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got the receiver running and recording. the problem now's the transmitter. seem's that it can't get enough juice from the audio output of the headphones socket. using a digicam, can't see any light(digicams can see IR)
A headphones output is not powerful enough to light an LED. You need to light the LED with its resistor with a DC power supply or battery then modulate the DC with the audio from the headphones jack capacitor-coupled to it.
To calculate the correct value of a current-limiting resistor for the IR LED, we need to know its forward voltage at 20mA and its max continuous current ratings. We also need to know the supply voltage of the transmitter and which type of battery it uses.
will try to see what i can do. I'd like to ask more questions/guidance next time. si i cloud just use a dry cell(batt) and put it in series with the IR transmitter-Resistor combo. how bout the capacitor?
An IR LED needs about 1.2V at about 15mA. A 3V battery and two 62 ohm resistors in series with the IR LED would produce 15mA. The audio from the headphones jack would feed through a 470uF capacitor to the junction of the two resistors. Then the IR LED would be AM modulated by the sound. The headphones output would have a 31 ohms load.
the receiver that i've made is connected to the printer port. the data it receives is not in audio( mp3, wav) how can i get the input from the remote via the microphone jack? in that way, the IR would be in audio format.
Exactly what I said. Just feed the IR sensor output directly to the microphone jack, no circuit. The sound cards microphone pre-amp will amplify the signal sufficently for detection, even if it didn't most IR sensors should produce enough voltage to be detectable on a sound card with 16 bit samples.
A photo-diode is an IR sensor that will have a low level signal when it receives close-up IR radiated data.
But I doubt that a mic input can pickup 38kHz IR modulation. It probably cuts frequencies above 20kHz.
Depends on your sound card, but most go up to 96khz, like I said though some of them have a 22khz low pass filter on the input regardless of the 96khz sampling rate (the increased sampling rate is for stereo seperation in the higher frequency ranges) On my card it appears that cut off frequency is pretty sharp, but you'd have to test it yourself. Worse case you're going to at least be able to see the modulation.