Pulse Counter?

Discussion in 'The Projects Forum' started by jr2233, Jan 2, 2010.

  1. jr2233

    Thread Starter New Member

    Jan 2, 2010
    3
    0
    I have a single push button switch S1 (like a doorbell), I would like to press S1 one time and after 30 minutes an LED will turn on and off. I do this now with a one-shot timer circuit using a 4093 or a 555 timer. I would like to be able to press S1 2 times and the delay to the LED would be 60 minutes. Or press S1 3 times (in a row) and the delay to LED would be 90 minutes, etc... The output (LED) would go high just momentarily. I need help on how to do this with minimum of parts, the 30 minute time period does not have to be precise, I can use a single R/C. I am clueless on how to store or latch the counts and then add them to the timer, hope someone has an idea, thanks...jr
     
    Last edited: Jan 2, 2010
  2. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    You could use a 4017 decade counter with each output feeding a 4066 analog switch. The analog switch would then tie increasing size timing caps into the timing circuit. If you only want three possibilities, tie the 4th output back to the reset of the 4017.
     
  3. jr2233

    Thread Starter New Member

    Jan 2, 2010
    3
    0
    thanks for the 4017 advice, I just don't see how the 2 or 3 pulses would be directed to the correct 4066 inputs?
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    How long is momentary? Bill's idea looks good. Trigger both 555 & 4017 at the same time. First time period uses a permanant timing cap[30uF], second count adds a 30 uF, 3 rd replaces 30uF with 60 uF. 4017 reset derived from LED ckt. the 555 is not affected by pulses after first one. Switch needs to be de-bounced, 555 ok but 4017 could get multiple counts on one switch closure. Timing resistor about 1M. This is for seconds, for minutes it becomes a problem, ie 5400 uF for 90 min., leakage becomes a possible limitation. 'need to think about a flip-flop & another counter.
     
    Last edited: Jan 2, 2010
  5. jr2233

    Thread Starter New Member

    Jan 2, 2010
    3
    0
    Thanks for your ideas. Momentary output can be high for less than a second because it will trigger a small SCR gate (not an LED). The rest of the circuit is working fine.The more I am gathering here I think I need a 3 or 4 step sequencer. Touch S1 1-4 times in a row and the sequencer jumps to the coresponding output and produces a short high to turn on an SCR, then the sequencer resets and waits for another S1 signal. My other part of my circuit operates on 5 volts. I could live with 3 steps but a few more would be nice. I could also reduce the 30 minute time to 15 minutes as long as I would get at least 6 steps. (6x15=90 minutes) precision is not that critical. Thanks so much for your input...JR
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    We have not forgotten you. Here's an outline: Switch de-bounced by 555, which advances counter from 1 to 15 counts, sets flip-flop, which enables slow clock, 15 to 30 min advancing counter from 15 min to 7.5 hours . Comparator, 74C85 gives output when both counters are equal, resetting flip-flop, triggering 555 which provides reset & desired delayed pulse por triggering SCR. Counters: 74C93, 74C161, 40161 or dual CD4520. May need a gate or two.
     
  7. Tahmid

    Active Member

    Jul 2, 2008
    344
    25
    Hi jr2233,
    You can do this with discrete circuitry but for minimum parts, a microcontroller should be used. You can use a cheap 10F or 12F for this and if you are willing I can help you in this.
     
Loading...