Abstract
An automatic ventilation system with an exhaust fan included with a supply fan is presented in this report. With this smart system being proposed, detailed annual energy-efficient operation strategies and methods of control for the air-handling unit are presented. Compare to the traditional type of exhaust fan, the proposed smart system shows that not only does it maintain the indoor air quality but also improve the energy efficiency. Due to the increased outdoor air, the proposed smart system can improve indoor air quality further. An external DC motor will be driven the fan. The reason why an external DC motor is used is because it is able to make the exhaust fan to have the ability of air exhausting and illumination. It also helps to reduce the noise and power consumption of the exhaust fan efficiently. So the proposed smart system is not only energy saving but also environmentally friendly.
Acknowledgement
This final year report is the end of my long journey in obtaining my Degree in Electrical and Electronic Engineering at University of Sunderland. I have not travelled alone in this journey. There are people who made this journey easier by offering different places to look to expand my theories and ideas.
I should specially thanks to my supervisor, Mr Bob Young, for his great interest and assistance of helping me for preparation of this report. Besides, encouragements, supports and advices are continually given by him from the start. It helps me to develop an understanding of the subject thoroughly.
Besides, I would also like to thanks to the staffs in the lab, Chris and George for their availability of resources, readiness and skills. Their help in finding the materials that are needed is invaluable. My project will not be in shape without their helps.
Last but not least, my deepest thanks to my family, friends and others encouragement and constructive advices that have make the full support of my report completion.
Chapter 1: Introduction
Overview
The purpose of this chapter is to give a rough idea of Intelligent Cooker Hood Exhaust Fan (ICHEF) and how it integrates into and changes the lifestyle of human beings and most importantly, being green.
The usual perception of an exhaust fan by the public is simply act as a ventilation system which ventilates the air in an area. But often there are things which are important and being neglected by the public, health. Cooking does not only produce aroma, it often produces more than that, particles of smoke, grease and combusted gasses which are not healthy to breathe in and is environmental pollutants. Food like pepper and onions also produce irritants which can be unpleasant to be continuously exposed to. Exhaust fan are used to remove these pollutants from the air in a specific area.
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Health, has been an important concern to all of us these days. Because of that, having lots of biological pollutants and dust mite in the living place may cause a serious threat to our health. Thus, the improvement of the indoor air quality is an increasing concern to many people. Molds and dust mites will grow at a high relative humidity and there is one area in the home where moisture is generated, kitchen. Thus, adequate control of moisture in the kitchen is necessary and important.
It is generally known that global warming is a severe issue that is happening in the world right now which eventually will bring unwanted natural disasters due to the overheating in the atmosphere and dilapidates the ability of earth to deal with these situations accordingly.
To save the world, a few methods are being suggested by ecologists. Energy saving, one of the most effective and most commonly applied by the industries, are used throughout the world in order to avoid the earth from overheating. As a result, the concept of energy saving is being applied in the project to reduce the use of power thus saving money as well.
To achieve the goals mentioned above, integrated circuits and sensors are needed to provide aids to control the exhaust fan to either on or off and the speed of the fan according to the data received from the sensors. It is also a low-cost solution and differs from the already-in-market exhaust fan which will cost a fortune.
Aims
The primary aim for this project is to develop an intelligent cooker hood exhaust fan to make one’s life easier with the help of electronic knowledge and most importantly environmental friendly due to energy saving.
Objectives
The objective of this project is to design a system or programme to determine whether to on or off the exhaust from the readings of the sensors by using MicroCode Studio Plus. An effective and low-cost hardware is designed with sensors attached onto it to obtain data. It will increase or decrease the speed of the exhaust fan according to the level of the heat and smoke detected.
Chapter 2: Project Background
2.1 Overview
This section presents the general information and history of exhaust fan. It also provides short statement and the application and the hardware which are constructed on Intelligent Cooker Hood Exhaust Fan (ICHEF). Other than hardware, a brief of the software will be provided in this chapter as well.
