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High Speed IR receiver design

Discussion in 'Electronic Design' started by [email protected], Feb 12, 2007.

  1. Guest

    I've seen lots of schematics on the net for receiving signals
    modulated at around 30-40kHz, but I'm trying to design a system that
    will work at around the 1Mhz range. I've practically tried the
    designs at those frequencies, but there seems to be a lot of
    atenuation at higher frequencies. I've been told this is because the
    photodiode acts like a cpaacitor when reverse biased, and that
    capacitor causes attenuation with high frequencies. Is there any way
    round that?

    I know it must be possible because IRDA manages data rates of up to
    4Mbps (although using a PPM system). I'm trying to achieve a data
    rate or atround 500bps, using any standard as I'm designing
    transmitter and receiver. Any suggestions?
     
  2. Tim Wescott

    Tim Wescott Guest

    If IRDA has solved this problem already, why not use it? If not the
    whole of IRDA, how about finding front-end designs for its receiver?

    My knee-jerk reaction to this is to use a good fast PIN diode, and feed
    it into a common-base transistor stage. So long as you use a modulation
    method that can be AC coupled this should be pretty easy to do.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  3. RHRRC

    RHRRC Guest

    Have a look at the Vishay IR receiver modules at 455Khz. http://
    www.vishay.com/ir-receiver-modules/
    These will comfortably give you 10K+ bps. - they are cheap and easy.
    Similar modules are available from others

    Don't forget to drive the LED(s) properly - at these speeds the diode
    capactance can become significant and you need to drive the LEDs on
    and off. Sticking the LED(s) on a collector with a series R will not
    do unless you are only looking for a short range.
    Also, whilst you are playing around with any cicuitry, be aware of the
    eye hazard of IRleds.
     
  4. Antony

    Antony Guest


    I always thought the eye hazards were minimal. After all, IR is what
    is used in Laser Tag/MILES and its deemed safe in that application. I
    don't see why it would be unsafe here.
     
  5. RHRRC

    RHRRC Guest

    What makes you think the eye hazard is minimal.
    What do others do to avoid eye hazard with IR?
    A class 1 product is indeed not deemed a hazard (under normal
    conditions).Class2 and upwards may be hazardous.
    Start off with EN (or IEC) 60285. A reading and understanding of this
    is imperative and has a legal enforcement.
     
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