I have an idea for a project but need some help on achieving what I want to do. I want to create a device which will insert into the audio jack of my iPhone which will emit IR signals to control my TV. Most IR devices use signals in the 35-45K range and the audio out has a max frequency of around 20K. So, since I cant directly tell the IR LED what frequency to emit, I'm thinking this device will need to have a microcontroller in the middle.
So what I'm thinking of doing is, having my iPhone app send a signal via the headphone jack to the device, have the device interpret it and then generate the appropriate IR signal to control the TV.
Any suggestions on how I might achieve this at a high level?
Any suggestions for kits which might allow me to easily prototype this kind of thing?
Any alternatives to my suggested solution which might work better?
Best Answer
This problem is really not that bad at all. You do not need to send the carrier frequency over the headphone jack. Instead, you should build the oscillator into your device a-la http://jap.hu/electronic/infrared.html (or just use a micro) and then you just need to switch it on and off based on a much slower signal from the headphone jack.
According to the internets, almost all remote control receivers expect a 38kHz carrier wave. You will need to turn it on and off at 2-4kHz. See also http://en.wikipedia.org/wiki/RC-5
If you are as clever as off-the-shelf iPhone headphone jack infrared transmitters then you can get your power from the audio signal, but if I were you I'd just use batteries.