2.2 History of Exhaust Fan and Ventilation
As all of us understand that the purpose of ventilation is to reduce or dilute the indoor contaminants, the experienced engineers should determine how much air is necessary to dilute and reduce the contaminants to a desired level. The existence of ventilation and indoor air quality can be traced back to 17th century. However, concerns about the “bad air” go back much farther than that. One of the earliest reasons to implement the idea of ventilation is to ventilate the indoor air to a desired level and environment and it is probably still the same problem we have today as why we implement ventilation system in the house is to reduce and remove the products of combustion used for heat, light or cooking. People dated back to 17th undoubtedly learned very quickly that if one brought fire inside the house for cooking, one needed to take the smoke out. The design for ventilation has changed quickly over the time, but it has usually been associated with the indoor contaminants or biological pollutants that can cause health or comfort problems.
Looking back into the archeological records, several examples can be found on how houses are built to accommodate ventilation and improve the indoor air quality. There are a few different approaches to deal with the use of fires in the roof. Back in 4000-5000BC, the Banpo villagers in China had implemented chimneys into their houses. The Romans put a hole in the middle of their houses’ roofs to suck the smoke out of the living place. The basket weaver’s pit houses found in Mesa Verde National Park, circa 750 AD, use the same approach.
The Romans then invented and created a heating system called hypocaust heating system and it is usually for the big buildings. The hypocaust was then preceded and integrated into British parliament buildings in the late 1800’s due to its superior heating design in that time. It works by getting the outdoor air into the hypocaust and gains heat from the fire and channeled all the way through the under floor channels and then go up through channels in the walls and vented to the outdoor which acts like a heating system. A system is also built in the late 1880’s that uses a similar approach and directs the outside air to the building. The air from the outside is directed over the steam pipes in a heating chamber and conveys into the building. Exhaust openings in the upper reaches of the building provides a stack effect to pull the air through the building.
But in year 1631, after one finds that bad indoor air quality can cause health problems, King Charles I ordered that the ceilings in the houses must be at least 10 feet high and that the windows should be higher than the width to allow rooms for ventilation. These improvements were slowly implemented into the buildings in the UK. After the great London fire of 1666, implementations of good ventilations were being speed up because a lot of houses were destroyed. Thus, it makes way for construction of bigger and better ventilated houses with chimneys and large windows which leads to have better indoor air quality when the air ventilates in the house.
2.3 Modern Background of Exhaust Fan and Ventilation
With all the history in the previous section, we do of course have some modern background about the exhaust fan and ventilation. Nonetheless in the modern times which due to large demand in the world now, end-product of exhaust fans are being produced in a way of mass production. An american company specialized in kitchen exhaust fan, American Hood, has came out with some different products, ie, fire suppression system. It consists of smoke detector and fire alarm system and use a special wet chemical agent that provides quicker flame knockdown and superior fire prevention if extremely high level of smoke and temperature is detected.
2.4 Introduction to Microcontroller
Figure 2.1 Microcontroller
What is microcontroller? Microcontroller is sometimes called as a microcomputer or commonly called as MCU, is a kind of small or mini computer that you can find in almost all electronic devices and products. Some examples of common products that we have microcontroller built-in are microwave oven, handphone and etc.
If there are buttons and a digital display in a product, chances are it also has a programmable microcontroller brain. Often, microcontrollers are called as an embedded microcontroller, it is mainly because they are often part of an embedded system and usually integrated into a larger device or system.
Microcontroller is designed specifically for a particular tasks or jobs such as controlling a particular system which is different with the general purpose microprocessor, the one that is generally used in a PC. A typical microcontroller consists of an integrated CPU (Central Processing Unit), RAM for data storage and ROM for programme storage. Other than that, it also provides input and output interfaces on the same chip. It has its advantage because a general purpose microprocessor may require another addition chip to support similar function.
2.5 Introduction to PIC16F876A
PIC, initials refer to Peripheral Interface Controller, is a type of microcontroller made by a company called Microchip. They are 8 bit microprocessors with small RAM, ROM and simple peripherals bundled on a same chip. The figure below shows the number of pins and functions of each pin.
