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Wireless infrared headphones

Discussion in 'Electronic Design' started by Apparatus, Sep 12, 2005.

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  1. Apparatus

    Apparatus Guest

    I recently designed and built myself a pair of wireless infrared
    headphones. The project is documented on my website for anyone
    interested. Feel free to learn from the design and to send me
    questions.

    http://www.its.caltech.edu/~hiszpans/wih/

    Cheers,
    Chris
     
  2. Ban

    Ban Guest

    There are a few design flaws in your work, did you really pass that class?
    Worst is the transmitter stage The current through the LEDs is only
    determined by their forward voltage it can vary a lot and will degrade
    performance since the max. permissable current is surpassed. Your
    calculation "current sourcing" is completely wrong. The LEDs are in the
    collector line and do not contribute to the Vbe calculation.
    The transmitter will have big noise problems, as you amplify any ripple on
    the supply voltage through your bias resistors, some of which can be
    omitted...
     
  3. Apparatus

    Apparatus Guest

    Yes, I did well. This was for an introductory class.
    The forward voltage did not vary all that much since it is set by the
    current through V_cc / (R_9 + R_10). However, I have allowed ample room
    for variance, taking into account the 50% duty cycle.
    You are right. Should be as I stated above. Thank you for bringing the
    error to my attention.
    The supply is quite stable, but yes I see your point. Noise could
    potentially be a problem in a particularly noisy environment.
    Yes, R10 can be omitted, and R9 doubled to have a near equivalent
    effect.

    Cheers,
    Chris
     
  4. John Smith

    John Smith Guest

    I think you did quite allright. Of course there are improvements possible,
    but hey, only 10 weeks for a clean working prototype with pcb etc and a
    paper is not bad at all. One small point though, your paper references
    several components that I could not find in the schematic drawing: D8, D9,
    C17, C18, C24, R30 and there maybe others.

    -- John
     
  5. Apparatus

    Apparatus Guest

    Thank you John. I appreciate the support. Hopefully the improvements
    will come with time.
    Ah, the PDF contained an old version of the schematic. Should be fixed
    now. Thanks for bringing this to my attention.

    Cheers,
    Chris
     
  6. ehsjr

    ehsjr Guest

    Haven't had a chance to read it yet - just scanned through.
    But it was darn nice of you to post it! Thanks!

    Ed
     
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