Heaven’s light is our guide

Rajshahi University of Engineering & Technology

ME 6603

Applied Mechatronics

Prepared by:
Prangon Das
Roll No. : 1904102009
Department of Mechanical Engineering,
Rajshahi University of Engineering & Technology.
01-Oct-21 1
 Outlines
• Introduction to Programable Logic Controller (PLC).
• Hardware Components of PLC.
• Comparison with Relay.
• Comparison with Microcontroller.
• PLC is Superior over Microcontroller.
• Microprocessor vs Microcontroller.
• Applications of Microcontrollers
• Applications of PLCs.
• PLC Programming.
• Practice Problems
References:
 Programmable Logic Controllers by W. Bolton (pdf)
 Mechatronics by W. Bolton (pdf)
01-Oct-21 ME 6603: Applied Mechatronics 2
 PLC
A programmable logic controller (PLC) is a special form of microprocessor-based controller that uses programmable
memory to store instructions and to implement functions such as logic, sequencing, timing, counting, and arithmetic in
order to control machines and processes

Fig. 1.1: A programmable logic controller Fig. 1.2: Siemens S7 1200

01-Oct-21 ME 6603: Applied Mechatronics 3

 PLC Hardware
Components: the basic functional components of processor unit, memory, power supply unit, input/output interface section,
communications interface, and the programming device.
• The processor unit or central processing unit (CPU) is the unit containing the microprocessor. This unit interprets the input
signals and carries out the control actions according to the program stored in its memory, communicating the decisions as
action signals to the outputs.

Fig. 2.1: The PLC System PLC by Bolton (Chapter 1)

01-Oct-21 ME 6603: Applied Mechatronics 4
 PLC Hardware (Cont.)
• The power supply unit is needed to convert the mains AC voltage to the low DC voltage necessary for the processor and the circuits in
the input and output interface modules.
• The programming device is used to enter the required program into the memory of the processor. The program is developed in the
device and then transferred to the memory unit of the PLC.
• The memory unit is where the program containing the control actions to be exercised by the microprocessor is stored and where the
data is stored from the input for processing and for the output.
• The input and output sections are where the processor receives information from external devices and communicates information to
external devices.
• The communications interface is used to receive and transmit data on communication networks from or to other remote PLCs.

Fig. 2.2: The PLC System

01-Oct-21 ME 6603: Applied Mechatronics 5
 Comparison with Relay Systems
Features Electro-mechanical Relays PLCs
1. Size of Controller Bulky Compact
2. Programming Time Consuming Easy
3. Flexibility Rewiring Required Reprogramming Required
4. Cost Expensive Less Expensive
5. Maintenance Much Less
6. Fault Finding and Troubleshoot Difficult Easy to identify & repair
7. Robustness Less More
8. Operation Speed Slow Faster

01-Oct-21 ME 6603: Applied Mechatronics 6

 Comparison with Microcontroller
PLC: A digitally operating electronic apparatus that uses a programmable Microcontroller: Microcontroller is a microprocessor with
memory for internal storage of instructions for implementing specific functions internal input and output and memory i.e. RAM, ROM,
such as logic, sequencing, timing, counting and arithmetic through digital PORTS.
or analog input/output modules. interface, and the programming device.
• In case of Microcontroller the programming is somewhat
• Its microprocessor based high end thoroughly developed Product for
tedious because of machine language (C/C++)
Industry which can be programmed through high end programming
• A microcontroller is also a logic controller but used in
software uses its different simple to understand Ladder programming
dedicated systems which are programmed once and for
Language.
all, the program for which will not be accessed by the
• PLC developed for Industrial Automation. user, and whose program will not need to be altered
frequently.
• Development Time is less this seems to be cost effective solution in Service
• Used for project based/small applications.
Industry.
• Microcontrollers Developed for Dedicated equipment.
• Troubleshooting a PLC system is much more technician friendly and very • Development Time is more.
easy to adapt and change. • With a microcontroller, you may have to design your own
signal interfacing.
• PLC is an infinitely expandable input/output logic controller usually
Microcontroller is not an infinitely expandable
programmed with an external PC program input/output logic controller.
• They are highly reliable, fast and flexible.
• They can handle severe conditions such as dust, humidity etc.
• They can communicate with other controllers.

01-Oct-21 ME 6603: Applied Mechatronics 7

 PLCs are Superior than Microcontroller
Why PLCs are preferred over microcontroller in automation is like asking why laptops/Desktops preferred over microprocessors?

• Modular Design - The PLC capacity and design can easily modify to suite customer need post implementation stage. This is not
feasible with relays or microcontroller-based solutions.
• Distributed architecture - For large application a distributed system can be implement with communication between various
PLC using protools like Modbus or profibus etc.
• Industrial Grade - PLCs are designed with tolerance to withstand various hazardous condition for Industries such as
Electromagnetic interference, high temperature, power fluctuation etc.
• Safety - PLCs manufacturers also provide safety features such are SIL certification as per customer requirement for
Protection/Emergency Shutdown System.
• Utility - PLCs can interface with a large no of drives and actuators ranging from analog and digital to special type such as speed
measurement and RTD/thermocouples etc. These can be done easily by changing the I/Os modules and configuring them.
• Easy Maintenance and Spares - Due to modular design the troubleshooting is easier, and the no of spares requirement is
reduced and easily manageable. Even field maintenance is easy as it is similar to other relay-based or analog systems.
• Inbuilt Function and Algorithms - There are inbuilt functions like PIDs, Feedforward, State observer etc in the PLC logic
software that can be used for logic design.
• Diagnostic features - PLC have inbuilt diagnostics for Lan failure, power failure, logic issues, Disconnection of I/Os and
alarms.
01-Oct-21 ME 6603: Applied Mechatronics 8
 Microprocessor vs Microcontroller
Microprocessor (MPU) Microcontroller (MCU)

1. Mainly used in designing general purpose systems. 1. Mainly used in automatic controlled systems.

2. Usually, It can perform complex tasks. 2. Usually, It can perform simpler tasks.

3. Very high computational capacity. 3. Less computational capacity than MPU.

4.MPU based system can perform numerous tasks. 4. MCU based system can perform only single task.

