Notesale: Turn your study into money

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HNEE 108 Engineering Design

Contents
Acknowledgment
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4
Background:
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6
Objectives
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7
Block diagram of a thermostat
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11
Possible design solutions
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12
Selection of the optimum design solution
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14
Explanation of the key features of a computer-aided design system
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15
Conclusion
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18
Reference
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Also thanks to other class mates who helped me and guided me to give this project a
realistic and physical shape
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After some time pondering and brainstorming with my project
colleagues, we settled on designing a thermostat with temperature sensor and to be utilised
inside a house
...
As part of the project we
will clarify in depth our design, so we have prepared a comprehensive and detailed report
which contains the following outlines:
1
...

2
...
Also producing
a conceptual design of the final product
...
Utilisation of computer-aided design system during the process of designing the
product, and demonstrating an understanding of the principles of ECAD
...
Arduino is based on the open
source software named “Wiring” said to be a derivative of C++++ software language
...
It can be adapted
without difficulties in a project, means that an extensively tested code is integrated into the
system software code
...


Final Report

Page 5

HNEE 108 Engineering Design

Introduction
In this paper we advance the proposition that the project we will present is called
“Thermostat sensing temperature” illustrating the relation between the temperature and
the thermostat
...
The purpose of thermostat is to control the temperature of the
house by simply resetting the thermostat when you’re asleep or away and this can be done
automatically by installing a programmable thermostat and also we have thought that it will
be beneficial to provide for our clients the best way to save money by utilizing energy
...
To control the temperature, a thermostat is
connected to HVAC unit (heating, ventilation and air conditioning) and Arduino which is a
single board microcontroller to make using electronics devices attached to an LCD to control
the heating and the cooling system
...
When the temperature goes
over 25 the thermostat will automatically switch off the heating system and when it goes
below 18 it would switch on the heating system
...
According to our users
preference they can change it according to their wants during different times or seasons

Final Report

Page 6

HNEE 108 Engineering Design

Customer requirements
Performance: capable of controlling the room temperature and setting it between 18 and
25 Celsius
Functions: switching on the heater when the room temperature goes under 180 and
switching it off when the room temperature exceeds 250
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Aesthetics: plastic enclosure with two colour finish and a LCD screen and five push buttons
...
5 kg and not bigger than 5×15 cm

Block diagram of a thermostat

LCD

+24
Temperatur
e sensor

Heat
latching
relay

Arduino Uno

Cool latching
relay

Up
Run/hold

program

time/date
Down

Fig
...
Usually these are supposed to be just data processors performing
exhaustive numeric operations
...


• At home in Ovens, Washing Machines, Alarm Clocks, etc
...

• At office in Typewriters, Photocopiers, Elevators, etc
...

• On roads in Cars, Traffic Signals, etc
A microcontroller is a highly integrated chip, which includes on single chip, all or most of the
parts needed for a controller
...

Microcontrollers can be classified on the basis of internal bus width, architecture, memory
and instruction set
...
4)TYPES OF MICROCONTROLLERS
When the ALU performs arithmetic and logical operations on a byte (8-bits) at an
Instruction, the microcontroller is an 8-bit microcontroller
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Examples of 8-bit microcontrollers are Intel 8051 family and
Motorola MC68HC11 family
...
It works by
sensing the air temperature, switching on the heating when the air temperature falls below
the thermostat setting, and switching it off once this set temperature has been reached
...

How quickly the room heats up depends on the design of the heating system, for example,
the size of boiler and radiators
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Turning a room
thermostat to a lower setting will result in the room being controlled at a lower
temperature, and saves energy
...


Final Report

Page 8

HNEE 108 Engineering Design

Principle of thermostat:
One of the key principles of a main thermostat, and indeed any thermostat, is the
technological method by which the thermostat senses the ambient temperature
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These
are bimetallic sensors and electronic thermistors
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Electronic thermistors are an electronic component that
increases its electrical resistance with increasing temperature, and as such can be used to
break a circuit when a particular temperature is reached
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This key
principle of main thermostats is based around the idea that some thermostats
work simply by turning a heating system on or off when a particular temperature is reached
or constantly adjusting the heat output of the heating system across a range of possible
outputs
...


