954405410210UNIVERSITY OF ZIMBABWE
FACULTY OF ENGINEERING
DEPARTMENT OF ELECTRICAL ENGINEERING
…in partial fulfilment of
BSC. Hons in Electrical Engineering
CANDIDATE: RUZIYE BERNARD
REG NUMBER: R159035F
SUPERVISOR: PROF E CHIKUNI
PROJECT TITLE: DESIGN OF A TEMPERATURE CONTROLLED WATER BOILING URN
I wish to extend my gratitude to my supervisor support and valuable guidance throughout the prototyping, design and documentation of the project.
I would also like to acknowledge my mother Fortunate Kanda who sacrificed her resourses financing this project.
I would like to thank the lab technicians at the University of Zimbabwe Electrical Engineering Laboratory and also not forgetting my friends who also assisted me in this project.
to those with the drive and motive in this electrical engineering field, that are able to handle the pressure until the end.
Water temperature control has been crucial in the everyday life of every individual. This project presents temperature controlled water boiling urn that is capable of self regulation of temperature and also maintain temperature at a constant value. Temperature was measured using a water proof temperature and an Ardunio on played a critical role in the water temperature control. The value of the temperature measured and the set temperature where displayed on an liquid crystal display. The system proved to be able to regulate temperature accurately and also maintain temperature at a constant value.
Water boiling urns are metal containers used to brew teas or boil water in large quantities in factories, canteens or churches and have a small tap at the base for extracting either tea or hot water. Urns have a higher capacity than domestic kettles thus supply enough hot water for canteens. Electric kettles were previously used to provide hot water in offices, however since a large number of people need hot water in the offices boiling the kettle over and over wastes energy thus the relevance of the urn. Unlike a kettle, table top hot water boiling urns provide an endless supply of water saving money on electricity bills they are also energy efficient. Depending on the model hot water boiling urns can provide from 140 to 180 cups of boiling water an hour, thus removing the need for continual boiling of a kettle, saving valuable time and electricity over traditional office hot water supplies(Angel). Angel (2017) also states that “When working in an office or any other environment, nobody can afford to waste time, yet much of an employee’s time is squandered in the kitchen waiting for the kettle to do its job so that they can get on with their job! If you were to install a hot water boiling urn in the office, not only would a vast amount of time be saved but also energy and cost”. Since the urn provides hot water to a large number of people at different times, the temperature of the water in the urn must be kept at a constant required temperature at anytime of the day. Temperature control is a process in which a change in temperature of a system is measured or detected and passage of heat into or out of the system is adjusted to achieve a desired average temperature(Wikipedia). Various thermostats can be used to control water temperature in the urn. Bimetallic switching thermostats can be used, but these thermostats cannot display the exact temperature. Digital thermostats are now used because the can be easily programmed to a desired temperature and also can easily display the current temperature of the water.
Water boiling urn
PROBLEM STATEMENTDesign of a temperature controlled water boiling urn with a “boil dry protection”
AIMDesign and implementation of a temperature controlled water boiling urn with a boil dry protection
To design a system that is able to sense temperature change in the water boiling urn, adjust the temperature and also display the current temperature of the water
To design and implement an urn that is able to keep the temperature water of the boiling water constant.
To design and implement a system that is able to control temperature of which the value of the wanted temperature will be set manually
Water boiling urns are used to supply hot water at work places, canteens and school, hence there is need for temperature controlled water urn that provide hot water at all times thus saving time and increasing productivity at these places since people will not have to boil the urn each and every time they need hot water. The boil dry protection of the urn protects the heating element of the urn hence it becomes economic. According to Ian Boughton “The correct temperature for making tea and coffee remains a hotly debated subject, green and white teas don’t respond well to boiling water and every coffee has its temperature” thus a temperature controlled urn with a digital display provides hot water for each type of tea at a desired temperature.
The following methods are aimed at coming up with the best implementable solution for the aim and objectives of the design.
Personal Interviews – the researcher will interview canteens owners and restaurant owners who use water boiling urns
Brain storming – the researcher would hold brainstorming sessions with other students and lecturers to find solutions to the design of the temperature controlled water boiling urn
Document analysis – the researcher reviews existing authoritative academic literature on the subject
Concept generation – conceive and analyse possible solutions based on the literature review study.
Design analysis and selection – analysis of the generated concepts and simulation of the circuit components. The best solution will be selected and improved further.
Programming and simulation –software development aspects of the including coding of the microcontroller running simulations.
Implementing and testing – development of the chosen solution accompanied by the final report of the project followed by circuit testing.
The following tables will show the estimated time for project completion and the estimated budget of project.
