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HNC Electrical and Electronic Engineering
Year One - 2013/14
Module: Programmable Logic Controllers

Programmable Logic
Controllers

PLCs

Keith A
...
Hudson

2

PLCs
05 November, 2013

Contents
1

Introduction
...
1
1
...
7

1
...
6

Rack Mounted
...
9
2
...
9

2
...
1
2
...
10

MELSEC FX-Series
...
2
...
2
...
13

2
...
3
3

The FX3U
...
18

Modular
...
1

MELSEC L-Series
...
1
...
22

Rack mounted
...
1

MELSEC Q-Series
...
1
...
1
...
28

4
...
3
5

Future Expansion – option 1
...
28

Task 2
...
1

I/O Devices Task 2 (i)
...
2

Type of Communication Links Task 2 (ii)
...
2
...
30

5
...
2

PLC to LAN
...
3

PLC Internal Architecture Task 2 (iii)
...
4

PLC Scanning Task 2 (iv)
...
4
...
4
...
32
Mass I/O copying
...
33

HNC Electrical and Electronic Engineering

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6
Figure 2: The L-Series showing how the modules plug into each other
...
8
Figure 4: Exploded view of the FX3U
...
12
Figure 6: The FX3U CPU
...
13
Figure 8: Adapter
...
14
Figure 10: Analogue O/P
...
14
Figure 12: MELSEC-F series Selection Tool - Special Function Blocks
...
16
Figure 14: Analogue O/P
...
16
Figure 16: The L-Series features
...
20
Figure 18: the system with increased I/O
...
23
Figure 20: PSU (red), CPU (grey) and base (green)
...
24
Figure 22: Digital I/P
...
24
Figure 24: Analogue O/P
...
25
Figure 26: -Q series Model Selection System with additional base unit and modules
...
28
Figure 28: RS-485 Parallel Link
...
30
Figure 30: Internal architecture of a PLU (K, 2008)
...
32

HNC Electrical and Electronic Engineering

Year One: 2013/14

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8
Table 2: The Alpha 2 product range
...
9
Table 4: The PLC with all the necessary Special Adapters
...
13
Table 6: The PLC with all the necessary Special Function Blocks / Adapters
...
16
Table 8: System Requirements – Compact PLC
...
Special Function Blocks
...
20
Table 11: System Requirements – Modular PLC
...
22
Table 13: Initial Q-Series PLC with all the necessary Modules
...
24
Table 15: System Requirements – Rack Mounted PLC
...
27
Table 17: Complete (expanded) Q-Series PLC with all the necessary Modules
...
Hudson

5

PLCs
05 November, 2013

1 Introduction
This document details the suitability of a number of Programmable Logic Controllers (PLCs) to meet the
requirements of a process to be controlled
...
compact
2
...
rack mounted
In order to make the selection process simpler, one manufacturer (Mitsubishi Electric) was selected because they
produce a range for each class of PLC
...
GX Works2 is a
programming environment for the development and testing of PLC programs
...

For a compact PLC, the Alpha/Alpha2 range was considered
...

The more powerful, higher priced FX range would easily meet the requirements with potential for further expansion
of the system
...
Finally
the rack mounted System Q

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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1 Compact
A Compact PLC has the processor, power supply and I/O all contained within one unit
...
They were small, cheap and had no facility for future expansion, so they were only suitable
for tasks that would not change in the future
...
Today’s Compact PLCs are more powerful, and have some
scope for expansion
...
Extra I/O, communications, A/D, D/A or other specialised control would be performed via expansion units
connected to the main unit
...


Figure 1: FX3U PLC (centre) with Special Adapters (left) and Special Function Blocks (right)

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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2 Modular
A Modular PLC consists of a number of modules that slot into a base unit to make up the PLC
...
There may also be space for other specialized modules if required
...

Some modular systems consist of an enclosure that can accept a fixed number of modules
...
This allows a module to be plugged into the side of the
last module currently fitted
...
The disadvantage of this type of system is the number of slots is finite, limiting future expansion
...

The difference between Compact and Modular PLCs is no longer clear
...
With the expansion options available on some Compact
PLCs there may be significant overlap of size / functionality with a Modular PLC, even within the ranges of a single
manufacturer
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

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3 Rack Mounted
This is a similar concept to the modular design but the modules are on standard cards that slot into a standard rack
inside a cabinet
...

