LED Switchbox HELP!!!

Discussion in 'The Projects Forum' started by Chris15, May 28, 2009.

  1. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    Hey guys i have a rotary switch and 3 multicoloured LED's (red, green) i need this to happen:
    I have 3 gates, when the circuit is active i need the gate in use to have a green LED showing and the other 2 to be red, however when i change the switch to another gate i want them to go red except the one in use (which will be green). the LED's are 20ma and i have a 24V supply so i think i need a 1.2k resistor but if anyone can help, thankyou.

    P.S If you guys can i need a quick answer but i dont want to sound like some goy that comes here and expects you to do it all now, but if you can help please do.
  2. Wendy


    Mar 24, 2008
    There are several schemes for multicolor LEDs, which one is yours?

    1. 3 leads, one common, the other 2 each color

    2. Back to Back LEDs in the same case, current direction determines color.
  3. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    oh they have 3 leads, 2 + and 1 -, the centre is negative, and depending on if u want red or green it is left or right lead, i tried to put a schematic up but couldn't sorry, but yeh that is them
  4. franzschluter

    Active Member

    Jun 1, 2009
    You can easily do this with a couple of NPN and PNP transistor or relays... But relays are expensive and transistor is cheap..
    Any normal BJT NPN and PNP will do...
    You need to put Rb or a 100 ohm resistor on the base of the transistor to limit the current..

    I have uploaded a schematic so just follow it... Depending on what voltage your LED is.. you might adjust a bit.. But basically this is it..

    I assume 1 common which is cathode and two anodes to determine color right? Btw the resistors might need adjustments depending how much mA you intend to give it.. Good luck

  5. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    THANK YOU Franz
    Thank you alot youve saved me tonnes of time, BUT it says 5v+ if i connect 24V, not sure of the current cause it is from the mains into a transformer 20:1 and into a rectifyer WO4 then out at 24V then i want to connect that will it still work, and were do i add the 1.2K resistors.

    Thanks, Chris
  6. SgtWookie


    Jul 17, 2007
    Sorry, Franzschulter's circuit just won't work.
    There is no way the NPN transistors (T4 thru T6) will source current to the LEDs.
  7. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    How could i fix this problem? and would it work with 24V? i just need a 1.2k resistor on all of the trans bases