Chapter 1 1.1 INTRODUCTION 1.1.1 ENERGY METER It is a device that measures the amount of electric energy consumed by a residence, business, or an electrically powered device. In settings when energy savings during certain periods are desired, meters may measure demand, the maximum use of power in some interval. "Time of day" metering allows electric rates to be changed during a day, to record usage during peak high-cost periods and off-peak, lower-cost, periods. Also, in some areas meters have relays for demand response load shedding during peak load periods Electromechanical energy meters have been the standard for metering the electricity since billing began. But these are now being gradually replaced by electronic digital energy meters. Presented here is a simple energy meter using Analog Device’s ADE7757 chip for single-phase, 2-wire (phase and neutral) systems used in households. IC ADE7757 is a low-cost, single-phase solution for electrical energy measurement. You can use this solution even for individual appliances to see how much energy they are consuming. Its salient features are: 1. Can read up to 999999 units (kWh) with a resolution of 0.01 units 2. Designed for normal 230V AC and maximum line current of 30 amps 3. The meter count is 100 pulses/kWh, i.e., 100 pulses will be required to register one unit 1.1.2 History of electricity meter:
An electricity meter or energy meter is a device that measures the amount of electric energy consumed by a residence, business or an electrically powered device. As commercial use of electric energy spread in the 1880s, it became increasingly important that an electric energy meter. Many experimental types of meter were developed. Edison at first worked on a DC electromechanical meter with a direct reading register, but instead developed an electrochemical metering system, which used an electrolytic cell to totalize current consumption. The electrochemical meter was labor-intensive to read and not well received by the customers.
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In 1885 Ferranti offered a mercury motor meter with a register similar to gas meters; this had the advantage that the consumer could easily read the meter and verify consumption. The first accurate, recording electricity consumption meter was a DC meter by Dr. Hermann Aron, who patented it in 1883. Hugo Hirst of the British General Electric Company introduced it commercially into Great Britain from 1888. Meters had been used prior to this, but they measured the rate of energy consumption at that particular moment. The first specimen of the AC kilowatt-hour meter produced on the basis of Hungarian Otto Blathy's patent and named after him was presented by the Ganz Works at the Frankfurt Fair in the autumn of 1889, and the first induction kilowatt-hour meter was already marketed by the factory at the end of the same year. These were the first alternating-current watt meters, known by the name of Blathymeters. The AC kilowatt hour meters used at present operate on the same principle as Blathy's original invention. Also around 1889, Elihu Thomson of the American General Electric company developed a recording watt meter (watt-hour meter) based on an ironless commutator motor. This meter overcame the disadvantages of the electrochemical type and could operate on either alternating or direct current. In 1894 Oliver Shallenberger of the Westinghouse Electric Corporation applied the induction principle previously used only in AC ampere-hour meters to produce a watt-hour meter of the modern electromechanical form, using an induction disk whose rotational speed was made proportional to the power in the circuit. The Blathy meter was similar to Shallenberger and Thomson meter in that they are two-phase motor meter. Although the induction meter would only work on alternating current, it eliminated the delicate and troublesome commutator of the Thomson design. The most common unit of measurement on the electricity meter is the kilowatt hour [kWh], which is equal to the amount of energy used by a load of one kilowatt over a period of one hour. In addition to metering based on the amount of energy used, other types of metering are available. Meters which measured the amount of charge (coulombs) used, known as ampere hour meters, were used in the early days of electrification. Some meters measred only the length of time for which charge flowed, with no measurement of the magnitude of voltage or current being made. These were only suited for constantload applications. Neither type is likely to be used today.
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1.1.3 Types of meters:
Electricity meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) and finding the product of these to give instantaneous electrical power (watts) which is then integrated against time to give energy used Meters for smaller services (such as small residential customers) can be connected directly in-line between source and customer. For larger loads, more than about 200 ampere of load, current transformers are used, so that the meter can be located other than in line with the service conductors. The meters fall into two basic categories, electromechanical and electronic.
1. Electromechanical meters The most common type of electricity meter is the electromechanical induction watt-hour meter. The electromechanical induction meter operates by counting the revolutions of an aluminum disc which is made to rotate at a speed proportional to the power. The number of revolutions is thus proportional to the energy usage. The voltage coil consumes a small and relatively constant amount of power, typically around 2 watts which is not registered on the meter. The current coil similarly consumes a small amount of power in proportion to the square of the current flowing through it, typically up to a couple of watts at full load, which is registered on the meter.
Fig 1 Electromechanical meter
2. Electronic meters Electronic meters display the energy used on an LCD or LED display, and can also transmit readings to remote places. In addition to measuring energy used, electronic meters can also record other parameters of 3
the load and supply such as maximum demand, power factor and reactive power used etc. They can also support time-of-day billing, for example, recording the amount of energy used during on-peak and offpeak hours.
3. Prepayment meters The standard business model of electricity retailing involves the electricity company billing the customer for the amount of energy used in the previous month or quarter. In some countries, if the retailer believes that the customer may not pay the bill, a prepayment meter may be installed. This requires the customer to make advance payment before electricity can be used. If the available credit is exhausted then the supply of electricity is cut off by a relay. In the UK, mechanical prepayment meters used to be common in rented accommodation. Disadvantages of these included the need for regular visits to remove cash, and risk of theft of the cash in the meter. Modern solid-state electricity meters, in conjunction with smart cards, have removed these disadvantages and such meters are commonly used for customers considered to be a poor credit risk. In the UK, one system is the pay point network, where rechargeable tokens (Quantum cards for natural gas, or plastic "keys" for electricity) can be loaded with whatever money the customer has available. Recently smartcards are introduced as much reliable tokens that allow two way data exchange between meter and the utility. Around the world, experiments are going on, especially in developing countries, to test prepayment systems. In some cases, prepayment meters have not been accepted by customers. There are various groups, such as the Standard Transfer Specification (STS) association, which promote common standards for prepayment metering systems across manufacturers. Prepaid meters using the STS standard are used in many countries.
