LogixPro
Traffic Control Exercises
Utilizing TON Timers

Exercise #1 -- Traffic Control using 3 Lights

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

Using your knowledge of cascading timers, develop a ladder logic program which will sequence a set of green, amber and red lights in the following manner:

Sequence of Operation:

1. Light O:2/00 (Red) = 12 seconds ON
2. Light O:2/02 (Green) = 8 seconds ON
3. Light O:2/01 (Amber) = 4 seconds ON
4. The sequence now repeats with Red = ON.

Exercise #2 -- Traffic Control using 6 Lights

Modify your program so that the 3 lights which represent the other traffic direction are also controlled. It is tempting to use six timers for this task, but the job can be done with just four, and you'll end up with a much cleaner program as a bonus.

Still getting the odd Crash? Well it's pretty obvious that these drivers aren't paying much attention to Amber Lights! No need for any more wiring however. You can solve this problem, but it's going take a little more programming.

Exercise #3 -- Traffic Light With Delayed Green

Modify your program so that there is a 1 second period when both directions will have their RED lights illuminated. Note that there are actually 2 such overlaps that need to be accounted for. The timing diagram below shows the six discrete timing intervals required to accomplish the desired sequence of operation, and with proper cascading you should be able to come up with an easy to follow solution using just 6 timers.

If a one second delay is not enough to get these drivers under control then just go ahead and jack the delay up to two!

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