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:
- Light O:2/00 (Red) = 12 seconds ON
- Light O:2/02 (Green) = 8 seconds ON
- Light O:2/01 (Amber) = 4 seconds ON
- The sequence now repeats with Red = ON.
RED |
GREEN |
AMBER |
12 Sec. |
8 Sec. |
4 Sec. |
<-------------------------------- Time in Seconds ------------------------------>
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.
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. |
8 Sec. |
4 Sec. |
<-------------------------------- Time in Seconds ------------------------------>
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.
Red = O:2/00 |
Green = O:2/02 |
Amber = O:2/01 |
R |
Green = O:2/06 |
Amber = O:2/05 |
Red = O:2/04 |
8 sec. |
4 sec. |
1s |
8 sec. |
4 sec. |
1s |
<-------------------------------- Time in Seconds ------------------------------>
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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