LOGIC PROBLEM (Switching/Trigger)

Discussion in 'Homework Help' started by johncena, Mar 3, 2011.

  1. johncena

    Thread Starter Member

    Aug 15, 2010
    32
    0
    HI, i would like to ask if there is a logic switch that will trigger and will output with the following conditions..

    BEFORE TRIGGERING:
    The input is negative
    The output is negative (0)

    SWITCHING MODE:
    If i trigger the switch (or when a current pass through a NPN transistor), the positive 5 volts (timed input for 19secs) will enter and goes to the output for "1 second only" and goes back again to 0 and it will remain negative for the whole 4sec or 19 secs.

    Just like entering the 5 volts for 1 sec in the output, and the output will return to negative again..

    Input for 4 or 19 secs | Output for 1 sec | Output after 1 sec
    0 | 0 | 0
    1 | 1 | 0


    I was building a traffic light circuit with the red and green lights will light up for 19 secs and the countdown 7 segment will trigger from 19secs to 0secs.. (19 secs because the yellow light was already included in the countdown)i am using 4017 IC, the Traffic light's 555 will produce 2 secs per cycle and each output of 4017 will last for 4 secs.. and the 7 segment's 555 will produce 1 sec per cycle.

    Pls refer to this pic....

    [​IMG]



    Due to 555 imperfect clock .. sometimes the 7-segment will not be synchronize to the 4017 or from that 19sec gap.. so i would like to trigger the RESET button of all the 74192's and 4511's when the clock positive volt reaches Q6 to Q9 at 4017's pin.
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
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