Greetings everyone! I am currently taking on the challenge of learning on my own and following along with Frank's textbook and lab manual. I have encountered a roadblock on problem 5-6 and could use some guidance to help me navigate through it. The issue I am facing pertains to Rung 0 & 3 in my attempted solution. When PB1 & LS1 are both true on Rung 1, CR1 locks itself along with PL1, regardless of PB1. However, when control relays are removed, the signal cannot be locked in despite PB1. Initially, I considered replacing CR1 with LS1, but this would make PB1 unnecessary. Similarly, on Rung 3, the same problem arises where PB2 becomes unnecessary with the solution I have come up with. Thank you in advance for any assistance, and I hope I have not made a mess of my first post. - Thunda
Consider this question: If I were to have CR1, which part of the program would consistently match CR1 after the initial rung? Pose the same question for CR2 and CR3 as well. This may seem like a simple issue, but it's important to ensure you're not overlooking any nuances.
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Inquiring about the constant value of a specific bit in a program after the initial rung execution is a common query among programmers. Typically, this value remains the same for specific rungs, such as PL1 for rung 0, Sol A for rung 1, and Sol C / PL2 for rung 3. While it may seem straightforward to use contacts based on these outputs instead of contact relays, one might question if this truly eliminates the need for contact relays or simply replicates the same principle. Is this issue as straightforward as it appears, or is there a subtle detail that I am overlooking? Sometimes, it's easy to overthink such matters. If the solution is indeed simple, I will humorously subject myself to 10 lashes of shame. Welcome to the forum, and thank you for the warm greeting!
Consider utilizing a countertop to substitute the coil.
Robb B suggested utilizing a counter as a potential alternative to replacing the coil in this situation. However, it is important to note that the lab manual only extensively covers counters in Chapter 8. Therefore, it is assumed that the solution to this problem involves using only the specified I/O without a counter. Ultimately, the best course of action may involve working within the parameters given, despite any uncertainties.
Hello Thunda, welcome to the forum! It seems like you're dealing with a latch and unlatch issue. The fact that CR1 stays latched regardless of PB1 sounds like you may have it wired in a way that it only unlatches when PB1 & LS1 are false, making it an AND circuit. You may want to consider changing your wiring so that CR1 unlatches when either of the two conditions aren't met (OR circuit). The same holds for PB2 becoming unnecessary in Rung 3. Flip your logic around and see if that helps! Keep us posted on your progress. Good luck!
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Answer: Answer: Thunda is encountering issues related to Rung 0 & 3 in their attempted solution, particularly regarding the behavior of PB1, LS1, CR1, and PL1.
Answer: Answer: In the described scenario, CR1 locks itself along with PL1 regardless of PB1 due to a specific control logic setup that causes the signal to be locked in.
Answer: Answer: Thunda has identified PB1 and PB2 as becoming unnecessary in their solutions for Rung 1 and Rung 3, respectively, which is causing confusion in their logic design.
Answer: Answer: Thunda may explore different ways to design the ladder logic to address the issues with PB1 and PB2, such as considering the roles of LS1 and CR1 in the control system.
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