A significant number of cards can be added to a Rack Mounted PLC, resulting in a very large, well organized system
...
Typically used in a large manufacturing / factory setting
...

Table 1: Comparison of PLC types showing typical I/O

Expandable

← Less

More →

Traditional Defn
...


Micro

Compact

Modular

Rack

Range

α-Alpha

Fx-Series

L-Series

Q-Series

Total I/O

8

10-384

24-4096

32-4096

As Table 1 shows the amount of I/O for different classes of PLC can have an overlap
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

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1 Alpha2 (XL)
The Alpha is a compact PLC
...

From the Alpha 2 specifications we have the following Compact PLC models:
Table 2: The Alpha 2 product range

Base units AL2-10MR-D AL2-10MR-A AL2-14MR-D AL2-14MR-A
AL2-24MR-D
AL2-24MR-A
PSU
24V DC
110-240V AC
24V DC
110-240V AC
24V DC
110-240V AC
Digital i/p
6
8
15
Analogue
capable
6
N/A
8
N/A
8
N/A
digital i/p
Relay o/p
4 * 8A
4 * 8A
6 * 8A
6 * 8A
9 * 8A
9 * 8A
Max funct
...
AC powered: AL2-nnMR-A or
2
...

Table 3: System Requirements – Alpha 2

Requirement

Details
AL2-10MR-A, AL2-14MR-A, AL2-24MR-A

Requirement Met
Yes

Mains powered

AL2-10MR-D, AL2-14MR-D, AL2-24MR-D

Yes - using Alpha Power 24-1
...
Hudson
2
...
1

10

PLCs
05 November, 2013

Suitability
In order for the Alpha to meet the specification it would require a number of expansion modules
...
This and the fact that no further expansion is possible
make the Alpha unsuitable for the system specified
...
Hudson

11

PLCs
05 November, 2013

2
...
The current FX is Mitsubishi
Electric's third generation of compact PLCs
...
These new controllers
feature a second "adapter bus" allowing even greater expansion options
...

The FX3U controllers are fast with processing speeds of 0
...
The instruction set contains 209
instructions, functions and modules for tasks such as positioning, analogue signal processing and communications
...
GX Developer also provides PLC simulation for debugging programs prior to
installation
...
Along with improved PID auto-tuning, up to 100 kHz counters at 10 ms and 50µs hardware interrupts
Communications: RS-422, RS-232, RS-485, PLC-PLC and modules for Ethernet, CC-Link (Master / Slave), Profibus DP
(Master / Slave), DeviceNet, AS-i and networked I/O
...


Figure 4: Exploded view of the FX3U

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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2
...
Using the FX3U as the base PLC there are a number of routes for the
design to take
...
Special Adapters
2
...
A combination of the two
The following system was designed using the Mitsubishi MELSEC-F series Selection Tool Version 1
...
6: This system
was designed using Special Adapters to add the functionality not present in the base PLC
...

Table 4: The PLC with all the necessary Special Adapters

No
...
00

2

Analogue

FX3U-4AD-ADP

1

197
...
13

4

Temperature Sensor

FX3U-4AD-PT-ADP

1

243
...
50

6

Expansion Board

FX3U-CNV-BD

1

20
...
19
Source: (Magento eCommerce from Mulberry Square, 2013)

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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2
...
Dual system-bus
promotes versatility
...


Figure 6: The FX3U CPU

The FX3U-485ADP-MB module enables
communication betwen the PLC and other
(RS485 enabled) devices
...

This module also permits Modbus (RTU and
ASCII)
...


Figure 8: Adapter
Figure 7: Modbus module

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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Each
channel can be configured for
voltage or current
...
Each
channel can be configured for
voltage or current
...
Hudson

PLCs
05 November, 2013

15

Once again the MELSEC-F series Selection Tool was used to create a system
...


Figure 12: MELSEC-F series Selection Tool - Special Function Blocks

The internet was then used to find a supplier who had all the components available to purchase
...

Product Name
1
Main Unit
2
Analogue
3
Analogue
4
Temperature Sensor
5
Communication
6
Expansion Board
Total (excl VAT)

Model Name
FX3U-48MT/ES
FX3U-4AD
FX3U-4DA
FX2N-4AD-PT
FX3U-485ADP-MB
FX3U-CNV-BD

Qty
1
1
1
1
1
1

List Price (£)
672
...
63
346
...
88
94
...
56
1599
...
Hudson

16

PLCs
05 November, 2013

Table 7: Special Function Blocks descriptions

The FX3U-4AD input module
provides 4 analogue inputs
...


