Help Needed Inverting "Lighthouse" Sweep with 4017 and PNP

Discussion in 'The Projects Forum' started by OldSkoolEffects, Mar 16, 2014.

  1. Bernard

    Expert

    Aug 7, 2008
    5,204
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    Not much difference on power use for the series connected versions. Line operated power supply to battery brings up more questions.
    How long does display need to operate at a time?
    Alk. or rechargeable? Go with re chg., flatter discharge V.

    How bright do LED need to be, a small drop in current might not be noticeable.
    My suggestion, use 8 AA's ' use 2N3904 as common emitter drivers [ emitters grounded ], or IC equivalent . @ 2600 mAh a drain of 320 mA about 8 hours.
    For longer times try SLA 12V battery.

    Ignore use of 74AC02, forgot about other 3 groups.
     
  2. OldSkoolEffects

    Thread Starter Member

    Nov 18, 2009
    68
    1
    I'll be using a 12V 9800mAh battery, probably in parallel with another, since this circuit is just the tip of a large iceberg of a big project.

    My overarching concerns are prioritized thusly:

    1) Supply is 12V
    2) Stable performance
    3) Limit current draw where possible
    4) LED brightness

    There are going to be micro-controllers involved in the larger project, so I could multiplex and all that, but I'm trying to keep non-dynamic circuits as isolated as I can; basically, apply power and they work. I may run a timing pulse from an MCU into the 4017 just for the ability to change the frequency with software, but that's not important at the moment.
     
  3. OldSkoolEffects

    Thread Starter Member

    Nov 18, 2009
    68
    1
    Quick update:

    I got the parts for this circuit and am in the process of bread boarding it (which I hate). I got my 4047 working, and my 4017 works, but I'm having issues with the 4001s. I tested them individually to make sure I was connecting them correctly, but it raised a question. How quickly are these gates supposed to switch? They seem to be switching correctly (I'm using an LED to see the state change), but there's a lag or so where the LED seems to go bright-dim-off instead of bright-off. I'm not testing with a decoupling cap, but would that really affect it? I can't find anything int he datasheet that states how quickly it should switch, but I would imagine it should be faster than my eye can pick up on.
     
  4. Bernard

    Expert

    Aug 7, 2008
    5,204
    600
    Which schematic are you using?
    Are you using a common colector driver for your test LED?
    Switching times should be less than a μS.
     
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