How To Send An Audio Signal Via Infrared?
July 9, 2009 by admin
Filed under Audio Video
I want to send an audio signal via infrared and then receive it and play it through speakers (headphones).
The plan is to use some sort of ADC to convert the audio signal to digital, send the signal wirelessly, receive and clean it up using a schmitt and then a DAC to convert the signal back to an analogue one.
It will then be played through the speakers. Can anyone help with any aspect of this – particularly some possible ways to send the digital signal via infrared.
Thanks in advance.
You could use a delta-modulator instead of an adc.
The premise is, the wave is almost always changing, so send “1″ if the present sample is greater than the previous sample, otherwise, send 0.
Use AM modulation to modulate 1’s onto a carrier. 56k or higher might work, then pulse the IR transmitter with 56k to send “1″, leave it off to send “0″.
At the other end, detect the 56k, and rectify it to generate your bitstream again.
Feed the bitstream into the direction input of an up/down counter, with a free running clock at approximately the same sample frequency.
If this method doesn’t appeal to you, try using a “parallel to serial shift register” or UART chip (16550) to turn the ADC 8 bit output to serial, and then use another matching UART or shift register at the other end tto create a parallel stream from the serial stream. No modulation required . Using a UART requires programming some registers, but can synchronize by themselves (run asynchronously) unlike the shift registers.
have you thought about doing this in a strictly analog way? Use the audio signal to drive IR LEDs and then detect and amplify the received signal to drive speakers. This system would probably have a lot of nonlinearity but if you don’t care to much about fidelity it may be a lot simpler.