0
\$\begingroup\$

I was looking at this tutorial about how to decode an infrared signal. One of the posts says

For the scoped challenged (like me), a PC microphone jack works great for reverse engineering IR protocol. It even has power (5V through a 200-ohm resister, I think) to drive the IR transistor. To see the signal, use any audio recorder that lets you zoom in on the waveform (like Audacity).

So I am just wondering if I can plug an IR demodulator (say, this one here) into my microphone jack, record the output, and decode the signal binary from the sound waves?

\$\endgroup\$

1 Answer 1

Reset to default
1
\$\begingroup\$

Yes you can plug it in the microphone jack with a few extra components.

Here what schematic I have found on LIRC's webpage (by Matthias Ringwald):

enter image description here

As far as I know most IR signals are Manchester coded:

  • high to low transition means 1
  • low to high transition means 0

Or the other way round because there are two conventions.

Be sure to check SB-Projects for information regarding different IR protocols.

To view the signal on your PC I recommend Christian Zeitnitz's Scope and to record it try Audacity.

\$\endgroup\$
1
  • 1
    \$\begingroup\$ It may be worth noting that some IR receiver assemblies are extremely sensitive to power-supply noise. What's drawn above as simply "+5" should probably--at minimum--have a bypass cap located very close to the receiver assembly. I vaguely recall those decoders as often having open-collector rather than totem-pole outputs, in which case some form of pull-up might be necessary. On the other hand, with some sound-card microphone inputs, eliminating the cap might eliminate the need for the pull-up [many microphone inputs include a weak current source to power electret mics]. \$\endgroup\$
    – supercat
    Commented Apr 28, 2014 at 16:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.