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Figure 2.2 Integrated Circuit PIC16F876A
The PIC16F876A was chosen for this project because it has the function of Pulse Width Modulation (PWM) in the integrated circuit itself, which is located at pin 12 and 13. The PWM function can be set through the configuration during the progamme codes writing in the software. PWM will be explained more in details in the next few chapters. By using this integrated circuit, it helps to save the trouble and works to construct an external circuit to perform a similar function.
2.6 Introduction to L293D
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Figure 2.3 Integrated Circuit L293D
The L293D is a quadruple high-current half-H driver. It is designed to provide a bidirectional drive currents of up to 600mA at voltages ranging from 4.5V to 36V. Not only that, it drives the inductive loads such as relays, DC motors, solenoids as well as other high current or voltage loads in positive supply applications. In this project of Intelligent Cooker Hood Exhaust Fan (ICHEF), L293D was chosen to drive one DC motor to show the speed of the motor driven by the frequency (PWM) from the microcontroller.
2.7 Introduction to MAX232
Figure 2.4 Integrated Circuit MAX232
MAX232 is a communication tool used mainly for serial commands to and from a flash rom. Besides, it is also an integrated circuit that changes the signals from RS232 serial port to signals that is compatible to use in TTL (Transistor-Transistor Logic). The MAX232 is a duo driver and receiver and typically converts the RX (Receive), TX (Transmit), CTS and RTS signals. Figure 2.4 shows MAX232’s structure and pin in/out of MAX232 chip. MAX232 chip was chosen for converting signals because it has long been used for microcontroller boards. It provides 2-channel RS232 port and requires external 10uF capacitors.
2.8 Introduction to Temperature Sensor (LM35)
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Figure 2.5 LM35
The LM35 is an integrated circuit sensor that is used to measure the temperature with an electrical output which is about the same compare to the temperature in degree celsius. LM35 acts as temperature sensor in this project. It was being chosen because it does not require any extra calibration or trimming to keep its accuracy to measure the temperature. There is another main characteristic of the LM35 which act as a temperature sensor is that it takes 60mA from its supply only. Since the main objective of this project is being green and save energy, LM35 was chosen instead of other type of thermistor.
2.9 Introduction to Light Dependent Resistor (LDR)
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Figure 2.6 Light Dependent Resistor (LDR)
A light dependent resistor (LDR) is a small semiconductor. LDR is used to recharge the light during different changes in light or made to turn a light on during certain changes in lights. One of the most commonly used areas that LDR implemented is in fire alarm system. It relies upon on the smoke which is produced in the event of a fire. When this smoke passes and covered the LDR and the amount of light falling on the LDR decreases, it will then send a signal to the microcontroller. Microcontroller will act accordingly from the pre-set programmes, in this case of the project, the microcontroller will drive the motor according to the data received.
The aim of a LDR is to vary the brightness of a light in the different conditions. This can be described easily by the concept of a digital watch. Some watches get to glow in the dark so that it is possible to tell the time without pressing any buttons. It is the LDR that let the watch to know when it is dark and changes the emission level of the light accordingly.
There are of course many good benefits and advantages to the LDR. A smaller amount of power will be consumed with the aid of LDR in many different kind of lights. It also helps lights to last much longer which is good for environment in a way.
2.10 Computer Interfacing Module
Even though it’s easy especially when there is plug-and-play internal hardware solution for the computer, connecting some of the external tools or devices may still require a certain amount of technical knowledge and experience. There are generally two types of ways for data transmission, parallel and serial. Serial transmission has been chosen for this project.
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Figure 2.7 Layout of DB-9 Female
In the past, old type of computer used 25 pins connectors while in fact that only 9 pins were actually used. Thus nowadays most of the connectors are manufactured in 9 pins instead. Each of the 9 pins usually connects to a wire. Besides the two wires which are used for transmitting (TD) and receiving (RD) data shown in Figure 2.7, the other pin is for signal ground. The voltage on any other wire is measured with respect to the ground. So, the minimum number of wires of a connector to use for 2 way transmission of data is 3.
Although it has been known that it works without the signal ground wire, it will degrade the performances and often with errors. There are more wires which are for controlling purposes and not for sending bytes. Even though all of the signal can share on one wire, but there is still a separate wire dedicated to every type of signal instead.
