The scenario
A 24 V PNP proximity sensor output must interface to an NPN-sinking PLC input; an interposing relay isolates the sourcing sensor from the sinking input.
What is in this drawing
Read the decisions behind it.
01
Use a relay with coil driven by the PNP output and a flyback diode across the coil
02
Wire the relay common to the PLC input and NO to 0 V so the closed contact sinks current from the PLC pull-up
Reusable for any PNP sensor to NPN PLC input conversion using a single interposing relay and DC coil supply.
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