PLC input output connections and scan

PLCs work with data information and output that are expressed in the form of electrical voltage, electric current, and switches. And the signal used can be in the form of disk and analog signals. And for voltage and electric current used in PLC, it varies depending on the needs of the user.

The Input / Output section is intended to work as an ‘interface’, which is to connect the instrument in the field with the PLC.

The type of I/O in the PLC includes

Discrete I / O:

Which is a digital input and output in the form of logic with a high level of 24VDC or low 0V or in the form of relay contact output that can be fed up to 240 VAC.

Example: Discrete Input

Example: Discrete input

Special I / O:

Namely, I / O which has special functions.

  • Analog Input Module

  • Temperature Module namely PT100 or thermocouple (low level analog input)

  • High Speed Counter Modules, namely the frequency of logic with a high level are generally 5V, 12V or 24V.

  • Fuzzy Logic Module.

  • PID Module

  • Servo Module

  • Communication modules in the form of protocols made by each manufacturer, for example, Fieldbus, Modbus, Profibus, Ethernet, Sysmac way, Device Net, Control Net.

Example: Analog Input

Example: Analog output