Figure 13: Analogue I/P

The FX3U-4DA output module
provides four analogue outputs
...


Figure 14: Analogue O/P

Figure 15: Temperature control

Permits the connection of four Pt100
sensors to the FX3U controller
...
Hudson

17

PLCs
05 November, 2013

Table 8: System Requirements – Compact PLC

Requirement

Details

Requirement Met

Mains powered

100-240 V AC (+10% -15%) 50/60Hz

Yes as standard
FX3U-48MT/ES

Digital inputs
16 x 24VDC PNP
opto-isolated
Analogue inputs
4 x <= +24V
Pt100 i/p -50 to 150 𝒐 𝑪; 20mA
Digital outputs
8 x 24VDC NPN @2A
opto-isolated
Analogue input
4 x 0 – 10VDC

24 * 24 V (±10%) PNP or NPN
Photo-coupler Isolation

24 * 5-30 V DC NPN
Photo-coupler Isolation

Analogue outputs
4 x <- +10V

Comms module

Modbus

3 term PID control

Battery backup

Program entry

up to 2000 steps

Rapidly change program /
operation

Basic arithmetic operations

Future expansion

50% increase in I/O
Digital I/O
Analogue I/O

Yes as standard
FX3U-48MT/ES
Yes using
FX2N-2LC or
FX3U-4AD-PT-ADP
Yes as standard
FX3U-48MT/ES
Yes using
FX3U-4AD or
FX3U-4AD-ADP
Yes using
FX3U-4DA
FX3U-4DA-ADP
Yes using
FX3U-485ADP-MB
Yes using
FX2N-2LC or
FX3U-4AD-PT-ADP
Yes as standard
FX3U-48MT/ES
(See Figure 4
Yes using Windows based
Melsoft GX Developer
+ lead FX3U-USB-BD
Yes using
FLROM cassettes or
PC + USB lead
Yes as standard
FX3U-48MT/ES
Yes
...

FX3U-4AD-ADP, FX3U-4DA-ADP,
FX3U-4AD-PT-ADP

Table 9: Special Adapters vs
...
Hudson

18

PLCs
05 November, 2013

2
...
3 Suitability
If speed was an issue then Special Function blocks should be used
...
They are smaller in size and cheaper to buy
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
...
1 MELSEC L-Series
The L series is designed for use in mid-size control applications
...
The powerful
CPU has many features built in giving it a high performance to cost ratio
...
The L-Series also has built-in I/O for such operations as positioning or counting
...
5ms high speed version)
...
Program memory of 80K steps with 12,288 data registers and a further 32,768 extended data
registers
These PLCs are programmed using Melsoft GX Developer, a Windows based programming environment offering
Ladder, List or SFC languages
...
The more advanced Melsoft GX Works2 is also available
...
Up to 30 modules can be added (40 on the high speed CPU)
...
There is also an
Ethernet connection and a micro USB2 port, which allow a PC to be connected to the PLC on site for updates,
amendments and fault finding
...


Figure 16: The L-Series features

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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1
...

Table 10: L-Series PLC with all the necessary Modules

No
...
38
784
...
13
587
...
00
430
...
38
118
...
65

Source: (Magento eCommerce from Mulberry Square, 2013)

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
...
Hudson

PLCs
05 November, 2013

22

Figure 18 shows what the system would look like if was given a 50% increase in I/O (analogue and digital)
...


Figure 18: the system with increased I/O
Table 12: L-Series PLC with extra Modules to increase I/O

No
...
65
L60AD4
238
...
50
L60TCRT4
587
...
28
Source: (Magento eCommerce from Mulberry Square, 2013)

3
...
1 Suitability
As Table 11 shows, all requirements have been met, so I would recommend the use of Mitsubishi Electric's L-Series
as a Modular PLC
...
Hudson

PLCs
05 November, 2013

23

4 Rack mounted
4
...
1
...
13

QJ71MB91
QH42P
Q64AD

1
1
1

457
...
25
238
...
00

Q64TCRT

1

518
...
89

Source: (Magento eCommerce from Mulberry Square, 2013)

