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BACHELOR OF ENGINEERING (Hons)
in ELECTRICAL & ELECTRONICS ENGINEERING 3+0
in collaboration with UNIVERSITY OF BRADFORD UK
INTELLIGENT POWER METER
PENG FEI
Project Supervisor: Ms. Zuraidah bt. Harith
INTI INTERNATIONAL UNIVERSITY
Stage 3 BEng Project
JUNE 2011
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Abstract
Nowadays, people consume electricity everyday. But electricity mostly is produced from
coal which is limited on earth. The huge amount of producing coal causes deep damage on
environment. Some people still does not have the awareness of saving electricity. Besides
this, the common power meter is not able to display the amount of electric bill. Therefore,
this project is designed to help electricity consumer directly understand how much the
electricity cost them. The waste in residence is not only electricity but also the consumers
money.
This project consists of two parts: 60% hardware implementation and 40% software
programming. The main focus of this project is to measure the power consumption from
devices.
The measurement system is designed to measure voltage and current from AC line. Then
the value of them will be stepped down or amplified as the input of PIC microcontroller.
PIC16F877A is used as the control system of this project. With the aid of this
microcontroller, the program can be performed to calculate the real power consumption
simply multiplying two inputs (voltage and current) together from measurement system. And
according to the local tariff, the amount of electric bill will be carried out based on power
consumption during certain time period.
The result from the calculation will be displayed on LCD display module in order to
notice the users how much power they consume and how much it will cost them. After one
month, the power consumption and amount of electric bill will be reset.
This Intelligent Power Meter is successfully built to meet the specifications and aims.
This project provides a great opportunity to improve designerspractical skills on hardware
and software.
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Acknowledgement
I really appreciate University of Bradford to give this precious opportunity to us so that we
have the exposure to practical world.
First of all, I would like to thank Ms. Zuraidah bt. Harith being the greatest supervisor to
provide ideas, give guidance to solve problems on this project and keep monitoring my
progress. Without her assistance, this project would not be working successfully.
Next, I would like take this opportunity to thank INTI International University laboratory
assistances. They tried to give all their helps to us making us feel so comfortable in the
laboratory.
I want to thank my friends especially Vincent Chan, Kim Siong and Chen Zijian for their
kindness and helpfulness. They gave me really constructive suggestions and lend their tools to
me.
Finally, I like to thank my parents are always being supportive and understanding on my
oversea study. I really appreciate what I am doing and being the one of this greatest family
members.
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Declaration
I, Peng Fei, declare that the project is entirely my own work where due references are
made. The project was completed under the supervision of Ms. Zuraidah bt.Harith.
Yours faithfully,
.
Peng Fei
UoB No:08028913
14thJune 2011
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Table of Contents
Chapter 1 Introduction ................................................................................................................... 1
1.1 Project title ........................................................................................................................... 1
1.2 Background .......................................................................................................................... 1
1.3 Project aims and objectives ................................................................................................... 2
1.4 Report outline ....................................................................................................................... 2
1.5 Scenarios of project .............................................................................................................. 4
1.6 Phase of project .................................................................................................................... 4
Chapter 2 Literature Review........................................................................................................... 5
2.1 Introduction .......................................................................................................................... 5
2.2 Power supply system ............................................................................................................ 52.2.1 Transformer ................................................................................................................... 5
2.2.2 Regulator and rectifier ................................................................................................... 6
2.2.2.1 Regulator ................................................................................................................. 6
2.2.2.2 Rectifier ................................................................................................................... 7
2.3 Measurement system ............................................................................................................. 8
2.3.1 Transformer ................................................................................................................... 8
2.3.2Shunt resistor .................................................................................................................. 8
2.3.3 Operational amplifier ................................................................................................... 10
2.3.4 Rectifier ....................................................................................................................... 10
2.4 PIC control system .............................................................................................................. 11
2.4.1 PIC16F877A ................................................................................................................ 11
2.4.2 LCD display module .................................................................................................... 12
2.5 Software ............................................................................................................................. 12
2.5.1 Multisim ...................................................................................................................... 12
2.5.2 MikroC pro .................................................................................................................. 12
2.5.3 Eagle ........................................................................................................................... 12
2.6 Comparison with current power meter project ..................................................................... 13
Chapter 3 Methodology ................................................................................................................ 14
3.1 Hardware overview ............................................................................................................. 14
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3.2 Power supply system .......................................................................................................... 15
3.3 Measurement system ........................................................................................................... 16
3.3.1 Current measurement ................................................................................................... 17
3.3.1.1 Shunt resistor ......................................................................................................... 17
3.3.1.2 Voltage follower ................................ .................................................................... 18
3.3.1.3 Rectifier ................................................................................................................. 19
3.3.2 Voltage measurement .................................................................................................. 19
3.3.2.1 Transformer ........................................................................................................... 19
3.3.2.2 Voltage divider ...................................................................................................... 19
3.3.2.3 Voltage follower ................................ .................................................................... 20
3.3.2.4 Rectifier ................................................................................................................. 20
3.4 PIC control system .............................................................................................................. 20
3.4.1 Hardware ..................................................................................................................... 21
3.4.1.1 PIC microcontroller ............................................................................................... 21
3.4.1.2 LCD display module .............................................................................................. 22
3.4.2 Software ...................................................................................................................... 23
3.4.2.1 Initialization ........................................................................................................... 25
3.4.2.2 ADC conversion .................................................................................................... 26
3.4.2.3 Calculation of power consumption and electric bill ................................................ 273.4.2.4LCD display............................................................................................................ 29
Chapter 4 Results ......................................................................................................................... 31
4.1 Simulation approach ........................................................................................................... 31
4.1.1 Power system ............................................................................................................... 31
4.1.2 Current measurement ................................................................................................... 33
4.1.2.1 Shunt resistor ......................................................................................................... 34
4.1.2.2 Voltage follower ................................ .................................................................... 34
4.1.2.2 Rectifier ................................................................................................................. 36
4.1.3 The current measurement of two lamps ........................................................................ 37
4.1.4 Voltage measurement .................................................................................................. 39
4.1.4.1 Workability of measuring voltage in Multisim ....................................................... 39
4.1.4.2 Transformer ........................................................................................................... 40
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4.1.4.3 Voltage divider ...................................................................................................... 41
4.1.4.3 Voltage follower ................................ .................................................................... 42
4.1.4.4 Rectifier ................................................................................................................. 42
