AUTOMATIC INDIVIDUAL LOAD SHEDDING USING GSM ON BASIS OF UNITS CONSUMED

Project Advisor

Engr. Munawar Sultan

Project Title

Session: 2007-2011

Group Members

Humayun Khurshid Khan 07-EE-112

Saad Yasin 07-EE-150

Shahzaib Shabbir 07-EE-113

Inam-ul-Haq 07-EE-148

What is Load Shedding?

When supplying company receives more demand for electrical power than its

generation or installed capacity , the company has to resort to manage the available

electricity to its customers. This act is called Load Shedding.

Load shedding which often occurs in places where the total electrical power

load which can be taken by consumers greatly exceeds the available amount of energy

which can be generated by the local power station or national network of power

stations. This is a situation which is common in many developing countries. As soon as

total power demanded exceeds a certain percentage - usually 98% - of the maximum

possible power that can be generated, parts of the distribution network have to be

disconnected. Such disconnections are known as "load shedding".

If load shedding was not done the generating equipment's overload breakers

would automatically shut down the whole power station to protect its alternators

(electrical generators) from very severe damage. Such damage would be extremely

expensive to repair and would take a lot of time to do.

Why Load Shedding is carried out??

Forced outage due to breakdowns.

Planned outages for routine maintenance

Restrictions of usage of water (Hydro Generation).

Restrictions of availability of Gas (Gas Turbine).

Theme of Project

This is a Microcontroller based Project on Automatic Load Shedding using

GSM. The aim of the project is to design and develop an embedded system

to perform the AC LOAD shedding using GSM technology. Individual

consumer’s load is shed by this system using GSM modules.

Energy meter at user end is digitalized and number of units consumed is

stored in memory.

Limit of Units is specified by the server. Server sends a message to the user

end and user end sends back units consumed. If these units exceed the limit

specified by the server then command is generated that cuts off the power of

that user.

Theme of Project

The purpose of this project is to remote monitoring and control of the Domestic Energy meter. This

system enables the Electricity Department to read the meter readings regularly without the

person visiting each house. This can be achieved by the use of microcontroller unit that

continuously monitors and records the Energy Meter readings in its permanent (non-volatile)

memory location. This system also makes use of a GSM modem for remote monitoring and

control of Energy Meter.

    

The Microcontroller based system continuously records the readings and the live meter reading can

be sent to the Electricity department on request. This system also can be used to disconnect the

power supply to the house in case of non-payment of electricity bills. A dedicated GSM modem with

SIM card is required for each energy meter.

Block Diagram

Serial MUX

GSM Unit

MicrocontrollerControl unit for MUX

PC

Server End

Analog Energy Meter

Pulse Reader

GSM Unit

MicrocontrollerDISC

User End

Components

Electrical Energy Meter

IR Disc Beam Reader

Electromagnetic Relay

Microcontroller AT 8051

Multiplexer

De-multiplexer

GSM Modules

MATLAB

Electrical Energy Meter

The energy meter is an electrical measuring device, which is used to record Electrical Energy consumed over a specified period of time in terms of units. Electric meters are typically calibrated in billing units, the most common one being the kilowatt hour. Periodic readings of electric meters establishes billing cycles and energy used during a cycle.

CONSTRUCTION OF ENERGY METER

Where, CC = Current Coil ( Series Magnet ) VC = Voltage Coil ( Shunt Magnet )

CONSTRUCTION OF ENERGY METER

The watt meter has two laminated electrometers, one of which is excited by the

current in the main circuit its exciting winding being jointed in series with the

circuit, hence it is also called a series magnet. Current, which is proportional to

the voltage of the circuit, excites the other, its exciting coil is jointed in parallel

with the circuit hence, and this magnet is sometimes tested as short magnet. 

Aluminum disc is so mounted that its cuts fluxes of both magnets, hence two

eddy currents are produced due to interaction of these eddy current and the

inducting fluxes. The deflection tongue is produced due to interaction of these

eddy currents and the inducting fluxes.