Final Report

Page 9

HNEE 108 Engineering Design

The flowchart of the operation:

START

Set up
microcontroller

Calculate
temperature

Display on screen

If Temp <18 or
>25

Wait X sec
...
The Arduino consists
of a simple open source hardware board designed approximately an 8-bit Atmel AVR
microcontroller or a 32-bit
...

-Humidity sensor: it senses particularly its environmental situation and input the Data into
the Arduino where it will measure the moisture (humidity) content in the air
...

-Temperature sensor: it’s a chip to measure or tells you the average temperature or
required in the house or between two locations
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They use the fact as temperature
increases, the voltage across a diode increases at a known rate and technically this is known
as the voltage drop
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The tmp36 by adafruit is placed inside the actual thermostat to
sense the outside temperature and then coupled to the LCD screen
...

now we connect the 24v power source to the thermostat by the heating and cooling terminals and
then by putting a relay between the lines we can actually program the switch to flip on and off by
itself
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Production and evaluation of the conceptual design
The conceptual part of any design where many decision are to be made is considered the
most innovative phase of that design
...
Since the cost of electricity is high these days, we set off
to make the design as costs friendly as possible in a short amount of time
...
That’s why the prototype
can evaluate its performance by the end of the project to ensure that the performance is at
high levels
...


Fig
...
The
connections here have to be properly arranged and connected
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The main idea of that
design is to get the received temperature to be displayed on the LCD screen
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3: Configuration diagram

Selection of the optimum design solution
Putting different reliable components has enabled us to produce a highly functional and
operational low-cost system
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Which are:
1
...
The
choice for Arduino was taken after some time
searching the internet and other resources for the
optimum design in sensing the temperature
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The time: the time requirement is also an important
factor when we set to design our thermostat
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3
...
Our design ensured an
optimum safety when used that would satisfy our
customer needs and also would not put the customer
at the risk of injury when operating the thermostat
...
The illustration of the process of our
compliance check is better presented as bullet points below:


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Final Report

Customers reported an ease in the understanding of
the functionality of the device
...

The customer was proved with good service in order to
assist him if he needed any help with the operation
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A feedback of our progress is given to our customers
throughout the development stage
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Computer-aided design or CAD is a modelling tool used by engineers and architects to
design three-dimensional objects
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Great work accuracy
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Huge libraries of engineering components which can be easily imported
...


Application of a suitable computer based software in the engineering
design process
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4: 5V + - Power supply (Thermostat)

The above circuit shows an AC to DC power supply used to feed our temperature sensing
thermostat with 5V of DC power
...
Two voltage regulators (LM7805C and LM7905C) used for voltage regulation, two 1k
resistors, and 8 further capacitors of different values to smooth out any voltage ripples
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Final Report

Page 16

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HNEE 108 Engineering Design

Conclusion
The End of Term Documentation helps conclude our first semester of working on the
temperature sensing thermostat with Arduino project and will satisfy our lecturer
expectation
...
Brainstorming was a large portion of our
initial beginnings which were a bit time consuming ,and now our focus has shifted quite a lot
to documentation and polishing what we have been working on for 15 weeks
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There were times when
the team contemplated on changing the project a little bit like the customer requirements,
some projects headed towards a completely new topic
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The team is proud of what we have created
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I would say that the hardest part that I came across in the
assignment was applying computer aided-design software to our project
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Overall, I’m confident to say that finishing this project has brought me the knowledge and
skills I need to tackle any challenges I might face in my future career as an engineer
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freescale
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pdf
(accessed on the 8th of April, 2014)

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http://home
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no/~hansha/documents/lab/Lab%20Equipment/arduino/Introductio
n%20to%20Arduino
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homexpertbyhoneywell
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aspx (accessed on the 20th of April, 2014)
http://www
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com/list_7639102_principles-mainthermostat
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about
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htm (accessed on
the 4th of May, 2014)

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http://www
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co
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php?page=vb2 (accessed on the 8th of June, 2014)

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http://www
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com/what-is-cad-software
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bbc
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uk/schools/gcsebitesize/ict/software/1graphicssoftwarerev4

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