Timer circuit

Discussion in 'The Projects Forum' started by venividifoto, Nov 2, 2010.

  1. venividifoto

    Thread Starter New Member

    Nov 1, 2010
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    Hi there, I need to design a timer circuit that has two output (let's call them P1 and P2) that follows this cyclic timeline:

    P1 high and P2 low for 1 minute
    P1 and P2 low for 57 minutes
    P1 low and P2 high for 2 minutes
    repeat this until shut down...

    furthermore it would be great to regulate all the timings above (near their values...) like the first one varys from 30 sec to 3 min, second one from 50 minutes to 60, and last one from 1 min to 4 min more or less...
    thanks a lot for every hint
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    I think you might be able to use a 556 dual timer and a counter for this. The first timer would give you a one minute interval, which would advance the counter from one state to the next. The second timer could be enabled by the state of the counter. So digital zero gives you the first state. A minute later, digital 1 gives state 2.

    Not sure how this would all work out - just a general idea.
     
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    555's or 556's for 1 - 5 minutes is ok, but a 555 accurately timing increments between 50 and 60 minutes would be difficult.
     
  4. venividifoto

    Thread Starter New Member

    Nov 1, 2010
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    what about this one attached?
    I used 3 555 to generate clock (first one 6.8 hz, second and third 0.68 hz) linked to 3 4040 as

    first one 6.8hz * 120s = 816
    2nd one 0.68 * 3420 = 2325.6 (rounded down to 2325)
    3rd one 0.68 * 3600 = 2448

    any suggestion?
     
  5. venividifoto

    Thread Starter New Member

    Nov 1, 2010
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    nobody get any suggestion? come on people!!!
     
  6. venividifoto

    Thread Starter New Member

    Nov 1, 2010
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    ok I'm trying to do it, I've built up on a protoboard the first part of the circuit, the 555 linked to the 4040, but it doens't work...
    I've built up it with 0.68 Hz config as after 81 beats it should mark 2 min...
    The 555 works properly giving the 0.68 Hz beat (checked with a LED) but the 4040 sometimes works and sometimes doesn't going crazy... I've put out some LED out of it and it doens't work properly... any idea why?
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    I can't open your schematic, but I'm guessing you need bypass caps on the power pins to your counter. It sounds like you're getting bounce from noise at the power pins.
     
  8. venividifoto

    Thread Starter New Member

    Nov 1, 2010
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    you can find attached here an image with the schematic...
    I can't understand what you mean with bypass caps...
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    A bypass cap is typically a small 0.1 µF ceramic cap mounted physically as close as possible to the IC, across the power pins of the IC. Sort of a local power supply to smooth out incoming noise.

    It's a cure-all and the first go-to solution when things are behaving oddly. Kind of like restarting your computer. You'll learn to love it.
     
  10. venividifoto

    Thread Starter New Member

    Nov 1, 2010
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    ok the circuit now seems to work (thanks a lot for the tip of ceramic cap), the last problem seems to be the power-on-reset circuit, anybody can suggest me the best way to deal with this last issue?
    thanks in advance
     
  11. venividifoto

    Thread Starter New Member

    Nov 1, 2010
    10
    0
    assuming that I'm quite a lot newbie, why such a configuration doesn't set the Q at logic level high when I turn on the device? furtermore does a config with J, K and clock grounded works for having the 4027 simply doing
    - when Set goes high, Q goes high
    - when Reset goes high Q goes low??
    thanks for any hint
     
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