Hello everyone, I am seeking assistance with Modicon ladder logic and its conversion to Rockwell. I am new to Modicon logic and would appreciate any guidance on the following questions: 1. Does the vertical short passing through the highlighted horizontal short in the logic tie the two rungs together? Can either contact to the left of the short pass power between the two rungs? 2. Are the SUB instructions positioned side by side linking all three outputs from the SUB on column 3 to the input side of the SUB on column 4? If so, is this a method to create a limit instruction where power is only passed through if the data in 41001 falls between 25 and 33?
1. Both contacts can trigger activation of all branches simultaneously. 2. When Value 2 in the middle is greater than Value 1 at the top, the lower right pin in the sub box will be set to true. Similarly, the first box pin will also be true if the CIP step number exceeds 24, and so forth.
Thank you for your response bb76. In the initial lower sub instruction, do all three output pins link to the subsequent sub instruction? It seems that when placed together, all three output pins are automatically connected to the next sub. How can one determine which output is being utilized?
VSandhu expressed gratitude for bb76's response and asked for clarification on the lower sub-instruction's output pins. It seems that all three output pins are connected to the next sub-instruction when placed side by side. How can one determine which output is being utilized? This particular block also functions as a comparison block, with the top representing "value 1 greater than value 2," the middle representing "value 1 equal to value 2," and the bottom representing "value 1 less than value 2." Since all outputs are linked, the assumption is that the first comparison may not have any effect. It is suggested to download Schneider Control Expert for coding and simulation, supporting 984 ladder files. Users with old Lmodsoft or Proworx files should be able to open them on Control Expert. Please note that L984 requires a separate selection for enabling. Control Expert can be used for 21 or 30 days without a license.
Thank you for responding, Lare. It now makes sense to me that all connections need to be linked for comparison purposes. Surprisingly, the instruction manual does not clearly mention that this sub can be used in this way. It only specifies one top input. This made me question whether a visible horizontal short should be made from each output to the top. I appreciate the simulation tip you provided, as it will be useful moving forward.
VSandhu expressed gratitude towards Lare for the response. It was clarified that the sub should be connected properly and used for comparison. However, the manual did not mention that the sub could be utilized in this manner. It only stated that the sub has one top input, leading to some confusion. The tip for simulation was appreciated and will be useful. In reality, the sub has only one input but with three outputs, it may appear that they are all interconnected when placed next to another block. If there is space between the blocks, it would show that the top pin is connected and there are no other inputs. It is essential to compare if the value is greater than 29 for the input of another block. With old modsoft PLCs, unnecessary lines between objects could consume more programming memory and were often optimized by programmers. The spacing on the rung was also limited. It is hoped that there are not too many extended floating-point math operations as they can be confusing without real PLC values. It has been a while since reading modsoft code.
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Answer: Answer: Yes, the vertical short passing through the highlighted horizontal short in Modicon logic ties the two rungs together.
Answer: Answer: In Modicon ladder logic, SUB instructions are positioned side by side to link all three outputs from the SUB on column 3 to the input side of the SUB on column 4. This method is used to create a limit instruction where power is only passed through if the data in 41001 falls between 25 and 33.
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