syazana meter report

8/7/2019 Syazana Meter Report

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DESIGN AND MODELLING OF INTELLIGENT ENERGY METER

Abstract: Common electricity meters, whichare currently used in houses, shops and some

factories are bulky expensive and inaccurate. Such

features are incompatible with modern technological

trends of miniaturization accuracy and neat devices.This project presents the design and the model of

intelligent energy meter to overcome the

shortcomings of the present meter. It is anticipatedthat a new neat design based on integrated circuit

technology employing digital measurement technique

will have a great impact on electricity meters locally

and worldwide. With a data storage capability and

some form of processing, it can provide theconsumers with vital information on the trend of their

energy consumption. Such information will assist

them in rationalizing their consumption. Intelligent

energy meters may be seen as most suitable and

efficient way to facilitate easy solutions to theproblem of rational consumption.

1.0 IntroductionEnergy meter or Watt-hour meter is a common

sight that can be seen whether in residential,

commercial or industrial area. Ranging from

electromechanical Ferraris counters (which have

rotating disk) to fully electronic meters, the energy

meters keep evolving at spectacular pace. Thefunction of energy meter is to measure the electrical

energy supplied to or energy consumption of the

residential, businesses or machines. Energy metersare evolving at an accelerated pace fromelectromechanical Ferraris counters to fully

electronic meters. Electronic meters enable

automated meter reading (AMR) and a host of other

features, including increased measurement accuracy

and measurement of previously unattainable

parameters like power factor [1]. Thus, it shows how

energy meter is evolving and becomes one of the

most important tools in our lives.

For energy meter, the most common type is a

kilowatt hour meter which it calculates the energy

consumption in 1 hour duration. In electricity

retailing, invoice can be generated by using thismeter to record the measured electricity valuesconsumptions. They can also record other variables

such as the amount of time when the electricity is

used.

Currently, there are various types of energy

meter in the market. Energy meter such as

electromechanical meter and solid state meter is the

widely used in both the residential and industrial

area. Their different is in the architecture design.

However, even with the various type of energy meter,

its basic function is still the same that is to measure

energy consumption

2.0 Literature ReviewThere are several journal related with this

topic- Design and modeling of low cost Intelligent

energy meter. In this section, we will discuss some of

the journal that we use as a reference for this project.

There are two types of energy meter that can be used,

either a single phase or three phase energy meter. Fora single phase energy meter, we refer to a journal

presented during Technology Conference, in May

1998 title A single phase microcontroller basedenergy meter[2]. In this paper, it discuss on the

implementation of single phase electrical energy

meter based on a microcontroller from Microchip

Technology, as an alternative to the conventionalelectromechanical meters. This paper is divided into

several sections. The first and second sections of this

paper discuss about the introduction and the basic

calculation used in this paper. The basic equation of

electrical energy computation used is as follow:

E

(1)

Where the v(t) = supply voltage and i(t) = load

current.

For the third part of the paper, it discussed

the general overview of microcontroller energy meter

and also the detail of each component used inside theenergy meter. In the circuit design, an 8 bits A/Dconverter (ADC0831) is used to convert the signal to

a digital form whereby the voltage and current is

transferred serially to the microcontroller. A noninverting, unity gain differential op-amp is also used

in designing the circuit to prevent noise problems.

PIC16C84 is used in the circuit since it can utilize

CMOS technology and having RISC type

architecture. It also consists of EEPROM memory

that stores the measured energy value even in the

presence of a power outage.

The second journal that we used as a

reference is Digital Part of Digital ElectricityMeter[3], by Ing. Rastislav Michlek, et. al. In this

journal, it discuss on digital three-phaseregistration/calibration electricity meter. The first

part of the journal discusses in brief the introductionof digital electricity meter based on several methods

such as Hall effects, pulse-width modulation and

several others. Here, it emphasize on the accuracy

since accuracy plays an important role in electricity

meter. The accuracy here depends on the accuracy of


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analogue input circuits, the accuracy of A/D

conversion and the accuracy of digital calculations.

The second part of the journal discuss on the

description of the electricity meter. The proposed

block diagram for this journal is as below:

Fig. 2.14: Block diagram of the designated energy

meter

This block diagram is used to measure all

basic three-phase net parameters including rms

values of voltages and currents, active, reactive and

apparent power, power factor, net frequency, andenergy delivered into the load.

