minimum pin to drive 4 bi-color leds

Discussion in 'General Electronics Chat' started by bug13, Aug 31, 2016.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Hi guys

    What's is the minimum pins I need to drive 4 bi-color leds? I have some d-latchs, inverters. But I don't have shift register. The bi-color leds are common ground/cathode.

    Thanks guys!

    NOTE: the least I can come up with is 6 pins, in a multiplexing arrangement.
     
  2. hp1729

    Well-Known Member

    Nov 23, 2015
    1,964
    219
    No transistors?
     
  3. hp1729

    Well-Known Member

    Nov 23, 2015
    1,964
    219
    Design 824 B Four red or green LEDs.PNG
    Each LED can be turned on individually so you can have red, green, yellow or off.

     
  4. hp1729

    Well-Known Member

    Nov 23, 2015
    1,964
    219
    Design 824 C Four red or green LEDs.PNG

    You have latches? You can have red or green but not yellow or off.
    Use the current limiting of the high side driver as the LEDs resistor.

     
  5. hp1729

    Well-Known Member

    Nov 23, 2015
    1,964
    219
    Design 824 A Four red or green LEDs.PNG
    All the same color? Red, green, yellow or off.
     
  6. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Thank you all!!

    And yes, I can use transistors diode and something like that.
     
  7. dannyf

    Well-Known Member

    Sep 13, 2015
    1,828
    365
    depending on the led used but 3 pins (two drive pins and 1 ground/rail) will produce (theoretically) unlimited colors.
     
  8. hp1729

    Well-Known Member

    Nov 23, 2015
    1,964
    219

    What kind of LEDs do you have? 3-pin with a common cathode can only get two LEDs. The "any color" LEDs I have seen have 3 LEDs and 4 leads. Do you want "off" to be an option?
     
  9. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    I will need 3 states:
    Green
    Red
    Off
     
  10. hp1729

    Well-Known Member

    Nov 23, 2015
    1,964
    219
    Individually controlled? I suggest the 74259 version unless you need high brightness. There is a CMOS version of the chip but I don't think the high side driver would drive them.
     
Loading...