4.2 Practical approach ............................................................................................................... 43
4.2.1 Current measurement ................................................................................................... 43
4.2.2 Voltage measurement .................................................................................................. 47
4.2.3 Power supply system ................................................................................................... 50
4.3 LCD analog inputs measurement ........................................................................................ 50
4.4 Hardware constructions....................................................................................................... 52
Chapter 5 Discussion.................................................................................................................... 53
5.1 Result discussion ................................................................................................................ 53
5.2 Problems encountered and solutions.................................................................................... 55
5.3 Validity of the project ......................................................................................................... 58
5.4 Limitation of Intelligent Power Meter ................................................................................. 58
Chapter 6 Conclusion ................................................................................................................... 59
6.1 Technical specifications ...................................................................................................... 60
6.2 Future Enhancement ........................................................................................................... 61
References ................................................................................................................................... 62
Appendix A: Gantt chart .............................................................................................................. 66Appendix B: Schematic diagram .................................................................................................. 67
Appendix C: PCB layout .............................................................................................................. 68
Appendix D: Software .................................................................................................................. 69
Appendix E: List of Components ................................................................................................. 75
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List of figures
Figure 1.1 Table of energy loss due to power meter....1
Figure 2.1 Transformer5
Figure 2.2 LM7805 regulator.......6
Figure 2.3 MICW04M bridge rectifier .....7
Figure 2.4 the operation of bridge rectifier7
Figure 2.5 Connection shunt resistor...8
Figure 2.6 5W 10 shunt resistor....9
Figure 2.7 High current rating and low resistance shunt resistor.....9
Figure 2.8 MCP6004 OP-AMP...........10
Figure 2.9 PIC16F877A..11
Figure 2.10 416 characters LCD Module...12
Figure 2.11 Electromechanical meter...13
Figure3.1 Block diagram of Intelligent Power Meter. .14
Figure 3.2 The circuit of power supply system15
Figure3.3 The circuit of measurement system.....16
Figure 3.4 Voltage follower (unity gain differential amplifier) ...18
Figure 3.5 Voltage divider ...19
Figure 3.6 Schematic diagram of PIC control system .....21
Figure 3.7 Schematic of PIC16F877A.22
Figure 3.8 Schematic of LCD display module.....23
Figure 3.9 Flow chart of power meter.....24
Figure 3.10 Configuration of LCD display module .25
Figure 3.11 Initialization of parameters... 25
Figure 3.12 Configuration of input and output ports ...25
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Figure 3.13 Calculation of voltage ......26
Figure 3.14 Calculation of current ...27
Figure 3.15 Calculation of power consumption...27
Figure 3.16 Calculation of electric bill28
Figure 3.17 Calculation of electric bill29
Figure 4.1 Simulation of power supply system...31
Figure 4.2 Waveform of the output from transformer.32
Figure 4.3 Waveform of the output from bridge rectifier32
Figure 4.4 Waveform of the output from LM7805 voltage regulator..33
Figure 4.5 Simulation of measuring current33
Figure 4.6 Waveform of output voltage from shunt resistor...34
Figure 4.7 Waveform of output voltage from voltage follower in current measurement35
Figure 4.8 Waveform of output voltage from rectifier in current measurement.36
Figure 4.9 Simulation of measuring current on two lamps. .37
Figure 4.10 Waveform of voltage across shunt resistor in the simulation with two lamps.38
Figure 4.11 Waveform of output of voltage follower in the simulation with two lamps.38
Figure 4.12 Waveform of output of rectifier in the simulation with two lamps..38
Figure 4.13 Simulation of measuring voltage ..39
Figure 4.14 Workability of measuring voltage in Multisim40
Figure 4.15 Output of transformer...40
Figure 4.16 Voltage across line 10 and line11.41
Figure 4.17 Output voltage of voltage follower on voltage measurement ..42
Figure 4.18 output voltage of rectifier on voltage measurement.42
Figure 4.19 Output of shunt resistor with one lamp43
Figure 4.20 Output of shunt resistor with two lamps ..43
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Figure 4.21 Output of voltage follower with one lamp44
Figure 4.22 Waveform of voltage follower with one lamp .44
Figure 4.23 Output of voltage follower with two lamps44
Figure 4.24 Waveform of voltage follower with two lamps45
Figure 4.25 Output of rectifier with one lam45
Figure 4.26 Waveform of rectifier with one lamp46
Figure 4.27 Output of rectifier with two lamps46
Figure 4.28 Waveform of rectifier with two lamps.46
Figure 4.29 Input of transformer..47
Figure 4.30 Input of transformer..47
Figure 4.31 Output of voltage divider ..47
Figure 4.32 AC output of voltage follower..48
Figure 4.33 DC output of voltage follower..48
Figure 4.34 Waveform of voltage follower.49
Figure 4.35 Output of rectifier.49
Figure 4.36 Waveform of rectifier...49
Figure 4.37 Output of power supply system50
Figure 4.38 LCD display with one lamp..50
Figure 4.39 LCD display with two lamps51
Figure 4.40 ADC module readings..51
Figure 4.41 The display of electric bill52
Figure 4.42 Hardware construction..52
Figure 5.1 Fault in LCD55
Figure 5.2 Program of AAA loop56
Figure 5.3 Readings in current measurement with oscilloscope.57
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Page 1
Chapter 1
Introduction
1.1 Project title
The final year project is given as Intelligent Power Meter. To achieve this project
successfully, the essential knowledge is required such as display devices, digital electronics,
microcontrollers and programming.
1.2 Background
The targets to measure in this project are light bulbs and a fan. The light bulb is a
resistive device [1]. And the fan is an inductive device. Any inductive device with a coil ofwire like motor will cause the current and voltage are out of phase. It contributes power
factor is less than one. Hence, there will be energy loss in the inductive devices. However,
the consideration of power meter is not necessary in Intelligent Power Meter project. Because
the modern devices such as washing machine and air-conditioner are designed with power
factor correction and power management system to reduce the energy loss due to power
factor. This information can be referred to High-End Solution from Texas Instrument [2] [3].
Besides it, there is a proof that the power factor from inductive home appliances does not
give significant effect on the electricity bill. The further calculation and explanation involved
in this proof is stated in Powerelectronics.com [4].
Figure1.1 Table of energy loss due to power meter [5]
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As Figure1.1 shown above, the energy losses due to power factor for refrigerator,
washing machine, clothes dyer and air conditioner cost less than 20 cent/month. Such low
cost from power factor is negligible.
As the result of two reasons stated above, Intelligent Power Meter will not be considered
to measure and calculate with power factor even though it measures the apparent power.
1.3 Project aims and objectives
The aim of this project is to design and implement an Intelligent Power Meter by
developing the objectives and specifications.
The objectives of this project:
1. Meter should read the power consumed from one or two devices.
2. Meter should consist of total power and monthly power consumed.
3. Based on monthly power consumed. Student must be come up with the amount that needs
to be paid shown on LCD
4. Monthly power reader part can be reset.
1.4 Report outline
Chapter 1 Introduction
In this chapter, the background, specifications, aim of this project are introduced to
readers. This provides the understanding of Intelligent Power Meter that why the project
initiated and how it is going to achieve. With the aid of chapter 1, the reader is easy to
understand the deeper analysis in the following chapters.
Chapter 2: Literature review and theoryChapter 2 will discuss about the difference of current existed power meter and this
Intelligent Power Meter. Besides this, the components are introduced to provide the
justification of the most suitable one. Hence, the selection of components can be done
according to components introduction.
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Chapter 3: Methodology
With the decision of selecting components and the design of power meter, the method to
achieve power meter is explained in detail. It has two major parts: hardware and software. It
focuses on how the circuit functions and the software programming.
Chapter 4: Results
The chapter consists of two approaches to obtain the results which are either from
Multisim simulation approach or practical approach. The results are showing with diagram
and description. The understanding of power meter from users is enhanced with how the
measurement system and PIC control system works.
Chapter 5: Discussion
Discussion will investigate the major problems encountered and the results between
Multisim simulation approach and practical approach. This provides effective explanation to
readers so that they can fully comprehend the operation of power meter.
Chapter 6: Conclusion
The designer will conclude the achievement of this project and comment on the results.
Despite of these, the future enhancement will be discussed.
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1.5 Scenarios of project
The devices will be placed on the 240VAC line. The voltage will be stepped down by the
transformer. The current will be converted into voltage using shunt resistor connected in
series with Neutral line. Both voltage transformer and current shunt resistor have two outputs.
PIC16F877A only understands one ADC input from transformer and shunt resistor.
Therefore, the voltage follower is used to convert two inputs into one output. The voltage
across two inputs is equal to the voltage between the output and ground. The output of
voltage follower is still AC voltage which will not keep constant in PIC16F877A so the
calculation cannot be done.
Next, the rectifier will cap the peak voltage of AC voltage. PIC16F877A will take these
values to calculate the actual voltage and current. The power consumption will be obtained
from the multiplication between voltage and current. Hence, the electric bill will be carried
out.
There are four values showing on LCD display: voltage, current, power consumption and
electric bill. The reason to display current is because there is electric breakdown happened in
residences due overload. The residences can refer to current to adjust how many loads should
work simultaneously.
1.6 Phase of project
Intelligent Power Meter project are categorized into six phases as shown below:
Phase 1: Comprehend the project aim and objectives.
Research the theory of power meter.