Fig 2 Prepayment meters using magnetic strips
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1.2 LITERATURE SURVEY Nabil Mohammad , Anomadarshi Barua and Muhammad Abdullah Arafat on “A Smart Prepaid Energy Metering System to Control Electricity Theft” and this paper proposed that power utilities in different countries especially in the developing ones are incurring huge losses due to electricity theft.This paper proposes prepaid energy metering system to control electricity theft. In this system a smart energy meter is installed in every consumer unit and a server is maintained at the service provider side. Both the meter and the server are equipped with GSM module which facilitates bidirectional communication between the two ends using the existing GSM infrastructure. Arne Ellerbrock , Ahmad Abdel-Majeed, and Stefan Tenbohlen on “Design and Building of a Cheap Smart Meter” and this paper propose a cheap smart meter which is designed not only to measure the customer’s power consumption and generation but also to enable and support the new operation and control functions in the distribution networks. It is based on open source hardware (Arduino and Arduino Ethernet Board) and offers a plurality of communication possibilities, like USB, Ethernet, ZigBee or Bluetooth. The smart meter uses an ADE7753 as converter and saves only the most important data (voltage, current, frequency, active- and reactive energy) on a SD-card so that all further calculations can be performed by an external central system. Mayur S. Thacker, Sanjay R. Yadav on “Domestic Energy Meter Interfacing Using Avr Open Source Microcontroller & Matlab” and this paper proposed a high potential energy savings solution by impacting the behavior habits of individual in their households. To solve this scenario it requires that consumers do have a sophisticated feedback system, which provides better understanding and comparison of, how their action relates to their energy consumption, and by doing so they can optimize the use of electricity. To optimize the use of electrical energy, it is necessary to provide a sophisticated interface of energy consumption, with feedback system for motivating household to save it. Md. Mejbaul Haque, Md. Kamal Hossain , Md. Mortuza Ali , Md. Rafiqul Islam Sheikh on “Microcontroller Based Single Phase Digital Prepaid Energy Meter for Improved Metering and Billing System” and this paper propose a single phase digital prepaid energy meter based on two microcontrollers and a single phase energy meter IC. This digital prepaid energy meter does not have any rotating parts. The energy consumption is calculated using the output pulses of the energy meter chip and the internal counter of microcontroller (ATmega32). A microcontroller (ATtiny13) is used as a smart card and the numbers of units recharged by the consumers are written in it. Stephen McLaughlin, Dmitry Podkuiko, and Patrick McDaniel on “Energy Theft in the Advanced Metering Infrastructure” and this paper proposed that adversary means of defrauding the electrical grid by manipulating AMI systems. We document the methods adversaries will use to attempt to manipulate energy usage data, and validate the viability of these attacks by performing penetration testing on commodity devices. Nagaraju Kommu, Pammi.Nagamani ,Manoj Kollam on “ Designing of an Automated Power Meter Reading with Zigbee Communication” and this paper proposed a design and implementation of Automatic Power Meter (APM), The APM is implemented using an ARM and Zigbee Based power meter Communication Module. The design presents a new methodology for avoiding the high construction and maintenance costs in the existing meter reading technology. Using an APM with network technologies has become a trend today. 5
. Chapter 2
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2.2 WORKING Energy meter worked around energy-metering IC having integrated oscillator ADE7757 (IC1), .With other IC’S : Microcontroller AT89c52 (IC2), EEPROM AT24C02 (IC3), 5V voltage regulator 7805 (IC5), optocoupler MCT2E (IC4) and an LCD display. In this ade7757 give Working is explained with explanation of working of each IC used in project. IC ADE7757: It is a low-cost, single chip solution for electrical energy measurement. In operation, the chip interfaces with a shunt resistor (used as the current sensor) and AC analogue voltage sensing the inputs and outputting the consumed power as explained below. It has two analogue input channels designated as V1 and V2, respectively. Channel V1 (also called ‘current channel’) is used for current sensing and channel V2 (also called ‘voltage channel’) is used for voltage sensing. The differential output from the current-sensing resistor is connected between V1P and V1N inputs, whilst the differential output signal proportional to the AC line voltage, obtained through a resistor divider, is connected between pins V2P and V2N.IC ADE7757 has a reference circuit and a fixed DSP function for calculation of the real power. A highly stable oscillator integrated into the chip provides the necessary clock for the chip.
It supplies the average real-power information on the F1 and F2 low-frequency outputs. The meter is designed for 100 pulses/kWh and the pulses can be counted by any counter for power consumption calculation. Here, microcontroller AT89C52 is used for counting the pulses. ADE7757 provides a highfrequency output at the calibration frequency (CF) pin (here, it is 3200 pulses/kWh), which is selected via S1 and S0 pins .This high-frequency output provides instantaneous real-power information, which is used to speed up the calibration process.
The power supply for IC ADE7757 is derived directly from mains using the capacitor divider network comprising C13 and C14. Most of the voltage is dropped across C13 (0.47μF polyester capacitor rated for 30V), whilst resistor R11 (470-ohm, 1W) is used as the current limiter. The output across C14 is limited to 15V DC, which serves as an input to regulator IC5. The regulated 5V is fed to IC1. The F1 output of IC1 is coupled to port pin P3.2 of microcontroller IC2 via opto-coupler IC4 hilst LED1 indicates that IC1 is working.
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AT89C52: It is a low-power, high performance CMOS 8-bit microcontroller IC2 takes the meter reading through its pin 12 and stores it in EEPROM IC3, and at the same time displays it on the LCD, which requires additional 5V regulated and isolated supply to avoid extension of live mains to the counter section. A conventional 5V regulator circuit incorporating a bridge rectifier (BR1), smoothing capacitor (C20) and regulator IC 7805 (IC6) has been used for the purpose of additional power supply. Pins 21 through 28 of microcontroller IC2 are connected to the LCD data pins D0 through D7, respectively. pins 15, 16 and 17 of IC2 are connected with the control pins RS, R/W and EN of LCD, respectively. Power-on reset is provided by the combination of resistor R14 and capacitor C16. Switch S1 is used for manual reset. A 12MHz crystal along with two 22pF capacitors provide basic clock frequency to the microcontroller. Preset VR2 is connected with pin 3 of LCD for contrast control.
