Chapter 2 Programmable Logic Controller (PLC) and Relay Ladder Logic (RLL).

Transcription

1 Controller PLC and Relay LAdder Logic RLL -IE337 Chapter 2 Programmable Logic Controller (PLC) and Relay Ladder Logic (RLL). 1

2 Controller PLC and Relay LAdder Logic RLL -IE PLC Operation using scanning technique Analog Input Networking module Analog Ouput Modem Fig. 2.1 Internal structure of a PLC. Fig. 2.3 Scanning technique in PLC. 2

3 2.1 PLC Operation using scanning technique Two modes of operations: 1. Programming mode. 2. Automatic or running mode(scanning mode) Fig PLC Programming technique using PC computer through serial port. 3

4 2.2 Understanding Relay Ladder Diagram (RLL) Power circuit Control circuit Fig. 2.5 Simple control circuit of a bell Fig. 2.6 A typical industrial relay. Switch Relay Coil Relay Ladder Development 4

5 2.2 Understanding Relay Ladder Diagram (RLL) Fig. 2.7 Contact relay symbol (RLL). Fig. 2.8 Output relay symbol (RLL). Fig. 2.9 RLL for bell control circuit. + - Switch Relay Ladder Development Relay Coil Main input instructions Normally open contact : Normally closed contact : Main output instructions Normally open relay Normally closed relay 5

6 2.3 Basic Instructions of RLL Some simple illustrated RLL circuit Fig.2.11 Control and RLL for AND Boolean operation. Fig Amended RLL using Normally closed switch for switch SW2. The Boolean logic equation will be : Coil = SW1. SW2 6

7 2.4 Motor control RLL network, two push buttons and motor starter Here two push buttons switches (Start/Stop) are used to switch the motor on/off. These switches are connected to the two PLC inputs discrete type), as shown in Fig One of the output ports (discrete outputs) of the PLC used to switch motor starter on/off, which will start/stop the electric motor. PLC Motor starter Output Input Fig Motor control using PLC, motor starter and two push bottoms. Motor Two bush bottom switches 7

8 2.4 Motor control RLL network, two push buttons and motor starter 1 Q1.1 Relay Coil Current flow (Scan 1) Motor starter 2 3 Q1.1 Current flow (Scan 1) Q1.1 Current flow (Scan 2) Q1.1 PLC Output Latch conditions Input Motor Two bush bottom switches Switch and S2 Q1.1 8 Current flow (Scan 2)

9 3 2.4 Motor control RLL network, two push buttons and motor starter S2 Q1.1 Relay Coil Q1.1 Motor starter S2 Q1.1 Output Motor 4 5 Q1.1 S2 Q1.1 PLC 6 Input Two bush bottom switches Switch and S2 S2 Q1.1 Q1.1 Q1.1 9

10 2.5 Motor control RLL network, two push buttons and motor starter Adding Two Indicators Green (G) and Red (R) S2 Motor starter Q1.1 G R Outpu t Two indicators Input Two push bottom switches Fig Amended RLL for motor control after adding two indicators. 10

11 2.5 Motor control RLL network, two push buttons and motor starter Adding Two Indicators Green (G) and Red (R) S2 Memory Unit Motor starter Q1.1 G R Relay coil Green indictor Outpu t Two indicators Input Two push bottom switches Fig Amended RLL for motor control after adding two indicators. Reed indictor 11

12 2.5 Motor control RLL network, two push buttons and motor starter Adding Two Indicators Green (G) and Red (R) + Overload Switch (OV) S2 OL Memory Unit Motor starter Q1.1 G R Relay coil Green indictor Outpu t Two indicators Input Two push bottom switches Fig Amended RLL for motor control after adding two indicators. Reed indictor 12

13 Controller PLC and Relay LAdder Logic RLL -IE Setting and resetting memory elements using ADD and OR gates S2 S3 Memory Unit AND Gate for setting S3 Memory Unit OR Gate for setting S2 13

14 Controller PLC and Relay LAdder Logic RLL -IE Setting and resetting memory elements using ADD and OR gates S2 S3 Memory Unit OR Gate for Resetting S2 Memory Unit AND Gate for Resetting S3 14

15 Controller PLC and Relay LAdder Logic RLL -IE PLC Programming and Networks 15

16 Controller PLC and Relay LAdder Logic RLL -IE PLC Programming and Networks 16

17 Controller PLC and Relay LAdder Logic RLL -IE PLC Programming and Networks 17

18 Controller PLC and Relay LAdder Logic RLL -IE337 18

19 Controller PLC and Relay LAdder Logic RLL -IE337 19