Phase 2: Circuit design
Algorithm of measurement system and PIC control system
Phase 3: Circuit test and development of software
Phase 4: Troubleshooting on circuit and software
Phase 5: Design and implementation of PCB board
Phase 6: Test and troubleshooting on PCB board
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Chapter 2
Literature Review
2.1 Introduction
In real life, power meter runs 24 hours continuously to monitor the power consumption of
devices. If it stops working for certain time, this will result in inaccuracy to the electric bill.
Therefore, this project must equip with a power supply which can work continuously without
any failure. The best solution is to convert 240VAC to 5 VDC for PIC control system.
For home appliance AC line, it works with 240VAC and 13A MAX in 50HZ. The aim of
measurement system is to convert 240VAC and 13A MAX into a value in such manner
where it is compatible with PIC microcontroller. In measurement system, there are voltage
measurement and current measurement. The output of measurement system will be processed
to PIC controller.
In PIC control system, the PIC microcontroller must be able to have ADC module,
perform calculation and interface with LCD display module.
2.2 Power supply system
2.2.1 Transformer
Transformer has two coils, primary coil and secondary coil. It uses magnetic field formed
by primary coil to move electrons to secondary coil. Thus, the electricity current is
produced. The secondary voltage is proportional to the primary voltage with the ratio of
Figure 2.1: Transformer [6]
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the number of turns in secondary coil to the number of turns in the primary coil. Theformula of this fact is shown as below:
The 220VAC to 9VAC transformer is selected based on the availability. This transformer
has the largest ratio between primary and secondary in the market. Since 5VDC power
supply is needed in this project. Therefore, the 10V AC to 5VDC converter is required.
2.2.2 Regulator and rectifier
2.2.2.1 Regulator
Voltage regulator can convert AC voltage into DC voltage. There are various outputs
available among the regulator products. The most common one is with starting series number
78 and 79. 78 series are with a positive output and 79 series are with a negative output.
LM7805 is applied into this project. It is able to regulate 10 VDC into 5 VDC. LM7805
is picked is to meet the 10VAC output from transformer.
Figure 2.2 LM7805 regulator [7]
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2.2.2.2 Rectifier
The bridge rectifier MICW04M is applied as shown in Figure 2.3. It has the function to
convert AC input voltage to DC ripple output voltage. And it fully utilizes four diodes in
bridge to perform the full-wave rectification. Full-wave rectification brings the fact that no
matter rectifier circuit is in positive half cycle or negative half cycle, the current will flows inthe same direction through the load.
Figure 2.3 MICW04M bridge rectifier [8]
Figure 2.4 The operation of bridge rectifier [9]
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2.3 Measurement system
2.3.1 Transformer
The operation of transformer in measurement system is the same as the one using in
power supply system. The reason to use two separated transformers with same characteristics
is because of the consideration of safety. If power supply system fails, the independent
measurement system is still able to operate.
2.3.2Shunt resistor
When the device switches on, the current will flow through the device and shunt resistor.
As current appears, voltage will be across shunt resistor. Based on Ohms law, the current
can be obtained by
Where R=10.
5W10Neutral
Line
Current I
Voltage V
The shunt resistor is very crucial for power meter that must be protected from damage.
The fixed cement power resistor is adopted as the shunt resistor.
Figure 2.5 Connection shunt resistor
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2.4 PIC control system
2.4.1 PIC16F877A
PIC16F877A plays the roles as a microcontroller which consists of input/output pins,
ROM, RAM, CPU, Oscillator and A/D converter. The reason to choose microcontroller but
not microprocessor is that the microcontroller has low power consumption, high performance
of computation and low economical price but it is only designed to perform a specific task.
These characteristics are more suitable for hobbyists project like this Intelligent Power
Meter. Microprocessor has powerful CPU which is able to perform multitasking. It is built in
most commercial products.
Comparing to others PIC microcontroller with PIC16F877A, PIC16F877A meets the
requirements of ADC converter, I/O port, EEPRO M and oscillator.
Fi ure 2.9 PIC16F877A 13
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2.4.2 LCD display module
JHD204A LCD Module is involved in this project because it can interface with
PIC16F877A. It has 416 characters. This LCD module shown as below will display the
current, voltage, power consumption and electric bill.
2.5 Software
2.5.1 Multisim
National Instrument MULTISIM is powerful software which provides the platform for
users to achieve simulation of design without taking time to implement the circuit in real life.
The measurement system circuit testimony will be done in Multisim.
2.5.2 MikroC pro
MikroC pro is a C compiler for PIC microcontrollers to design for the development,
building and debugging PIC-based embedded application [15]. Therefore, PIC16F877A can
be compiled using this software.
2.5.3 Eagle
Easily Applicable Graphical Layout Editor is software with the function of schematic
capturing and PCB layout. It can automatically generate PCB layout from schematic. It is
more convenience than Express PCB.
Figure 2.10 416 characters LCD Module [14]
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2.6 Comparison with current power meter project
For the common power meters, they are electromechanical meter which applies two coils
for voltage and current measurement using the effect of magnetic flux. It only displays power
consumption. The residences are confused how much it will cost them. Besides these, the
amount of power consumption is increment. If the residences want to know how much the
power consumption is, they have to take current power consumption to minus with the power
consumption from last month.
Intelligent Power Meter will apply microcontroller to measure the power consumption.
The results will be in digital form which can be accurate as electromechanical meter. This
project can provide more convenience to the residences.
Figure 2.11 Electromechanical meter [16]
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3.2 Power supply system
The circuit design of power supply system from 10VAC to 5VDC is drawn in EAGLE
software as shown below:
GND
10VAC
RectifierRegulator
5VDC
GND
In this project, the operational amplifier MCP6004, PIC16F877A and LCD module
requires 5V power supply. Power supply system steps down 240 VAC to 10VAC using
transformer. Then, it converts 10VAC to 5VDC using rectifier and voltage regulator. And in
order to smooth the ripple voltage, the C1, C2 and C3 are used.
In this project, the 220V input to 9 V output transformers is applied. Hence, the ratio of
number of turns is
The theoretical output from the transformer in this project is
Then, the ratio between transformer and AC power line is
The ratio of LM7805 is . Therefore, the output of LM7805 or the output of
power supply system is
Figure 3.2 The circuit of power supply system
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3.3 Measurement system
In measurement system, there are two parts involved:
1. Voltage measurement: it consists of transformer, voltage divider, voltage follower
and rectifier.
2. Current measurement: it consists of shunt resistor, voltage follower and rectifier.
The following is the circuit of measurement system drawn in EAGLE software.
The output of measurement system will be the input of PIC control system.
GND 5V
Voltage measurement
Current measurement
Voltage divider Voltage
follower
Voltage
follower
Rectifier
Rectifier
Output of
transformer
Output of shunt
resistor
PIC ADC chann
PIC ADC chann
V3
V4
V1
V2
Figure3.3 The circuit of measurement system
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3.3.1 Current measurement
3.3.1.1 Shunt resistor
The wattage rating of shunt resistor is 5w and resistance is 10. According the formula
The maximum current can be obtained as
This current rating is not only for shunt resistor but also for this Intelligent Power Meter
project. Approximately, it can support four 40W lamps at the same time.
There is 240V 40W lamp on AC line. Hence, the current it draws is
According to this, the current of shunt resistor when one lamp works on AC line is also
0.167A. Then, based on Ohms law, the voltage across it is
Then, when two lamps switch on, the voltage across shunt resistor will be
This voltage will be the input of current measurement and voltage follower.
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3.3.1.2 Voltage follower
This voltage follower is constructed with differential amplifier. The voltage output of
differential amplifier is
Where V1 and V2 are marked in Figure 3.3
When
=
=
, this differential amplifier has the unity gain (gain =1). It is called
voltage follower. Then,
Where is RMS voltageThe voltage follower is implemented by the operational amplifier MCP6004.Before
designing the circuit, the safety must be considered as mention in section 2.3.3. There are
two formulas for analog inputs protecting resistors which are squared in Figure 3.3.
In this case, the designer has chosen 17.7Kas protecting resistors.
