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Bi-color LED help

Discussion in 'Electronic Basics' started by Lucky225, Jul 12, 2006.

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  1. Lucky225

    Lucky225 Guest

    Okay, so I bought a 2 lead bi-color led, but my application requires a
    3 lead shared anode led. Is there any circuit I can build that would
    detect the presence of negative to reverse the polarity automatically
     
  2. Don McKenzie

    Don McKenzie Guest

    Is this a trick question? :)

    yes, install a 3 lead shared anode led is the simplest.

    or get two standard LED's and hook them up as a standard 3 lead shared
    anode.

    Don...


    --
    Don McKenzie
    E-Mail Contact Page: http://www.dontronics.com/e-mail.html

    Micro,TTL,USB to 1.5" color LCD http://www.dontronics.com/micro-lcd.html
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    World's smallest USB 2 TTL Conv http://www.dontronics.com/micro-usb.html
     
  3. jasen

    jasen Guest

    this maybe.

    K1 A
    ----|<---+----+--[330R]-----+---
    | | |
    \ / -+- |
    -+- / \ |
    K2 | | |
    ----|<---+----+--[330R]-----+

    these two big
    diodes are the LED.

    The litle diodes are 1n914 or similar.

    This circuit will give no light when both cathodes are low,
    so you can get red or green but not yellow.

    Bye.
    Jasen
     
  4. John Fields

    John Fields Guest


    ---
    Please bottom post.

    There's not enough information in your post to give you actual
    circuit values, but here's the basic idea: (View in Courier).


    | \ | \
    IN>--+--| >O---O| >--+
    | | / | / |
    | [R]
    | |
    | [LED]
    | | \ |
    +-----------| >O-+
    | /

    "IN" is one of the signals used to drive the 3 lead LED.

    If the LED's colors light up reversed, just swap the LED in the
    circuit.

    You may be able to get rid of two of the inverters depending on what
    "IN" looks like. Post some more information about your circuit and
    you'll get more help.
     
  5. Ban

    Ban Guest

    You could modify your circuit if both LEDs are *not* lighted at the same
    time:
    +--------+-----o
    | | +
    V red V gn
    - -
    | |
    .-. .-.
    | |Rred | |Rgn
    | | | |
    '-' '-'
    | |
    |/ |/
    -| -|
    |> |>
    | |
    === ===
    GND GND

    +---------+-----o
    | | +
    .-. .-.
    | |Rgn | |Rred
    | | | |
    '-'. '-'
    | |
    | red |
    +-+-|<-+--+
    | | | |
    | +->|-+ |
    | gn |
    |/ |/
    -| -|
    |> |>
    | |
    === ===
    GND GND
    (created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
     

  6. As so often, it depends.

    Suppose the cathodes are driven by (microcontrollers) outputs that can
    source and sink enough current *AND* you only need one of the colors at a
    time *THEN* you can simply connect the 2 lead component between the cathode
    cathode joints of the original LED. You may need to add a resistor to limit
    the current. If the outputs cannot source enough current, you need buffers.
    If the outputs can only sink current, you can use the upside-down circuit.
    See below.


    CA
    |
    |
    C1---|<--+-->|---C2

    Original 3 lead bi-color LED


    +--->|---+
    C1---+ +---C2
    +---|<---+

    2 lead bi-color LED


    +--->|---+ ___
    C1---+ +--|___|---C2
    +---|<---+

    Series resistor


    +--------------+- Vcc
    | |
    .-. .-.
    | | | |
    | | | |
    '-' '-'
    | |
    | +--->|---+ |
    +--+ +--+
    | +---|<---+ |
    | |
    R3___ |/ \| R4___
    C1--|___|--| |--|___|--C2
    |> <|
    | |
    | |
    ------+--------------+-----Gnd

    You may need buffers. R3 and R4 may by ommitted.



    -----+---------------+-----Vcc
    | |
    | |
    R3___ |< >| R4___
    C1--|___|--| |--|___|--C2
    |\ /|
    | |
    | |
    | |
    | +---->|---+ |
    +--+ +--+
    | +----|<---+ |
    | |
    | |
    .-. .-.
    | | | |
    | | | |
    '-' '-'
    | |
    --------+---------------+-------Gnd

    If the cathode connections can only sink current the voltage
    should be able to raise above Vcc-0.7

    All this may not be usefull if my assumptions are not correct. So provide
    more detailed info now or the next time you have a question.

    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    petrus bitbyter
     
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