Led clock by yingyingong

Discussion in 'The Projects Forum' started by bertus, Nov 2, 2011.

  1. bertus

    Thread Starter Administrator

    Apr 5, 2008
    15,645
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    Hello,

    I got an email from yingyingong asking the following question:

    As I do not answer emails I posted the question over here.

    If only one led is on at the time the ciruit could be quite easy.
    The request to have a growing number of leds will need some kind of latching circuit.

    Perhaps others have their idea's about it.

    Bertus
     
  2. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
    26
    I'd start by examining the LM3916 - Dot/Bar Display Driver
     
  3. jimkeith

    Active Member

    Oct 26, 2011
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    Last edited: Nov 2, 2011
  4. yingyingong

    New Member

    Nov 1, 2011
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    i have try it. it will only work if i put a NOT gate in front of every LEDs. is this correct? if not how should i correct it? anyone can help?
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    I would use a 4017 Johnson counter, wired to 60 LEDs.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    RiJoRI,
    The LM3916 is a VU meter display; it would be very difficult to use that IC.
    I think you meant the LM3914, which is in the same family, but linear. That could be made to work, but it would be rather difficult to set up, as yingyingong would have to go from digital to analog in order to get the LEDs to increment.

    Bill,
    yingyingong wants the LEDs to light sequentially, and stay on. Using the 4017 would make it easy to light them sequentially, but they wouldn't stay on like yingyingong wants them to.

    jimkeith,
    The 74HC164 shift register is a good idea. You might find that the 74HC595 is easier to use. If more current is needed, the TPIC6C595/TPIC6D595 or STPIC6C595/STPIC6D595 have eight open-drain outputs that can sink (not source) up to 100mA; other than that, their functionality is similar to the 74HC595.

    You would need 8 of the 595 shift registers; the last 4 bits would not be used.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I had missed that, but it still would be no problem. Small MOSFET drivers and steering diodes, lighting that many LEDs at once (more if you include seconds as well as minutes) is going to be a current hog though.

    It will be component intensive, around 5 parts per LED, not counting the 4017 circuitry.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Well, one of the '164 or '595 shift registers would require one IC and one resistor array for 8 LEDs, so that's a pretty low parts count.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Don't forget the drivers, LEDs, and resistors. I didn't.

    *****

    OK, I missed the resistor array. Debatable if that really reduced part count, but I'll count it.

    Are there any MOSFET array's out there?
     
    Last edited: Nov 9, 2011
  10. Fenris

    Active Member

    Oct 21, 2007
    288
    2
    High there

    This circuit may be of use for your needs? It's actually for a 'Ghostbusters' Power pack prop.

    Get rid of the U4 portion of the circuit and U3 can be replaced with a more accurate timer chip.

    BC547/548 for the transistors and replace the lamps with LED's and an appropriate resistor.

    If the #11 pin on the last half chip was used this circuit would light 15 LED's in sequence. You would need 8 of the 4015 IC's.

    Hope this is of some help.

    regards

    Fenris
     
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