Digital Systems Lab 14

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Lab 14: Traffic Light State Machine

Breaking Lab 14 Into Parts

You may not be able to finish this circuit if you do not have a solid plan for building the circuit. Here are the steps you should take to build the circuit.

  • First wire up the monostable timers with active LOW pushbuttons to ensure that they function correctly (use LEDs on the output pins).
  • Then build the FSM and put LEDs on the flip-flop outputs to ensure that the FSM cycles through each state properly (you should see the LEDs light up consistent with your state assignments).
  • Finally, include the synchronous output LEDs. Don’t remove any of the other diagnostic LEDs until you get everything working.

Other Tips

  • Use a clock frequency of at least 500 Hz once the monostable timers are wired into the finite state machine
  • Keep notes of what’s connected to each logic gate
  • Use wire colors to stay organized


Watch/read the following resources prior to attending this lab. This information will teach you how to use lab equipment and provide suggestions and technical tips for successfully completing the lab.