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Output Coil
An Output Coil is a fundamental component in PLC Ladder Logic Programming. It represents an output device that is activated when the conditions leading to it in the ladder logic are met. When the logic flow reaches the output coil and the conditions are true, the coil energizes, triggering the associated output device, such as a motor, light, or valve. Output coils are essential for controlling various actuators and devices in industrial automation systems.
Note that an output coil only outputs when its recieving a signal from the left side of the rung. If that signal stops for any reason, the output coil will de-energize and turn off the connected device.
Using an Output Coil
Output coils are used to control physical output devices connected to the PLC. Each output coil is assigned a specific address within the PLC's output memory (e.g., Q0.0 for the first digital output). When the conditions in the ladder logic leading to the output coil are met (i.e., the rung is true), the coil energizes, activating the corresponding output device.
Note that the output coil will only remain energized as long as the conditions on the left side of the rung are true. If those conditions change and the rung becomes false, the output coil will de-energize, turning off the connected device.
Behavior Table
The below table summarizes the behavior of an Output Coil:
| Input Condition | Coil State | Output State |
|---|---|---|
| False (No Signal) | De-energized | Device Off |
| True (Signal Present) | Energized | Device On |