Current up to 100A can be handled by such wattmeter directly but for current

greater than this value they are used in conjunction with current transformers.

The pressure coil as much as inductive as that the flux through it should lag

behind voltage by 900.

IR Disc Beam Reader

IR disc beam reader is used to detect the IR

rays. In our project it is used to digitalize the

analog meter reading by sensing cut in the

aluminium disc.

Microprocessor

• CPU is stand-alone, RAM, ROM, I/O, timer are separate

• Designer can decide on the amount of ROM, RAM and I/O ports.

• Expensive• Versatility • General-purpose

Microcontroller

• CPU, RAM, ROM, I/O and timer are all on a single chip

• Fix amount of on-chip ROM, RAM, I/O ports

• For applications in which cost, power and space are critical

• Single-purpose

Microprocessor vs. Microcontroller

VS

• A smaller computer.• On-chip RAM, ROM, I/O ports...• Example：Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X

A single chip (Microcontroller)

Microcontroller:

CPU RAM ROM

I/O Port TimerSerial

COM Port

Block Diagram

Counter Inputs

CPU

On-chip RAM

On-chip ROM for program

code

4 I/O Ports

Timer 0

Serial PortOSC

Interrupt Control

External interrupts

Timer 1

Timer/Counter

Bus Control

TxD RxDP0 P1 P2 P3

Address/Data

Counter Inputs

CPU

On-chip RAM

On-chip ROM for program

code

4 I/O Ports

Timer 0

Serial PortOSC

Interrupt Control

External interrupts

Timer 1

Timer/Counter

Bus Control

TxD RxDP0 P1 P2 P3

Address/Data

RAM – 128 Bytes (Data

memory)

ROM – 4Kbytes (ROM signify the on

– chip program space)

Serial Port – Using UART makes it simpler to interface for serial

communication.

Two 16 bit Timer/ Counter

Input/output Pins – 4 Ports of 8 bits each on a single

chip.

6 Interrupt Sources 8 – bit ALU

(Arithmetic Logic Unit)

Harvard Memory Architecture – It has 16

bit Address bus (each of RAM and ROM) and 8 bit

Data Bus.

8051 can execute 1 million one-cycle

instructions per second with a clock frequency of

12MHz.

Features of 8051

Pin Description of the 8051

 Pin No  Function  Name

1-8 8 bit input/output port (P1) pins P1.0-P1.7

9 Reset pin; Active high Reset

10 Input (receiver) for serial communication RxD

8 bit input/output port (P3) pins

P3.0

11 Output (transmitter) for serial communication TxD P3.1

P3.212 External interrupt 1 Int013 External interrupt 2 Int1 P3.3

14 Timer1 external input T0 P3.4

15 Timer2 external input T1 P3.5

16 Write to external data memory Write P3.6

17 Read from external data memory Read P3.7

18Quartz crystal oscillator (up to 24 MHz)

Crystal 219 Crystal 120 Ground (0V) Ground

21-288 bit input/output port (P2) pins/

High-order address bits when interfacing with external memory  P2.0/ A8- P2.7/ A15

29 Program store enable; Read from external program memory PSEN

30Address Latch Enable ALE

Program pulse input during Flash programming Prog

31External Access Enable;  Vcc for internal program executions EA

Programming enable voltage; 12V (during Flash programming) Vpp

32-398 bit input/output port (P0) pins/

 Low-order address bits when interfacing with external memory  P0.7/ AD7- P0.0/ AD0

40 Supply voltage; 5V (up to 6.6V) Vcc

A multiplexer can use addressing bits to select one of several input bits to be the output. Enable two or more transmission sources to share a common circuit.

A selector chooses a single data input and passes it to the MUX output

It has one output selected at a time.

Multiplexer (MUX)

A de-multiplexer (or de-mux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input.A multiplexer is often used with a complementary de-multiplexer on the receiving end.

