Digital energy meter

M.VEERABABU K.MAHESH

E.U.ASHOK KUMAR S.N.PREETI U.DURGA PRASAD RAJU

UNDER THE ESTEEM GUIDANCE OF Mr V.RAMA KRISHNA.(M.TECH)Assistant Professor

ABTRACT

 To calculate Power utilization, cost in a home and display its values, and also implement the prepaid card system using “Embedded system technology” and also display using “LCD”

It has three separate parts1. Power sensing part2.Power and Cost Calculation Part 3.Displaying part by using “LCD” display control

Prepaid Cards

We are using one prepaid card and card reader. The card reader is read the credit values from prepaid card, this value is stored in controller. Sensors sensed the power the sensing values are given to micro controller . When ever the utilization cost values is equal to prepaid amount, the controller turnoff the power supply

Embedded Systems An embedded system is a microcontroller-based, software driven,

reliable, real-time control system Embedded System is a combination of hardware and software used

to achieve a single specific task. Embedded systems are computer systems that monitor, respond to

or control an external environment. Environment connected to systems through sensors, actuators and

other I/O interfaces. Embedded system must meet timing & other constraints imposed

on it

Relays A relay is usually an electromechanical device that is

actuated by an electrical current. Relays are used in a wide variety of applications throughout

industry, such as in telephone exchanges, digital computers and automation systems.

Input may be electrical and output directly mechanical or vice versa.

Relays are like remote control switches and are used in many applications because of their relative simplicity, long life, and proven high reliability.

Micro Controller

The micro-controller is a chip, which has a computer processor with all its support function, memory (both program storage and RAM) and I/O built in to the device.

Micro-controllers getting faster, smaller and more power efficient they are also getting more and more features.

Micro controllers programmers can be built very cheaply or even built in to the final application circuit eliminating the need for a separate circuit.

Advantages Of Using a Microcontroller Over Microprocessor

A designer will use a microcontroller to Gather input from various sensors Process this input into a set of actions Use the output mechanisms on the Microcontroller to do

something useful RAM and ROM are inbuilt in the MC. Cheap compared to MP. Multi machine control is possible simultaneously. Examples: 8051 (ATMAL), PIC (Microchip), Motorola(Motorola),

ARM Processor

Pin Diagram Of PIC 16f874A/877A

Functional Block Diagram Of PIC 16F877A

Interfacing PIC Microcontroller To LCD

LCD Display• Liquid crystal display (LCD) has material which combines the properties of both liquid and crystals. They have a temperature range within which the molecules are almost as mobile as they would be in a liquid, but are grouped together in an order form similar to a crystal.• Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrode• LCDs with a small number of segments, such as those used in digital watches and pocket calculator, have individual electrical contacts for each segment. 

Control lines from the microcontroller.

Enable (E)This line allows access to the display through R/W and RS lines. When this line is low, the LCD is disabled and ignores signals from R/W and RS. When (E) line is high, the LCD checks the state of the two control lines and responds accordingly.

Read/Write (R/W)

This line determines the direction of data between the LCD and microcontroller. When it is low, data is written to the LCD. When it is high, data is read from the LCD.

Register select (RS)

With the help of this line, the LCD interprets the type of data on data lines. When it is low, an instruction is being written to the LCD. When it is high, a character is being written to the LCD.

ENERGY METER

An electricity meter or energy meter is a device that measures the amount of electric energy consumed by a residance,business or an electrically powered device. Electricity meters are typically calibrated in billing units, the most common one being the kilowatt hour.There are three types of meter in common use in households.

1.Standard meters2.Variable rate meters3.Prepayment meters

•

TYPES OF ENERGY METERSStandard meters: A standard meter is a basic electromechanical induction meter measures electricity consumption in terms of kilowatt-hours the amount of energy used by a load of one kilowatt over the period of one hour. Meter is installed all electricity units are charged at the same rate 24 hours a day.

Variable rate meters: Referred to as “economy 7″ meters as they are used for the economy 7 tariffs Suppliers offer variable rate meters operate on the same principle as standard meters they give two readings one for daytime electricity usage and one for night-time electricity usage.

Cont…This allows your supplier to charge you a different (usually cheaper) rate for electricity used at night time under the economy 7 tariff.

Prepayment meters: Prepayment meters usually accept tokens or cards that can be bought or topped up respectively. Customer stops paying for electricity, the electricity supply will be cut off by a relay fitted into the meter.The advantage of this kind of meter is that you can budget for how much electricity you use by paying for it before you use it.

Block Diagram of Digital Energy Meter With Cost Indicator

Simplified Diagram

Block Description The major components of this project are PIC microcontroller, CT & PT

and LCD display

The main process of this project is to measure the High voltage and high current of the major equipments, this is done through CT & PT.

These parameters are reads into controller through signal conditioning unit and first the controller converts into digital unit inbuilt ADC

The power supply unit maintains the power as necessary for the entire project using regulator, 7812 for 12v supply and 7805 for 5v .

After getting the digital value of current and voltage controller calculates parameters of power consumption, number of units and cost of energy consumed.

Multiple tariff (variable rate) meters

Electricity retailers may wish to charge customers different tariffs at different times of the day. This is because there is generally a surplus of electrical generation capacity at times of low demand , such as during the night (see supply and demand). 

Some multiple tariff meters use different tariffs for different amounts of demand. These are usually industrial meters.

Circuit Diagram

Circuit Description Power supply unit consists of Step down transformer, Rectifier,

Input filter, Regulator unit, Output filter. The Step down Transformer is used to step down the main

supply voltage from 230V AC to lower value. The Rectifier circuit is used to convert the AC voltage into its

corresponding DC voltage. There are Half-Wave, Full-Wave and bridge Rectifiers available

for this specific function The most important and simple device used in Rectifier circuit

is the diode. The circuit used for removing the ripples is called Filter circuit.

Power Supply Unit

•Step Down Transformer•Rectifier Unit•Input Filter•Regulator Unit•Output Filter 

Calculation of Power, Energy and Cost of Energy Electricity bill will be charged on per unit basis. Cost of one Kilowatt-hour (kWh)

1 Kilowatt-hour (kWh) x cost of 1 Kilowatt-hour (kWh)

1 Kilowatt-hour (kWh) x cost of one unit. 

[power =voltage x ampere] The kW is a unit of power. It is 1000 W or 1000 J/s.

Power = Energy / Time : Energy = Power × Time

If we choose to measure power in kW and time in hours,

Energy (kWh) = power (kW) × time (h)

Conclusion

The System “DIGITAL ENERGY METER WITH COST INDICATOR” is developed and operated successfully in the laboratory.

The circuit having potential and current transformers which gives the power consumption in analog form. This is converted to digital and the converted one is again converted into KWH form i.e. one unit.

According to the tariff rates stored in the microcontroller, the consumed units and cost are displayed on the LCD. 

Future Enhancement

In future this circuit can also be used as a prepaid energy meter using a smart type arrangement. For we want to add a smart card reader and relay in extra. Due to this every customer has a smart card with some credits and after completing these credits we again go to EB and recharge the card.

The energy meter reading can be send to the EB by implementing small kind of SCADA system, using this the readings can be straightly monitor by the EB.

References

e-book –“Complete guide to PIC microcontroller” John Peatman- “Embedded PIC microcontroller” Kirk Zurell- “C programming for embedded systems” Myke Predcko- “Customizing and programming your PIC

microcontroller” Onathan W.Valvano(2000)-“Embedded Microcomputer

system” Stan Giblisco –“Teach yourself electronics

THANK YOU…

QUERYS