NOV DEC JAN FEB MAR APR MAY
Literature review Requirements of design Generation of concepts Design and simulation Implementation and testing Recommendations, conclusion CHAPTER TWO
2.1 LITERATURE REVIEW
EVOLUTION OF WATER TEMPERATURE CONTROL
Over the years water temperature control has played a vital role in human lives. Water temperature control has played an important part in human lives, from industry upto households.
2.1.1PREVIOUS METHODS OF WATER TEMPERATURE CONTROL
non electric means of temperature controlnWater temperature control was crucial even before the use of electric heaters. Firewood was used in temperature control. People would put the urn on a fire place when the water had reached the estinmated water temperature they would hence removed the water boiling urn from the fire. When the water temperasture had cooled down and required heating again they would place the heater on the fire again. This method is still used in some areas in Zimbabwe where electricity is still not available, or in areas there are continous electricity cut or in areas where the people try to save the cost of electricity because they cannot afford the electricy.
Advantages of the system
cheap since firewood is easily accessible
easy to maintain as it does not required skilled man power to operate
major cause of deafforeststioncontributes to global warming
produces soot hence cleaning of the urn is difficult
cutting down of trees now illegal; in some areas hence source of fuel now hard to find
the system is tiresome because it is operated manually
the system is not accurate as people uses their hands to estimate the temperature of the water
use of electrical heaters with thermostats
In order overcome challenges encountered when using non electric heaters where used. These water heaters heated water to a certain preset temperature. Once the water had reached that temperature you couldn’t change the water set temperature. Also these systems could not display the temperature being read also you could only assume the water has reached your wanted temperature.
Advantages of the system
A better system environmentally that the non electrical method
a certain preset temperature can be set
can only heat water upto a certain preset value of the thermostat
canot display wanted temperature hence user can only estimate that his water has reached a certain wanted temperature
difficult to maintain as semi skilled people can only maintain
2.2 Proposed Solution
A system that uses an Arduino microcontroller and a temperature sensor is to be designed. The system is supposed to display the set temperature and also display the current temperature of the wanted.
Proposed system Overview
Arduino uno MIcrocontrollerRelay acting as switching circuit
16×2 LCD display
Proposed system block diagram for urn
3.1 SYSTEM DESIGN AND METHODOGY
3.1.1 Hardware DesignThe hardware design shall be split into five sub components:
The microcontroller unit
Liquid Crystal Display
3.1.1 Component Analysis
A relay is an electrically operated switch. An electromagnet is used in the relay to make it operate like a mechanical swithch. Relays are used wher we require isolation between the control circuit and the circuit being controlled. Relays are also used when we control a circuit using a low power signalore when we can control multiple components using a single signal. When electrical relays used to allow low power electronic computer type circuits toswitch relatively high voltage and current both on and off some form of relay switchingcircuitry is required to control it. In this project we are using a one channel relay. The relay used also requires five(5) volts and has a maximum rating of 10 amps. The relay is also an inductor and not just an electromagnet. In this project the relay will be connected in the NC (normal open channel) mode as a result if the set temperature is above the current temperature the microcontroller
2. Luquid crystal display
LCD (Liquid Crystal Display) screen is an electronic display module and find a wide
range of applications. A 16×2 LCD display is very basic module and is very commonly used
in various devices and circuits. These modules are preferred over seven segments and other
multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have
no limitation of displaying special ; even custom characters (unlike in seven
segments), animations and so on.
A 16×2 LCD means it can display 16 characters per line and there are 2 such lines. In
this LCD each character is displayed in 5×7 pixel matrix. This LCD has two registers, namely,
Command and Data.The command register stores the command instructions given to the LCD. A
command is an instruction given to LCD to do a predefined task like initializing it, clearing its
screen, setting the cursor position, controlling display etc. The data register stores the data to
be displayed on the LCD. The data is the ASCII value of the character to be displayed on the
LCD.Pin number Function name
1 Ground ground
2 Supply voltage Vcc3 Contrast adjustment Vee4 Selects command register Register select
5 Low to write to the register. High to read from the register Read/write
6 Sends data to data pins when a high to low pulse is given Enable
7 10 data pins Db0
15 Back light VccLed+
16 Backlight Ground Led –
Arduino is an open-source platform used for building electronics projects. Arduinoconsists of both a physical programmable circuit board (often referred to as a microcontroller)
and a piece of software, or IDE (Integrated Development Environment) that runs on your
computer, used to write and upload computer code to the physical board.
The Arduino platform has become quite popular with people just starting out with
electronics, and for good reason. Unlike most previous programmable circuit boards, the
Arduino does not need a separate piece of hardware (called a programmer) in order to load
new code onto the board – you can simply use a USB cable. Additionally, the Arduino IDE
uses a simplified version of C++, making it easier to learn to program. Finally, Arduinoprovides a standard form factor that breaks out the functions of the micro-controller into a
more accessible package.
