555 RBG LED circuit

Discussion in 'General Electronics Chat' started by adamclark, Aug 28, 2014.

  1. adamclark

    Thread Starter Member

    Oct 4, 2013
    472
    6
    Hello again... Heres the deal, My son volunteered for a project in science today at school and hes now obligated to build a circuit that uses a 555 timer and controls an RGB LED cycle through the 4 colors...
    I Know I seen a schematic on here.. I think it was from Bill Marsden.. but I cannot find it.. We have to breadboard it tonite for class tomorrow. Anyone know where I can find this Drawing?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    What kind of RGB led are you using?
    A RGB led can have 7 different colors.
    You could use a 555 as oscillator to clock a 3 bit counter.
    The outputs of the counter could drive the RGB led.

    Bertus
     
  3. adamclark

    Thread Starter Member

    Oct 4, 2013
    472
    6
    just 4 colors,, it has 4 legs on it,, I think it does red green blue and white.. Common anode I think.. We are trying to just use whats in my parts box.. I have a bunch of 555's a few of Those LEDs, a couple 4017's a couple other ic's a wide assortment of npn and pnp transistors and resistors.. then the normal stuff like diodes can various sizes and votlages of caps.. electrolytic and ceramic..Got some various pots too.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    Use the 555 as the clock (astable multivibrator) to advance the 4017 counter. You shouldn't need external transistors for a typical (<20mA) LED. I think you'll want to reset the counter on "4" to restart the sequence. Maybe it's "3". I always get confused until I see it drawn out.

    BTW, with 4 pins you get 7 "colors" without introducing varied brightnesses. R, G, B and white (R+G+B) are just 4. You probably also can have R+B, R+G, and B+G.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    adamclark likes this.
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