5 led chaser.

Discussion in 'The Projects Forum' started by whynotsneeze?, Nov 23, 2009.

  1. whynotsneeze?

    Thread Starter New Member

    Nov 6, 2009
    2
    0
    Hey.

    How complicated would a 5 led chaser be to design? Id want it to go back and forth rather than run through the leds and "start from beginning"?

    I just beginning electronics and digital tech so i dont want to start with too daunting a task. what would be the absolutely essential theoretical aspects to cover for completing such a design? Im planning to design it on logisim for now and see how things work.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    The article beenthere pointed to is a work in progress, I'll be updating it now and again. You want to see a neat variation of this concept check this thread out...

    http://forum.allaboutcircuits.com/showthread.php?t=26977

    For your project a 555 and 4017 chip is needed, along with a handful of diodes (general purpose, exact P/N unimportant), resistors, transistors, and LEDs. If you have any specific questions feel free to ask.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
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    Use the 4017 as a ring counter,use diodes to make 5 OR gates- output to directly drive 5 lo current LED's, or buffer amp. Connect stages 0 & 9, 1 & 8, 2 & 7, 3 & 6, 4 & 5.Disadvantage- end LED's stay on for 2 cycles
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Make the counter drive the LEDs when it counts from 1 to 5 then make the 6th output light the 4th LED through a diode, the 7th output lights the 3rd LED through a diode, the 8th output light the 2nd LED through a diode and the 9th output resets the counter so it can start with the 1st output lighting the 1st LED again.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    This is basically what Audioguru's talking about:

    [​IMG]

    For this schematic, you'll need to use a diode on any 4017 output that powers an LED, if only to keep the voltage drop consistent; thus the light from the LEDs consistent. You could use 1N4148/1N914 or 1N400x series diodes.

    The value of R3 will need to be adjusted depending upon your supply voltage and LEDs.
    A rough calculation is:
    R3 >= (Vsupply - (Vf(LED) + 0.7v)) / 12mA (the 0.7v is the approximate Vf of the diodes)
    So, if you were using a 12v supply and LEDs that had a Vf of 2.2v:
    R3 >= (12v - (2.2v+0.7v))/12mA
    R3 >= (12v - 2.9v)/0.012
    R3 >= 9.1 / 0.012
    R3 >= 758
    A table of standard resistance values is here: http://www.logwell.com/tech/components/resistor_values.html
    758 is not a standard E24 (green columns) value. However, 758 Ohms is so close to 750 (99%) that I'd just use 750 Ohms.

    I used CD4093 NAND gates wired as a bistable multivibrator. You could use a CMOS 555 timer instead if you wished.

    Note that any unused CMOS inputs must be wired to something; whether Vdd, ground or a signal that stays between the power rails. Otherwise, you will have problems.
     
    Last edited: Nov 24, 2009
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