1.0 INTRODUCTION

Programmable Logic Controller (PLC) consists of a Central Processing Unit

(CPU) containing an application program and input and output interface module, which is

directly, connected to the field I/O devices. The program controls the PLC so that when

an input signal from an input device turn ON, the appropriate response normally involve

turning ON an output signal to some sort of output devices. PLC is a specialized

computer to control machines and processes. It uses a specialized computer to store

instruction and execute specific functions that include on/off control, timing, counting

and data handling.

Programmable logic controllers offer several advantages over a conventional

relay type of control. Relays have to be hardwiring to perform a specific function. When

the system requirements change, the relay wiring also must be changed or modified. In

extreme cases, such as in auto industry, complete control panels had to be replaced since

it was not economically feasible to rewire the old panels witch each model changeover.

The programmable controllers have eliminated much of the hardwiring associated with

conventional relay control circuits. It is small and inexpensive compared to equivalent

relay based process control systems.

In addition to cost savings, PLCs provide many other benefits including:

Increased Reliability

More Flexibility

Lower Cost

Communication Capability

Faster Response Time

Easier Troubleshoot

Figure 1: PLC System Architecture

The PLC is primarily used to control machinery. A program is written for the

PLC which turns on and off outputs based on input conditions and the internal program.

In this aspect, a PLC is similar to a computer. However, a PLC is designed to be

programmed once, and run repeatedly as needed. In fact, a crafty programmer could use a

PLC to control not only simple devices such as a garage door opener, but their whole

house, including turning lights on and off at certain times, monitoring a custom built

security system, etc.

A typical PLC divided into parts, as illustrated in Figure 2. These components are

the central processing units (CPU), the input/output (I/O) section, the power supply and

the programming device.

Figure 2: Parts of PLC

The PLC was invented in response to the needs of the American automotive

manufacturing industry. Programmable controllers were initially adopted by the

automotive industry where software revision replaced the re-wiring of hard-wired control

panels when production models changed. Before the PLC, control, sequencing, and safety

interlock logic for manufacturing automobiles was accomplished using hundreds or

thousands of relays, cam timers, and drum sequencers and dedicated closed-loop

controllers. The process for updating such facilities for the yearly model change-over was

very time consuming and expensive, as electricians needed to individually rewire each

and every relay.

In 1968 GM Hydramatic (the automatic transmission division of General Motors)

issued a request for proposal for an electronic proposal came from Bedford Associates of

Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford

Associates' eighty-fourth project, was the result. Bedford Associates started a new

company dedicated to developing, manufacturing, selling, and servicing this new

product: Modicon, which stood for Modular Digital Controller. One of the people who

worked on that project was Dick Morley, who is considered to be the "father" of the PLC.

The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German

Company AEG and then by French Schneider Electric, the current owner. One of the

very first 084 models built is now on display at Modicon's headquarters in North

Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired

after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the

end of its product range until the 984 made its appearance.

The automotive industry is still one of the largest users of PLCs. Most commonly, a

PLC is found inside of a machine in an industrial environment. A PLC can run an

automatic machine for years with little human intervention. They are designed and to

withstand most harsh environments a PLC will encounter.

OBJECTIVES:

1) To understand PLC’s terminology, configuration, I/O modules addressing and

types of PLC memory devices.

2) To learn the program instruction that perform logical operations and ladder logic

programs,

3) To understand and program the control of outputs using the timer instruction

control bits.

4) To apply the PLC counter function and associated circuitry to control systems

5) To install hardware components used in PLC systems.

3.0 SCOPE

In the end of this experiment we found that:

Student able to draw a basic electro-pneumatic circuit with PLC, install and test

run it to move an actuator.

Student able to design, construct, and troubleshoot of this PLC circuits.

Student able to identify and operate a few types of electro pneumatic components

including relay and its contactors.

4.0 SAFETY PRECAUTION

1. Never disconnect electro pneumatic lines or disassemble electro pneumatic

equipment when the pneumatic system power motor is running. 

2. Make sure I/O and extension connector are installed correctly.

3. Use the PLC in an environment that meets the general specification contained in

this manual.

4. Make sure all external load connected to output does NOT exceed the rating of

output module.

5. Install a safety circuit external to the PLC that keeps the entire system safe even

when there are problems with the external power supply or PLC module.

Otherwise, serious trouble could result from erroneous output or erroneous

operation.

6. Never manually actuate switches, solenoids, relays, or valves on pneumatic

systems under pressure unless you are competent and qualified to perform these

actions. 

7. All personnel taking part in and observing operation of power equipment must

remain alert, keep clear of moving parts, and be thoroughly familiar with the

safety precautions applicable to that equipment. At no time should skylarking be

allowed in the vicinity of operating power equipment.

8. Never use electrical or electronic equipment known to be in poor condition.

9. Use the right voltage. Most pneumatic devices are powered by air and controlled

with an electronic control valve.

10. Check and secure all of the mountings, fittings, piping, tubing, connectors and

connections before connecting any electro pneumatic components or systems to a

power supply.

