LED chaser circuit

Discussion in 'General Electronics Chat' started by Mikonovich, Nov 3, 2011.

  1. Mikonovich

    Thread Starter New Member

    Nov 3, 2011
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    In the 90's I was working in an electronics parts supply warehouse and read a build article in an old magazine about a very simple billboard marquee type led chaser circuit. I built a couple and can't figure out the circuit now. I am looking for help...

    The circuit would control 3 strings of leds, with one string either on or off depending on which way the leds were connected. The only other components were 3 resistors and 3 capacitors and a 9V battery. I have been racking my brain trying to figure out the circuit and haven't hit on it yet. I am hoping that someone would be able to help me figure it out or maybe have the article. It was published sometime in the 80's or 90's, but I can't remember anything else about the magazine...

    Thanks for any help you may be able to give.

    Mike
     
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Last edited: Nov 3, 2011
  3. Mikonovich

    Thread Starter New Member

    Nov 3, 2011
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    Thanks iONic. If I can get this circuit again I'm going to use it in the wing of a model airplane for night flying so I'd like it to have fewer components.

    Mike
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    A CD4017 IC can directly drive LEDs dimly (15mA) with a 9V supply. A 74HC4017 IC can drive LEDs brighter (25mA) with only one current-limiting resistor and a 5V supply.
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
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    A couple simpler circuits with less parts...

    [​IMG]


    Here's an interesting circuit that creates a clock pulse for a 4017 from a flashing LED. The flashing LED takes almost no current between flashes and thus the clock line is low via the 1k to 22k resistor. When the LED flashes, the voltage on the clock line is about 2v -3v below the rail voltage (depending on the value of the resistor) and this is sufficient for the chip to see a HIGH.
    [​IMG]
     
  6. Wendy

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    Mar 24, 2008
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  7. Mikonovich

    Thread Starter New Member

    Nov 3, 2011
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    I think I figured it out. I wasn't remembering correctly. There was an inverter chip in the circuit. I had a simulation working, but it sometimes goes into a weird mode on start. I will try to get a schematic up for what I have and see if there are any recommendations on how to stabilize it on startup.

    Thanks for the suggestions so far!

    Mike
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    You reminded me, I need to update some of my schematics. You need an RC circuit on the reset pin(s) to have the circuit start up correctly. Something like this...

    [​IMG]

    This from the thread 25 LED Open Ended Sequencer,

    Note C2 and R5.
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Do you mean like charlieplexing, where one LED has the cathode toward positive, and the other LED has the cathode toward negative, and logic hgih/low outputs are used to determine which LED is on in that single line with two options?
     
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