What is digital input in PLC?
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A digital input in a Programmable Logic Controller (PLC) is a signal that indicates an ON or OFF binary state. Devices such as
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Switches,
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Sensors, &
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Buttons
provide these inputs, which enable the PLC to determine the condition of different automation system components.
Binary Condition
The ability to be in either of two states: HIGH (ON) (or) LOW (OFF), that are frequently denoted by the numbers 1 or 0 which defines digital inputs.
Signal Source
Devices with only 2 possible states, such as an open or closed switch, provide digital inputs.
PLC Function
The PLC receives a signal as a digital input is triggered, such as when a switch closes. After processing this signal in accordance with its preprogrammed logic, the PLC is able to regulate outputs and make system selections.
Ex: Digital inputs for PLC systems are frequently obtained from proximity sensors, limit switches, push buttons, and photoelectric sensors.
Voltage Levels
In a standard digital input system, the ON state (1) is represented by a greater voltage (e.g., 24V DC), whereas the OFF state (0) may be represented by a voltage of 0V.
Function in Automation
By enabling the PLC to react to changes in system’s state, digital inputs serve an essential function in triggering control logic, keeping track on the condition of field devices, and guaranteeing safety.