The third part of the journal discuss on the

error correction in the electricity meter. To makes itpossible to average the samples with good accuracy

even during one period of net frequency, the

sampling frequency chosen is 50 kHz. As for the lastpart of the journal, it discuss on the error of rms value

measurement without frequency synchronization. The

formula used in this journal to measure the error of

measurement is

(2)In which:

N = number of sample;

(3)

And

(4)

Last but not least, since we include the SMSmonitoring system application, we used the journal

presented during the 1st International Conference of

The IET Brunei Darussalam Network, in May 2008,title Automatic Power Meter Reading and

Distribution Control Using ICT and GSM Networks[4]. In this paper, it explained about the

development of GSM Power Meter Reading and

Distribution Control. The GSM Power Meter is the

integration of a single phase Class 1, IEC61036

standard compliance digital kWh power meter, Power

to Communication (P2C) interface system and a

GSM modem which utilize the GSM network to send

the power usage reading back to the energy provider

wirelessly.

This paper consists of 4 parts. For the first

part of this paper, it gives an overview of Global

System for Mobile Communication (GSM), thehistorical background, and how it can be used as a

source for sending information from one source toanother. Nevertheless, it also shows the advantages of

using GSM system over several other system such as

Power Line Control (PLC), Bluetooth, and ZigBee.The GSM Power Meter Reading and Distribution

Control (GPMDC) System presented in this paper

takes advantage of the available GSM infrastructure

nationwide coverage in the country and the Short

Messaging System (SMS) cell broadcasting feature to

request and retrieve individual houses and building

power consumption meter reading back to the energy provider wirelessly. The store and forwarding

features of SMS allow reliable meter reading delivery

when GSM signal is affected by poor weather

condition. The stored SMS is archived in the mobileoperator and can be later retrieve for billing

verification purpose.

The second part of this paper shows the

overview of GPMDC system. The complete system ismade up of multiple GSM power meters installed in

the city, SMS gateway, Application Terminal,

Database Server, Email Server, Printer and Web

server. The GSM power meter is working in

conjunction with the GSM network to retrieve powermeter reading. The GSM power meter is a single

phase digital kWh power meter which utilizes the

GSM network to send the power usage reading back

to the energy provider wirelessly upon request fromthe energy provider SMS gateway. The GSM Power

Meter is the integration of a single phase Class 1,

IEC61036 standard compliance digital kWh powermeter and a GSM modem. A SIM card with a unique

special service number is require for the GSM power

meter to receive and to reply its meter reading to the

energy provider using SMS.

As for the third part of the paper, it discuss

on the design of GSM Power Meter. The basic blockdiagram for the GSM Power Meter should look like

this:


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Fig. 2.15: Block Diagram of GSM Power Meter with

Distribution Control.

The digital power meter is used to measure

the power consumption drawn from the energy

provider substation to the consumer in kWh unit. The

GSM modem used a RS232 serial communication

protocol and AT command to communicate to the

power meter. During normal operation the P2C

interface board synchronizes the impulse count and

wait for any SMS request from either the energy

provider or the consumer. Once a request SMS isreceive from the GSM modem, the P2C interface

board retrieve the last meter reading from theEEPROM memory. After obtaining the meter reading

it compose the meter reading in standard short

message format and reply back to the sender or

energy provider. Figure below shows the meter

reading by the consumer using mobile phone SMS.

Fig. 2.16: SMS Meter Reading using Mobile Phone

The last section of this paper discuss on the

demonstration of the completed system. Overall,

these three journals have been used as our mainreference in completing our project. Several other

journals have also been reviewed for the completion

of this project

3.0 Methodology

3.1 Introduction

The theoretical study that we have done

about the energy meter leads us to conclude that

electronic microcontroller based intelligent meter is

much more reliable and low cost compared to other

types of meter such as electromechanical ones.

The power meter which is going to be

produced consists of several properties which are:

1. Measure AC power instantaneously and average(around 03500 W).

2. Measure AC energy consumption in kilowatt-hours.

3. provide digital readout of power or energy4. Easy to hook up by plugging it into the main and

plug the appliance into output socket

5. Consist of low-cost parts.6. Integrated with SMS monitoring system3.2 Basic design of Intelligent Energy Meter

The component of energy meter can be

explained further after understanding the basic

concept. The electrical energy meter is just another

branch of modern technology. As one of the majortechnology that has high potentials in future daily

application it is important to actually understand how

the energy system works. Basically, a normal block

diagram of an energy meter will consists of a voltage

and current sensor, an A/D convertor, microcontroller, a display screen and also a clock. Figure

3.1 below shows the basic block diagram of energy

meter. In addition, the function of SMS monitoring

system is also included.

