HELPPP using LED!

Discussion in 'General Electronics Chat' started by cityhunter, Mar 8, 2013.

  1. cityhunter

    Thread Starter New Member

    Mar 8, 2013
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    0
    How to make one led on and the other off if they started to be in off state?
    and if the input is logic 1, the green led will light but if input is logic 0, the red led will lit.

    Thanks!
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    More details please. It is not clear what you want. Post a circuit diagram
     
  3. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
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    A single pole double throw switch, center off, will do what you want but it must be switched manually. More info will get you a better answer.
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    According your logics then you can using two stages of NPN transistors or using two inverters of 74LS04.
     
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  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    How about 2 inverters (1 IC)?

    Not near schematic software at the moment, but...

    Input signal to inverter #1, inverter 1 acts as a buffer/amplifier.
    Output of inverter 1 to LED, current limiting resistor, then ground. (On when input is low).
    Output of inverter 1 to Input of Inverter 2.
    Output of Inverter 2 to LED, current limiting resistor, then ground (On when input is High).
     
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  6. tshuck

    Well-Known Member

    Oct 18, 2012
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    How about 1 inverter? Or none, depending on what the input is capable of?

    Input to the inverter, the output is connected to Vdd through a resistor and the red LED, and connected to ground through a resistor and the green LED.
     
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  7. ScottWang

    Moderator

    Aug 23, 2012
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    Below are some other ideas, the Fig1 will lose about 19.3mA when input is 0(the red LED in ON), the loss current is for nothing not for the LED, so you better not to use it with battery.

    If any errors please let me know.

    [​IMG]
     
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