555 Timer help

Discussion in 'Homework Help' started by Chris15, May 10, 2009.

  1. Chris15

    Thread Starter Active Member

    Apr 15, 2009
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    Hi
    I want to make an electronic timer that will sound an alarm like for in the kitchen, i want it to run off 9V and range from 1min - 30min if possible. have a Pot for ajusting it and a start push button, thanks

    Chris
     
  2. mik3

    Senior Member

    Feb 4, 2008
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  3. bertus

    Administrator

    Apr 5, 2008
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  4. mik3

    Senior Member

    Feb 4, 2008
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    Good point Bertus.
     
  5. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    252
    0
    hey thanks guys finally i find what i wnated, so if i replace the resistor with a 10M pot how will i know what time it is on do i set it wait and mark it?, and another thing what value shoud the capacitor, im thinking 1000uf
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    You need to calibrate it. Use something erasable at first, set it then see how long it goes for a random setting (or space them out regularly). You can extrapolate the settings after several points.

    Or you can use a DVM to set the resistor for a specific time setting, and put a mark there.

    Did you read this?

    555 Monostable
     
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