Page 245 - Electronic Mechanic - TP - Volume - 2

ELECTRONICS MECHANIC - CITS

EXERCISE 181 : Wire in various digital input and output

device to respective modules of PLC
(Programmable Logic Devices)

Objectives

At the end of this exercise you shall be able to
• to demonstrate various wiring I/O device in PLC
• to identify suitable circuits
• to demonstrate the connection of I/O device to respective modules.
Requirements

Tools/Materials
• PLC Module • Sensors and Actuators
• Power Supply • LED Indicators
• I/O modules(devices) • Programming device
• Wiring Materials and connectors

Procedure

Theory
In this article, we are studying the basic concepts of PLC and DCS control systems Wiring Diagrams for Digital
Input (DI), Digital Output (DO), Analog Input (AI), and Analog Output (AO) signals.
Note that these diagrams are without a Barrier or isolator, fuses, or surge protector to keep them very simple and
understandable.
Wiring Diagrams of PLC and DCS
The basic types of wiring connections available for DI, DQ, AI, and AQ Signals:
Digital Input (DI) Signals
Digital Outputs(DQ) Signals
Analog Input(AI)
Analog Output (AQ) Signals
Digital Input Signals to PLC / DCS
Input type with respect to the system Terminal type/connection, Shield is not shown for simplicity.
The two-wire connection is used to connect field instruments like limit switches, proximity switches, motor run
feedback, Pump start permissive, etc.
An additional power supply (24 VDC, 110 VDC, 230 VAC, etc) in the marshaling cabinet (at the control room side)
to power the field instrument.
This configuration is generally used for hooters, beacons, high-power solenoid valves, etc.
Interfacing with Other Control Systems (DCS/PLC/ESD)
This configuration is widely used in industries for interfacing with third-party control systems.
DO with Line Monitoring
The line monitoring for digital output cards is also possible but up to relay coil and/or up to field shall be confirmed
by the system vendor.
Analog Input Signals to PLC / DCS
Two-wire Connection with AI Card
This configuration is used to connect two-wire transmitters like PT, TT, FT, LT, etc.
We may use barriers also after the AI card for safety precautions. These are not shown in the diagrams.

Result : Thus the Different I/O Modules of PLC have been identified successfully.

228