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Figure 2.8 Connection of MAX232 and Microcontroller
While communicating with different type of microcontrollers, one needs to convert the RS232 levels down to lower levels, usually 3.3V or 5V. Serial RS232 communication works with voltages -15V to 15V for high and low. On the other hand, TTL logic operates between 0V and 5V. Modern low power consumption logic operates in the range of 0V and 3.3V or even lower.
The MAX232 chip from Maxim was the first integrated circuit in the market contains the necessary drivers and receivers to adapt the RS232 signal voltage levels to TTL logic. The reason why it became popular was because it needs only one voltage (3.3V or 5V) to generates the necessary RS232 voltage levels.
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2.11 MicroCode Studio
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Figure 2.9 Layout of MicroCode Studio
MicroCode Studio is integrated development software which has the capability to debug and was developed and used for microEngineering labs PICBASIC and PICBASIC PRO compiler. Microcode Studio is packed with a code explorer that helps to jump automatically to files, constants, variables, symbols, defines and labels, which are consisted in respected source code. Besides, there are too other features available in this software such as cut, copy and paste, undo and replace options. Not only that, it has the ability to correct and identify the assembler errors. It features views for serial output from the external of the microcontroller.
The software helps the user to set up assembler and compiler options. Other than that, it has auto-search feature included in the software which helps the user to do all the work which is involved. It too has the error result window which helps to identify errors and correct them easily. The good thing about this compiler is that when the user clicks on the errors in the compiler, MicroCode Studio will automatically jump into the line location and it efficiently helps the users to know where and how to debug the serial output from the microcontrollers.
Chapter 3: System Description
3.1 Overview
This chapter focuses on the system design, description and illustration of block diagram of the Intelligent Cooker Hood Exhaust Fan. Several descriptions of the systems will be explained in this chapter as well.
3.2 Introduction
The system consists of mainly 4 parts, namely:-
Temperature sensor (LM35) / LDR (act as a smoke sensor) and its readings
The temperature sensor and LDR will sense the heat or smoke level. If the level exceeds the pre-set level, the fans will be activated automatically via the control of microcontroller.
Liquid Crystal Display (LCD)
A LCD will be installed in the system to display the temperature reading and LDR values according to the data received. It is to give the user an insight or idea of what is the current values of temperature or light density at that particular time.
Speed of exhaust fan by Pulse Width Modulation (PWM)
The speed of exhaust fan will be adjusted according to the heat level detected and generate the pulses accordingly. The speed may go higher only when the heat level is higher thus saving the wasted energy which is required to run the fans to full speed at all time. This type of exhaust fan differs from the traditional type of exhaust fan.
The fans will then still be activated for a short period of time after the reading drops back to the pre-set heat level in order to remove all the excessive smoke or odour away.
Driver Circuit
A circuit by L293D to control DC motors with external power supply.
3.3 System Design
Microcontroller (PIC16F876A)
Temperature Sensor (LM35)
Light Dependent Resistor
Fans
High Speed
Low Speed
LCD Display
Determine speed according to heat & smoke level
Fans still on for a pre-set time
Controller Circuit
Figure 3.1 Overall Block Diagram of Intelligent Cooker Hood Exhaust Fan
The concept of Intelligent Cooker Hood Exhaust Fan is smart. It helps to reduce the workload of human beings and also it will save energy as well. The microcontroller which uses PIC16F876A serves as a main brain of the whole system. It uses 2 types of sensors which are the temperature sensor (LM35) and light dependent resistor (LDR). With the help of both sensors, data are easily received and displayed on the LCD Display with some aids of the programming. After the data are received and displayed on LCD Display, pulses will be generated by the function of Pulse Width Modulation (PWM) in PIC16F876A and it sends the signal to the controller circuit, DC motor in this case, and drive the motor accordingly to what the readings are being obtained. The fans should still be on for a period of time to ensure the remaining smell and odour are sucked away.
