How long can a cycle of the IC 555 be?

Discussion in 'The Projects Forum' started by mikejones, Sep 4, 2007.

  1. mikejones

    Thread Starter Guest

    i know it depends on the the resistors and the capacitor, but in theory with 2 220K resistors and a 1500 microF you can get a 11 minuts cycle, is that near to what happens on implementation?

    i'm using a diagram like this, and this formula.

  2. John Luciani

    AAC Fanatic!

    Apr 3, 2007
    The timing equations are only valid for a range of R's and C's. IIRC 1500uF is outside
    the valid range. You should check the manufacturer's datasheets for component

    If you need that long a time period you may want to look at a counter.

    (* jcl *)
  3. Neo1130


    Sep 3, 2007
    FWIW, I am trying to design a circuit that will stay on for a couple of hours... So far, upon testing, I have NOT connected the discharge, threshold or control voltage pins and it has been on for a couple of hours now...