the receiver circuit.

My question is, will your regular IR LED & IR receiver bought from your local electronics supplier do the trick. Can anyone see any issues or hurdles I may face designing such a circuit? All the detector needs to do is sense when the emitter goes by. Any suggestions or ideas would be appreciated, thank you.


You'll have to modulate the signal somehow, otherwise ambient light will influence it. Most IR receivers are the kind that things like TV's use, they receive a (nominal) 38khz signal and turn it into solid on or off signals on an output line. They however won't respond to either a solid 38khz carrier (as Nigel pointed out to me once) or to a solid IR light, they're not supposed to. So you'd need two 555's, one to generate the 38khz carrier, and a second one to turn the first one on and off and at much slower rate. The receiver will output a signal that blinks at the rate of the slower 555. If you do say 1khz as the 2nd 555's on/off speed you can connect a speaker up to the output of the IR receiver and you'll hear a 1khz tone when it can detect the transmitter.
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