LogixPro Index

Traffic Control Lab
Utilizing Word Comparison


Exercise #1 -- Traffic Control utilizing 1 Timer

From the Simulations Menu at the top of the LogixPro screen, Select the Traffic Light Simulation

Utilizing a single timer, employ the use of Word Comparison instructions to control our simulated traffic light. The sequence of operation and timing durations are set out in following timing diagram.

Your program should incorporate a 1 second period (delayed green) when both directions will have only their RED lights illuminated. Note that the timing diagram below only shows one of these 1 second intervals, but two are actually required.

Red = O:2/00 Green = O:2/02 Amber = O:2/01
Green = O:2/06 Amber = O:2/05 Red = O:2/04
8 Sec. 4 Sec. 1 8 Sec. 4 Sec.

If a one second delay proves insuficient to get these drivers under control then just go ahead and jack the delay up to two!



Exercise #2 -- Dealing with Pedestrians

Modify your program so that the crosswalks are also controlled. This is not necessarily a word comparison exercise, but it's a task that needs doing, and you should now have sufficient expertise to accomplish it. It might not be all that easy however!

Your program should operate as follows:

  • When depressed, the crosswalk pushbutton will cause the appropriate Walk Sign to be illuminated at the next occurence of a Red to Green transition for the appropriate direction.
  • If the Green light is already illuminated when the button is pressed then the Walk signal sequence will be delayed until the next Red to Green transistion ocurrs.
  • Once the Walk Sign is illuminated, it will remain so for the duration of the Green signal.
  • When the Amber light appears, the Walk Sign will commence to flash On and Off and continue to do so until the Red signal appears.

You might consider using a bit from the free-running timer located in S2:4 to create the cautionary flashing effect.






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