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Driving an LED

Discussion in 'Electronic Basics' started by Confused Soul, Sep 1, 2004.

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  1. Hello Everyone,

    I am a novice in Electronic Design. I need to drive an LED depending on
    the signal I am getting out of a modem. The modem gives the output as
    two different frequence (ie FSK modulated). I wanted to know different
    ways to do this. As of now, I could come up with the following ideas.

    1)
    Vcc
    |
    |
    |
    /
    \ Rc
    /
    |------------
    Rb C
    o/p of modem -----/\/\/\/----B (NPN) LED
    E
    |
    |------------
    |
    |
    GND

    2)
    Vcc
    |
    |
    |
    /
    \ Rc
    /
    ---
    LED
    ---
    |
    |
    Rb C
    o/p of modem -----/\/\/\/----B (NPN)
    E
    |
    |
    |
    |
    GND

    3) Another way, I was thinking of using an opamp, in which case i can
    operate the LED in linear region and vary the amplitude. But the
    frequency seems to be a limit.

    In case 1 and 2, the LED is operated in Saturation and cutoff (like a
    switch).

    Is there any better ways of doing this? Please suggest me ... any
    materials/links related to this wud be helpful.

    Regards,
    ConfusedSoul
     
  2. What is the LED supposed to indicate?
     
  3. Rich Webb

    Rich Webb Guest

    Here's a handy tool for creating ASCII circuit diagrams. MUCH easier
    than fighting to do it in a text editor:

    http://www.tech-chat.de/AAcircuit.html
     
  4. Spajky

    Spajky Guest

    you need a very narrow band audio filter IMHO 2-band for 1,1Khz &
    2,1kHz to separate 0 & 1 signal (not sure about frequencies) first;
    than IMHO aplify it to drive LEDs ... you can not do it directly IMHO
     
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