Figure 3.4 Voltage follower (unity gain differential amplifier) [17]
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3.3.1.3 Rectifier
The rectifier is designed with bridge diode to provide full wave output. The output of
voltage follower will be in AC voltage. However, ADC module of PIC only can read
constant DC voltage. To meet this, the idea of designing rectifier is created. The rectifiertakes the as the output of itself. Then,
3.3.2 Voltage measurement
3.3.2.1 Transformer
The transformer is adopted as the same from power supply system. The output of the
transformer is 9.8VAC as mentioned in section 3.2.
3.3.2.2 Voltage divider
Vd
The ratio of two resistors and is determined the output voltage. After thetransformer, the voltage is too high for the operational amplifier MCP6004. The purpose of
voltage divider design is to step down the voltage. Depending on the resistance of voltage
divider, the designers can get the suitable output voltage in their design. The formula of
voltage divider is shown as below:
Figure 3.5 Voltage divider [18]
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In this voltage divider, the ratio between input voltage and output voltage is 0.09 as
shown below.
Then, the output of the voltage divider will be
Where 9.8V is the output of transformer
3.3.2.3 Voltage follower
The voltage follower in voltage measurement has the same operation as the voltage
follower in current measurement in section 3.3.1.2. The output of voltage follower in voltage
measurement is
Where V3 and V4 are marked in Figure 3.3
3.3.2.4 Rectifier
The rectifier in voltage measurement has the same operation as the rectifier in current
measurement in section 3.3.1.3. The output of rectifier in voltage measurement is
3.4 PIC control system
In Figure 3.6, the PIC control system is presented. It functions to control inputs and
outputs according to the programming. With the aid of LCD display and PIC16F877A, PIC
control system is able to read analog inputs from measurement system and to perform the
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calculation to gain the actual current and voltage. These actual values will be showed on the
LCD display module.
5V
GND
Output of voltage
measurement
Output of current
measurement
3.4.1 Hardware
3.4.1.1 PIC microcontroller
There must be 5VDC power supply to pin 1 (VPP) with 1K resistor, pin 11(Vcc) and pin
21(Vdd). The ground must be provided to pin 12 and pin 31 (Vss/Gnd). Pin 13 and pin 14
(Osc1 and OSc2) needs to connect with 8M crystal oscillator with two 22pF capacitors.
The output of current measurement is connected with pin 2 ADC module (ADCON0).
The output of voltage measurement is connected with pin 3 ADC module (ADCON1). And
pin 33 to pin 38 will be connected with LCD display module.
Figure 3.6 Schematic diagram of PIC control system
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3.4.1.2 LCD display module
The LCD display module is adopted to display the current, voltage, power consumption
and electric bill. As shown below, it is the list of LCD display module connection.
LCD Pins PIC port B pins
Pin1 Ground
Pin2 5V
Pin3 Ground with 1K resistor
Pin4 Pin 37 RB4
Pin5 Ground
Pin6 Pin 38 RB5
Pin7 Null
Pin8 Null
Pin9 Null
Pin10 Null
Pin11 Pin 33 RB0
Pin12 Pin 34 RB1
Pin13 Pin 35 RB2
Pin14 Pin 36 RB3
Pin15 5V
Pin16 Ground
Figure 3.7 Schematic of PIC16F877A
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5V
Ground
PIC16F877F
3.4.2 Software
The flow chart of the whole process to measure power consumption is presented as
following Figure 3.9. It is processed in PIC control system using C language. This software
programming is written with the configuration hardware input and output pins. There are 3
major parts in this program:
1. Voltage reading2. Current reading3. Power consumption and electric bill calculation
Figure 3.8 Schematic of LCD display module
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Start
Initialization
Is curret reading
larger than last
reading?
Case:AAA
No
Yes
Calculate and
display actual
voltage
Read from analog
input channel 1
No
Yes
Calculate and
display actual
current
Read from analog
input channel 0
Calculate and
display power
consumption P=VI
Calculate electric
bill
Is curret reading
larger than last
reading?
After 1 hour,
electric bill
increment
After 1 month,
power meter reset.
Voltage
reading
Current
reading
Power
consumption
and electric bill
Figure 3.9 Flow chart of power meter
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3.4.2.1 Initialization
Figure 3.10 shown above is the configuration of LCD display module. The pins of LCD
are connected according to the list of LCD display module connection.
Figure 3.11 shown above is the initialization of parameters which are going to be used in
the program.
Unsigned char has 8 bits size and the range from 0 to 255. Unsigned long has 32 bits
and range from 0 to 4294967295 which are sufficient for calculation and readings. Unsigned
int has 16 bits and range from 0 to 65535.
Figure 3.10 Configuration of LCD display module
Figure 3.11 Initialization of parameters
Figure 3.12 Confi uration of in ut and out ut orts
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Figure 3.12 shown above is the configuration of input and output ports. RA0, RA1 and
RA2 in Port A are configured as inputs. All pins in Port B are outputs. Besides these, the
LCD display module is initialed.
3.4.2.2 ADC conversion
ADC conversion is to convert analogue voltage input into digital form which is
understood by microcontroller. The output of measurement system is read by ADC module in
PIC16F877A. This ADC module has 10 bits with 1024 sampling levels to represent the ADC
inputs. 1024 sampling levels have 0 to 1023 resolutions.
In ADC module, the voltage reference is 5V by default in PIC16F877A. Hence, one
resolution represents 0.0048V,
Figure 3.13 above shows the actual voltage calculation. The output of voltage
measurement will be read by Channel 1 in ADC module of PIC16F877A. The output of
voltage measurement is 0.568 (obtained in 4.1 voltage measurement). And the input of
voltage measurement is 244V. Then, the ratio between them is
Figure 3.13 Calculation of voltage
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Because the operation in MikroC pro does not accept decimal, 429.57 is represented by
42957/100.
Figure 3.14 shows the actual current calculation. The output of current measurement will
be read by Channel 0 in ADC module. And it is 1.788 (obtained in 4.2 current measurement).
And the input of voltage measurement is 1.67V (mentioned in 3.3.1.1 Shunt resistor). Then,
the ratio between them is
1.07 can be represented by 100/107.
3.4.2.3 Calculation of power consumption and electric bill
To get power consumption is to simply multiply voltage with current as Figure 3.15. u
and i isthe output from voltage and current calculation.
The home user in Malaysia is charged by domestic tariff from Tenaga Nasional Berhad.
The domestic tariff is RM0.218/KWH which is represented by[19]. To obtain how much
the power consumption costs the home appliances users is to multiply power consumption
with RM0.218/KWH in each hour. For the demonstrate purpose, the one hour time is
represented by 1 second (1000ms).
Figure 3.14 Calculation of current
Figure 3.15 Calculation of power consumption
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C1< 9
a=power0.218RM/kwh
Display amount ofelectric bill
m=a+b
Voltage, current,power consumption
calculation
Initializationb=0
Case:AAA
C1=C1+1
b=m
Reset
Delay 1 second
As to the calculation of electric bill, in the initialization, b=0. The program goes through
the voltage, current, power consumption calculation. At the beginning of electric bill
Figure 3.16 Calculation of electric bill
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program, the 10 loops are set with parameter C1. C1 increments from 0 to 9. Since there is 1
second delay, the 10 loops will be defined as 10 second.
The 10 loops command checks whether the current loop is bigger or equal to 9. If it is, it
will proceed to reset all the parameters and goes back to case: AAA. If it is less than 9 times,
the program will perform calculation and following command lines.
When the loop is less than 9 times, the calculated amount of money is put in a. Then,
the total amount m equals to a + b. The sum of a + b is displayed on LCD. C1 increments
by the step of 1.
Next, the m will be stored in b. After 1second, the program will go back to case: AAA.
Therefore, by following this method, the amount of money can increment with 1 second and
all parameters can be reset when 10 loops reached.
For the demonstration purpose, one hour is represented by 1 second. And 720 hours
(30days24hours=1 month in hours) are represented by 10 seconds.
3.4.2.4LCD display
For display of voltage, current and power consumption, they are 5 digits. The decimal
point is between the third digit and the fourth digit. For electric money, it needs 6 digits.