Figure 3.1: The block diagram of Intelligent Energy

Meter

3.2.1 System Design for Energy Meter Block

The proposed design of the energy meter is

based on the Silicon Chip energy meter. The power

source of the meter circuit can be from main powersupply or 9-V back-up battery. In addition, the

energy meter will include 4 switches. These switches

function are:

1. To set the display modes.2. To reset the values3. To set the calibration value (up and down

button)


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The energy meter will also include brownout

protection. Brownout means when the voltage value

is too low due to supply fault, it can damage

appliances. When operating, the meter can cut offpower to an appliance during a brownout and return it

after that.

3.2.2 Measurement3.2.2.1 Power Measurement

The Energy Meter will measure the true power drawn by the load. In a DC (direct current)

system, the power can be determined by:

P = IV (5)

Where I is the current through load and V is the

applied voltage.

In AC (alternating current) we will consider

the instantaneous current and instantaneous voltage

and multiply them. Generally, in AC system, for the

current and voltage waveforms which are both sine

waves and are in phase with each other, the

instantaneous power is above zero and positive value.This is because we multiply positive value I and V,

which will produce positive value. It is also the samewhen we multiply negative value I and V, we will get

positive result. From figure 3.1, the dotted line

represents average (or real) power. By filtering the

signal and obtaining the DC component we will get

the average power value.

Fig 3.1 Instantaneous voltage (V) and instantaneous

current (I) and average power of AC supply

3.2.2.2 Lagging CurrentFor the in phase current and voltage, we

would not face a lot of problem since the voltage can

be multiplied directly with the current to produce thepower measurement. It usually happens with purely

resistive material. However, for inductive and

capacitive type of load, the phase might be different.

For inductive load, the current will lag the voltage

and for the capacitive load, the current will lead the

voltage. The only way to have a correct

measurement of power is by considering the power

factor which is the cosine of phase angle between the

current and voltage.

(6)Where I is the current, V is the voltage and

is the phase between the current and voltage. If thecurrent is lagging in 45 we must consider =0.707 as the power factor to calculate the power.

3.2.3 IC ADE7756ANIC ADE7756AN is used in Silicon Chip

energy meter. It is an IC from Analog Device (also

called as Active Energy Metering IC). The figure 3.2will show the main connection and main internal

block for ADE7756AN and how it is connected to

make current and voltage measurement.

Fig3.2 Internal block of ADE7756AN (for main

block only)

3.2.3.1 Current and voltage measurement

From Fig 3.2, there are two inputs channelswhich are used to monitor voltage and current. The

first input, Amplifier 1 (Amp1) will monitor the load

current by monitoring the voltage resulted from

0.01 (R1) which will be passing the load current.

The resistor has maximum dissipation of 10A or 1W

and gives 30 temperatures. Thus, a low-temperature

coefficient resistor is used to minimize resistance

change as temperature rises.

The gain for Amp1 can be set to 1, 2, 4, 8 or

16 and for full-scale output is 1, 0.5 or 0.25V. It canbe set by using serial communication lines by writing

to appropriate registers within the IC. For the proposed circuit, we will set the gain to 1 and thefull-scale output at 250mV.This is because it will suit

the 100mV RMS (141.4mV) that develop through R1when 10A current is passing through the load.

For Amp2, it is the same as Amp1 with an

exception where the full-scale output voltage is set to

1V and the gain to 4. The Active input from the main

is divided using 2.2M and 1k. The divided output

is 100mV RMS (141mV peak) for 220V input which

later fed to Amp2. Thus, the signal output will be


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400mV RMS (564mV peak) which is within the 1V

full-scale output capability.

3.2.3.2 Analog to Digital converter

From the amplifiers, the output signal will

be converted to digital using analog-to-digital

converter ADC1 and ADC2 (internal). The samplingrate is 894 kHz with 20 bit resolution. In addition, ananalog low pass filter (LPF) is inserted in front of

ADC to prevent error conversion if there is high

frequency signal pass into the ADC. The outputs of

both ADC then digitally filtered with LPF filter to

remove noise. It will affect the rolls of frequency

above 2 kHz. (40Hz 1 kHz will remain).

After that, the ADC1 will be applied to

multiplier. Here, the digital value fed into it will be

altered according to gain adjust value (applied to

multiplier second input). Next, the high pass filter

(HPF) is used to process the adjusted signal and

remove any DC offset in digital value. The outputwill be applied to multiplier 2.

3.2.3.4 Voltage Sag detectionsWhen the voltage is below the user define

value in ADE7756 for a certain period of time, it will

interrupt the microcontroller (PIC16F628A). It will

later take necessary action just like the proposed

circuit. In ADC2 inside ADE7756, it includes LPF to

roll off frequencies above 156Hz. It then will be fed

to SAG detection circuit where it will monitor the

voltage level and output to determine whether it will

drop below SAG register value.

