LOGIC PROBLEM (Switching/Trigger)

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

  1. johncena

    Thread Starter Member

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

    The input is negative
    The output is negative (0)

    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....


    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


    Nov 25, 2009