DESIGN AND CONSTRUCTION OF A FAN SPEED CONTROL SYSTEM
Abstract
This temperature control fan can be controlled using a microcontroller when it detects a certain temperature that has been set. The purpose of this project is to prevent the waste of voltage usage when it is not hot enough for fan to be needed. The temperature control fan has three di?erent speeds. Each speed will change according to a certain level of temperature that is set. This project is a combination of electric supply, fan, temperature sensor and microcontroller (ATMEL). To complete this project, there are a few steps need to be taken which are the selections of temperature sensor, power supply, fan, design controlling using ATMEL, developing a source code for the ATMEL and use a suitable apparatus to design all circuit. As a conclusion, this project is to design and construct a temperature fan system using temperature sensor which will be controlled by microcontroller. The fan speed can be changed according to a certain level of temperature
TABLE OF CONTENTS
1    INTRODUCTION    1
1.1    Background to the Study    1
1.2    Statement of the Problem    2
1.3    Aim and Objectives    3
1.4    Scope of the Study    3
1.5    Signi?cance of Study    4
 
2    LITERATURE REVIEW    5
2.1    Types of Temperature Controller    5
2.1.1    On/of control    5
2.1.2    Proportional control    6
2.2    Methodology    7
2.3    Description of the Functional Block Diagram    8


    2.3.1    Temperature sensor    8
    2.3.2    Error ampli?er    8
    2.3.3    Ramp generator    8
    2.3.4    Opto-coupler    8
    2.3.5    Power triac    9
    2.3.6    Mains supply and load    9
    2.3.7    Display    9
2.4    Theory    of Components Relevant to Design    9
    2.4.1    Silicon bandcap temperature sensor    9
    2.4.2    Optocoupler    10
    2.4.3    The power triode    12
    2.4.4    Snubber network    13
    2.4.5    Pulse width modulation (PWM)    13

3    DESIGN METHODOLOGY    15
3.1    Design Speci?cation    15
3.2    Design of Power Supply    16
 
3.3    Temperature Sensor    17
3.4    Design of the Analog to Digital Converter    18
3.5    Ramp Generator    21
3.6    Comparator    22
3.7    Optocopular Driver Stage    22
3.8    Power Drive Circuit    24
3.9    Operational Principle of the Room Temperature Fan Speed Controller    25
4    CONSTRUCTION AND TESTING    27
4.1    Construction    27
4.2    Casing    28
4.3    Testing    29
4.4    Test Result    29
4.5    Bill of Engineering Measurement and Evaluation    30
5    CONCLUSION AND RECOMMENDATIONS    31
5.1    Conclusion    31
5.2    Recommendations    32
References    33
A High Level Language Codes for the Project    35
B Bill of Engineering Measurement and Evaluation    45
 
LIST OF TABLES



4.1    Temperature controller test result    29
B.1  Bill of Engineering Measurement and Evaluation    45


LIST OF FIGURES



2.1    Block diagram of the Room Temperature fan Controller    7
2.2    LASCR    11
2.3    Opto - TRIAC    12
3.1    Power Supply schematic    16
3.2    LM35 Temperature Sensor and ampli?er circuit    18
3.3    ICL 7107 analog to digital converter circuit    19
3.4    LED Display    21
3.5    A stable Multivibrator (ramp generator)    21
3.6    Pin layout of the �A741 op-amp    23
3.7    MOC3041 Optocoupler    23
3.8    Complete circuit diagram of the temperature controller    26
4.1    Circuit diagram    28
 
 
CHAPTER 1
INTRODUCTION

1.1    Background to the Study

is very important when it comes to processes that require certain level of temperatures for quality control of most products during their production cycle. These processes do requires precision temperature control to help achieve set goals of such production process. This is also particularly important as it will help preserve items like drugs within their expected active life expectancy before expiration. Failure to follow storage recommendations of phar- maceutical products can result in subpotent products and potentially, therapeutic failure. In addition, hundreds of thousand of medications are discarded each year because of improper storage conditions resulting in millions of dollars wasted.It is important to recognize when pharmaceutical products have not been stored according to the manufacturer�s speci?cations and take appropriate action. To accurately control process temperature without extensive operator involvement, a temperature control system relies upon a controller, which accepts
a temperature sensor such as a thermocouple or RTD as input. It compares the actual tem- perature to the desired control temperature, or setpoint, and provides an output to a control
element. The controller is one part of the entire control system, and the whole system should be analyzed in selecting the proper controller (Hughes, 1995). The following items should be considered when selecting a controller:
1.    Type of input sensor (thermocouple, RTD) and temperature range.


2.    Type of output required (electromechanical relay, solid state relay, analog output).


3.    Control algorithm needed (on/o?, proportional, PID).

4.    Number and type of outputs (heat, cool, alarm, limit).


This controller embarked on in this work was occasioned by the need to design a room temperature controller that can be used to control the speed of a fan to help control the temperature of the room. When the temperature of the room is increasing above a set range (which is the nominal temperature of the room) the controller will send more power to the fan to increase its speed to cool the temperature and vice-versa.

1.2    Statement of the Problem

A thorough observation has shown that some times the temperature of our homes can be intolerable especially during sunny days with less wind ?ow and cold days after heavy down pours. Both scenarios do create unbearable levels of temperatures. A device that can automatically track these temperature changes and appropriately control the speed of a fan to keep the temperature fairly constant with a selected range especially for those not having air-conditioning units will be very helpful in this regard (Theraja and Theraja, 1998).
On cold days the speed of the fan will be low but will be high on sunny days. The work shows a typical temperature controller that does ?nd application in our homes and can be applied in bedrooms also or in any temperature control demanding environments.

1.3    Aim and Objectives

The aim of the project is to design and construct an electronic room temperature fan con- troller.
� The temperature controller would have a temperature sensing device and be able to sense temperatures up to 99 degree celcius
� The device is designed to control the brightness of an incandescent bulb proportionately with temperature change.
� The controller would be designed to have both direct control relationship and inverse control relationship.
� Both relationship would be switch-selectable for the bulb brightness or any load con- nected to the output.

1.4    Scope of the Study

The project work is about design and construction of an electronic room temperature fan controller to control the speed of a fan to keep the temperature of the room with a tempera- ture range. The design uses proportional band control for this controller. The circuit designwould be embarked upon with determination of relevant design parameters. The construc- tion or implementation of the circuit would be carried out after design and acquisition of the materials and components from the market.

1.5    Signigcance of Study

This work o?ers an insight into temperature controlling techniques involving the proportional band control and how it is o?ers improvement over the traditional on/o? control system. The understanding of this control systems helps in better designs with better control features for precision temperature control The work also o?ers a controller that could be said to be two-in-one as it can control fans and also can be used for light zinc temperature which results in savings in having two devices with both control relationships and in electric bills due to the fact that the devices are not using the full rated power at all times (Mazidi, 1989).