using 555 and 4017 to cycle 7 LED's

Discussion in 'Digital Circuit Design' started by Tony Spence, Jun 23, 2016.

  1. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    Hi there i have been round and round this project using different IC's and I am back to using these two IC's.
    I have built a 7 LED chaser circuit but i dont want them to chase the one LED i want them to cycle round, this is my circuit below is it correct.
     
  2. wayneh

    Expert

    Sep 9, 2010
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    This circuit looks right and will light one LED at a time in order. Is that what you want?
     
  3. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    Yes that is what i want but instead they are chasing one LED what have i done wrong
     
  4. wayneh

    Expert

    Sep 9, 2010
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    What does that mean? Are they all on except for one at a time going off, in order?
     
  5. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    sorry i meant to say one stays on and the others run towards it and then it turns off
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    Could you draw the timing sequence of leds, it may more clear to describe what you really want.
     
  7. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Can you take a video of your project with your phone,and post it.
     
  8. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    I want it to go 7654321 and repeat with one LED on per pulse

    but its doing this and the last one is constantly on until all off
    7 1
    6 1
    5 1
    4 1
    3 1
    2 1
    all off
    and then repeats

    does this help describe it better
     
  9. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    745
    Sounds like number 1 led is wired backwards.
     
  10. ScottWang

    Moderator

    Aug 23, 2012
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    Your two described there were little different.
    I will provide an idea and you check it if anything needs to modify.

    The numbers from 7...1, about this you can reverse the sequence of leds and labeling as 1→7, 2→6, 3→5, 4→4, 5→3, 6→2, 7→1, and if you want any led to keep at lighting then you can using 7 1N4148 connecting to a resistor and connecting to the base of npn bjt, e connecting to gnd, c connecting to a current limits resistor and to the negative of led, the positive of led connecting to 9V.
     
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  11. wayneh

    Expert

    Sep 9, 2010
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    So if LED #1 (using your numbering here, which is opposite to the schematic, right?) were removed, you would say this is working fine for what you want, less the #1 LED?
    Does your table indicate that LED #1 is on all the time except briefly when all are off? You must have it miswired to the wrong pin of the 4017. Check the leads of the LED to make sure they have not laid over onto the wrong pin. A photo may also help us see something you have missed.
     
  12. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Led 1 is wired reversed, its being used as the negative path along with the resistor for the other leds.
     
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  13. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    I turned the 1
    is it possible that an LED could be manufactured backwards
     
  14. wayneh

    Expert

    Sep 9, 2010
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    Possible? Yes. Likely? No.

    Is it fixed?
     
  15. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    how would i correct this?
     
  16. wayneh

    Expert

    Sep 9, 2010
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    I though you already turned it around?
     
  17. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    when i turned it around the LEDs lit very faintly if at all but they looked like it was doing what i intended
     
  18. wayneh

    Expert

    Sep 9, 2010
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    Try resetting on 8 instead of 7. I think you're getting a near simultaneous clock and reset, skipping over "0", your LED #1
     
  19. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    how would i reset on 8?
     
  20. Tony Spence

    Thread Starter Member

    Dec 20, 2013
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    i connected the reset to pin 9 and added an led but i still got the same problem both of the LEDs stay lit until all off then they blink and stay on again kind of like a count down to the led thats on then they all go off for a second
     
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