This rule is to prevent the Walk Light (and a pedestrian from walking) when there is not enough time left to get across.2 Exercise #2 ‐‐ Dealing with Pedestrians Modify your program so that the crosswalks are also controlled. The Walk light is not to be lit EXCEPT after a button has been pushed, and at the NEXT occurance of a Red to Green transition. Remember your "specifications" for this program. PS: The LIM instruction is also one of the Comparison instructions, so it is "legal" to use LIM to solve the LogixPro Traffic Control Exercises 1 & 2. Also, the retentive OTL and OTU instructions may be utilized freely at your discretion. The utilization of Binary or Integer Table bits to Flag specific conditions within your program would be appropriate.Once movement is halted by the either of the foregoing actions, the operating criteria associated with the previous exercise will again take effect.Door movement will remain halted when the switch is released.
In this exercise we want you to modify your program so that it adheres to this additional criteria: We do not recommend proceeding with this exercise if you do not have an instructor or experienced PLC programmer to call upon for assistance. Quote: Supplemental Programming Exercise #4: This can be reduced down to more consise logic this way: IF T4:1.ACC is LESS THAN 140, then turn on N/S Red light. Rung 2, N/S Red light: Branch 1 says IF T4:1.ACC is LESS THAN or EQUAL to 20, OR (Branch 2 says) IF T4:1.ACC is GREATER THAN 10 OR LESS THAN 140, then turn on light. Third, some of your comparison logic is a little flaky. Think about it some, then if you can't solve it, look at the attached LogixPro program. I am sure that many pedestrains would curse your soul if such a scheme was actually used! You need to come up with a way to save a button-push for use later in the cycle. Your method so far for the Walk depends upon a pedestrian pushing the button when the Timer T4:0 is at a certain stage (E/W Amber On, or N/S Amber Not On). Second, your walk light logic needs to be designed so that a pedestrian can walk up AT ANY TIME and push the Walk button. Delete either rung 8 or 9 for the O:2/3 E/W Walk Light. First off, you should not normally have two rungs with the same digital output (redundant outputs).
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