Audio Modulated 4017 Chaser

Discussion in 'The Projects Forum' started by luvv, Feb 9, 2012.

  1. luvv

    Thread Starter Member

    May 26, 2011
    Hello AAC,

    So last night i was floating around youtube and seen this

    It reminded me of the ghetto blasters from the late 80's early 90's they where covered in leds w/ many modes for the lights.

    You could switch from a VU meter function to a chaser etc,lights all over the place, around the speakers and such.

    While the chaser in the vid don't function "smoothly", i think it is because it is a one 4017 "knightrider" circuit or perhaps something to do w/ the way the audio input is not sure.

    So i set about trying to figure out how it was done,and from what i could find its a 555 VCO,oddly one 555 project i hadn't done.

    So i set about bread boarding a standard 4017 chaser w/ the 5 pin of the 555 connected to + of a mono jack .

    Nadda, has no effect on the clock speed or at least doesn't appear to, i assumed it's because the radio doesn't output enough voltage to effect the CTRL pin, but again im guessing.

    Am i going about this the wrong way?


    Audio signal comeing from a 1$ AM/FM radio running on 2xAAA batteries.

    Power is from my adjustable benchtop @ 3.5v-5v

    I've seen the other threads around AAC mentioning something about Vin vs. Ctrl voltage vs.frequency but was kinda Greek to me.

    After i get this worked out i would like to make this a "knightrider" w/ two 4017's if that changes anything.

    Any ideas to make it work?

  2. Wendy


    Mar 24, 2008
    Try using a capacitor to inject the signal to pins 2/6.

    I would do this a different way, but I've put a lot of suggestions out in my LED/555 article.

    You may need to build a simple transistor or op amp amplifier to boost the audio signal to large enough levels so the digital inputs can see it.

    LEDs, 555s, Flashers, and Light Chasers
    luvv likes this.
  3. luvv

    Thread Starter Member

    May 26, 2011
    Thanks Bill M.

    I'll give that a try, and yes I've thoroughly searched the led threads of yours. Seriously if it where a paper back, pages would be falling out now.

    T.I maybe owes you little coin for upping the 555 sales ;)

    Did discover the signal is to weak as a direct 5v to the #5 pin does indeed slow the clock.

    So would need some sort of driver aand would have to be inverted to suit my want's of faster clock at more positive voltage.


  4. luvv

    Thread Starter Member

    May 26, 2011
    Well, turns out had 2 issues .
    #1 was indeed a weak signal source(switched to a beefy coyote call i acquired recently ;))

    #2 i wasn't using a cap on the signal input(used a 10uf E-cap)

    And discovered the sequence wasn't inverted, count goes faster as the voltage climbs.

    Now that problem is solved, new request, i want zero lights lit when the volume drops out.

    Is there a way to use a comparator to switch the Vin on the 4017?

    I have a LM393 handy, but im not sure how i could apply it in this case.

    Anyone have a idea how to go about it?