Sequencial circuit help #2

Discussion in 'The Projects Forum' started by wdkh68, Jun 23, 2010.

  1. wdkh68

    Thread Starter New Member

    Jan 12, 2010
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    Sequencial circuit help
    Please look at the attached circuit and see if you can find anything wrong. The first LED's 1-17 should sequence followed by LED's 18-22 with each one fading off in about 3 seconds, and then starting over after LED 22 fades off. I have breadboarded this, but only hooked up Led,s #18 &19 circuit, so, I hooked up pin 15 (res) of IC2 to pin 7 of IC4. The first 9 do not light and 10-17 only light and sequence when I touch the metal base on my breadboard (crazy huh). I have checked the wiring and have swapped out IC's to no effect.
    OK - I saved in paint as png. so I hope this works!
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    You may have bad clips in your breadboard. If you have used wire larger than for which the breadboard was designed, it can spread the connection tabs in the holes. There is there is likely a bad connection.

    Also, have you checked to be SURE the 555 is operating properly?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Do you have a data sheet for an LM555? I ask because yours is incorrectly set up for astable operation. Pin 5 also needs a .01 uF cap to ground.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    That schematic looks extremely familiar. I'm betting you lifted it off my article LEDs, 555s, Flashers, and Light Chasers. I put the LED into the circuit off the 555 as a diagnostic, it shows the pulse from the 555.

    I see no problem with 555, it is a standard hysteresis oscillator, same as the schematic I have, just relaid out. A 0.1µF on pin 5 would improve stability, but it is also optional.

    I'm looking at it a bit harder to see what else. You bread boarded this you say, on a protoboard?

    ******************

    Eliminate the 7809 regulator, it is not needed. The circuit will run fine on 12VDC. You are trying for too much LED current out of the 4017, this has been discussed more times than I care to count on other threads. Figure 10ma max without transistors, so if the power supply is 12VDC then you need 1KΩ.

    The protoboard failure sounds extremely plausible. The current crop made in China simply aren't as robust as they used to be. Look for opens around small leads, such as the diodes.
     
    Last edited: Jun 23, 2010
  5. wdkh68

    Thread Starter New Member

    Jan 12, 2010
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    It is a brand new breadboard designed for 20-28 AWG wire, the only wire that I have used is 24 AWG and smaller, even the .020 dia. diode leads are very tight in the sockets. The schematic was designed from parts of 3 different sources, one of which has nothing to do with this website. I added a 0.1uf cap to pin 5 of NE555 - no difference. I will redraw and add a 2N3904 to each LED 1-17 Thanks for your help! I also removed the 7809CT and are running direct from a 12V -
    1 amp switching wall wart.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    That is interesting. Note the layout of the diodes. Mine is an original schematic.

    [​IMG]
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    Right you are, Bill. I saw the resistor between pin 3 & 6 as a pot, and pin 7 connected to the wiper.
     
  8. wdkh68

    Thread Starter New Member

    Jan 12, 2010
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    0
    Yes, I did look at your schematic, but I used a design from another website which included fader circuits - where is the faders in your design? I drew mine from this other website BEFORE I saw yours. I didn't know that we are not allowed to copy parts of schematics from Allaboutcircuits, so I will delete this site, as it's no help!
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Actually I've done faders, I helped out Fenris with his project...

    Project: Knight Rider style sweeping light.

    This was where he put his final design at my suggestion. He has earlier threads where we worked on the concept.

    I also am in the process of rewriting LEDs, 555s, Flashers, and Light Chasers (forum edition) to cover this ground so folks don't have to reinvent the wheel.

    As for coping schematics, be my guest, it was put there to help. The similarities just jumped out, and I commented on it. People like their work acknowledged don'tcha know.

    You'll find we're a very helpful bunch here. I would add the LEDs to check the sequencing. From what I've heard so far it sounds like a handoff problem, and I still suspect a wire isn't making good contact somewhere. It is always possible you have a wiring error, no one is immune from those.

    4017s are pretty robust chips, the actual spec for current draw is around 6.8ma, though this has also been discussed to death in other threads. For CMOS this is pretty good. It is also possible one gave out under the strain of 20ma.

    The basic circuit is pretty popular, it keeps coming up one way or another, so you have a lot of resources to draw from. SgtWookie has some driver chips he likes with this circuit, basically transistors/resistors in a DIP style package.
     
    Last edited: Jun 24, 2010
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