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Infrared Receiver Module

Discussion in 'Electronic Basics' started by Thomas Karpiniec, Sep 17, 2003.

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  1. Hello everyone,

    I'm trying to use a 3-pin IR Receiver Module (numbers on back: 3834, 73A),
    for detecting infrared frequencies between 30 and 40 Khz. I'm having a bit
    of trouble operating it. I have seen somewhere a schematic that had external
    components around it, but I don't know what these are. At the moment I'm
    running it stand-alone as follows:

    Pin 1 - Signal (to LED)
    Pin 2 - Ground
    Pin 3 - +5V

    It seems to work at least a little bit. I have an LED hooked up, and as soon
    as I apply power, it turns on partially, whether I have the other end
    connected to the +5V or ground line (a voltage somewhere between the two
    rails from pin 1 then I presume?). When I get a standard VCR remote control
    and press a button, the LED wavers a bit. It's too fast to tell exactly
    whether it's flashing brighter, or dimming, but it certainly changes.

    I was wondering if anyone could enlighten me on what it is doing. The
    application is a mini-sumo robot, which needs object detection. I want to
    use one of these modules as the receiver.

    Thanks for any help,

    -- Thomas
  2. Joe

    Joe Guest

    Hi Thomas,

    I am no expert, but I just went thru a few months of hobbying around with a
    TSOP1238 IR receiver and transmitter myself.

    What I learned is that when the (close to )correct frequency IR hits the
    receiver, the receiver output goes low. The receiver strips off the carrier
    frequency which can be 36,38, or 40khz. Sounds like yours might be 38khz
    (just by the 3834 designation you mentioned). I don't know if you have an
    oscope, but i dont. I was using a piezo buzzer a voltmeter, and a red LED
    to 'tell' me what was going on. You can also use the LED by connecting the
    anode to the plus 5V (using a 270ohm resistor in series). Then connect the
    cathode(negative side) of the LED to the output (pin 1) of the IR receiver.
    Then apply the IR signal. If the LED lights, then you know your receiver is
    active low and you can drive a 555 as a oneshot directly from it.

    My application was not for robotics and I am sure you need to be careful
    about where the IR source is in relation to the receiver so you don't get
    false triggers. You can also post the schematic of the circuit you mentioned
    to alt.binaries.schematics.electronics
    and then reference it so others may be able to help you.
    If you scan it, try to make it into a .gif file tho so it is not too big
    (maybe under 100k is good).

    Also try a web search for "IR receiver" and "IR transmitter" using google.
    There's lots of info on the web, especially for robotics applications.

  3. Colubris

    Colubris Guest

    Another tip to remember about many of the IR detector modules is that
    they usually have some sort of Automatic Gain Control (AGC) - the
    effect being that the modules can not be used to detect a contiuously
    ON carrier.

  4. Anand Dhuru

    Anand Dhuru Guest

    Hi Thomas,
    Yes; a resistor of about 100 ohms between the +5 volts of the supply
    and the +5 of the module, with a 10uF cap. between the + and ground of
    the module helps a lot.
    No; this is the noise that the module is generating / catching; the
    above components should give you a steady '1' on the output in the
    absence of a modulated IR signal.
    Now, the output LED (if connected between +5 and output, since the
    output is active low) will be lit only when you point an IR signal
    from the remote onto your module.

    There is a simple way of actually seeing the IR signal without an
    oscilloscope; just feed the output of your module into the sound card
    in your PC, and save the sinal as a .wav file. Then, open it into any
    sound editor (like GoldWave, downloadable free) and keep zooming till
    you can see the individual bits of the original signal. Helps in
    debuggging like nothing else can!


    Anand Dhuru
  5. If the IR receiver is in a metal can, don't forget to ground the can.
    It makes a major difference in the amount of noise output from the
    detector. It's the difference between a clean, usable signal and a
    bunch of worthless noise. You aparently have a high level of noise if
    the LED is lighting in either orientation. The output pin of the
    detector is normally at a high level (5V), it goes low upon detection of
    the proper carrier frequency.
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