AT24C02: It is an I2C-bus compatible 2-kilobit EEPROM organised as 256×8 bits that can retain data for more than ten years. To obviate the loss of latest setting in the case of power failure, the microcontroller can store all data of user in the EEPROM. The memory ensures that the microcontroller will read the last saved data from EEPROM when power resumes. Using SCL and SDA lines of EEPROM, the microcontroller can read/write the data from/to AT24C02 memory. SCL and SDA lines of IC3 are interfaced to pin 10 and 11 of microcontroller IC2, respectively.
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CHAPTER 3 List of Components Semiconductors: a) IC1 - ADE7757 energy metering IC b) IC2 - AT89C52 microcontroller c) IC3 - AT24C02 EEPROM d) IC4 - MCT2E opto-coupler e) IC5, IC6 - 7805, 5V regulator f) T1 - BC547 npn transistor g) D1 - 1N4007 rectifier diode h) LED1, LED2 - 5mm LED i) LCD1 - 16×2 LCD j) BR1 - Bridge rectifier module 1A k) ZD1 - 15V, 1W zener diode Resistors (all 1/4-watt, ±5% carbon, unless stated otherwise): a) R1, R3, R7, R8 - 499-ohm b) R2 - 6.2-kilo-ohm c) R4 - 1-kilo-ohm d) R5, R6, R19 - 680-ohm e) R9 - 350-micro-ohm shunt f) R10 - 1-mega-ohm g) R11 - 470-ohm, 1W h) R12-R16 - 10-kilo-ohm i) R17 - 100-ohm j) R18 - 470-ohm k) VR1 - 500-kilo-ohm preset l) VR2 - 10-kilo-ohm preset Capacitors: a) C1, C6, C16 - 10μF, 16V electrolytic b) C2, C3, C7-C10, c) C17, C21 - 0.1μF ceramic disk d) C4, C5, C11, C12 - 0.068μF ceramic disk e) C13 - 0.47μF, 630V polyester f) C14 - 470μF, 35V electrolytic g) C15 - 0.01μF ceramic disk h) C18, C19 - 22pF ceramic disk i) C20 - 1000μF, 25V electrolytic Miscellaneous: a) X1 - 230V AC primary to 9V, b) 500mA secondary transformer c) XTAL1 - 12MHz crystal oscillator 9
d) e) f) g) h) i) j) k)
MOV - 140J metal oxide varistor (14mm, 275V) L1, L2 - ferrite bead L3, L4 - 3.5mm × 9mm axial, filter choke (bead core) S1 - Tactile switch CON1, CON2 - 2-pin 5mm terminal connector CON3 - 2-pin connector
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CHAPTER 4 4.1 ADE7757
Fig 4 Block diagram of ADE7757
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1. Description The ADE7757 is a high accuracy electrical energy measurement IC. It is a pin reduction version of the ADE7755 with an enhancement of a precise oscillator circuit that serves as a clock source to the chip. The ADE7757 eliminates the cost of an external crystal or resonator, thus reducing the overall cost of a meter. The chip directly interfaces with the shunt resistor and operates only with ac input.TheADE7757 specifications surpass the accuracy requirements as quoted in the IEC 61036 standard. The AN-679 Application Note can be used as a basis for a description of an IEC 61036low cost watt-hour meter reference design. The only analog circuitry used in the ADE7757 is in the ADCs and reference circuit. All other signal processing (e.g., multiplication and filtering) is carried out in the digital domain.
This approach provides superior stability and accuracy overtime and extreme environmental conditions.
The ADE7757 supplies average real power information on the low frequency outputs F1 and F2. These outputs may be used to directly drive an electromechanical counter or interface with an MCU. The high frequency CF logic output, ideal for calibration purposes, provides instantaneous real power information.
The ADE7757 includes a power supply monitoring circuit on the VDD supply pin. The ADE7757 will remain inactive until the supply voltage on VDD reaches approximately 4 V. If the supply falls below 4 V, the ADE7757 will also remain in active and the F1, F2, and CF outputs will be in their non active modes. Internal phase matching circuitry ensures that the voltage and current channels are phase matched while the HPF in the current channel eliminates dc offsets. An internal no-load threshold ensures that the ADE7757 does not exhibit creep when no load is present..
12
S.no
Mnemonic
Description
1
Vdd
Power Supply. This pin provides the supply voltage for the circuitry in the ADE7757. The supply voltage should be maintained at 5 V ± 5% for specified operation. This pin should be decoupled with a 10 μFcapacitor in parallel with a ceramic 100 nF capacitor.
2,3
V2P,V2N
Analog Inputs for Channel V2 (voltage channel). These inputs provide a fully differential input pair. The maximum differential input voltage is ±165 mV for specified operation. Both inputs have internal ESD protection circuitry; an overvoltage of ±6 V can be sustained on these inputs without risk of permanent damage.
4,5
V1N,V1P
Analog Inputs for Channel V1 (current channel). These inputs are fully differential voltage inputs with a maximum signal level of ±30 mV with respect to the V1N pin for specified operation. Both inputs have internal ESD protection circuitry and, in addition, an overvoltage of ±6 V can be sustained on thes inputs without risk of permanent damage.
6
AGND
This provides the ground reference for the analog circuitry in the ADE7757, i.e., ADCs and reference. This pin should be tied to the analog ground plane of the PCB. The analog ground plane is the ground reference for all analog circuitry, e.g., antialiasing filters, current and voltage sensors, and so forth. For accurate noise suppression, the analog ground plane should be connected to the digital ground plane at only one point. A star ground configuration will help to keep noisy digital currents away from the analog circuits.