Figure 3.17 Calculation of electric bill
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Figure 3.17 shown above is the 5 digits display program. To obtain the individual digit is
to make the parameter (i or v) divide by . X is the number of digits. For example, thedesigner wants to extract 5 digits with decimal between the third digit and the fourth digit.
Then, it will
Extracting 4 digits, 3 digits and 2 digits etc. follows the above algorithm as shown in
Figure 3.17.
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Chapter 4
Results
This chapter provides the practical evidence of each system in this project. There are two
approaches to verify the operation of power meter. The first is simulation approach on
Multisim and another is practical approach from constructed circuits.
4.1 Simulation approach
4.1.1 Power system
The following is the simulation of power supply system.
As the result shown in Figure 4.1, the output from the power supply system in simulation
is 4.99V.
In order to observe the whole process of AC to DC conversion, at first, the operation of
transformer is investigated.
`
Figure 4.1 Simulation of power supply system
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Figure 4.2 is showing that of the transformer output is 11.173V.And .
The bridge rectifier is the next process after transformer. It rectifies the 11.173VAC into
9.57VDC as shown in Figure 4.3 so that voltage regulator is able to accept this as an input.
LM7805 voltage regulator has the ability to step down 10VDC input to 5VDC output. As
shown in Figure 4.4, the output of LM7805 voltage regulator is 5.001VDC. This will supply
to all the systems. Then,
Figure 4.2 Waveform of the output from transformer
Figure 4.3 Waveform of the output from bridge rectifier
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4.1.2 Current measurement
The simulation of measuring current in Multisim is done as shown below in Figure 4.5.
The result is obtained as the following. In this simulation, since Multisim does not support
the AC power line with Life, Neutral and Earth, the single line AC power source is applied
instead. Based on the theory of AC power line, the negative part of this AC power source can
be seen as Neutral line and the positive part of it can be seen as Life line.
Figure 4.4 Waveform of the output from LM7805 voltage regulator
Figure 4.5Simulation of measuring current
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In the simulation, the output voltage of voltage follower in current measurement is
0.09VAC shown in Figure 4.5 XMM3. The ratio between voltage followerand shunt resistor is
There is difference between simulation and theory on the output voltage of voltage
follower in current measurement is because the output of voltage follower also connects to
the bridge rectifier where is the voltage cancelling certain voltage from 0.165VAC to obtain
0.09VAC.
The waveform of output voltage from voltage follower in current measurement is
investigated in oscilloscope as shown in the following. It has the same butonly with half cycle because the operational amplifier MCP6004 is not able to accept
negative input.
The output of voltage follower proves that it successfully change two inputs into an
output with same value. Therefore,
The ratio of Vpeak between voltage follower and shunt resistor with one lamp is
Figure 4.7 Waveform of output voltage from voltage follower in current measurement
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4.1.2.2 Rectifier
The minimum output of rectifier is 175.614nV and the maximum output of rectifier is
176.716nV.
There is still a small ripple voltage existing in output after smoothing capacitor 220uF C4.But, this output becomes DC voltage in the PIC analog input manner.
Figure 4.8 Waveform of output voltage from rectifier in current measurement
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4.1.3 The current measurement of two lamps
This is the testimony for more than one device on the AC power line to observe the
difference with the simulation with one device. The two exactly same lamps are added in this
simulation.
From the readings shown in Figure 4.9, the voltage across shunt resistor, , , andoutput of voltage follower all are doubled comparing the readings in the simulation with one
lamp shown in Figure 4.5. This shows that the voltage across the shunt resistor is proportion
to the drawing current from devices. More devices operates at the same time, more current
will be drawn. Then, higher voltage across shunt resistor presents.
The voltage across shunt resistor in the simulation with two lamps is measured as the
following Figure 4.10. The ratio between this voltage and 0.234V from section 4.1.2.1Shunt resistor is
Figure 4.9 Simulation of measuring current on two lamps
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The output of voltage follower is obtained from Figure 4.10 as following with the same
from Figure 4.11. And it becomes half cycle due to the negative input limitation ofMCP6004.
The output of rectifier in Figure 4.12 is obtained with slight increase from 175.614nV to
179.77nV comparing to Figure 4.8.
Figure 4.10 Waveform of voltage across shunt resistor in the simulation with two lamps
Figure 4.11 Waveform of output of voltage follower in the simulation with two lamps
Figure 4.12 Waveform of output of rectifier in the simulation with two lamps
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As shown below Figure 4.14, the outputs from the same circuit with different sources and
lamps are different. The circuit with 240V lamp has much lower voltage output. But the
circuit with 120V 100W lamp can get the expected output 5V. This states Multisim does not
have the ability to simulation with 240V Lamp. However, it is still able to simulation with
output. The results from the simulation 240V lamp have the value to make the comparison
with practical results. This method is workable.
4.1.4.2 Transformer
Figure 4.14 Workability of measuring voltage in Multisim
Figure 4.15 Workability of measuring voltage in Multisim
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The output from transformer is obtained as above in Figure 4.15. is 0.904V.Then, . is 1.818V. This output will be the input forvoltage divider. It is supposed to be the same as the transformer in power supply system. Due
to the workability mentioned in section 4.1.4.1, the transformer is failed in Multisim.
The ratio between transformer and AC power line is
4.1.4.3 Voltage divider
In the waveform Figure 4.16, it is obtained by oscilloscope across line 10 and line 11.
The is 82.265mV. Then,
And the output from transformer in Figure 4.15 is 904.853mV.The ratio between voltage divider and transformer is
The output voltage across transformer will undergo the operation of voltage divider to getthe output across line 10 and line 11
Figure 4.16 Voltage across line 8 and line10
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4.1.4.3 Voltage follower
The output of this voltage follower is 90.031uV. Then, Because of Multisim standard as discussed in 3.3.2.1 Workability of measuring voltage
in Multisim, 240V lamp does not work properly in this voltage measurement. it brings the
fault that 5VDC power supply is not generated. Hence, the Op Amp MCP6004 does not turn
on. The functionality of voltage follower is not performing in this case.
The ratio between voltage follower and voltage divider is 4.1.4.4 Rectifier
Figure 4.17 Output voltage of voltage follower on voltage
Figure 4.18 Output voltage of rectifier on voltage measurement
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The output of this rectifier in Figure 4.18 is 391.615nV. Then, without proper inputfrom voltage follower, the result has fault also. But the waveform is still rectified into DC
voltage.
4.2 Practical approach
4.2.1 Current measurement
The output of shunt resistor with one lamp shown in Figure 4.19 is 1.696VAC. This is the
actual current one lamp draws.
The output of shunt resistor with two lamps shown in Figure 4.20 is 3.355VAC. This is
the actual current the lamp draws. It is the double of the current with one lamp in shunt
resistor.
Figure 4.19 Output of shunt resistor with one lamp
Figure 4.20 Output of shunt resistor with two lamps
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The output of voltage follower with one lamp shown in Figure 4.21 is 0.983VAC. The
ratio between voltage follower and shunt resistor is . The waveform of voltage
follower with one lamp is shown in Figure 4.22 which has Vrms 1.27VAC
Figure 4.21 Output of voltage follower with one lamp
Figure 4.23Output of voltage follower with two lamps
Figure 4.22 Waveform of voltage follower with one lamp
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The output of voltage follower with two lamps in Figure 4.23 is 1.717VAC. It is the
double of the current with one lamp in voltage follower. The ratio between voltage follower and shunt resistor is
.
Comparing Figure 4.21 and Figure 4.23, the Vamp ( ) of waveform in voltagefollower with two lamps is about double of the Vamp ( ) of waveform in voltagefollower with one lamp.
The output of rectifier with one lamp in Figure 4.25 is 1.788VDC. The ratio between
rectifier and voltage follower is.
Figure 4.25 Output of rectifier with one lamp
Figure 4.24 Waveform of voltage follower with two lamps
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The output of voltage follower with two lamps as shown in Figure 4.27 is 3.175VDC. It
is the double of the current with one lamp in voltage follower. . In the waveformof rectifier with two lamps in Figure 4.28, its amplitude is 3.24VDC.
