Competency and practice field guide
Photoeye digital-input wiring scenario: practice plan
Direct answer
The learner can identify sensor conductors, supply, common and switching path, then prove both input states without relying on wire color or LED alone.
Written for pLC and electrical learners connecting a photoelectric sensor to a digital input and relating current path to the input tag.
Scope
Sensor function, PNP or NPN behavior, supply, common, output conductor, PLC input type, channel, input image and process meaning.
Signal path
Target condition through sensor electronics and switching path into module common, channel indication, controller tag and program consumer.
Baseline practice
Known clear and blocked conditions producing coherent device, channel, tag and logic states with expected voltage relationships.
Edge cases
Wrong common, incompatible switching type, broken conductor, leakage current, short circuit, channel mismatch, force and supply return.
Fault practice
A target, sensor, supply, common, conductor, input circuit, channel, image or program-meaning mismatch.
Transfer to the job
The wiring verified against exact sensor and input specifications, protection design and approved test procedures.
How do I wire a photoeye to a PLC input?
Match supply voltage, output type and input-module circuit first. Trace the current path through sensor output, channel and common using the exact manuals rather than relying only on conductor color.
What is the difference between PNP and NPN sensors?
In common DC use, PNP outputs source current toward the load while NPN outputs sink current from it. The PLC input and common arrangement must be compatible.