Issues with PLC indicator lights
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A newcomer is asking: on a PLC, what do the indicator lights in the upper row and those in the lower row mean when they light up? If it’s related to the wiring terminals, it seems that there aren’t as many indicator lights as there are wiring terminals in the upper row
This is an S7-200 PLC. The upper row in the diagram represents the outputs, while the lower row represents the inputs. Among the outputs, 1L refers to the 1# load line, 2L refers to the 2# load line, and 3L refers to the 3# load line; by \"load\" is meant the external power supply line. Then, Q0 01234567 denotes the first set of outputs (Q0.0~Q0.7), and the same applies to Q1! N and L1 are the power supplies for the PLC, connected to AC220; many people get this wrong! The I0 01234567 below represents inputs from I0.0 to I0.7; similarly, I1 and I2 work in the same way! This is the 226 model with 24 INPUTs and 16 OUTPUTs, of the RLY relay output type!
To add, 1L is the common line for Q0.0 to Q0.3, connecting to one pole of the load power supply; whereas 1M represents the common line for input I0.0 to I1.0, connecting to one pole of the power supply in the input section.
The S7-200 has been discontinued; it is recommended to purchase spare parts as soon as possible