Figure 4.27 Output of rectifier with two lamp
Figure 4.26 Waveform of rectifier with one lamp
Figure 4.28 Waveform of rectifier with two lamps
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The output of voltage divider is 0.870VAC as shown above in Figure 4.31. Then, the
ratio between voltage divider and transformer is
The AC output of voltage follower is 0.456VAC as shown above in Figure 4.32. Then,
the ratio between voltage follower and voltage divider is .
The DC output voltage is 0.563V in Figure 4.33 and the waveform showing the Vrms
output of voltage follower is 0.472V in Figure 4.34. It has the 0.02V difference with Vrms
measured in multimeter in Figure 4.33
Figure 4.32 AC output of voltage follower
Figure 4.33 DC output of voltage follower
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The DC output of rectifier is 0.568V as shown above in Figure 4.35. Then, the ratio
between rectifier and voltage follower is . The waveform of rectifier shown inFigure 4.36 has the amplitude 0.560mV with ripple voltage.
Figure 4.35 Output of rectifier
Figure 4.34 Waveform of voltage follower
Figure 4.36 Waveform of rectifier
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4.2.3 Power supply system
The Figure shown above in Figure 4.37 is the output of power supply system from
voltage regulator. The output voltage is 0.496VDC
4.3 LCD analog inputs measurement
The result of LCD display is obtained as above in Figure 4.38. With one lamp
working, the current showing is 0.16V and the voltage is 244.14. The power
consumption is 39.06W . The electric bill is below powerconsumption with increment with 1 second time.
Figure 4.38 LCD display with one lamp
Figure 4.37 Output of power supply syestem
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With two lamps working, the current showing in Figure 4.39 is 0.31V and the voltage is
244.14. The power consumption is 75.68W
. It shows that with more
devices adding the voltage stays at 244.14V.
The resolution read from channel 0 for current measurement is 360. To convert it to
voltage is shown in Figure 3.13 Calculation of voltage. The result of this conversion is the
output of voltage measurement from rectifier shown in Figure 4.40.
VThe resolution read from channel 1 for current measurement is 111. To convert it to
voltage is shown in Figure 3.14 Calculation of current. The result of this conversion is the
output of current measurement from rectifier shown in Figure 4.40.
V
Figure 4.39 LCD display with two lamps
Figure 4.40 ADC module readings
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At this moment in Figure 4.41, the power consumption is 37.26W. According to the tariff
0.218RM/KWH, 37.26W will cost the user .As shown in Figure 4.41, the amount of electric bill is exactly displayed on LCD
4.4 Hardware constructions
Power plug
to devices Power plug
from wall outlet
TransformerShunt
resistor
Power supply
system
Voltage
follower
Rectifier
Voltage divider
PIC control
system with
LCD
Measurement
system
As shown in Figure 4.42, the hardware of power supply system, measurement system and
PIC control system are constructed on PCB board.
Figure 4.41 The display of electric bill
Figure 4.42 Hardware construction
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Chapter 5
Discussion
5.1 Result discussion
Systems Parts Theory
(output)
Simulation
approach(output)
Practical approach(output)
Power supply
system
Regulator 4.9VDC 5.001VDC 4.98VDC
Current
measurement
Shunt resistor 1.69VAC 1.65VACRatio
0.545
1.696VAC
Ratio
0.579
Voltage follower 0.9VAC(M)1.65VAC(O)
0.983VAC(M)
1.27VAC(O)Rectifier 0.175uVDC 1.788VDC
Voltage
measurement
Transformer 9.8VAC 0.639VAC Ratio to
58mV is
0.09
10.3VAC Ratio to
0.87V is
0.0834
Voltage divider 0.882VC 58mVAC Ratio
0.001
0.87VAC Ratio
0.534Voltage follower
63.6uVAC 0.456VAC(M)
0.47VAC(O)
Rectifier 91.615nVDC 0.568VDC(M)0.560VDC(o)
The results obtained from three approaches: theory in Chapter 3 Methodology, simulation
approach and practical approach in Chapter 4 Results. The capital O beside the values states
that the value taken from waveform in oscilloscope. The capital M beside the values states
that the value taken from multimeter.
In power supply system, the output 4.9VDC in theory is proven with 5.001VDC in
simulation approach and 4.98VDC in practical approach.
Table 1 Results
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In current measurement, the outputs of shunt resistor and voltage follower are obtained
with only 2.7% errors.
.
But for rectifier, there are very large errors. It is because in the database of Multisim it is
lack of bridge rectifier. The only type of bridge rectifier is applied in Multisim which is not
the one in practical approach. Therefore, with different components, the result definitely will
be different.
In voltage measurement, due to the workability of measuring voltage in Multisim, the
results are not reliable. But the operating evidence still can be found in the ratio between two
components. The ratio between voltage divider and transformer in simulation approach is0.09. And the ratio between them in practical approach is 0.0824. It proves that transformer
and voltage divider are operating.
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5.2 Problems encountered and solutions
Problem 1: the value from measurement system keeps jumping when it shows in LCD display
module.
Reason: The first design of this power meter is without the consideration of rectifier. The output
of measurement system is AC voltage. The ADC module in PIC 16F877F is to converting DC
voltage into a resolution by the method of sampling.
Solution: The rectifier is added in order to convert AC voltage into DC voltage. With the aid of
rectifier, the output of itself is still not the perfect DC voltage but is the ripple voltage as mention
in section 4.1.2.2 and section 4.1.4.5.
Problem 2: the LCD display module does not show the characters but showing the blocks on the
1stand third row.
Reason: the program compiled inside LCD display module is tested in other project which is
workable. And the hardware is synchronized with LCD pins. The only reason will be PIC
hardware connection with faults.
Solution: the fault is found in PIC hardware connection where the MCLR pin1 is connected to
GND with 1k resistor. the correct way is to connect MCLR pin1 to 5 V with 1k resistor.
Figure 5.1 Fault in LCD
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Problem 3: even though the ripple DC voltage is obtained in measurement system, the LCD
display output according to the ripple DC voltage is not stable still having different values in
short period.
Reason: if ripple DC voltage is zoomed in, it is AC voltage with very low peak to peak voltage.
Hence, PIC ADC module will read the voltage along with sinusoidal of ripple DC voltage.
Solution: there is correction in program. The correction is to put the case AAA in front of the
program and check the new reading (vol) whether is larger than last reading (t1). If new reading
(vol) is larger thanthe last reading (t1), the program proceeds to calculation and display actual values. If
new reading (vol) is smaller than the last reading (t1), the program goes back case: AAA.
Problem 4: there is short circuit caused during the wave measurement in oscilloscope. Theoscilloscope is not able to measure the waveform across transformer and input of voltage
follower.
Reason: in order to implement the wave measurement, there is current generated from
oscilloscope. Therefore, any floating point without ground is not the target of oscilloscope. One
of the two probes must connect to GND being reference point.
Solution: the floating point can be monitor in Multisim using oscilloscope. In practical, the
output waveform with common reference point GND can be measured in oscilloscope.
Figure 5.2 Program of AAA loop
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Problem 5: During measuring output of voltage follower in the current measurement, the results
change when the oscilloscope is attached. As shown below Figure 5.2, the current is not zero
when no lamps are on. It shows 1.22A from the current measurement which is not expected.
Reason: as mention in problem 4, the oscilloscope generates current to measure waveform.
Solution: there is no solution for this problem since the reason is from the characteristic of
oscilloscope.
Problem 6: The output voltage from current measurement is not accurate. With one lamp
working, the voltage is 2.1V and with two lamps working the voltage is 2.7 V. they are in the
relation of double values.
Reason: the capacitor adopted at first is 220uF which is small for discharging and charging.
Solution: the designer replaced 220uF with 470uF. The output voltage with two lamps is double
of the output voltage with one lamp.
