Tugas

Programmable Logic Controllers

1. Apa keuntungan dan kerugian PLC?

2. Sebutkan alat apa saja yang termasuk dalam

Input PLC?

3. Sebutkan alat apa saja yang termasuk dalam

Output PLC?

4. Jelaskan prinsip kerja dari dua Simple Relay

Circuit berikut ini!

Struktur / Elemen Makatronika

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Programmable Logic Controllers( Definition according to NEMA standard ICS3-1978)

A digitally operating electronic apparatus which uses a programming memory for the internal

storage of instructions for implementing specific functions such as logic, sequencing, timing,

counting and arithmetic to control through digital or analog modules, various types of machines or

process.

Advantages and Disadvantages

1. armored for severe conditions (dust, moisture, heat, cold,

2. have the facility for extensive input/output (I/O) arrangements

3. Cost effective for controlling complex systems.

4. Flexible and can be reapplied to control other systems quickly and easily.

5. Computational abilities allow more sophisticated control.

6. Trouble shooting aids make programming easier and reduce downtime.

7. Reliable components make these likely to operate for years before failure.

1. Too much work required in connecting wires.

2. Difficulty with changes or replacements.

3. Difficulty in finding errors; requiring skillful work force.

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Leading Brands Of PLC

AMERICAN 1. Allen Bradley2. Gould Modicon3. Texas Instruments 4. General Electric5. Westinghouse6. Cutter Hammer7. Square D

EUROPEAN 1. Siemens2. Klockner & Mouller3. Festo4. Telemechanique

JAPANESE 1. Toshiba2. Omron3. Fanuc4. Mitsubishi

PLC

CPU

System

User LadderDiagram

Working memoryregisters

Input

Flag

Output

Input Module

OutputModule

SWITCHES

Non-locking Locking

Normally Open Normally Closed

Multiple Throw

P1

P2

Multiple Pole

Break-before-make Make-before-break

RELAYSA switch whose operation is activated by an electromagnet is called a "relay"

contact

coil

input

Relay coil Output contact

COUNTERDigital counters output in the form of a relay contact when a

preassigned count value is reached.

Register

Accumulator

contact

input

reset

output

Input

Reset

Output

Count 0 1 2 3 4 5 0 1

5

TIMERA timer consists of an internal clock, a count value register, and

an accumulator. It is used for or some timing purpose.

Clock

Accumulator

contact

reset

output

Register

Contact

Time 5 seconds.

Clock

Reset

Output

Count 1 2 3 40 5

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Relay Ladder Logic

• Ladder logic is possibly the simplest

programming language.

• The principle behind the language is illustrated

by a simple electrical relay. (Electrical relay

logic preceded PLC’s as initially all logic was

implemented in hard wired panels using actual

relays, timer, Counters etc.)

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Simple Relay Circuit

Eng. R. L. Nkumbwa @ CBU 2010 20

Circuit representation in Ladder Logic

• The above circuit is represented in Ladder

logic as shown in figure below (only the low

voltage circuit is used in ladder logic

diagrams):

AN EXAMPLE OF RELAY LOGIC

AN EXAMPLE OF RELAY LOGIC

L1

LS1 PB1 LS2 R1

R1

R1TIMER

R2

PR=5

For process control, it is desired to have the process start (by turning on a motor) five seconds after a part touches a limit switch. The process is terminated automatically when the finished part touches a second limit switch. An emergency switch will stop the process any time when it is pushed.

LS1

PB1LS2

R1

TIMER

5Motor R2

AN EXAMPLE OF RELAY LOGIC

Programming a PLC

Oil is consumed

randomly. The tank

needs to be refilled by

turning on a pump.

Two hydrostatic

switches are used to

detect a high and low

level.

AN EXAMPLE OF RELAY LOGIC

Ladder Logic for Tank

AN EXAMPLE OF RELAY LOGIC

Logic for Ladder Solution

#1

Initially the tank is empty.

Therefore, input 0000 is TRUE

and input 0001 is also TRUE

AN EXAMPLE OF RELAY LOGIC

Logic for Ladder Solution

#2

The internal relay is turned on as

the water level rises.

AN EXAMPLE OF RELAY LOGIC

Logic for Ladder Solution

#3

After scan 2 the oil level rises

above the low level sensor and it

becomes open. (i.e. FALSE)

AN EXAMPLE OF RELAY LOGIC

Logic for Ladder Solution

#4

After scan 4 the oil level rises

above the high level sensor at it

also becomes open (i.e. false)

AN EXAMPLE OF RELAY LOGIC

Logic for Ladder Solution

#5

Since there is no more true logic

path output 500 is no longer

energized (true) and therefore

the motor turns off.

AN EXAMPLE OF RELAY LOGIC

Logic for Ladder Solution

#6

After scan 6 the oil level falls

below the high level sensor and

it will become true again.

PROGRAMMING EXAMPLE 1

Part

microswitch

Bar code reader

Stopper

Conveyor

MachineRobot

id description state explanation

MSI microswitch 1 part arrive

R1 output to bar code reader 1 scan the part

C1 input from bar code reader 1 right part

R2 output robot 1 loading cycle

R3 output robot 1 unloading cycle

C2 input from robot 1 robot busy

R4 output to stopper 1 stopper up

C3 input from machine 1 machine busy

C4 input from machine 1 task complete

SOLUTION

01

02

03

04

05

11

12

13

14

15

InputOutput

Programmable Controller PLC

MS1

C1

C2

C3

C4

R1

R2

R3

R4

01 14 11

02

14 04 03

14

12

1305 03

Rung 1. If part arrives and no part is stopped, trigger the bar code reader.

Rung 2. If it is a right part, activate the stopper.

Rung 3. If the stopper is up, the machine is not busy and the robot is not busy, load the part onto the machine.

Rung 4. If the task is completed and the robot is not busy, unload the machine.