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Time delay

  1. Feb 25, 2008 #1

    Mc.

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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.

    http://cache.national.com/ds/LM/LM555.pdf

    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

    Mc.

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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

    berkeman

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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

    NoTime

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    Science Advisor
    Homework Helper

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

    Mc.

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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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