7
REF(in/out)
This pin provides access to the on-chip voltage reference. The on-chip reference has a nominal value of 2.5 V and a typical temperature coefficient of 20 ppm/°C. An external reference source may also be connected at this pin. In either case, this pin should be decoupled to AGND with a 1 μF tantalum capacitor and a 100 nF ceramic capacitor. The internal reference cannot be used to drive an external load.
8
SCF
Select Calibration Frequency. This logic input is used to select the frequency on the calibration output CF. Table III shows calibration frequencies selection. 13
9,10
S1,S0
These logic inputs are used to select one of four possible frequencies for the digital-to-frequency conversion. With this logic input, designers have greater flexibility when designing an energy meter. See the Selecting a Frequency for an Energy Meter Application section.
11
RCLKIN
To enable the internal oscillator as a clock source to the chip, a precise low temperature drift resistor at a nominal value of 6.2 kΩ must be connected from this pin to DGND.
12
REVP
This logic output will go high when negative power is detected, i.e., when the phase angle between the voltage and current signals is greater than 90°. This output is not latched and will be reset when positive power is once again detected. The output will go high or low at the same time that a pulse is issued on CF.
13
DGND
This provides the ground reference for the digital circuitry in the ADE7757, i.e., multiplier, filters, and digital-to-frequency converter. This pin should be tied to the digital ground plane of the PCB. The digital ground plane is the ground reference for all digital circuitry, e.g., counters (mechanical and digital), MCUs, and indicator LEDs. For accurate noise suppression, the analog ground plane should be connected to the digital ground plane at one point only, i.e., a star ground.
14
CF
Calibration Frequency Logic Output. The CF logic output provides instantaneous real power information. This output is intended for calibration purposes. Also see SCF pin description.
15,16 F0,F1
Low Frequency Logic Outputs. F1 and F2 supply average real power information. The logic outputs can be used to directly drive electromechanical counters and 2-phase stepper motors. See the Transfer Function section.
Fig 5 Pins with its Description of ADE7757 14
2.Operation Of ADE7757
Fig 6 Internal diagram of ADE7757
The two ADCs digitize the voltage signals from the current and voltage sensors. These ADCs are 16-bit with an oversampling rate of 450 kHz. This analog input structure greatly simplifies sensor interfacing by providing a wide dynamic range for direct connection to the sensor and also simplifies antialiasing filter design. A high-pass filter in current channel removes any dc component from the current signal. This eliminates any inaccuracies in the real power calculation due to offsets in the voltage or current signals.
The real power calculation is derived from the instantaneous power signal. The instantaneous power signal is generated by a direct multiplication of the current and voltage signals. In order to extract the real power component (i.e., the dc component), the instantaneous power signal is low-pass filtered. Figure 3illustrates the instantaneous real power signal and shows how the real power information can be extracted by lowpass filtering the instantaneous power signal. This scheme correctly calculates real power for sinusoidal current and voltage waveforms at all power factors. All signal processing is carried out in the digital domain for superior stability over temperature and time. 15
The low frequency outputs (F1, F2) of the ADE7757 are generated by accumulating this real power information. This low frequency inherently means a long accumulation time between output pulses. Consequently, the resulting output frequency is proportional to the average real power. This average real power information is then accumulated (e.g., by a counter) to generate real energy information. Conversely, due to its high output frequency and hence shorter integration time, the CF output frequency is proportional to the instantaneous real power. This is useful for system calibration, which can be done faster under steady load conditions.
Channel V1 (Current Channel) The voltage output from the current sensor is connected to the ADE7757 here. Channel V1 is a fully differential voltage input. V1P is the positive input with respect to V1N. The maximum peak differential signal on Channel V1 should be less than 30 mV (21 mV rms for a pure sinusoidal signal) for specified operation.
Maximum Signal Levels, Channel V1the maximum signal levels on V1P and V1N. The maximum differential voltage is 30V. The differential voltage signal on the inputs must be referenced to a common mode, e.g., AGND. The maximum common mode signal is 6.25 mV.
Channel V2 (Voltage Channel) The output of the line voltage sensor is connected to the ADE7757 at this analog input. Channel V2 is a fully differential voltage input with a maximum peak differential signal of 165 mV. Figure 6 illustrates the maximum signal levels that can be connected to the ADE7757 Channel V2.
Maximum Signal Levels, Channel V2 is usually driven from a common-mode voltage
,i.e., the
differential voltage signal on the input is referenced to a common mode (usually AGND). The analog inputs of the ADE7757 can be driven with common-mode voltages of up to 25 mV with respect to AGND. However, best results are achieved using a common mode equal to AGND.
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Microcontroller IC2 takes the meter reading through its pin12 and store it in EEPROM IC3,and at the same time display it on the IC3 ,and at same time display it in LCD ,which require additional 5v regulated and isolated supply (to avoide extension of live main to counter section).
4.2 CAPACITOR
A capacitor is a passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (i.e., insulator). The conductors can be thin films of metal, aluminum foil or disks, etc. The 'non-conducting' dielectric acts to increase the capacitor's charge capacity. A dielectric can be glass, ceramic, plastic film, air, paper, mica, etc. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, a capacitor does not dissipate energy. When there is a potential difference across the conductors (e.g., when a capacitor is attached across a battery), an electric field develops across the dielectric, causing positive charge (+Q) to collect on one plate and negative charge (-Q) to collect on the other plate. If a battery has been attached to a capacitor for a sufficient amount of time, no current can flow through the capacitor. However, if an accelerating or alternating voltage is applied across the leads of the capacitor, a displacement current can flow.
Fig 7 Capacitor
The SI unit of capacitance is the farad (F), which is equal to one coulomb per volt (1 C/V). Typical capacitance values range from about 1 pF (10−12 F) to about 1 mF (10−3 F).