HNC Electrical and Electronic Engineering

Year One: 2013/14

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(Input power 100 – 240V AC)
Information about this range
 Latest generation of modular CPUs
 Foundation for the iQ platform system
 Can be combined with motion, robot & NC PLCs
 Integrated mini USB interface
 Integrated Ethernet interface
 Extremely fast bit processing, 9
...
1A/point, sink type, 32 points/common
Information about this range
 Potential isolation between process & control is standard
 LED indication of input status
 Modules with 16 points have removable terminal blocks with
screws
 Modules with 32/64 points are connected with a D-Sub or 40pin plug
 Assembled cables available for modules with D-Sub plugs

Figure 22: Digital I/P

Q64AD - Analogue Input Module
A/D input module, 4 channel, 0 to 16000 -10 to +10 V, 0 to 12000 0 to 20mA

Figure 23: Analogue I/P

HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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Hudson

26

PLCs
05 November, 2013

Table 15: System Requirements – Rack Mounted PLC

Requirement

Details
100-240 V AC (+10% -15%) 50/60Hz

Mains powered
Digital inputs
16 x 24VDC PNP
opto-isolated
Analogue inputs
4 x <= +24V
Pt100 i/p -50 to 150 𝒐 𝑪; 20mA
Digital outputs
8 x 24VDC NPN @2A
opto-isolated
Analogue input
4 x 0 – 10VDC

Requirement Met
Yes using Q00UJCPU

24 * 24 V (±10%) PNP or NPN
Photo-coupler Isolation

Yes using QH42P

Yes using Q64TCRT
24 * 5-30 V DC NPN
Photo-coupler Isolation

Yes using Q64AD

Analogue outputs
4 x <- +10V

Comms module

Yes using Q64DAN

Modbus

3 term PID control

Standard:
Upgrade:

Program entry

up to 2000 steps

Rapidly change program /
operation

Basic arithmetic operations

HNC Electrical and Electronic Engineering

Yes using QJ71MB91

Yes standard using Q00UJCPU

Battery backup

Future expansion

Yes using QH42P

Yes
Q2MEM-BAT
Q6BAT (180mAh) or Q7BAT
(5000mAh)
Yes using Windows based
Melsoft GX Developer
+ lead FX3U-USB-BD
Yes using
L1MEM-2GBSD / L1MEM-4GBSD or
PC + USB lead
Yes using Q00UJCPU

50% increase in I/O
Digital I/O
Analogue I/O
Extension Base Unit

Yes
QH42P has spare capacity
Q64TCRT, Q64AD, Q64DAN
Q63B

Year One: 2013/14

Keith A
...
1
...
It is connected to the
original system bus using an extension cable
...
Additional modules provide the necessary
temperature control, analogue to digital and digital to analogue for the expanded system
...


Figure 26: -Q series Model Selection System with additional base unit and modules
Table 16: Expanded Q-Series PLC with all the necessary Modules

No
1
2
3
4
5
6

Product name
System before expansion
Extension base
Extension cable
Extension power supply
Analog-digital converter
module
Digital-analog converter
module
Temperature control module

Model

Qty
1

Q63B
QC06B
Q62P
Q64AD

1

List Price (£)
2,576
...
25
55
...
00
238
...
00

Q64TCRT

1

518
...
15

Source: (Magento eCommerce from Mulberry Square, 2013)
HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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1
...
Figure 27 shows what expanded system would look like
...


Figure 27: Q series Model Selection System with extra capacity
Table 17: Complete (expanded) Q-Series PLC with all the necessary Modules

No
1

2
3
4
5
6

Product name

Model

Universal model QCPU,
power supply,
base
MODBUS interface module
I/O composite module
Analog-digital converter
module
Digital-analog converter
module
Temperature control module

Qty

List Price (£)

Q00UJCPU-S8

1

432
...
63
362
...
63

Q68DAVN

1

651
...
76

Total (excl VAT)

3,370
...
1
...

The cost of the initial system would be £2,576
...
With a 50% increase in I/O in the future, the cost of the system
would rise by £1,474
...
15 (assuming prices remain static)
...
This would cost £3,370
...
69 more than the
original system, but it is £680
...

If the system is definitely going to be expanded in the future and sufficient finance is available, I would recommend
option 2: building the system with extra capacity
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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1 I/O Devices

Task 2 (i)

The following are INPUT devices:







Switch,
Optical sensor
Differential Pressure transmitter
Start/stop button station
Limit switch
High level switch

The signals from input devices that the PLC is monitoring are not usually in a form that can be directly processed by
the PLC
...

