555 timer question

Discussion in 'The Projects Forum' started by Jassper, Oct 20, 2008.

  1. Jassper

    Thread Starter Active Member

    Sep 24, 2008
    84
    1
    I need a timer that will give me a 30 minute off time and a 30 secend on time + Manual trigger ON. Mathmatically I can do this with an astable 555 but I am not sure it is practical.

    thoughts?
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Unless you need precision a 555 will work just fine, but it will take two, one for each duration.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    30 minutes is too long for a 555 because the huge timing capacitor will have a higher leakage current than the high value timing resistor's current.

    Use a CD4541 timer IC that has an oscillator and an adjustable digital divider.
    A CD4060 is also an oscillator and an adjustable divider.
     
  4. Jassper

    Thread Starter Active Member

    Sep 24, 2008
    84
    1
    Thanks for the tips, do you have any circuit examples for the CD4541?
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Its datasheet does not have applications circuits.
    Look at Texas Instruments datasheet for the CD4536 timer.
     
  6. jblueink

    Member

    May 27, 2008
    24
    0
    yea Adiouguru is right there is no applications circuit in the datasheet,and also CD4060 will do just fine.goto www.electronicsforu.com.
     
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