The capacitance is greater when there is a narrower separation between conductors and when the conductors have a larger surface area. In practice, the dielectric between the plates passes a small amount 17
of leakage current and also has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance.
Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems they stabilize voltage and power flow.
4.3 RESISTOR It is a passive two-terminal electrical component that implements electrical resistance as a circuit element. Resistors act to reduce current flow, and, at the same time, act to lower voltage levels within circuits. Resistors
may
have
fixed
resistances
or
variable
resistances,
such
as
those
found
in thermistors, varistors, trimmers, photoresistorsand potentiometers.
The current through a resistor is in direct proportion to the voltage across the resistor's terminals. This relationship is represented by Ohm's law:
where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of conductor in units of ohms (symbol Ω).
Fig 8 Resistor
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The ratio of the voltage applied across a resistor's terminals to the intensity of current in the circuit is called its resistance, and this can be assumed to be a constant (independent of the voltage) for ordinary resistors working within their ratings.
4.4 FERRITE CORE
It is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability coupled with low electrical conductivity (which helps prevent eddy currents). Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies, and ferrite loop stick antennas for AM radio receivers.
There are two broad applications for ferrite cores which differ in size and frequency of operation: signal transformers are of small size and higher frequencies, power transformers are of large size and lower frequencies. Cores can also be classified by shape: there are toroidal cores, shell cores, cylindrical cores, and so on. The ferrite cores used for power transformers work in the low frequency range (1 to 200 kHz usually) and are fairly large in size, can be toroidal, shell, or C shape, and are useful in all kinds of electronic switching devices -- especially power supplies from 1 watt to 1000 watts maximum, since more powerful applications are usually out of range of ferritic single core and require grain oriented lamination cores.
19
Fig 9 Ferrite Core
4.5 OPTO-ISOLATOR [ MCT2E]
Photo coupler, or optical isolator, is a component that transfers electrical signals between two isolated circuits by using light. Opto-isolators prevent high voltages from affecting the system receiving the signal. Commercially available opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 10 kV/μs.
A common type of opto-isolator consists of an LED and a phototransistor in the same opaque package. Other types of source-sensor combinations include LED-photodiode, LED-LASCR, and lamp-photo resistor pairs. Usually opto-isolators transfer digital (on-off) signals, but some techniques allow them to be used with analog signals.
Fig 10 Optocoupler 20
1. Feature Of MCT2E
Gallium Arsenide Diode Infrared Source
Optically Coupled to a Silicon npn
Phototransistor
High Direct-Current Transfer Ratio
Base Lead Provided for Conventional
Transistor Biasing
High-Voltage Electrical Isolation . . .
1.5-kV, or 3.55-kV Rating
Plastic Dual-In-Line Package
High-Speed Switching:
tr = 5 s, tf = 5 s Typical
Designed to be Interchangeable with
General Instruments MCT2E
absolute maximum ratings at 25 C free-air temperature (unless otherwise noted)†
Input-to-output voltage: MCT2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5kV MCT2E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.55 kV Collector-base voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70V Collector-emitter voltage . . . . . . . . . . . . . . . . . . . . . .
30 V
Emitter-collector voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V Emitter-base voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V Input-diode reverse voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 V Input-diode continuous forward current . . . . . . . . . . . . . . . . . . . . . 60 mA Input-air temperature: Infrared-emitting diode . . . . . . . . . . . . . . . . . . . . . . . . . . . Phototransistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
200 mW 200 mW
Total, infrared-emitting diode plus phototransistor (see Note 3) . . . 250 mW Operating free-air temperature range, TA . .. . . . . . . . . . . . . . . . 21
–
C
2. GRAPHS
Fig 11 Graph of MCT2E
22
Fig 12 Graph of MCT2E
23
4.6 VARISTOR
It is an electronic component with a "diode-like" nonlinear current–voltage characteristic. The name is a portmanteau of
variable resistor. Varistors are often used to protect circuits against excessive
transient voltages by incorporating them into the circuit in such a way that, when triggered, they will shunt the current created by the high voltage away from sensitive.
A varistor is also known as voltage-dependent resistor (VDR). A varistor’s function is to conduct significantly increased current when voltage is excessive.
Only non-ohmic variable resistors are usually called varistors. Other, ohmic types of variable resistor include the potentiometer and the rheostat.
The response time of the MOV is largely ambiguous, as no standard has been officially defined. The subnanosecond MOV response claim is based on the material's intrinsic response time, but will be slowed down by other factors such as the inductance of component leads and the mounting method. That response time is also qualified as insignificant when compared to a transient having an 8 µs rise-time, thereby allowing ample time for the device to slowly turn-on. When subjected to a very fast, <1 ns rise-time transient, response times for the MOV are in the 40–60 ns range.
Fig 13 Metal Oxide Varistor
Typical capacitance for consumer-sized (7–20 mm diameter) varistors are in the range of 100–1,000 pF. Smaller, lower-capacitance varistors are available with capacitance of ~1 pF for microelectronic protection, such as in cellular phones. These low-capacitance varistors are, however, unable to withstand 24
large surge currents simply due to their compact PCB-mount size. MOVs are specified according to the voltage range that they can tolerate without damage.
4.7 TRIMMER OR PRESET
It is a miniature adjustable electrical component. It is meant to be set correctly when installed in some device, and never seen or adjusted by the device's user. Trimmers can be variable resistors (potentiometers), variable capacitors, or trimmable inductors. They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is serviced. Trimpots are often used to initially calibrate equipment after manufacturing. Unlike many other variable controls, trimmers are mounted directly on circuit boards, turned with a small screwdriver and rated for many fewer adjustments over their lifetime. Trimmers like trimmable inductors and trimmable capacitors are usually found insuperhet radio and television receivers, in the Intermediate frequency, oscillator and RF circuits. They are adjusted into the right position during the alignment procedure of the receiver.