5. Basic component of personal computer. 5. Basic component of Embedded Systems.

6. CPU is standalone; ram-rom (memory), I/O ports are 6. CPU is standalone; ram-rom (memory), I/O ports are on a
connected externally. single chip.
7. Designers can decide on the amount of memory & I/O ports. 7. Always fixed amount of memory & I/O ports.

01-Oct-21 MTE 3103: Microcontroller and Interfacing 9

 Microprocessor vs Microcontroller (Cont.)
Microprocessor (MPU) Microcontroller (MCU)

8. Overall cost of MPU based system is high because of 8. Overall cost of MCU based system is low because all
external components required. external components are easily available.
9. It is general purpose or versatile. 9. It is single purpose only.

10. Power consumption is high. 10. Power consumption is low.

11. The clock frequency is very high usually in the order of 11. The clock frequency is low usually in the order of Mhz.
Ghz.
12. It is dependent on several other components. 12. It is self sufficient device.

13. Not generally used in real time systems. 13. Normally used to handle real time tasks.

14. Relatively slower speed as memory and I/O components all 14. Speed faster since components are internal and most
are external, each instruction will need external operation. operations are internal operations.
01-Oct-21 MTE 3103: Microcontroller and Interfacing 10
 Applications of Microcontrollers
Microcontroller Applications: Microcontrollers are intended for embedded devices, in comparison to the micro-processors
which are used in PCs or other all-purpose devices. Microcontrollers are employed in automatically managed inventions and
appliances like- power tools, implantable medical devices, automobile engine control systems, , office machines, remote controls
appliances, toys and many more embedded systems
 Applications of MCU in Day to Day Life Devices:  MCU in Industrial applications:
•Light sensing & controlling devices (Remote control).
•Industrial instrumentation devices
•Temperature sensing and controlling devices.
•Process control devices.
•Fire detection & safety devices.
•Engine control
•Industrial instrumentation devices.
•Security
•Process control devices.
•Instrumentation.
•Entertainment (Toys, PC, TV)

 Applications of MCU in Metering and Measurement Devices:  MCU in office applications:

•Voltmeter •Telephone, fax, photocopy machine, printer etc.
•Measuring revolving items.
•Current meter.
•Hand- held metering systems.
01-Oct-21 MTE 3103: Microcontroller and Interfacing 11
 Applications of PLCs
• It is used in civil applications such as washing machine, elevators working and traffic signals control.
• It is used in aerospace for Water tank quenching system.
• It is used to reducing the human control allocation of human sequence given to the technical equipment that is
called Automation.
• It is used in batch process in chemical, cement, food and paper industries are sequential in nature, requiring time or event
based decisions.
• It is used in the burner management system to control the process of purging, pilot light off, flame safety checks, main
burner light off and valve switching for changeover of fuels.
• It is used in printing industry for multistage screen washing system and Offset web press print register control system.
• It is used in travel industry for escalator operation, monitored safety control system.
• Glass industry
• Paper industry
• Cement manufacturing

01-Oct-21 MTE 3103: Microcontroller and Interfacing 12

 PLC Programming
PLC Programming Methods:
• Ladder Diagram
• Instruction List
• Function Block
• Sequential Functional Chart
• Structured Text
Ladder Diagram: Used for PLC Programs described in term of function blocks

Fig. 3: Basic Symbols PLC by Bolton (Chapter 5)

01-Oct-21 ME 6603: Applied Mechatronics 13
 PLC Programming (Cont.)

PLC by Bolton (Chapter 5)

01-Oct-21 ME 6603: Applied Mechatronics 14
 PLC Programming (Cont.)
Instruction List: A programming method that can be considered to be the entering of a ladder program using text is the
instruction list (IL)

Ladder Diagram Instruction List

PLC by Bolton (Chapter 6)
01-Oct-21 ME 6603: Applied Mechatronics 15
 PLC Programming (Cont.)
Timer: A common approach used by PLC manufacturers is to consider timers to behave like relays with coils which when
energized result in the closure or opening of contacts after some preset time.
• On Delay Timer (On after a particular time delay)
• Off Delay Timer (Off after a particular time delay Mechatronics by Bolton (Chapter 14)
• Pulse Timer (gives output for a fixed period of time)

01-Oct-21 ME 6603: Applied Mechatronics 16

 PLC Programming (Cont.)
Counter: Counters are used when there is a need to count a specified number of contact operations, e.g. where items pass along
a conveyor into boxes, and when the specified number of items has passed into a box, the next item is diverted into another box.
• Up Counter (Count from zero up to preset value)
• Down Counter (Count down from the preset value to zero)

Mechatronics by Bolton (Chapter 14)

01-Oct-21 ME 6603: Applied Mechatronics 17

 Practice Problems

Mechatronics by Bolton (Chapter 14)

01-Oct-21 ME 6603: Applied Mechatronics 18

 Practice Problems (Cont.)

01-Oct-21 ME 6603: Applied Mechatronics 19

 Practice Problems (Cont.)

01-Oct-21 ME 6603: Applied Mechatronics 20

01-Oct-21 ME 6603: Applied Mechatronics 21