1.0 INTRODUCTION

A programmable logic controller (PLC) or programmable controller is a digital

computer used for automation of industrial processes, such as control of machinery on factory

assembly lines. Unlike general-purpose computers, the PLC is designed for multiple inputs and

output arrangements, extended temperature ranges, immunity to electrical noise, and resistance

to vibration and impact. Programs to control machine operation are typically stored in battery-

backed or non-volatile memory. A PLC is an example of a real time system since output results

must be produced in response to input conditions within a bounded time, otherwise unintended

operation will result. Hence, a programmable logic controller is a specialized computer used to

control machines and processes.  It therefore shares common terms with typical PCs like

central processing unit, memory, software and communications.  Unlike a personal

computer though the PLC is designed to survive in a rugged industrial atmosphere and to be

very flexible in how it interfaces with inputs and outputs to the real world. The components

that make a PLC work can be divided into three core areas.

The power supply and rack

The central processing unit (CPU)

The input/output (I/O) section

Inputs and Outputs

Programmable logic controllers typically contain a variable number of input/output

(I/O) ports and usually employ reduced instruction set computing (RISC), which consists of

simplified instructions that are intended to allow for faster execution. PLCs are designed for

real-time use and often must withstand harsh factory environments, such as excessive vibration

and high noise levels. The programmable logic controller circuitry monitors the status of

multiple sensor inputs, which control output actuators such as motor starters, solenoids, lights,

displays and valves

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Advantages

This type of controller has made a significant contribution to factory automation. Earlier

automation systems had to use thousands of individual relays, timers and sequencers, which had to be

replaced or rewired whenever the automated process needed to change. In many cases, a

programmable logic controller allows all of the relays and timers within a factory system to be

replaced by a single controller. Modern PLCs deliver a wide range of functionality, including basic

relay control, motion control, process control and complex networking.

1.1 OBJECTIVE

I. To do the circuit using programmable logic control and Omron CX programmable

software.

II. To understand the different between Fluid Sim and Omron CX.

2.0 EXERCISES

2.1 CIRCUIT 1

I. Two Alternate Indicator

FLUID SIM

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As we can see from the circuit, there is the pushbutton which is normally open. When

the current is flow, it will flow through the normally closed contact relay and the indicator is

light up.

After the stop button is being push, the current will flow through CR1 and the CR1 is

energise thus this situation caused the make switch CR1 that normally closed become open and

vice versa thus the indicator is light up for closed CR1.

OMRON CX Programmer

II. Latching Circuit

FLUID SIM

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OMRON CX Programmer

2.2 CIRCUIT 2

I. Reset Latching Circuit with Stop

FLUID SIM

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OMRON CX Programmer

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II. Reset Latching Circuit with Limit Switch

FLUID SIM

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2.3 CIRCUIT 3

Memory Circuit Using Double Solenoid Valve

FLUID SIM

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i. When the push button A is pressed, the

contact relay (CR1) will energized thus

the contact relay from normally open

will become normally close. From that,

it will activated the solenoid 1M1 and

extend the cylinder

ii. Next, press the push button B to retract

the cylinder and contact relay (CR2)

will energized, it will activated solenoid

1M2. The cylinder is retracted.

2.4 CIRCUIT 4

Delay Operation Circuit Using Timer

FLUID SIM

i. Firstly the start button in pressed,

contact relay (CR1) will energized

and become normally close

connection. It will activate the

timer countdown.

ii. Next, after 5 second, solenoid

(1M1) will be energized.

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iii. The solenoid will change the

directional control valve (DCV) to

the second position and extend the

cylinder

iv. To reset the circuit, press the

STOP button, and connection of

the relay will become normally

open.

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v. The cylinder will retract

immediately due to spring return at

the DCV. The DCV will change to

the initial position.

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2.5 CIRCUIT 5

Automatically Return Using Limit Switch

FLUID SIM

i. Firstly, the push button is pressed

momentarily, contact relay (CR1)

will energized; it will activate

indicator and timer (T1). The timer

starts to countdown.

ii. After 5 second, the connection of

the timer will become normally

close and it will activate solenoid

(1M1).

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iii. Next, solenoid will change the

initial position of the DCV and

extend the cylinder.

iv. When the cylinder is fully extend,

the end tip of the cylinder will

touch the limit switch (LS1). The

LS1 will become normally open,

thus cut off the circuit.

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v. The cylinder will retract

automatically. The indicator will

turn off.

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3.0 QUESTION

I. Two double-acting cylinders are used to design pneumatic circuit by using PLC. The

operations of the circuit are as follow :

When the start button is pressed momentarily, cylinder A will fully extend and

indicator will on (simultaneously).

After 5 seconds cylinder B will fully extend.

When the stop button is pressed both cylinder will retract simultaneously.

The indicator still on.

When the emergency button is pressed the indicator will off.

Answer :

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4.0 CONCLUSION

With the speed of changing technology today it is easy to lose sight or knowledge of

the basic theory or operation of programmable logic. Most people simply use the hardware to

produce the results they desire. The idea of programmable logic is very simple to understand,

but it is the complex programs that run in the ladder diagrams that make them difficult for the

students to fully understand. This is the good software that student need to learn as knowledge

and as preparation for student third year to go to their practical industry.

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