3.2.3.5 Phase adjusterFor the active power to be calculated

correctly especially when the current and voltage is

out of phase, we use phase adjuster. The signal fromADC1 will be adjusted to be inphase with ADC2.

From the figure 3.2, the signal from ADC2 will also

be fed to phase compensation adjuster circuit (Phase

adjust). It is used to change signal phase relative to

ADC1. This output would also be connected to

multiplier 2.

3.2.3.6 Active power signalADE7756 will calculate the active oraverage power by, multiplying the instantaneous load

current and voltage that have been sampled. Thus, the

current and voltage value would be multiplied to

produce instantaneous power value. The

instantaneous power is

(7)

Where i(t) is the instantaneous current and v(t) is the

instantaneous voltage.

After that, it will be filtered to get the steady

value. The derived power value is then mixed to

Offset Comparator (with offset adjustment) to givezero reading when no current flowing to R1. The

output will be saved (stored) in waveform registerand will be continuously added to Active energy

register at 894 kHz rate. At the end, the data can be

read through microcontroller by Serial Data interface.

3.2.3.7 Energy CalculationAfter getting the active power output,

ADE7756 will fed it to energy calculation block.

Energy will be calculated as continuous sum of

product between time sampled and the output of

active power.

P =

(8)

Where T is the sample time period, n is the numberof sample and N is the total number of sample taken.For ADE7756, the sampled time is 1.4 s and the

product value will be inserted into 40 bit signed

active energy register. The length of the register will

maintain at least 10s worth of data before overflow.

Thus, PIC16F628A must have at least read the

energy data once for every 10s.

3.2.4 Hardware DesignFig 3.3 shows the proposed circuit design.

Other than ADE7756AN chip (IC1), there is another

microcontroller, PIC16F628A (IC2). The function ofIC2 is to process the data from IC1 and display it to

LCD module.

Fig3.3: The full circuit design of energy meter.

(Larger scale image will be attach in the appendix)

IC1 will be operating at 3.58MHz as set by

crystal X1 and would be used as ADC sampling

rates. This device will be supplied by +5 supply rail.


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However, the inputs at pins 4, 5, 6 and 7 can go down

below the 0V level.

When operating, the current and voltage

waveform would be sampled and applied to the

balanced inputs of internal amplifiers which are V1+and V1- for Amp1 (current) and V2+ and V2- for

Amp2(voltage). Balance input is used so that anycommon mode (noise) signals can be cancelled out at

the input.

Nevertheless, to archive this balance input,

both input amplifiers need to have the same input

impedance and signal path. For current signal, the

inputs are connected to 0.01 and 1k resistor. The

R1 (rated as 3W) would carry the load current whileR2 will simply consist of a short length fine-gauge

copper wire. R2 is necessary to mimic (cancel out)

the noise pick up by R1. For voltage monitoring

inputs, the Amp2 would be connected to a 2.2Mand 1k voltage divider. Both of these resistors

would also be connected across the Active and

Neutral lines.

In addition, all the inputs would be filtered

to remove high frequency hash above 4.8 kHz by

connecting it to 33nF capacitor to ground (from pins

4, 5, 6 & 7). All of the circuit would be referenced to

the mains neutral with 0V rail (including IC1 and

IC2). Still, the circuit should be treated as live and

dangerous since it is connected to main power

supply.

Parallel connected 100F and 100nF

capacitors are used for filtering at reference voltage(pin9) of C1. It is because the voltage reference

would be stabilized for ADCs. The reference voltagetypically would be 2.4V. The SAG output (pin 13)

would be held by 1k pull-up resistor. It will hold

MOSFET Q1 on and thus RLY1 will also be on. In

addition, the SAG output from IC1 will drive RA1 of

IC2 (pin 18) which in turn will instruct the IC2 to

send SAG indication data to LCD display when

brownout occurs. It also provides optional delayed

turn-on feature via RB0 and LK2. When SAG output

is low, RB0 will immediately becomes low and turn

off Q1. When brownout ends, RB0 remains low andgoes high again after 18-20 minutes delay. It willswitch on Q1 and RLY1 and restore power toappliance. The relay contact will break the power to

the load by opening Active connection. However, therelay is energized when there is no brownout and the

supply will be connected to the load.

3.3 Microcontroller PIC16F829A and LCD

module

IC1 1 and IC2 (PIC16F628A) connected via

serial interface and labeled as Data In, Data Out,

Serial Clock and Chip Select (pin 20, 19, 18 and 17).

