Programmable Logic Controller (PLC) Questions and Answers – 14

Siemens S7-200 PLC Questions and Answers

Suppose we have a Siemens S7-200 PLC connected to a pair of process switches and light bulbs as shown in this illustration:

Siemens PLC Block Diagram

Examine the following relay ladder logic (RLL) program for this Siemens PLC, determining the statuses of the two lamps provided the temperature switch senses 102 oF and the flow switch senses 4.7 GPM:

Siemens Ladder

Also, determine whether the inputs on this PLC are sourcing or sinking, based on how they are connected to the process switches.

Answer :

Green lamp is off, red lamp is on. The PLC inputs are configured here to sink current.

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Credits :  Tony R. Kuphaldt – under CC BY 1.0

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