Fig 14 Preset
Trimmers come in a variety of sizes and levels of precision. For example, multi-turn trim potentiometers exist, in which it takes several turns of the adjustment screw to reach the end value. This allows for very high degrees of accuracy. Often they make use of a worm-gear (rotary track) or a leadscrew (linear track). 25
4.8 FILTER CHOKE
It is an inductor used to block higher-frequency alternating current (AC) in an electrical circuit, while allowing lower frequency or DC current to pass. A choke usually consists of a coil of insulated wire often wound on a magnetic core, although some consist of a donut-shaped "bead" of ferrite material strung on a wire. The choke's impedance increases with frequency. Its low electrical resistance allows both AC and DC to pass with little power loss, but it can limit the amount of AC passing through it due to its reactance.
Fig 15 Filter Choke
The name comes from blocking—“choking”—high frequencies while passing low frequencies. It is a functional name; the name “choke” is used if an inductor is used for blocking or decoupling higher frequencies, but is just called an “inductor” if used in electronic filters or tuned circuits. Inductors designed for use as chokes are usually distinguished by not having the low loss construction (high Q factor) required in inductors used in tuned circuits and filtering applications.
4.9 ZENER DIODE
It is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but also permits it to flow in the reverse direction when the voltage is above a certain value known as 26
the breakdown voltage, "Zener knee voltage", "Zener voltage", "avalanche point", or "peak inverse voltage".
The device was named after Clarence Zener, who discovered this electrical property. Strictly speaking, a Zener diode is one in which the reverse breakdown is due to electron quantum tunnelling under high electric field strength—the Zener effect. However, many diodes described as "Zener" diodes rely instead on avalanche breakdown as the mechanism. Both types are used with the Zener effect predominating under 5.6 V and avalanche breakdown above. Common applications include providing a reference voltage for voltage regulators, or to protect other semiconductor devices from momentary voltage pulses.
Fig 16 Symbol of Zener Diode
4.10 DIODE It is to allow an electric current to pass in one direction (called diode's forward direction), while blocking current in the opposite direction (the reverse direction). Thus, the diode can be viewed as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, including extraction of modulation from radio signals in radio receivers—these diodes are forms of rectifiers.
. Fig 17 Symbol of Diode 27
Diodes can have more complicated behavior than this simple on–off action, due to their nonlinear currentvoltage characteristics. Semiconductor diodes begin conducting electricity only if a certain threshold voltage or cut-in voltage is present in the forward direction (a state in which the diode is said to be forward-biased). The voltage drop across a forward-biased diode varies only a little with the current, and is a function of temperature; this effect can be used as a temperature sensor or voltage reference.
Semiconductor diodes' current–voltage characteristic can be tailored by varying the semiconductor materials and doping, introducing impurities into the materials. These are exploited in special-purpose diodes that perform many different functions. For example, diodes are used to regulate voltage (Zener diodes), to protect circuits from high voltage surges (avalanche diodes), to electronically tune radio and TV
receivers
(varactor
diodes),
to
generate radio
frequency oscillations(tunnel
diodes, Gunn
diodes, IMPATT diodes), and to produce light (light emitting diodes). Tunnel diodes exhibit negative resistance, which makes them useful in some types of circuits.
4.11 AT89S52
1. Feature
Compatible with MCS-51Products
8K Bytes of In-System Programmable (ISP) Flash Memory
Endurance: 1000 Write/Erase Cycles
4.0V to 5.5V Operating Range
Fully Static Operation: 0 Hz to 33 MHz
Three-level Program Memory Lock
256 x 8-bit Internal RAM
32 Programmable I/O Lines
Three 16-bit Timer/Counters
Eight Interrupt Sources
Full Duplex UART Serial Channel 28
Low-power Idle and Power-down Modes
Interrupt Recovery from Power-down Mode
Watchdog Timer
Dual Data Pointer
29
Specification
Fig 18 Specification of AT89CS52
30
Fig 19 Pin description of AT89cs52
31
4.12 AT24C02 AT24C02 provides 2048 bits of serial electrically erasable and programmable read only memory organized as 256 words of 8 bits each. The device is optimized for use in manyindustrial and commercial applications where lowpower and low-voltage operation are essential. The AT24C01A/02/04/08A/16A is available in space-saving 8-lead PDIP,8-lead JEDEC SOIC, 8-lead MAP, 5-lead SOT23 (AT24C01A/AT24C02/AT24C04), 8lead TSSOP, and 8-ball dBGA2 packages and is accessed via a Two-wire serial interface. In addition, the entire family is available in 2.7V (2.7V to 5.5V) and 1.8V (1.8V to 5.5V) versions.
Fig 20 Pin Description of EEPROM
Pin name Function Pin Name
Description
AD0-AD2
Address Inputs
SDA
Serial Data
SCL
Serial Clock Input
WP
Write Protect
NC
No Connect
GND
Ground
Vcc
Power Supply Fig 21 Pin with its Description of EEPROM 32
Features -voltage and Standard-voltage Operation – 2.7 (VCC = 2.7V to 5.5V) – 1.8 (VCC = 1.8V to 5.5V)
-wire Serial Interface
Data Transfer Protocol
-timed Write Cycle (5 ms max) -reliability -free/Halogen-free Devices Available
4.13 LCD display
Fig 22 16x2 LCD display 33
FEATURES:
-in controller (KS 0066 or Equivalent)
15, pin 16 or A.K (LED)
Fig 23 Pin with its Description OF LCD
34
Chapter 5 5.1 Software In our project, we will use two electronics softwares. 1. Keil μ-vision 2. Eagle 6.5.0. Keil μ-vision: Keil is a cross compiler. We will use this program to construct a C program and source code for energy meter and its recharge unit.