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3.4 Pulse Width Modulation (PWM)
Pulse Width Modulation (PWM) is a useful technique that controls the analog circuits with the aids of the processor’s digital outputs. It is employed in different types of areas. It is widely used from power control and communications to measurement and conversion. To control the analog circuit in digital way, it helps to reduce the cost of the system and most importantly, it reduces the level of usage of power consumption as well.
3.4.1 Duty Cycle
PWM Signals
Figure 3.2 PWM Signals of Varying Duty Cycles
Figure 3.2 shows three different PWM signals. The upper figure shows a PWM output with a 10% duty cycle. It just means that the signal is on for 10% of the period and off the other 90% of the period, so the average is low. Likewise, the middle figure shows the analog signal value at 50% and lower figure shows 90%, so its average is half and high accordingly. If it is fully on, it requires 100% of the period while when it is 0%, it is off.
3.4.2 PWM Frequency
The PWM signal frequency is important depending on the hardware that one is using. If the main purpose is to create a DC signal then the high frequency will be required (kHz) so that the low pass filter can eliminate the frequency component. To determine how high the frequency, it is to depend on how much frequency components are allowed at the output and how it is used.
3.4.3 Communication and Control
One of the reasons why PWM is so popular is because that the signal remains digital at all times, from the microcontroller to the driver circuit. There is no Digital-To-Analog Conversion (DAC) is required. The noises in the signal will be reduced to minimum level because the signals are in digital form. Noises can affect’s digital form’s signal only if it is great enough to change from Logic 1 to Logic 0 and likewise.
PWM is often used for communication is mainly because PWM has the ability to increase the noise immunity over analog control. By converting the analog signal to PWM, it increases the length of a communication channel. An appropriate RC (Resistor-Capacitor) or LC (Inductor-Capacitor) network can remove the modulated high frequency wave form and return the PWM signal back to analog form at the recipient side.
3.5 DC Motor
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Figure 3.3 DC Motor
Almost all mechanical movement that surrounded us is caused by either an AC or DC electric motor. It converts the electrical energy into the mechanical movement. One needs to have a little background knowledge about electromagnet and electricity in general to understand how a motor works.
3.5.1 How It Works?
In any kind of electric motor, in this case, a DC motor, the operation is mainly based on a simple electromagnetism. A magnetic field is then generated by a current carrying conductor. By doing so, it will experience a force proportional to the current in the conductor when it is placed in the external magnetic field.
Everyone is well aware of playing the magnets when young. The opposite polarities attract, in this case, north and south pole. Vice versa, the same polarities repel, north-north and south-south. The operation of a DC motor has similar concept. The internal arrangement of a DC motor is outlined to compose the magnetic interaction between an external magnetic field and a current carrying conductor to generate rotational movement.
Image
Figure 3.4 Layout of DC Motor
Almost all the basic DC motor has these six common parts in them, namely axle, commutator, rotor, stator, brushes and field magnets. In most DC motor, the external magnetic field is produced by high level strength of permanent magnets. The rotor rotates according to the stator which is stationary as well as two or more permanent magnet pole pieces. The windings of the rotor are being connected electrically towards the commutator. The above figure shows a common motor layout with the rotor inside the stator magnets.
2-pole motor in action
Figure 3.5 Operation of DC Motor
The relationships between the commutator contacts, the brushes and the rotor windings are that when the power is being supplied to the motor, the stator magnets will be incorrectly aligned, the rotor will rotates till it is aligned with the stator’s field magnet and polarities of the energized winding.
The brushes will move to the next commutator contacts and next winding will be energized only when the rotor are in alignment. It can be given by the simple example of 2-pole motor. The rotation reverses the direction of current flow through the rotor winding, causing to the flip of the rotor’s magnetic field, making it to continue rotating.
Image
Figure 3.6 Inner view of DC Motor
Iron core armature is commonly used in a DC motor as it has a few advantages. The iron core provides a strong and firm support to the windings, it is specifically important considering for the high torque motors. The core, in a way, also dissipate the heat away from the rotor windings very well that it allows the DC motor to rotate even harder. And most importantly, to construct an iron core is comparably cheaper than other type of construction.