Figure 5.3 Readings in current measurement with oscilloscope
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5.3 Validity of the project
The components of this project are common in the market. The important component in
Intelligent Power Meter is shunt resistor. If the design acquires large current measurement,
the shunt resistor must equip with the high power consumption rating and low resistance.
With low rating shunt resistor, the maximum current of Intelligent Power Meter is only 0.7A.
The power meter is able to measure current and voltage, perform calculation of power
consumption and electric bill. The amount of money is able to increment in each one hour.
Finally, after one month, PIC16F877A can reset.
5.4 Limitation of Intelligent Power Meter
The project is successfully achieved. But there are few limitations due to the hardware
and software.
1. The Intelligent Power Meter cannot work with high current above 0.7A in theory.2. The time counting for one hour and one month is not accurate on PIC16F877A3. The operational amplifier MCP6004 in voltage follower is easily damaged.
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Chapter 6
Conclusion
The process of introduction, designing, implement and constructing is obtained in the
previous chapter to achieve the project of Intelligent Power Meter. The innovation of
Intelligent Power Meter is the convenience of user. The intelligent part of this project is able
to calculate power consumption and electric bill so that the users will not lost the track of
how much the power consumption cost to them.
The current is represented by voltage using a shunt resistor. The voltage follower is to
change the output of shunt resistor with floating point to the voltage output of voltage
follower with reference point GND. Because PIC inputs can only be with reference point but
not floating point. The rectifier is to convert AC voltage into DC ripple voltage. Then, PIC
16F877A can be stable to calculate. The output of current measurement shows that it is
proportional to the current in the AC power line.
The voltage is stepped down by transformer and voltage divider in order to compatible
with op-amp MCP6004. The function of voltage follower and rectifier has the same
functionality with current measurement. As chapter 4 results shown, the voltage output is not
affected by adding more devices in AC power line.
In conclusion, this project, Intelligent Power Meter is successfully completed based on
the results. The aims and objectives are fully achieved.
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6.1 Technical specifications
No. Technical specification Status and Explanation
1 To construct a circuit which is able to
measure voltage and current
The shunt resistor, voltage follower and
rectifier are constructed in the current
measurement design. Status: achieved.
The transformer, voltage divider, voltage
follower and rectifier are constructed in
voltage measurement design. Status:
achieved.
2 The Intelligent Power Meter is able to
calculate power consumption and electric
bills
According to the output from voltage and
current measurement system, the
PIC16F877 reads the outputs of them and
calculate with the outputs.
The electric bill increments with Malaysia
tariff in every one hour. Status: achieved.
3 The Intelligent Power Meter is able to
display power consumption and electric
bills
The PIC control system consists of
PIC16F877A and LCD display module.
They are interface to display the power
consumption and electric bill according to
the output from measurement system.
Status: achieved.
4 Intelligent Power Meter can monthly reset This specification is achieved in
programming by adding a loop to check the
time is meeting one month. Status:achieved.
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6.2 Future Enhancement
The table as shown below is providing the future enhancement for others designer refers to.
No. Future enhancement Explanation
1 Design wireless transmission and
database.
In each month, the power meter is able to transmit the
data (power consumption and electric bills
) to the database so that it cuts down the cost of
workforce so that the whole system does not need
workers to go every users home to check the power
consumption.
2 Built more robust power meter Short circuit in home appliances is common. If the
robust power meter is designed, it prevents any
damage from short circuit.
Also in order to suit with high load home appliances
users, the shunt resistor must with high rating.
3 Improve the accuracy of power
meter
To meet the accuracy requirement, the designer can
apply current precise sensing amplifier instead of
voltage follower and rectifier. And shunt resistor with
low resistance must be considered in this case.
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References
Web address
1. Basic electronic conceptAvailable from: http://sci301.uvi.edu/Electrical/ElectricalConcepts.htmlLast accessed: 20th October 2010
2. HVAC solution from Texas InstrumentsAvailable from: http://focus.ti.com/docs/solution/folders/print/399.html
Last accessed: 20th October 2010
3. Washing machine: highend solutions from Texas InstrumentsAvailable from: http://focus.ti.com/docs/solution/folders/print/397.html
Last accessed: 20th October 2010
4. MCP6004 datasheetAvailable from: http://ww1.microchip.com/downloads/en/DeviceDoc/21733j.pdf
Last accessed: 7th January 2011
5. Figure1.1 Table of energy loss due to power meterAvailable from:
http://powerelectronics.com/power_management/motor_power_management/705PET23.
Last accessed: 7th January 2011
6. Figure 2.1: TransformerAvailable from: http://best-b2b.com/userimg/545/570-1/power-transformer-628.jpg
Last accessed: 7th January 2011
7. Figure 2.2 LM7805 regulatorAvailable from: http://www.fairchildsemi.com/ds/LM/LM7805.pdf
Last accessed: 7th January 2011
8. Figure 2.3 MICW04M bridge rectifierAvailable from:http://www.binbin.net/photos/dc-components/wo2/wo2-1.5a-200v-
bridge-rectifier-rc.jpg
Last accessed: 7th January 2011
http://www.binbin.net/photos/dc-components/wo2/wo2-1.5a-200v-bridge-rectifier-rc.jpghttp://www.binbin.net/photos/dc-components/wo2/wo2-1.5a-200v-bridge-rectifier-rc.jpghttp://www.binbin.net/photos/dc-components/wo2/wo2-1.5a-200v-bridge-rectifier-rc.jpghttp://www.binbin.net/photos/dc-components/wo2/wo2-1.5a-200v-bridge-rectifier-rc.jpg8/13/2019 Power Meter design
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9. Figure 2.4 the operation of bridge rectifierAvailable from:
http://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/substation_equipm
ent/rectifiers.html
Last accessed: 7th January 2011
10.Figure 2.6 5W 10 shunt resistorAvailable from:
http://www.quickerbuy.com/assets/photo/avatar/51486/big__brtyucwbmk___kgrhqmh-
ceeunsbq1q_blzi6srnn____35.jpg
Last accessed: 7th January 2011
11.Figure 2.7 High current rating and low resistance shunt resistorAvailable from: http://www.rc-electronics-usa.com/current-shunt.html
Last accessed: 7th January 2011
12.Figure 2.8 MCP6004 OP-AMPAvailable from:http://ww1.microchip.com/downloads/en/DeviceDoc/21733j.pdf
Last accessed: 7th January 2011
13.Figure 2.9 PIC16F877AAvailable from:http://ww1.microchip.com/downloads/en/devicedoc/39582b.pdf
Last accessed: 7th January 2011
14.Figure 2.10 416 characters LCD ModuleAvailable from:
http://www.egochina.net.cn/eshop/ebay/Character/JHD762/P1090306.jpg)
Last accessed: 7th January 2011
15.MikroC PRO for PICAvailable from: http://www.mikroe.com/eng/products/view/7/mikroc-pro-for-pic/
Last accessed: 23rd January 2011
16.Figure 2.11 Electromechanical meterAvailable from:
http://img.diytrade.com/cdimg/214476/1494287/0/1218724437/Single_Phase_Long_Life
_Round_Power_Meter.jpg)
Last accessed: 23rd January 2011
