The interface of the PLC and the electrical circuit is completed by the input and output portion (I / O). I / O modules with integrated PLC's I / O circuit, the input registers reflect the state of the input signal, output point to reflect the state of the output latch. The input module electrical signals into a digital signal into a PLC system and the output module are the opposite. I / O module are divided into the digital input (DI), digital output (DO), analog input (AI), analog output (AO).
The switch means that only on and off the signal of the two states (or 1 and 0), analog refers to the continuous changes in the amount of The I / O are classified as follows:
Switch: the voltage level points, 220VAC, 110VAC, 24VDC, points by way of isolation and separation of relays and transistor isolation.
Analog: Signal type, current-(4-20mA, 0-20mA), voltage type (0-10V, 0-5V,-10-10V), etc., precision points, 12bit, 14bit, 16bit.
In addition to these general-purpose IO, there is special IO module, such as thermal resistance, thermocouple, pulse module.
I / O points to determine the module specification and quantity, I / O modules can be more or less, but the maximum number of the ability of the CPU can manage the basic configuration, that is, by the largest number of floor or rack slot limit.
Fifth, the power supply module
PLC power supply IC for the PLC module supplies power to operate. At the same time, some of the input circuit to provide 24V power supply. Power input type: AC power (220VAC or 110VAC), DC power supply (commonly used for 24VAC).