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Looking for instructive material on IR transmitters/receivers

  1. Aug 29, 2010 #1
    Unfortunately I have not been able to find anything reasonable online.

    I'd like an in depth all-inclusive explanation of IR transmitters and receivers, from a physical standpoint. I would also be glad to learn whatever else is included in the reading material, if anything.

    I have basic questions such as: how close does the IR receiver need to be to the transmitter, does it need to be within its 'line of sight,' will there be significant interference from visible light (I assume so, which is why I see shielding and modulation occurring), and how does it all work in the first place. I suppose the latter concept might be found in a semiconductor physics book, but I am not sure.

    Thank you very much.
  2. jcsd
  3. Aug 29, 2010 #2


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    Science Advisor

    Most of us have used a TV remote control, so you would have a feeling already for the range of IR control and the fact that it does travel in straight lines. It is just light even though it is infra red.
    The range of a good remote control would be maybe 10 meters. More than enough to operate from anywhere in a large room or even a large class room in a school.

    Yes, the better ones are always modulated. Actually, they are switched on and off rapidly at a rate of about 38 - 40 KHz and then this is switched a lot more slowly to carry data. There may be many functions on a remote control and there has to be a range of codes which can be sent to say which button you are pushing.

    The rapid switching is to reduce problems with other light sources which may also put out infra red light. Even this isn't perfect, though, as some compact fluorescent lights put out pulsed infra red light and this can make a remote control for a TV set useless.

    There are dedicated remote control receive chips and these are quite cheap and very good. They contain a phototransistor, a filter and an amplifier so that the fairly weak signal from the remote control can be amplified up to produce stable data output for the device being controlled.
  4. Sep 4, 2010 #3
    Thanks..that is indeed helpful information, and it provides me sufficient to start building simple projects in this realm and graduate forwards.

    Thanks again.
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