Unarguably, there are always pros and cons about almost everything. There are a few disadvantages about the construction of iron core. The high level of inertia in iron armature reduces the motor acceleration dramatically. This type of construction also causes the high winding inductances which reduce the life of the brush and commutator.
Chapter 4: Circuitry Explanation
4.1 Overview
This chapter is about the circuits that are used in this project. Circuit operation and the performance of the entire circuit are roughly explained in this chapter. All datasheets of the Integrated Circuits used in this project are attached in the appendixes section. Circuit diagrams for every part of the overall circuit in this project are provided so that the operation of the circuit can be understood easily by non-engineer readers.
4.2 Microcontroller Unit (PIC16F876A)
Figure 4.2 Microcontroller Unit
The PIC16F876A CMOS FLASH-based 8-Bit microcontroller consists of a 200 nanoseconds instruction execution, self programming, an ICD (In-Circuit Debugger), 2 comparators, 256 bytes of EEPROM data memory, 2 PWM functions and a UART. The main brain of this control unit replies upon on the PIC16F876A with a 4MHz resonator that produces the clock pulses which is required buy the targeted microcontroller.
4.3 Universal Asynchronous Receiver/Transmitter (UART)
Figure 4.3 Circuit of Universal Asynchronous Receiver/Transmitter (UART) with MAX232
An UART (Universal Asynchronous Receiver/Transmitter) is a type of computer hardware that converts the data between the serial and parallel forms. UART is often used with other types of communication means such as, RS232. It is usually a single IC (Integrated Circuit) that used for serial communication or through peripheral device serial port. UART is usually used for embedded system such as microcontroller with RS232. Different interface equipment is usually used to change the logic level of the UART to and from the external signaling levels. It doesn’t usually receiver nor generate the external signals which are used between the different types of equipment.
4.4 Light Dependent Resistor (LDR)
Figure 4.4 Circuit of Light Dependent Resistor
The circuit shown above is about the sensor of the circuit. LDR in this project is to activate the microcontroller. It acts as an input and will send the analogue data into microcontroller and microcontroller will determine the data received and perform a task accordingly. These values will be sent into microcontroller on PortA.0.
4.5 Temperature Sensor (LM35)
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Figure 4.5 Circuit of Temperature Sensor (LM35)
The power supply (Vcc) can be ranging from 4V to 20V depending on the project requirement, but 5V will be used in this project. To use the LM35 sensor, one can just connect the Vcc to 5V, Ground to Ground and the Out to the Analog-Digital Converter channel. The output varies with temperature obtained. The values will be sent to microcontroller via PortA.1.
4.6 Motor Controller (L293D)
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Figure 4.6 Circuit Connection of L293D to Microcontroller
The DC motor can be driven in clockwise or anti-clockwise direction depending to the requirements. To do so one first needs to connect the motor and find out the commands that are needed to give to the microcontroller to perform the specific rotation. Pin 1 and pin 8 will need to connect to 5V. Pin 3 and 6 are connected to the output which is DC Motor. Pin 4 and 5 are for grounding. Pin 2 and 7 act as an input which connect to PortC.7 and PortC.6 respectively. Pin 1 of the L293D will also connect to Pin 12 or 13 for Pulse Width Modulation (PWM) function in microcontroller.
4.7 Overall Circuit
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Figure 4.7 Overall Circuit
Chapter 5: Materials
5.1 Overview
The main purpose of this chapter is about the materials and tools that are used in this project whereby components, software and tools used will be listed for reference purposes. Budget and stores for all components are also listed at the end of this chapter as well.
5.2 Preface of Materials Used
All materials used in finishing this project can be further categorized into 3 main groups of computer software, apparatus and electronic components. These 3 major groups of materials will be further discussed in following subchapters.
5.2.1 Computer Software
Computer software used in this project is shown below.
No.
Computer Software
Function
1.
Live Wire
Do the simulation of the circuit
2.
Micro Code
Programming for the Microcontroller
3.
Microsoft Word
Report typing
Table 5.1 List and function of the software used to complete this project
5.2.2 Apparatus
The table below shows the apparatus that required for c
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