What is the difference between PLC input and output types

Programmable logic controller is a digital operation electronic system designed for use in industrial environments. It uses a programmable memory to store instructions for performing logic operations, sequential control, timing, counting and arithmetic operations, and controls various types of mechanical equipment or production processes through digital or analog input and output.

The input unit is the input interface between the PLC and the controlled device. It is the bridge for signals to enter the PLC. Its function is to receive signals from the main command element and the detection element. The input types include DC input, AC input, and AC/DC input.

The output unit is the connecting component between the PLC and the controlled device. Its function is to transmit the output signal of the PLC to the controlled device, that is, to convert the weak current signal sent by the central processor into a level signal to drive the actuator of the controlled device.

PLC output types are generally divided into the following three types:

1. Digital Output (DO): Digital output is usually a digital signal or binary signal, such as on/off or high/low, etc. It usually controls external devices such as motors, solenoid valves, etc. through relays or semiconductor switches.

2. Analog output (AO): Analog output is usually used to control devices that require continuous control, such as temperature, pressure, flow, etc. They usually use a current loop or a voltage loop to control the device, such as using a 4-20mA or 0-10V signal.

3. Pulse Output (PO): Pulse outputs are often used to count or measure position or speed in applications. They can provide a fixed digital pulse, such as a sensor signal, or obtain a different number of pulses through an encoder, thereby more accurately controlling the position and speed of the device.

The difference between PLC inputs and outputs lies in their function and how they are connected.

PLC input is to input the signals generated by external devices such as sensors and switches into the PLC so that the PLC can perform logical control. The most common input devices include digital input and analog input.

Digital inputs transmit information in the form of binary signals, usually representing the state of a signal generated by a switching device such as a switch, button, sensor, etc. Digital inputs are often connected via normally closed and normally open contacts.

Analog inputs are used to transmit continuous signals, such as temperature, pressure, flow sensors, etc. They usually output in the form of 0-10V, 4-20mA, etc. for PLC control.

PLC output is to transmit the control signal of PLC to the execution device to realize the control function. The most common output devices include digital output and analog output.

Digital outputs usually transmit information in the form of binary signals, such as switching devices such as solenoid valves, relays, lights, etc. Digital outputs are also usually connected via normally closed contacts and normally open contacts.

The signal continuity transmitted by analog output is usually used to control the continuity parameters of the actuator, such as the speed of the motor, the opening of the valve, etc. Analog output is usually connected in the form of PWM, 4-20mA, etc.

In general, the functions and connection methods of PLC inputs and outputs are very different. Inputs transmit signals to the PLC for its control, while outputs transmit the PLC's control signals to the actuators to realize the control functions.