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Timers -- notes for the less experienced (work in progress)

Discussion in 'General Electronics Discussion' started by (*steve*), Apr 17, 2010.

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  1. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,374
    2,769
    Jan 21, 2010
    This post has been moved to here.

    This thread will remain so that references it will not be broken, and also to allow comments.
     
    Last edited: Feb 18, 2012
  2. Externet

    Externet

    736
    158
    Aug 24, 2009
    When dealing with timers, it is necessary to define the events desired.

    An initial pulse that can go:
    -Low
    -High
    Will start some timing
    -At application of pulse
    -At release of pulse
    And the output state will
    -Not change
    -Will go high
    -Will go low
    When the time lapse ends, the output will
    -Immediately go high,
    -Immediately go low,
    -Emit a pulse
    During a set amount of time and then,
    -Return to high state,
    -Return to low state.

    There is a large number of permutations of the above posibilities.
    It is convenient that some flowchart or better wording than mine be made a standard to select the type of timer circuit desired.
    Suggestions ?
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,374
    2,769
    Jan 21, 2010
    Please feel free to suggest some text and I will incorporate it.

    The original purpose of this was to discuss the problems with very low frequency oscillators and timers rather than the triggering aspects thereof.

    I must get back to this with some circuit diagrams and graphs and stuff... Soon.
     
  4. vk5ajl

    vk5ajl

    8
    0
    Feb 1, 2010
    For either medium times or very long times up to weeks or months, there is nothing like a 32.768kHz crystal oscillator stuck to the side of a 4060 counter. Cascading counters is easy and they are cheap. A single 4000 series divide by n such as a 4059 can be used to make it time almost anything. Triggering is simply by the reset pin(s). No component tolerances to worry about and drift is very low. To make it even more accurate all you have to do is cook the cyrstal (electric temp oven using a thermistor).
     
  5. nbw

    nbw

    48
    1
    May 8, 2011
    I've heard about the cooking technique. Never tried it though. Have you vk or anyone else? Might be something else I can use my toaster oven for; as well as SMT / solder pasting :)
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Whilst the heating structure (and circuit) is referred to as an oven, I've not heard people refer to it as "cooking" -- cooking is almost universally an adjective used to describe bad things when used in conjunction with electronics.
     
  7. nbw

    nbw

    48
    1
    May 8, 2011
    A tip someone gave me ages ago was to send pin5 of the 555 to ground via a 0.1uF cap....
     
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