How to make a sequence of leds

Discussion in 'General Electronics Chat' started by Nicoli0012, Apr 13, 2013.

  1. Nicoli0012

    Thread Starter New Member

    Apr 13, 2013
    3
    0
    I am trying to build a miniature "christmas tree circuit" that has 4 leds that light up in sequence but when the last one is lit up have it stay lit. I also need it to be delayed about 1 second between less. I am novice at circuitry so the simpler the better. Oh and also if you could point me in the direction of a schematic or diagram that would be much appreciated
     
  2. JohnInTX

    Moderator

    Jun 26, 2012
    2,340
    1,022
    Check out Bill Marsden's blogs on the 555/ LED sequencing. Add your imagination and its pretty much all you need to know to get started.
     
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,795
    830
    Do the previous LEDs stay on? How long does the fourth led stay on?
    Is the desire sequence like this?
    1 for 1 second
    1 & 2 for 1 second
    1, 2 & 3 for 1 second
    All for how long?
     
  4. Nicoli0012

    Thread Starter New Member

    Apr 13, 2013
    3
    0
    Yes all of the previous leds stay on with about half a second in between each one being lit
     
  5. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,795
    830
    Do you want it to repeat or stay on once the fourth led is lit ? Also, when all LEDs are lit and you are repeating the sequence, should the fourth led stay on for more than a half second?
     
  6. Nicoli0012

    Thread Starter New Member

    Apr 13, 2013
    3
    0
    I have a button that activates the timer as long as i hold it in. so i want the 4th led to stay lit until i let go of the button and only repeat when i let go and push it again
     
  7. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,795
    830
    This post would have just been confusing, so I decided to delete the entire thing. Fortunately, I pondered on the problem a bit longer and came up with my next response...
     
    Last edited: Apr 15, 2013
  8. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,795
    830
    Take a look at the attached schematic. I am not promising it is complete, as I haven't simulated it yet, but it does include the alteration to work with a simple NO pushbutton. Also, please forgive me for not including the 2Hz clock circuit, but simply representing it as an input.

    "Sw" (your pushbutton) with the pullup resistor R1 provides a normally high input to the rest of the circuit. Hence, "Rst" is held high and the circuit (4017) will not count and will have 0 as the output. When the button is pressed, Rst is held low and counting can proceed.

    U1 (1/4 NAND gate) is wired as an inverter and U2 and U3 are wired as an AND gate. Hence, when Sw is not pressed, the output of U1 is low and the clock signal is prevented from passing through the AND gate to the counter. When the button is pressed, the clock signal is passed through to the counter.

    Note that since we reset the counter earlier by not pressing the button, output 4 will be low and the disable ("ClkInh") will allow normal counting.

    The dual Quad-input OR gates keep the preceeding LEDs lit as the counting sequence increases from 0,1,2,3,4. Once the sequence hits 4, that output is fed back into the ClkInh input to prevent the 4017 from counting further while maintaining the current count.

    The remainder of the circuit are transistor drivers for each LED.
     
    Last edited: Apr 15, 2013
    absf likes this.
Loading...