When operating, IC2 uses the lines to program the

register in IC1 and to retrieve the monitored data. IC2

will also drive LCD module (using RB7-RB4) which

will be connected to switch 4 (direct) and switch S1-S3 via diode D3-D5. The purpose of the diode is to

prevent the data lines from being short when morethan one switch is pressed at the same time. Other

than that, IC2 can determine when a switch is being

pressed by first setting RB4 data line to high and

check the RB3 input which connects to common side

of switches. RB3 will be held low (using 10k

resistor to ground if none of the switch is closed

(pressed). In contrast it will be held high when a

switch is closed. After that, the microcontroller IC2

will set all the data lines low again and then set each

data line high add later low again in sequence tosearch for the closed switch. The pressed switch will

produce high at RB3.

RA2 and RA0 of IC2 outputs (pins 1 & 17)

will be responsible for the LCD module by

controlling the register select (RS) and enable (EN- bar) inputs and to make sure the data displayed is

correct. The LCDs contrast can also be adjusted

using VR1 setting by varying the voltage applied to

pin 3.

3.4 Power Supply

The power source that will drive this circuit is

derived from two sources. The first one is from the

main power supply through transformer (T1). It

secondary output is rectified by BR1 and filtered byusing 1000 F. It later fed through rectifier diode D1,

filtered by a 100 F capacitor and fed through 3-terminal regulator REG1. REG 1 will provide +5V

supply to IC1, IC2 and LCD module.

The second source is from 9V backup battery. It

will be connected to diode D2 and fed throughREG1. The purpose of this back up supply is to make

sure the circuit can still operate even if the main

supply is cut off due to blackout. It can also maintain

the active register value for a long time and allow

timer to continue counting.

3.5 Intelligent energy MeterIntelligent meter is an advance type of meter. It

can calculate more details the energy consumptioncompare to conventional meter reading. Optionally, itcan include the capability of communicating that

information through the network to utility center for

billing and monitoring purposes.

3.5.1 BillingThe energy meter constructed will be able to

calculate the energy consume by the appliances and


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display it in the LCD display. In addition, the display

will also include the total cost for measured

appliance. It eliminates the need of manual readings

to calculate the billing in mechanical meter. For theenergy meter, we use the rate given by TNB to

calculate the total cost just like in the table 1 below.

Table 1: The tariff rates for domesticconsumer by Tenaga Nasional Berhad

To calculate the billing,

Cost= energy consume the rate (15)

The cost will be compute by the microcontroller and

will be show on the LCD display.

Figure 3.4: The rate is shown by the LCD display

3.5.2 Mobile Phone SMS Monitoring SystemAs mention previously, the intelligent

energy meter can be optionally linked to the local

utility center via the network. For this project, we

tried to improve the energy meter by linked it to the

GSM network and test it through the SMS receiver

(GSM phone). The technique used is reading the

electricity meter readings from remote server using

the existing GSM network for cellular phone

automatically. To save the cost, we decided to useGSM phone Nokia 3310 to do the remote monitoring

system. It is low cost, easy to use and a relatively safemedia, with sufficient message dimension and

rhythms of transaction for the normal functions in

residential domestics; it may also assure late

deliverance in case of momentary communicationbreaks.

3.4.3System design

Mobile phone Nokia 3310 is used as the

dedicated device to perform the communication

tasks. The interpretation and elaboration of messageswill be done by the microcontroller. The

microcontroller will manage the information between

the 3310 phone and the microcontroller. (namely the

detection of arrival messages, the delivery of other

messages, the removal of read messages, etc.). In

short, the model of the SMS monitoring system will

be as figure below

When there is change in the inputs, a

protocol byte sequence will be transmitted throughthe serial port of the fixed mobile phone. The phone

then will correspond to the command and send an

SMS to a specific number of mobile phone (customer phone). The customer than can receive update

regarding it appliances energy consumption and the

total cost of the appliances.

3.5.3 FBUS Protocol and commandsTo establish the connection between mobile

and SMS Center (SMSC) a communication protocol

the F-Bus protocol, from the manufacturer NOKIA is

use (NOKIA 3310 use FBUS protocol.) The F-Bus isbi-directional serial type bus running at 115,200bps,8 data bits. The serial cable contains electronics for

level conversion and therefore requires power. The

first thing to do is supply power to the cable

electronics and this is done by setting the DTR (DataTerminal Ready) pin and clearing the RTS (Request

to Send) pin.