Eagle 6.5.0. EAGLE ( Easily Applicable Graphical Layout Editor) by CadSoft Computer is a flexible, expandable and scriptable EDA application with schematic capture editor, PCB layout editor, auto-router and CAM and BOM tools developed by CadSoft Computer GmbH
5.2 PROGRAMMING OF ENERGY METER
1)FOR EEPROM
#include sbit sda=P3^1; sbit scl=P3^0; sbit led1=P0^1; sbit led=P0^3; sbit inter=P3^2; #include "lcd.h" #include "i2c.h" 35
unsigned char a1,a2,i,j;
// numeric value
unsigned
char
en_data_add,en_data_dat,digit1,digit2,digit3,digit4,digit5,digit6,digit7,digit8,dig1,dig2,dig3,dig4,dig5,dig 6,dig7,dig8,unit; unsigned long int count,reading,predata;
void i2c_write(unsigned char en_data_add,unsigned char en_data_dat) //save in EEPROM { a1=en_data_dat & 0x0F; a2=en_data_dat & 0xF0; i2c_strt(); send_byte(0xA0);
//device address
i2c_ack(); send_byte(en_data_add);
//word address
i2c_ack(); send_byte(a1);
//send data
i2c_ack(); send_byte(a2);
//send data
i2c_ack(); i2c_stp(); msdelay(20); i2c_ack(); }
i2c_read(unsigned char en_data_add) { i2c_strt(); send_byte(0xA0); i2c_ack(); send_byte(en_data_add); i2c_ack(); 36
i2c_strt(); send_byte(0xA1);
//device address
i2c_ack(); i=read_byte(); i2c_ack(); j=read_byte(); i2c_ack(); i2c_stp(); i=i&0x0F; unit=i+0x30; return unit; i2c_ack(); } void enter (void) interrupt 0 { reading++; msdelay(10); count = reading; temp = count%10; digit1 = temp; i2c_write(0x00,digit1); temp = count/10; temp = temp%10; digit2 = temp; i2c_write(0x10,digit2); temp = count/10; temp = temp/10; temp = temp%10; digit3 = temp; i2c_write(0x20,digit3); temp = count/10; temp = temp/10; 37
temp = temp/10; temp = temp%10; digit4 = temp; i2c_write(0x30,digit4); temp = count/10; temp = temp/10; temp = temp/10; temp = temp/10; temp = temp%10; digit5 = temp; i2c_write(0x40,digit5); temp = count/10; temp = temp/10; temp = temp/10; temp = temp/10; temp = temp/10; temp = temp%10; digit6 = temp; i2c_write(0x50,digit6); temp = count/10; temp = temp/10; temp = temp/10; temp = temp/10; temp = temp/10; temp = temp/10; temp = temp%10; digit7 = temp; i2c_write(0x60,digit7); temp = count/10; temp = temp/10; temp = temp/10; temp = temp/10; 38
temp = temp/10; temp = temp/10; temp = temp/10; digit8 = temp; i2c_write(0x70,digit8); msdelay(10);
}
void main() { IE = 129; TCON = 1; inter = 1; lcdint(); cmm(0x01); cmm(0x80); data_str("Energy Meter"); msdelay(10); cmm(0xC0); data_str("Unit : 000000.00"); msdelay(10); dig1=i2c_read(0x00); msdelay(5); cmm(0xCF); dat(dig1); msdelay(5); dig2=i2c_read(0x10); msdelay(5); cmm(0xCE); dat(dig2); msdelay(5); dig3=i2c_read(0x20); 39
msdelay(5); cmm(0xCC); dat(dig3); msdelay(5); dig4=i2c_read(0x30); msdelay(5); cmm(0xCB); dat(dig4); msdelay(5); dig5=i2c_read(0x40); msdelay(5); cmm(0xCA); dat(dig5); msdelay(5); dig6=i2c_read(0x50); msdelay(5); cmm(0xC9); dat(dig6); msdelay(5); dig7=i2c_read(0x60); msdelay(5); cmm(0xC8); dat(dig7); msdelay(5); dig8=i2c_read(0x70); cmm(0xC7); dat(dig8); msdelay(5); predata=((dig8*10000000)+(dig7*1000000)+(dig6*100000)+(dig5*10000)+(dig4*1000)+(dig3*1 00)+(dig2*10)+(dig1)); reading=predata; msdelay(20); 40
while(1) { dig1=i2c_read(0x00); msdelay(5); cmm(0xCF); dat(dig1); dig2=i2c_read(0x10); msdelay(5); cmm(0xCE); dat(dig2); dig3=i2c_read(0x20); msdelay(5); cmm(0xCC); dat(dig3); dig4=i2c_read(0x30); msdelay(5); cmm(0xCB); dat(dig4); dig5=i2c_read(0x40); msdelay(5); cmm(0xCA); dat(dig5); dig6=i2c_read(0x50); msdelay(5); cmm(0xC9); dat(dig6); dig7=i2c_read(0x60); msdelay(5); cmm(0xC8); dat(dig7); dig8=i2c_read(0x70); 41
msdelay(5); cmm(0xC7); dat(dig8); msdelay(100); } }
2)FOR I2C #include //For using [_nop_()] bit ack; unsigned char rd,i,j,write,write1; unsigned int temp;
void i2c_ack() //acknowledge condition { scl=1; _nop_(); _nop_(); scl=0; } void i2c_strt()
//start condition
{ sda=1; scl=1; _nop_();
//No operation
_nop_(); sda=0; scl=0; } void i2c_stp()
//stop condition
{ 42
sda=0; scl=1; _nop_(); _nop_(); sda=1; scl=0; } void send_byte(unsigned char value) //Send byte serially { unsigned int i; unsigned char send; send=value; for(i=0;i<8;i++) { sda=send/128; send=send<<1;
//Extracting MSB //Shiftng left
scl=1; _nop_(); _nop_(); scl=0; } ack=sda;
//Reading acknowledge
sda=0; } unsigned char read_byte()
//Reading from EEPROM serially
{ unsigned int i; sda=1; rd=0; for(i=0;i<8;i++) { rd=rd<<1; 43
scl=1; _nop_(); _nop_(); if(sda==1) rd++; scl=0; } sda=0; return rd;
//Returns 8 bit data here
} 3) FOR LCD #define dataport P2 void cmm(unsigned char item); void dat(unsigned char item); void data_str(unsigned char *str); void msdelay(unsigned char msec); void lcdint(); sbit rs = P3^5; sbit rw = P3^6; sbit en = P3^7; void cmm(unsigned char item) // Function to send command to LCD { dataport = item; rs= 0; rw=0; 44
en=1; msdelay(1); en=0; msdelay(1); return; } void dat(unsigned char item)// Function to send data to LCD { dataport = item; rs= 1; rw=0; en=1; msdelay(1); en=0; msdelay(1); return; } void lcdint() { cmm(0x38); cmm(0x0C); cmm(0x01); 45
cmm(0x06); cmm(0x80); } void msdelay(unsigned char msec) // Time delay function { int i,j ; for(i=0;i
46
Chapter 6 6.1 Future SCOPE The scope of the project work is to introduce advanced technology in converting dc voltage in to ac voltage and introducing smart energy metering concept. In future this project can be used to measuring natural gas or water consumption. These meters can be connected to GSM module and data (i.e. consumption) can be transmitted over GSM networks and the bills can be automatically issued to the particular customer through SMS. By making small modifications in the program (code) we can break the connection if user does not pay the bills in time. There is no need for the electricity officials to visit the spot to disconnect the connections i.e., everything can be controlled over the GSM module. The user can also sell the electricity to the government which is created in his home using solar cells. These meters can also be used as prepaid energy meters by slightly modifying them.
