18. PLC CONNECTION

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Many configurations and packages are available. But essential components are,

- power supply - Provides voltage/current to drive the electronics (often 5V, +/- 12V, +/- 24V)

- CPU - Where ladder logic is stored and processed, the main control is executed here.

- I/O (Input/Output) - A number of input/output terminals to connect to the actual system

- Indicator lights - Indicate mode/power and status. These are essential when diagnosing problems.

Common Configurations

- Rack - A rack, or number of racks are used to put PLC cards into, these are easy to change, and expand.

- Shoebox - A compact, all-in-one unit (about the size of a shoebox) that has limited expansion capabilities. Lower cost, and compactness make these ideal for small applications.