The easy way to achieve this is by using a

MAX232 or similar transceiver for the RS232 TXand RX pins and then connecting the DTR pin on the

serial cable to the V+ pin on the Max232. The same

is done for the RTS, however by connecting it to the

V- pin on the Max232. The V+ and V- pins arederived from internal charge pumps that double theinput voltage. ie. for a 5V Max232, the V+ will +10V

and the V- will be -10V.

The next step is to synchronize the UART in

the phone with microcontroller. This is done by

sending a string of 0x55 or 'U' 128 times. After that,

the bus is now ready to be used for sending frames.

3.5.4 Hardware CircuitThe Nokia 3310 has F/M Bus connection

under the battery holder. It requires a special cable to

make the connection. The left picture above shows

the 4 gold pads used for the F and M Bus. The right

picture shows the F-Bus cable connected to Nokia3310.


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Fig 3.6: The pins and connection for Nokia3310 to the serial cable

Fig 3.7: The DAU-9P cable for Nokia 3310

The serial cable from the NOKIA 3310 will beconnected to the level converter MAX232. The

phone runs on 3V but the PIC16F628A runs on

5V.So to avoid the phone from being damaged, the

5V on microcontroller Tx side need to be converted

to the corresponding phone Rx side. The total circuit

diagram for SMS monitoring system is as Fig 3.8

Fig 3.8: The circuit diagram for connecting

NOKIA 3310 to PIC16f628A

Fig 3.9: connecting the phone with the

energy meter

Figure 3.10: The complete circuit for theenergy meter with NOKIA 3310

Fig 3.11: the complete circuit

All in all, the communication between

NOKIA 3310 with PIC16F628A is established

through:

y PIC16F628A sends a command packagey NOKIA 3310 sends an acknowledge

package

y NOKIA 3310 sends reply package reportingsuccessfully delivery

y PIC16F628A sends acknowledgementcommands

The FBUS protocol uses signal with asynchronous

serial full-duplex data transmission, organized inoctets. The baud rate is 115,2 kbit/s, using 8 data bits,

1 stop bit and no parity bit. This signal will be send to

the phone through the FBUS cable.

4.0 Result

4.1 Power Supply for Energy Meter

Fig. 4.1: Circuit diagram for power supply

PIC16F628A


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For economical reason, we tapped the power

supply from ant transformer input. The 220V input

voltage will be stepped down to 12.6V using

220/12.6V transformer. Sadly, the 220V waveformcould not be captured and prove since the

oscilloscope in the laboratory is not suitable for220V. Beside for safety reason, we are advised not to

touch any part which directly connected to the main

supply. As for the 12.6 V AC output, the desired

graph is shown below:

Fig. 4.2: Graph for 12.6V AC output

As the voltage passes through the capacitor

1000uf, the voltage will be rectified and converted to

DC. At this point, the voltage increased to 17V. This

can be proved by measuring the voltage at the test

point using the oscilloscope.

Fig 4.3: The wave form after being rectified and

filtered

The function of the Regulator LM 2940 CT

here is to lower the voltage power from 17 V to only

5V. From this, 5V will then be used as the power

supply for the IC1 (ADE 7756). The measurement of5V can be proved by measuring the voltage between

the 100uF 16V using a multimeter and

oscilloscope.(Fig 4.10)

Fig 4.4: the supply voltage for the energy meter

4.2Voltage and Current measurement

After observing the power supply for the

energy meter, we then try to observe the signal from

the load. This signal is the one which is going to be

measured and computed. In this energy meter,voltage divider circuit is used as voltage sensing

circuit while high side current sensing method is usedfor current sensing. The sampled voltage will take the

waveform and values as displayed from the

oscilloscope.

Figure 4.5: The top trace shows the sampled voltage

at pin 7 (IC1) and the lower trace shows the currentwaveform at pin 4 of IC1

At pin 7 the voltage of the load is sampled

using 2.2M and 1k resistive divider. In this case

the load we use is 220V with 4.3A. By calculation,

The voltage division:

= 2200

Thus the voltage sampled:

But from the oscilloscope, the reading we

got is 94.4mV RMS. The difference between thereadings might be due to the resistor tolerance. Thus,

the reading receive will have a small differencewhich resulted in error. As for the current, it is

sampled by the 0.01

From oscilloscope the reading we got is 43.45mA

which quite accurate.

4.3 Calculated errors vs. Actual errors

The readings were taken for resistive loads. Multi-

meters measured the current on the line and thevoltage. The multiplication of these values was

computed, which was the real power. This value was

compared to the power being displayed by the meter

and the signal conditioning circuit was tuned to give

accurate results. The summary of the measured

values are given in the table 2 below. The time taken

to measured all the appliances, t = 1 hours


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Table 2: The energy measurement using multimeter, theoretical and the constructed meter

4.4 Accuracy

Accuracy is defined as the limits of the permissible

percentage error. Where the percentage error is

defined as:

Percentage Error =

x 100 (16)In short the accuracy of the energy meter can be

calculated using the equation and can be summarized

in the table 3.