De-Multiplexer (DEMUX)

Multiplexers & De-multiplexers

MAX232

The MAX232 IC is used to convert the TTL/CMOS logic levels to RS232 logic levels during serial communication of microcontrollers with PC. The controller operates at TTL logic level (0-5V) whereas the serial communication in PC works on RS232 standards (-25 V to + 25V). This makes it difficult to establish a direct link between them to communicate with each other.

The intermediate link is provided through MAX232. It is a dual driver/receiver that includes a capacitive voltage generator to supply RS232 voltage levels from a single 5V supply. Each receiver converts RS232 inputs to 5V TTL/CMOS levels. These receivers (R1 & R2) can accept ±30V inputs. The drivers (T1 & T2), also called transmitters, convert the TTL/CMOS input level into RS232 level.

The transmitters take input from controller’s serial transmission pin and send the output to RS232’s receiver. The receivers, on the other hand, take input from transmission pin of RS232 serial port and give serial output to microcontroller’s receiver pin. MAX232 needs four external capacitors whose value ranges from 1µF to 22µF

MAX232 Pin Description

Pin No Function Name

1

Capacitor connection pins

Capacitor 1 +

2 Capacitor 3 +

3 Capacitor 1 -

4 Capacitor 2 +

5 Capacitor 2 -

6 Capacitor 4 -

7 Output pin; outputs the serially transmitted data at RS232 logic level; connected to receiver pin of PC serial port 

T2 Out

8 Input pin; receives serially transmitted data at RS 232 logic level; connected to transmitter pin of PC serial port

R2 In

9 Output pin; outputs the serially transmitted data at TTL logic level; connected to receiver pin of controller.

R2 Out

10 Input pins; receive the serial data at TTL logic level; connected to serial transmitter pin of controller.

T2 In

11 T1 In

12 Output pin; outputs the serially transmitted data at TTL logic level; connected to receiver pin of controller.

R1 Out

13 Input pin; receives serially transmitted data at RS 232 logic level; connected to transmitter pin of PC serial port

R1 In

14 Output pin; outputs the serially transmitted data at RS232 logic level; connected to receiver pin of PC serial port

T1 Out

15 Ground (0V) Ground

16 Supply voltage; 5V (4.5V – 5.5V) Vcc

It is helpful to understand what occurs to the voltage levels. When a MAX232 IC receives a TTL level to convert, it changes a TTL Logic 0 to between +3 and +15 V, and changes TTL Logic 1 to between -3 to -15 V, and vice versa for converting from RS232 to TTL.

This can be confusing when we realize that the RS232 Data Transmission voltages at a certain logic state are opposite from the RS232 Control Line voltages at the same logic state. To clarify the matter, see the table below. For more information see RS-232 Voltage Levels.

RS232 Line Type & Logic Level

RS232 VoltageTTL Voltage to/from MAX232

Data Transmission (Rx/Tx) Logic 0

+3 V to +15 V 0 V

Data Transmission (Rx/Tx) Logic 1

-3 V to -15 V 5 V

Control Signals (RTS/CTS/DTR/DSR) Logic 0

-3 V to -15 V 5 V

Control Signals (RTS/CTS/DTR/DSR) Logic 1

+3 V to +15 V 0 V

Function of MAX232

GSM UnitsGSM (Global System for Mobile communication) is a digital mobile telephony system that is widely used all over the world.

First launched in Finland in 1991.

It operates at either the 850MHz, 900 MHz or 1800 MHz, 1900MHz frequency band.

More than 690 mobile networks provide GSM services across 213 countries.

More than 2 billion GSM mobile phone users worldwide.

MATLAB

• MATLAB is a high-level language and interactive environment that enables you to perform computationally intensive tasks faster than with traditional programming languages such as C, C++, and Fortran.

• MATLAB is a program that was originally designed to simplify the implementation of numerical linear algebra routines. It has since grown into something much bigger, and it is used to implement numerical algorithms for a wide range of applications.

MATLAB GUI (Graphical User Interface)

• The main reason GUIs are used is because it makes things simple for the end-users of the program. If GUIs were not used, people would have to work from the command line interface, which can be extremely difficult and frustrating.