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Timing Circuit

  1. Feb 25, 2012 #1
    Using an array of 555 timing chips I want to turn one output on for 3 minutes then turn it off, then turn another output on for three minutes then turn it off. I understand how to alternate each output but it is having no outputs after 6 minutes that is the problem.
  2. jcsd
  3. Feb 25, 2012 #2
    It would seem that two 555's, operated in monostable mode, would do the trick. The first is triggered and its output goes high. This output is tapped, and also drives a second, so when the output goes low it trips the second and its output goes high. When the 2nd times out the cycle is done. Check this website:


    Here is a short video of the circuit operating as you wish:

    The key is the small cap between the output of the first 555 (or first half of 556) and the trigger input of the second.

    Also, it looks like a 1 meg resistor and 100 uF cap in the timing circuit should give you 180 seconds. You probably already knew that. Hope that helps!
    Last edited by a moderator: Sep 25, 2014
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