Table 3: the percentage errors between the

constructed meter and the multimeter and also the

theoretical calculation

APPLIANCES Percentage error

%

(with multimeter)

Percentage error

%

(with theoretical)

1. Power Supply 3.14 4.31

2. Radio 5.45 3.33

3. Hand phoneCharger (Sony

Ericsson)

0.45 0.83

4. Laptop 0.47 0.46

From the table, we can see that thepercentage error of the meter is between 0.4 to 5%.

When we are comparing between the energy meter

and multimeter, the percentage error is 3.14% for the

power supply, 5.45% for the radio, followed by

0.45% for the hand phone charger and 0.47% for thelaptop. As the error between the energy meter and

theoretical value, for power supply, the percentage

error is 4.31%, while for the radio is 3.33% and thehandphone charger is 0.83%. Lastly, the percentage

error for the laptop is 0.46%. From the datasheet

given by Analog Devices, the error we suppose toobtain must be around

0.3%. However the error we

receive is much higher.

We can say that the different between the

readings might be due to some errors in our circuit.

Since we are using ADE7756 with internal ADC, the

error might come from the quantization process.

Beside, the power is not calculated by simply

multiplying the peak voltage and current detected.

The power is computed using numerical integration

causing some error compare to theoretical value. Inaddition, we can only calculate the energy for limited

time period for each appliance. In this case, wedecide to take 1 hour duration for each appliance.

The reason for this is that we feel afraid to leave the

circuit to operate for a long time due to safety reason.

Since we are using a very high voltage, the circuit

could not be switched on without any surveillance.

Therefore, the measurement values are taken in short

period causing the inaccuracy in result. Other than

that, the error can be resulted from the human error

when constructing the circuit. The connection between the components might not be soldered

properly causing error in reading. However, despite

the problems faced, we can say that we manage toachieve our objective to construct the circuit for

energy measurement and billing function.

4.7 Problems encountered

All the way through this project, we can see

there are several difficulties and technical problem

that we need to face. The main problem we encounter

is during the programming of the coding part for

PIC16F628A. Since we had never being exposed inthe PIC coding, we have to ask several people to help

us in the programming. Therefore, we suggested that

the Department of Electrical and ComputerEngineering will take this problem into consideration

and find a solution to it by either offering a subject or

lab dedicated to PIC programming.

Other than that, some of the components we

used are not available in the Malaysia. Thus, we have

to do special order and wait for a long time causing

delay to the progress of our project. There is also

component such as ADE7756 which is difficult to be

soldered due to its small size. The equipment in the

APPLIANCES MULTIMETER THEORETICAL MEASURED

Volt

(V RMS)

Current

(A RMS)

Power

(Watt)

Energy

(kWh)

Cost

(RM)

Power

(Watt)

Energy

(kWh)

Cost

(RM)

Energy (kWh) Cost (RM)

1. Power Supply 219.5 130.5m 28.65 28.65m 0.625 29 29m 0.632 27.75m 0.605

2. Radio 215.0 12.79m 2.75 2.75m 0.060 3 3m 0.065 2.9m 0.063

3. Hand phone

Charger (SonyEricsson)

217.8 163.18m 35.54 35.54m 0.775 36 36m 0.785 35.7m 0.778

4. Laptop 219.4 294m 64.4 64.4m 1.40 65 65m 1.417 64.7m 1.410


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lab is not well-suited to perform the soldering.

Hence, we have to send it to mobile phone shop and

request them to solder ADE7756 to the PCB board

causing several difficulties and delay to our work.

Overall, although we have faced severaldifficulties, we still manage to complete our project

and we are very grateful for it.

5.0 Conclusion and Recommendation5.1 Limitation of the Energy Meter Design

Throughout our project, we have identified

several limitations in the energy meter constructed.

Among them are:

y Single phase system:Since the meter constructed is can only be

use for single phase system, thus it cannot

be use in three phase system.

y Sampling rate is limited:Due to PIC16F628A limitations, there is the

limit of the highest sampling rate for

calculation which can be done.

y Accuracy of voltage transformer is limited:The accuracy of the transformer has limited

the accuracy of the meter

y Limited to only sinusoidal wave form:The energy meter can only measure

sinusoidal wave form

5.2 The Advantages of the Energy Meter

Comparing the digital energy meter weconstructed with analog meter, we can say there are

several benefits which cannot be done by analogmeter such as

1. Storage of power consumption historyThe digital energy meter can store its

consumption history in the RAM. Thus, it

can provide the power suppliers and the user

with a history record of power consumption

at any time period. This will also help in

record keeping and monitoring efficiency.

