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Time delay

  1. Feb 25, 2008 #1


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    Hi, everyone.
    I am currently involved in a small electronics project and I am required to produce a time delay for part of the project. I plan on using the famous 555 timer and not quite sure on what to do to produce this delay.So please anyone help explain how to produce a time delay of,say for example 44 seconds.
  2. jcsd
  3. Feb 25, 2008 #2
    There are many ways to create a delay. Two I'm thinking of now are here:

    1.) Use a 555 timer in monostable mode. This way, you'd push a button that activates the 555's trigger, and it would put out a pulse of a delay you'd specify. If whatever you're delaying for needs Vcc to be on, you could connect the 555 through an inverter or something to the device.


    2. You could do some things with voltage controlled switches and capacitor discharging, but honestly, I think option 1 is your best bet.
  4. Feb 26, 2008 #3


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    Yeh, thanks that works very well but I think my question was not clear enough and I apologise for that.The question should have been something like this;Say you have made a one shot time that actually has a time width of 44 seconds, how possible it is to split this interval to,say, two or three parts. The main idea I have is to use few times as possible.
  5. Feb 26, 2008 #4
    Did you mean it will run for 22s - stop - then run 22s?
  6. Feb 26, 2008 #5


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    Staff: Mentor

    I'd suggest that instead of using a 555, you could use a more stable oscillator and a long down-counter chain. You could use a 32kHz watch crystal, for example, and an HC4060 14 bit ripple counter to get close to a 1 second square wave, and then use another HC4060 to count out to multiple seconds. With a little logic, you can generate any delay you want out in the 44 second range.
  7. Feb 26, 2008 #6


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    Science Advisor
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    If you need multiple time delays of variable length then a uP come to mind.
  8. Feb 29, 2008 #7


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    Hey thanks guy for you answers they gave me more knowladge on digital stuff.
    I met my advisor and I asked him about the ideas I have on time delays and he said that a 555 time in one shot will work on a workbench but not practically. He also said that the frequency I will be using will be too high for pysical components.
    I will probably stick to timers.

    Thank you guy for your contributions.
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