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IR Audio Reciever

kpraytor

Oct 8, 2009
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Oct 8, 2009
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Hello everyone!

I am trying to make a simple go/ no go tester to determine if a remote control is outputting an IR signal. There is no need to clean up the signal or do anything else with it; I just need to know if the remote control is putting out any kind of IR.

I have attached the first design I had. This appeared to function correctly but the signal was not strong enough to make a very audible note, aka you had to hold the speaker up to your ear to here the noise being produced.

Unfortunately, I crossed some wires while testing it and fried the only speaker I had. Now, I am forced to go with a Piezo transducer to output an audio signal. It says on the packaging that it requires a driver circuit (?). I am new to the whole electronics thing and would like some advice concerning how to approach this driver circuit.

Thanks for all your help and I look forward to the responses!
 

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Resqueline

Jul 31, 2009
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Piezo buzzers are sometimes made with an internal driver circuit that only requires a dc voltage to make it buzz, while others contain only the piezo element and must be driven with ac to make a sound.
A piezo element is a capacitor that bends when you apply a voltage to it. Try it out on your 9V battery; first touch it makes a click, then shorting the piezo it also clicks. Touch it to the battery again, and then reverse the polarity - it makes a louder click.
An ordinary speaker conducts dc and needs a low voltage - high current signal to work, while the piezo requires a high voltage - low current signal and doesn't conduct dc.
To get the high current for the ordinary speaker your circuit has two emitter-follower amplifier stages. You'll need to rewire it to make two common-emitter amplifiers to get the high voltage needed for the piezo speaker.

But if you have a digital (cell phone/ web) camera you can use that to see the actual IR-light emitted by the remote instead.
 
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