2. Remote logging facility and automaticbilling possible

Having the data in digital format, the storage

can be easily accessed. The energy metercan be extend to a mechanism of central

billing station to access this data by

communication either through power line or

GSM network resulting in automated

monitoring and billing

3. Life cycle of digital componentsDigital integrated circuits do not changes

characteristic with time unlike the analog

energy meter. In other words, the digital

device will not become in accurate with

time.

5.3 Recommendations and Future WorksIn this part some recommendations is made

for this project. This project can be enhanced mushfurther by including potential applications. For

example, we can include multi tariffs for difference

hours. It can be made with the availability of powerconsumption record. With this, even distribution load

during the day and hence reduce the burden on the

transmission system at peak hour and thus reducing

load shedding.

Other than that, we can include remote

logging facility by developed a digital storage for

power consumption history, enabling access of this

data through any external device in a serial port. Bybuilding a module that will communicate this data to

a central billing station, automatic billing is possible.Last but not least, the application of energy

meter can be extended to prepaid energy meter. For

this application, we can deduct the cost from the

prepaid card just like in mobile phone prepaid

system.

5.4 ConclusionIn a nutshell, we have successfully

completed our Final Year Project. We have done theliterature review in order to understand more deeply

about the energy meter and its function. We also have

proposed a circuit design for the energy meter which

we then manage to construct.From our literature review, we have

understood in details about the energy meter and howit operates. It also helps us in developing the

proposed circuit of energy meter and helps us to

know about the software required to be embedded in

the microcontroller unit. After implementing the

design, the energy meter was successfully operated.

We than used a few appliances to experiment with

the energy meter circuit.

The single phase energy meter constructed

has several advantages compare to the other energy

meter such as low cost component, high reliability

and easier calibration. In addition, due to the existingmicroprocessor (PIC16F628A) in the design, the

meter can be customized to have additional functionfor instance tamper detection, load profiling, pre-

payment, multi-tariff and etc.

All in all, the energy meter will be seen as

one of the important tools which will able to help usmonitoring the household appliances. It can also help

us to reduced electrical energy by determining how


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much energy the appliances consumed. Hence

necessary action can be taken for each appliance by

either switching it off or pulling it out completely

from the wall plug to reduce the energy consumption.

REFERENCE

[1] Mike M. 2005. Single Phase Energy Meters Become SimplerYet More Advance. Metering Journal Texas Instrument , Pg 14-

15

[2] P. A. V. Loss/M.M. Lamego, G.C.D. Soma/ J.L.F. Vieira ASingle Phase Microcontroller Based Energy Meter IEEE

Instrumentation And Measurement Technology Conference St.Paul, Minessota, USA, May 18-21,1998

[3] Ing. Rastislav Michlek Ing. Peter Gbor Ing. Peter Fuchs,

Phd Doc. Ing. Jn Hribik, Phd Doc. Ing. Miloslav Hrukovic,Phd DIGITAL PART OF DIGITAL ELECTRICITY METER

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And Joo Palma. Remote Alarm AndCommand System For Residential Domotics Trough Gsm Sms

[6] Arghya Sarkar And S. Sengupta , Design And ImplementationOf A Low Cost Fault Tolerent Three Phase Energy Meter, IEEE

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June 5-10, 2005 Design And Test Architecture Of Integrated-Power-Meter Digital Part. Vol. I

[10] Bharath P, Ananth N And Et. Al. 2008. Wireless Automated

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[11] Etienne M. 2001. Energy Data Converter Reduce Cost And

Simplify Meter Design. Analog Device Retrieved On 10thSeptember 2009

[12]http://www.analog.com/static/importedfiles/data_sheets/ade7756.pdf Datasheet On ADE7756Retrieved On 29th November2009

[13]http://ww1.microchip.com/downloads/en/devicedoc/40044d.pdf

Datasheet On PIC16F628A Retrieved On 29th November 2009

[14] http://www.tnb.com.my/tnb/tariff/newrate_domestic.htm

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[17] Paul B. R. February-March 1996 A Watt Hour Meter IEEE

Journals On Potentials , Vol. 15, Pg 9-13. IEEE

[18] Paul Robinson, A Watt Hour Meter: The Solid State

Polyphase Kind, IEEE Potential, February/March 1996

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syazana meter report

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