5.0 METHOD AND STANDARD OPERATION PROCEDURE (S.O.P)

Figure 3: pneumatic circuit task 1

1. First, electro-pneumatic circuit was created according to the task given and was

installed into the electro-pneumatic trainer by double acting cylinder, 5/2 way

DCV single solenoids and internal relay.

2. Second, the input of push button 1(SA) and push button 1(SB) was connecting to

24V and the output SA & SB was connecting to normally close contact RB. The

output of RB was connecting to output component coil (internal relay RA).

3. Third, the input component contact RA was connecting to output of push button

SA and SB as OR gate style.

Double acting cylinder

5/2 way DCV single solenoids with spring return

Sensor (limit switch)

Output component (coil)

Solenoid (Y1)

Power supply

4. Fourth, the input of sensor (AE) was connecting to 24V and the output was

connecting to contact RA and output of RA was connecting to output component

coil (RB)

5. Fifth, the input component contact RB was connecting to output of sensor (AE) as

OR gate style.

6. Then, the input of relay contactor RA was connecting to 24V and the output was

connecting to normally close contact (RB). After that the output of normally close

contact (RB) was connecting to solenoid (Y1).

7. After that the circuit was operated and do same troubleshoot if got any problem

with the circuit.

Figure 4: Electrical circuit of PLC

Sensor

Output component(Solenoid)

PLC Input card PLC output card

Input component(Switch & sensor)

6.0 ANALYSIS / FINAL PRODUCT / OUTPUT

Task week 1

A simple drilling operation requires the drill press to turn on only if there is a part present

and the operator has one hand on each of the start switches. The precaution will ensure

that the operator’s hands are not in the drill. Switches 1& 2 and the part sensor must be

activated to make the drill motor operator.

1) Sequent Motion:

A+ A-

2) Tabular Plan:

Step Condition Action

1 Start (SA & SB press) A+

2 AE A-

3) Step Displacement Diagram:

SA&SB

Limit Switch

AEStart

Figure 5: full electro-pneumatic with PLC control circuit & power circuit

The diagram above showed an electro-pneumatic with PLC control circuit & power

circuit. This circuit install in electro-pneumatic trainer according to the task given. For

build this diagram, we used two push button (SA & SB), 5/2 way DCV single solenoid

valve and one double acting cylinder. The circuit supply by 24V and 0V.

Figure 6: Actuator extend position

The diagram above showed, when the SA and SB was pressed, the solenoid Y1

was activated. Once the solenoid Y1 was activated the 5/2 way DCV single solenoid

valve will change the position and the actuator will extend. Besides that, RA also

activated which is creating memory. The actuator also reach the limit switch AE

(replace for sensor) and touch the limit switch AE.

Figure 7: change the position of valve

After touched AE, RB was activated. Once the internal relay RB was activated the

5/2 way DCV single solenoid valve will change the position because the solenoid was

deactivated and spring return make this position changes. RB also deletes memory

which deletes the RA memory.

Figure 8: actuator in fully retracting position

Finally, the actuator was fully retracting position. All the internal memory was

deleted. The circuit will star after press SA and SB.

7. CONCLUSSIONS

In conclude, during this experiment, student was learning a lot about the basic and

early knowledge about the PLC. As we know, typical PLC part can be divided into parts,

these components are the CPU, Input / Output section, the power supply and

programming device.

Along this experiment also, we was learning about the method to build a ladder

diagram. Ladder diagram is uses standard symbols to represent the circuit components

and functions found in a control system. For this experiment, we were learning about

latching or self holding program. Latching program is used to hold an output device

maintain activated although the input contact has deactivated. Both of input and output

device has another device, which is setup parallel to their actual device. From the ladder

diagram of this experiment, we can see the latching technique at branch which has IRA

and IRB. IRA or Internal Relay A is function to create a memory, so it will hold the

output device. IRB or Internal Relay B is function to delete a memory which we hold at

the early as we can see at figure 1.2. Finally, we are success doing this experiment and

the cylinder also was move with smoothly.

Figure 9: Latching Program

REFERENCES

1. en.wikipedia.org/wiki/Programmable_logic_controller

2. www.logicdesign.com/inside/plc.html

3. en.wikibooks.org/wiki/Introductory_PLC_Programming

4. en.wikipedia.org/wiki/Power_line_communication

5. www.electronicspal.com/plc

6. www.plcdev.com/glossary/1

7. www.portlandonline.com/index.cfm?&a=fdjch

8. http://en.wikipedia.org/wiki/Electro-pneumatic_action

9. http://www.answerbag.com/q_view/157904

10. http://www.freepatentsonline.com/5437306.html?

query=valve+double+solenoid&stemming=on

11. http://answers.yahoo.com/question/

index;_ylt=AnGhbPJAQhAOcr5dOp5hNH4jzKIX;_ylv=3?

qid=20081004002957AAwO5VD

12. http://en.wikipedia.org/wiki/Parallel