The Arduino is a microcontroller board based on the ATmega8. It has 14 digital –
input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a
16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset
button. It contains everything needed to support the microcontroller; simply connect it to a
computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.
The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial
driver chip. Instead, it features the Atmega16U2 (Atmega8U2 up to version R2) programmed
as a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2
HWB line to ground, making it easier to put into DFU mode. Revision of the board has the
following new features:
??1.0 pinout: added SDA and SCL pins that are near to the AREF pin and two other
new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to
the voltage provided from the board. In future, shields will be compatible with both
the board that uses the AVR, which operates with 5V and with the Arduino Due that
operates with 3.3V. The second one is a not connected pin, that is reserved for future
??Stronger RESET circuit.
??ATmega 16U2 replace the 8U2.
Specifications for arduino UNO Description
Operating Voltage 5V
Input Voltage(recommended) 7-12v
Input Voltage(limits) 6-20V
Digital I/o pins 14(6 for PWM output)
Analogue input pins 6
DC Current per I/O pin 40 mADC Current for 3.3V pin 50 mAFlash Memory 32KB (0.5 KB is used by bootloader)
EEPROM 1 KB
Clock Speed 16 MHz
4. Temperature Sensor
In order to accurately measure temperatures in the cold and hot water tanks, this project requires waterproof temperature sensors, for which DS18B20 temperature sensor provided by Adafruit was chosen. This sensor has a built-in analog-to-digital conversion and outputs 16 bits serial signal to the micro-controller’s digital input pin. The maximum resolution of the digital signal is 12 bits, with a precision of 0.0625 degrees Celsius, and a range between -55 and +125 degrees Celsius. It has also pre-burnt a physical address to distinguish between other sensors of the same type, which allows multiple sensors’ digital output pin to connect to the same pin on the micro-controller. The micro-controller needs only recognizing the physical address of each sensor to acquire sensor readings accordingly. Because the sensor is covered to achieve waterproofing, the heat transfer rate between the environment and the sensor cover became a limitation of the response time of the sensor to immediate temperature changes. It takes approximately 3 seconds for the sensor to accurately reflect the temperature of water with an instant change. Figure 2.5 shows the connection details of this sensor.
Electricity is passed through the resisistive element of the water heater. The resistive element heats up and as a result it also inturn heats up the water. The base of the water urn is made of cast iron, the base acts as a stove top as a result it is also responsible for the heating of the water .
3.3 SOFTWARE DESIGN
Results and discussion
4.1 Waterproof Temperature Sensor Test
As mentioned above, due to human skin’s sensitivity, the requirement for this sensor is to measure temperature of water within +/- 0.5 degrees Celsius accuracy. Additionally, because these sensors are used in cold/hot water reservoirs, in which the temperature of water is ideally constant, the response time to temperature change of these sensors is not required to be as quick as within 1 second. By using hot water at 50 degrees Celsius, the testing procedure of these sensors is the comparison between the sensor readings and an analog thermometer reading for every degree while the water cools down naturally. Ice is added when the water reaches room temperature to acquire extra data. Figure 3.1 shows the plot representing the sensor readings meet our requirements.
The water heater had to be tested on the amount of current its draws and its resistance so as to determine the power consumption of the heater and also to determine its effieciency. A multimeter was used to measure the resistance.
Resistance measured = 34.5 Ohms
Voltage supplied = 220 volts
Current consumed = voltage/resistance =220/35.5
Power Consumed = (VOLTAGE)2RESISTANCE = 220235.5
= 1.363 KW
THE SYSTEM WAS ASSEMBLED AS SHOWN BELOW
The system continuously displays the temperature being read by the ds18b20 tempearature sensors and contionously checks whether the the temperature being read is above or below the set value of wanted temperature
TESTING IF THE SYSTEM MET THE CONDITIONS
WHEN TEMPERATURE IS BELOW THE SET POINT
The relay is turned on and the heater begins boiling the water the LCD was displaining both the set temperature and the current temperature being read by the temperature sensor.
WHEN THE TEMPERATURE WAS = TO THE SET POINT
The relay turned of when the temperature was 2 degrees above the set temperature which is allowed
WHEN THE TEMPERATURE WAS ABOVE THE SET POINT
The relay remained off and the LCD continued to display the wanted temperature and the current temperature of the water being read by the temperature sensor
WHEN THE SET TEMPERATURE WAS THEN SET BELOW THE CURRENT TEMPERATURE
The relay was turned off and allowed the water to cool to the set temperature. The LCD continued to display the set temperature and the water temperature sensor”s read temperature.