http://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/substation_equipment/rectifiers.htmlhttp://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/substation_equipment/rectifiers.htmlhttp://www.quickerbuy.com/assets/photo/avatar/51486/big__brtyucwbmk___kgrhqmh-ceeunsbq1q_blzi6srnn____35.jpghttp://www.quickerbuy.com/assets/photo/avatar/51486/big__brtyucwbmk___kgrhqmh-ceeunsbq1q_blzi6srnn____35.jpghttp://ww1.microchip.com/downloads/en/DeviceDoc/21733j.pdfhttp://ww1.microchip.com/downloads/en/devicedoc/39582b.pdfhttp://www.egochina.net.cn/eshop/ebay/Character/JHD762/P1090306.jpghttp://img.diytrade.com/cdimg/214476/1494287/0/1218724437/Single_Phase_Long_Life_Round_Power_Meter.jpghttp://img.diytrade.com/cdimg/214476/1494287/0/1218724437/Single_Phase_Long_Life_Round_Power_Meter.jpghttp://img.diytrade.com/cdimg/214476/1494287/0/1218724437/Single_Phase_Long_Life_Round_Power_Meter.jpghttp://img.diytrade.com/cdimg/214476/1494287/0/1218724437/Single_Phase_Long_Life_Round_Power_Meter.jpghttp://www.egochina.net.cn/eshop/ebay/Character/JHD762/P1090306.jpghttp://ww1.microchip.com/downloads/en/devicedoc/39582b.pdfhttp://ww1.microchip.com/downloads/en/DeviceDoc/21733j.pdfhttp://www.quickerbuy.com/assets/photo/avatar/51486/big__brtyucwbmk___kgrhqmh-ceeunsbq1q_blzi6srnn____35.jpghttp://www.quickerbuy.com/assets/photo/avatar/51486/big__brtyucwbmk___kgrhqmh-ceeunsbq1q_blzi6srnn____35.jpghttp://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/substation_equipment/rectifiers.htmlhttp://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/substation_equipment/rectifiers.html8/13/2019 Power Meter design
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17.Figure 3.4 Voltage follower (unity gain differential amplifier)Available from: http://www.electronics-tutorials.ws/opamp/opamp_5.html
Last accessed: 23rd January 2011
18.Figure 3.5 Voltage dividerAvailable fromhttp://www.ehobbycorner.com/pages/tut_resistors.html
Last accessed: 23rd January 2011
19.Tariff RatesAvailable from: http://www.tnb.com.my/tnb/residential/pricing-and-tariff/tariff-rates.html
Last Accessed: 2nd February
http://www.ehobbycorner.com/pages/tut_resistors.htmlhttp://www.ehobbycorner.com/pages/tut_resistors.html8/13/2019 Power Meter design
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APPENDICES
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Appendix A: Gantt chart
The Gantt chart shows as below Table 2
Table 2. Gantt chart
Projected
Actual
Task3 4 5 6 7 8 9 1
011
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Brainstorming
and planning
Research and
information
collection
First meeting
withsupervisor
Marketsearching forcomponents
Circuit Design
Developingsubsystemcircuit
Programming
Testing and
troubleshooting
Integratingsubsystems
Calibration
Project ReportWriting
Week
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Appendix B: Schematic diagram
1. Measurement system and power supply system
2. PIC control system
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Appendix C: PCB layout
1. Measurement system and power supply system
2. PIC control system
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Appendix D: Software
sbit LCD_RS at RB4_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB0_bit;sbit LCD_D5 at RB1_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB3_bit;
sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;
unsigned char ch;
unsigned long u,i,power,m;
unsigned int vol,t1=0,cur,t2,a,b=0,c1 = 0;
void main()
{
TRISA=0x03; //portA RA0 RA1 RA2 are inputs
PORTA=0x00;
PORTB=0x00; //portB is ouput
TRISB=0x00;
INTCON = 0;
Lcd_Init(); //initial LCD connected to PORTB
LCD_Cmd(_LCD_CLEAR); //clear display
LCD_Cmd(_LCD_CURSOR_OFF); //turn cursor off
while(1){
AAA:
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// VOLTAGE
vol=ADC_read(1); // get voltage output of voltage measurement system from ADC
channel 1
if(vol>=t1){
t1=vol;
u=(long)t1*5/1023; // covert adc resolution to voltage
u=u*(42957)/100; //calculate actual voltage
ch=u/10000 ; // extract 100.00V digit
if (ch==0)
{
LCD_Chr(2,2, 32); // write empty space if digit is 0
}else
{
LCD_Chr(2,2,48+ch); // write ASCii + CH at 2nd row, 2nd column
}
ch=(u/1000)%10; // extract 10.00 V
LCD_Chr_CP(48+ch);
ch=(u/100) %10; // extract 01.00 V
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor pointLCD_Chr_CP('.'); // write '.' at cursor point
ch=(u/10) %10; // extract 00.10 V digit
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
ch=u %10; // extract 00.01 U digit
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
LCD_Chr_CP('V'); // write 'V' at cursor point
LCD_Chr_CP(32);
LCD_Chr_CP(32);
LCD_Chr_CP(32);
LCD_Chr_CP('P');
LCD_Chr_CP('D');
LCD_Chr_CP('o');
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LCD_Chr_CP('g');
}
else if (vol=t2){
t2=cur;
i=(long)t2*5/1023; //covert adc resolution to voltage
i=i*100/107 ; //calclate actual current
ch=i/10000 ; // extract 100.00A digit
if (ch==0)
{
LCD_Chr(1,2, 32); // write empty space if digit is 0
}
else
{
LCD_Chr(1,2,48+ch); // write ASCii + CH at 1st row, 2nd column
}
ch=(i/1000)%10; // extract 10.00 A digit
LCD_Chr_CP(48+ch); // write ASCii + CH at 1st row, 2nd column
ch=(i/100) %10; // extract 01.00 A digit
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
LCD_Chr_CP('.'); // write '.' at cursor point
ch=(i/10) %10; // extract 00.10 A digit
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
ch=i %10; // extract 00.01 A digit
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
LCD_Chr_CP('A'); // write 'A' at cursor point
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LCD_Chr_CP(32);
LCD_Chr_CP(32);
LCD_Chr_CP('W');
LCD_Chr_CP('a');
LCD_Chr_CP('t');
LCD_Chr_CP('t');
LCD_Chr_CP('s');
LCD_Chr_CP('U');
LCD_Chr_CP('P');
}
else if (Cur
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LCD_Chr_CP('W'); // write 'W' at cursor point
//MONEY
if( c1 < 9){ //check whether it reaches 10 second
a=power*218/(1000*1000);
m=a+b;
ch=m/1000000 ;
if (ch==0)
{
LCD_Chr(4,2, 32); // write empty space if digit is 0
}
else
{
LCD_Chr(4,2,48+ch); // write ASCii + CH at 4st row, 2nd column}
ch=(m/100000)%10; // extract 10.00 RM
LCD_Chr_CP(48+ch); // write ASCii + CH at 4st row, 2nd column
ch=(m/10000) %10; // extract 01.00 RM
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
ch=(m/1000) %10; // extract 00.10 RMLCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
LCD_Chr_CP('.'); // write '.' at cursor point
ch=(m/100) %10; // extract 01.00 RM
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
ch=(m/10) %10; // extract 00.10 RM
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
ch=m %10;
// extract 00.01 RM
LCD_Chr_CP(48+ch); // write ASCii + CH at cursor point
LCD_Chr_CP('R'); // write 'R' at cursor point
LCD_Chr_CP('m'); // write 'M' at cursor point
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c1 = c1 + 1;
b=m;
delay_ms(1000);}
else if( c1 >= 9){ // if it reaches 10 second reset all parameters
u = 0;
i =0;
power=0;
m=0;
b=0;
a=0;
vol=0;
ch=0;
c1=0;t1=0;
cur=0;
t2=0;
}
goto AAA;
}
}
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Appendix E: List of Components
The components list is shown as below table 3:
Components Price per unit (RM) Units(s) Price (RM)
Terminal block 1.00 10 10.00
Voltage Regulator 1.00 1 1.00
Tact switch 0.40 1 0.40
Diode 0.10 4 0.40
Capacitors 0.50 3 1.50
Rectifier 1.00 2 2.00
Transformer 6.00 2 12.00
16x4 LCD display 36.00 1 19.00
PIC16F877A 17.50 1 17.50
8M Crystal oscillator 1.50 1 1.50
Op amp MCP6004 6.00 2 12.00
IC Socket 0.5 2 1.00
PCB Optic Fibre boards 33.00 1 33.00
Connectors (jumper wire) 0.1 100 10.00
Lamps 2.00 5 10,00
Single phase wire 2.00 5 10.00
Plug 1.00 2 2.00
Power plug extension 10.00 1 10.00
Grand total RM153.3