6.2 Advantages
Using this meter ,non linear loads and its metering is highly accurate and electronic measurement is more robust than that of the conventional mechanical meters
It reduces the cost of theft and corruption on electricity distribution network with electronic designs and prepayment interfaces
This Electronic energy meter measures current in both Phase and Neutral lines and calculate power consumption based on the larger of the two currents.
. EM improves the cost and quality of electricity distribution.
More accurate bills.
Lower bills.
Track of energy usage.
47
Chapter 7 Conclusion
since the inception of electricity deregulation and market-driven pricing throughout the world, utilities have been looking for a means to match consumption with generation. Energy meters are also believed to be a less costly alternative to traditional interval or time-of-use meters and are intended to be used on a wide scale with all customer classes, including residential customers .
Supporting Consumers:
An end to estimate bills, which are a major source of complaints for many customers
A tool to help consumers better manage their energy use - smart meters with a display can provide up to date information on electricity consumption in the currency of that country and in doing so help people to better manage their energy use and reduce their energy bills and carbon emissions.
Supports Power Grid: The Ability to remotely turn power on or off to a customer, read usage information from a meter, detect a service outage, detect the unauthorized use of electricity, know the maximum amount of electricity that a customer can demand at any time. It is projected to reduce the staff required to read meter data across the customer base.
Supports Environment: The billing is through HyperTerminal or GSM, so lot of paper can be saved .So Cutting of Trees can be avoided . It is believed that billing customers by time of day will encourage consumers to adjust their consumption habits to be more responsive to market prices thereby saving the power by which natural resources are protected.
It is a Greener, Smarter, New era of Energy Use.
48
Chapter 8 References 8.1 BOOK‘S USED :
Electronicsforu Plus:Feb2014Edition
Electricity meters: their construction and management: 1st edition ByCharles Henry William Gerhardi
Electricity meters: 3rd edition ByHenry G. Solomon
8.2 WEBSITE :
www.wikipedia.com
www.energymeter.com
www.thinkfast.com
www.8051projects.net/tags/prepaid-energy-meter
www.engineersgarage.com/contribution/electronic-energy-meter
en.wikipedia.org/wiki/Electricity_meter
8.3 RESEARCH PAPER USED :
Nabil Mohammad , Anomadarshi Barua and Muhammad Abdullah Arafat on “A Smart Prepaid Energy Metering System to Control Electricity Theft in proceeding Department of Electrical and Electronic Engineering ,Bangladesh University of Engineering and Technology ,Dhaka, Bangladesh.
Arne Ellerbrock , Ahmad Abdel-Majeed, and Stefan Tenbohlen on “Design and Building of a Cheap Smart Meter” in proceeding with Institute of Power Transmission and High Voltage Technology, Pfaffenwaldring 47, 70569 Stuttgart, Universität Stuttgart, Germany.
Mayur S. Thacker, Sanjay R. Yadav on “Domestic Energy Meter Interfacing Using Avr Open Source Microcontroller & Matlab” in proceeding PG Student, Electrical Engg., Govt. Engg. College, Bhuj, GTU, India.
49
Md. Mejbaul Haque, Md. Kamal Hossain , Md. Mortuza Ali , Md. Rafiqul Islam Sheikh on “Microcontroller Based Single Phase Digital Prepaid Energy Meter for Improved Metering and
Billing System” in proceeding with Dept. of Electrical and Electronic Engineering, Khulna University of Engineering & Technology, Khulna-9203, Bangladesh , Dept. of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur, Bangladesh , Dept. of Electrical and Electronic Engineering, Rajshahi University of Engineering & Technology, Rajshahi-6204, Bangladesh.
Stephen McLaughlin, Dmitry Podkuiko, and Patrick McDaniel on “Energy Theft in the Advanced Metering Infrastructure” in proceeding with Systems and Internet Infrastructure Security Laboratory (SIIS) ,Pennsylvania State University, University Park, PA.
Nagaraju Kommu, Pammi.Nagamani ,Manoj Kollam on “ Designing of an Automated Power Meter Reading with Zigbee Communication” in proceeding with Dept. of E.C.E,GSSSIETW, Mysore,India, Dept.of E.E.E, GSSSIETW, Mysore. India ,Dept. of E.C.E,ATME , Mysore,India
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