The steps are as follows:
1
...

2
...
This is known as
analogue-to-digital conversation (ADC)
3
...
This isolates the PLCs internal circuits from potentially
damaging voltages and currents
...

The following are OUTPUT devices:





Control valve
High level alarm
Motor
Solenoid valve

The output signals from the PLC may not be in a form able to drive all types of output devices
...

The process is:
1
...
Again this is to protect the internal circuits of
the PLC
...
If the output device is analogue then the digital signal from the opto-coupler is converted
...
The magnitude of the current and voltage is then amplified to match the requirements of the output
device
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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2 Type of Communication Links

Task 2 (ii)

5
...
1 PLC-to-PLC using a Parallel Link
Two Mitsubishi FX3U PLCs can be connected to allow data sharing using RS-485 modules
...
This
type of connection allows automatic updating of relays and registers between the two PLCs
...
2
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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3 PLC Internal Architecture

PLCs
05 November, 2013

Task 2 (iii)

Figure 30: Internal architecture of a PLU (K, 2008)

The Central Processing Unit (CPU) (like the CPU of a PC) executes the commands of the Operating System (OS)
...
It achieves this by putting data onto and reading data from the different data buses
...
This is non-volatile memory i
...
it remains even if power is lost
...
The results are then used to determine what signals should be output
...
The program is accessed by the CPU by fetching it (a bit at a
time) via the data bus
...
e
...

For that reason RAM may be kept ‘alive’ using a battery backup
...
Not all PLCs have this facility
...
’ (wikipedia
...
The Address Bus allows the CPU to communicate with the
rest of the system
...
The Control
Bus carries data necessary to control the operations of the internal system
...
system
...
The System Bus allows communication between the internal system and external devices
...
No
other components write to theses and the CPU doesn’t read from it
...


HNC Electrical and Electronic Engineering

Year One: 2013/14

Keith A
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More than one of the internal components puts data on and more
than one component reads data from these buses
...
4 PLC Scanning

Task 2 (iv)

The normal operation of a PLC is a continuously cycle as follows:
1
...

2
...

3
...

The term used to describe this sequence is ‘Scanning’ or ‘Program Scan’
...


Figure 31: The PLC Scan Cycle (Technocrat Automation (p) Ltd, 2011)

There are two types of scanning
...
4
...
There is typically a 3ms delays for read operations to filter out
contact bounce and other interference
...

The output state remains unchanged (‘latched’) until it is changed by the program during subsequent scans
...
4
...

If continuous scanning was used by larger PLCs with several hundred I/O points the scan time would be too long
...

At a specific point in the program all inputs are read
...

These are then processed by the program one value at a time
...
Any changes to output determined by the program are written to the output range of the I/O RAM
...


HNC Electrical and Electronic Engineering

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J
...
d
...
freestudy
...
SELECTION AND APPLICATIONS OF PROGRAMMABLE LOGIC CONTROLLERS
...
freestudy
...
uk
[Accessed 10 November 2013]
...
A
...
CPU | The Web's Where You Study In!
...
ustudy
...

Magento eCommerce from Mulberry Square, 2013
...
[Online]
Available at: http://www
...
com/
[Accessed 18 11 2013]
...
, 2013
...
FREE
...
plctalk
...
php?t=11208
[Accessed 16 November 2013]
...
Compact PLC - Mitsubishi Electric Factory Automation - United Kingdom
...
mitsubishielectric
...

Mitsubishi Electric Corporation, 2012
...
[Online]
Available at:
https://gb3a
...
com/fa/en/service/download/show?&doc_type=cat&scat=2&scountry=95&sprod=2
&sstr=fx&bt_submit=&portal_id=3
[Accessed 6 November 2013]
...
Mitsubishi Electric Catalogues
...
mitsubishi-automation
...
php?id=835
[Accessed 07 12 2013]
...
PLC Centre MRO Inventory and Industrial Repair Service
...
plccenter
...
uk
[Accessed 15 12 2013]
...
Plc Tutorial - Technocrat Automation: PLC SCAN PROCESS
...
blogspot
...
uk/2011/04/plc-scan-process
...

wikipedia
...
Bus (computing) - Wikipedia, the free encyclopedia
...
wikipedia
...


HNC Electrical and Electronic Engineering

Year One: 2013/14



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