Using my Android Phone's TRS Port as an Infrared (IR) Emitter & Receiver for TV Sign

Discussion in 'General Electronics Chat' started by btb125, Sep 20, 2011.

  1. btb125

    Thread Starter New Member

    Sep 19, 2011
    Hi, I'm new to this forum and was wondering if you could help me with a problem I've got...

    I want to use my Android phone as an Infrared transmitter and receiver to control my TV. The idea came to me when I was lying in bed and my TV remote was on the other side of the bedroom, I thought this would be a great and simple little application to create. I went to Google how to create the infrared transmitter and receiver for an Aux port, and it seemed simple enough. I know there are apps on the Market for this already, but I wish to create my own both because I want it to do what I want, and my University final year project is coming up and I think this will be a great and somewhat unique project to undertake. I’m studying Computer Science so the programming side shouldn’t be a problem, but what I thought would be a simple soldering session has definitely proven to be.

    I've now spent days Google'ing the problem in aid for a solution with no success, and as a result I’m turning to you guys in the hope that you could enlighten me on what ridiculously fundamental mistake I’ve made.

    The theory behind my project is that you solder IR bulbs to 3 or 4 pole 3.5mm AUX ports, record the IR light as a sound, and then playback the sound as IR light. This has been done, and I’m not so sure as to why I can’t get it working.

    I’ve tried using the phone as the recorder and the transmitter, but the light always seems too weak, and I was also worried that it made be cutting off the higher frequencies when it records. To overcome this I recorded the light-sounds as .wav files to my laptop using Audacity & SoundForge in hope that the sounds wouldn’t be compressed, but when playing back the light-sounds it still doesn’t work.

    What I have noticed is that when looking at the brightness of the light being emitted from both the phone and the laptop, is that it was very weak (I tested this using a digital camera) in comparison to the remote control that I was recording from.

    I’ve tried many different ideas, including searching this forum to see if there were any ideas, but I couldn’t find the information here either.

    I don’t wish to keep going on for the sake of your sanity, but if you have any questions on what I have tried, or require any links to what I have read, please ask… I hope my late night ramblings haven’t made you give up, and I will be very grateful for any help you can offer.

    Thanks for your time, B.
  2. DigitalReaper


    Aug 7, 2010
    IR remotes send bursts of 38khz light pulses so you need to be recording and playing back at 76khz or higher. Look at the waveform in your editor, it should look like bursts of a square wave. Record the output from your phone with the PC and do the same to check playback.

    The output from your phone may not be able to supply enough voltage and current to properly light an IR LED, these are typically driven at high currents but at a low duty cycle. You may need some sort of amplifier to drive the LED.

    There are 3 terminal IR receivers that are tuned to 38Khz, I think they may strip out the carrier and give you a lower frequency digital output so those may be worth looking into as well (just remember you still need a 38khz carrier to transmit!).
  3. btb125

    Thread Starter New Member

    Sep 19, 2011
    Thanks for the reply, I'll give this a shot when I get a chance. Thanks again.
  4. btb125

    Thread Starter New Member

    Sep 19, 2011
    I'm now currently using only my laptop to record and transmit the signals.

    Using [ ] as my receiver, I recorded 'Volume Up' as a series of short presses and long presses at 96KHz to produce the following:

    I then tried to transmit the signal using a [ ]. Again, using my phone to see how powerful/bright the signal was, it was a very weak/dull signal/light (even though I used VLC @200% volume and the system at 100% volume). Also, when tested on the TV, it didn't work.

    Is it a possibility that I am using the wrong bulbs for receiving and transmitting the information?

    TY in advance...
  5. bertus


    Apr 5, 2008

    The links on this page of the EDUCYPEDIA will give you a lot information on the IR remote control signals:
    IR remote control

    Last edited: Aug 13, 2012
  6. radiohead

    Distinguished Member

    May 28, 2009
    Does it work when you move it close to the TV? If so, concentrate on the amp for the distance as Digital Reaper said. If not, it's back to the drawing board.
  7. btb125

    Thread Starter New Member

    Sep 19, 2011
    Unfortunately it doesn't.


    Thanks for the link bertus, I'll give it a read and hopefully it will help.


    Again, both of you, thanks for taking your time to help.