Controlling of Electrical Equipments by Rf

8/2/2019 Controlling of Electrical Equipments by Rf

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CONTROLLING OF INDUSTRIAL APPLIANCES USING REMOTE

SRI SAI ADITYA INSTITUTE OF SCIENCE & TECHNOLOGY (249) 1

INTRODUCTION


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1. Introduction

A project work gives to students an opportunity to make a detailed study

of the various practical and theoretical aspects of the subject understudy. It is quite essential for students to choose a particular topic and

get acquired with the practical parts of it. Also a study of the theory is a

must for the students, apart from class subjects which they study. A

project work is an added advantage, since it improves their thinking

power and creates an interest for the subject. It also makes the students

to approach the subject properly and have a clear understanding of

various topics.

It enables to think own to achieve something remarkable. Hence he

undertaking of a project work by students is very necessary. It also

makes hem to achieve something remarkable


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CIRCUIT DIAGRAM


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HARDWARE COMPONENTS:

POWER SUPPLYMICRO CONTROLLERRF MODULEDEVICES


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HARDWARE

EXPLAINATION


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Power supply

The power supplies are designed to convert high voltage AC mains

electricity to a suitable low voltage supply for electronics circuits and other devices. A

power supply can by broken down into a series of blocks, each of which performs a

particular function. A d.c power supply which maintains the output voltage constant

irrespective of a.c mains fluctuations or load variations is known as Regulated D.C

Power Supply

For example a 5V regulated power supply system as shown below:


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TRANSFORMER:

A transformer is an electrical device which is used to convert electrical power

from one electrical circuit to another without change in frequency. Transformers convert

AC electricity from one voltage to another with little loss of power. Transformers work

only with AC and this is one of the reasons why mains electricity is AC. Step-up

transformers increase in output voltage, step-down transformers decrease in output

voltage. Most power supplies use a step-down transformer to reduce the dangerously high

mains voltage to a safer low voltage. The input coil is called the primary and the output

coil is called the secondary. There is no electrical connection between the two coils;

instead they are linked by an alternating magnetic field created in the soft-iron core of the

transformer. The two lines in the middle of the circuit symbol represent the core.

Transformers waste very little power so the power out is (almost) equal to the power in.

Note that as voltage is stepped down current is stepped up. The ratio of the number of

turns on each coil, called the turns ratio, determines the ratio of the voltages. A step-

down transformer has a large number of turns on its primary (input) coil which is

connected to the high voltage mains supply, and a small number of turns on its secondary

(output) coil to give a low output voltage.


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An Electrical Transformer

Turns ratio = Vp/ VS = Np/NS

Power Out= Power In

VS X IS=VP X IP

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

RECTIFIER:

A circuit which is used to convert a.c to dc is known as RECTIFIER. The process

of conversion a.c to d.c is called rectification

TYPES OF RECTIFIERS:

Half wave Rectifier


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Full wave rectifier1. Centre tap full wave rectifier.

2. Bridge type full bridge rectifier.

Comparison of rectifier circuits:

Parameter

Type of Rectifier

Half wave Full wave Bridge

Number of diodes1 2 3

PIV of diodesVm 2Vm Vm

D.C output voltage Vm/ 2Vm/ 2Vm/

Vdc,at 0.318Vm 0.636Vm 0.636Vm


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no-load

Ripple factor 1.21 0.482 0.482

Ripple

Frequency f 2f 2f

Rectification

Efficiency 0.406 0.812 0.812

Transformer

Utilization

Factor(TUF)

0.287 0.693 0.812

RMS voltage Vrms Vm/2 Vm/2 Vm/2

Full-wave Rectifier:

From the above comparison we came to know that full wave bridge rectifier as

more Advantages than the other two rectifiers. So, in our project we are using full wave

bridge rectifier circuit.


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Bridge Rectifier:

A bridge rectifier makes use of four diodes in a bridge arrangement to achieve

full-wave rectification. This is a widely used configuration, both with individual diodes

wired as shown and with single component bridges where the diode bridge is wired

internally.

A bridge rectifier makes use of four diodes in a bridge arrangement as shown in fig

(a) to achieve full-wave rectification. This is a widely used configuration, both with

individual diodes wired as shown and with single component bridges where the diode

bridge is wired internally.

Bridge Rectifier

OPERATION:


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During positive half cycle of secondary, the diodes D2 and D3 are in forward

biased while D1 and D4 are in reverse biased as shown in the fig(b). The current flow

direction is shown in the fig (b) with dotted arrows.

During negative half cycle of secondary voltage, the diodes D1 and D4 are in

forward biased while D2 and D3 are in reverse biased as shown in the fig(c). The current

flow direction is shown in the fig (c) with dotted arrows.

FILTER:


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A Filter is a device which removes th a.c component of rectifier output

but allows the d.c component to reach the load

Capacitor Filter:

We have seen that the ripple content in the rectified output of half wave rectifier is

121% or that of full-wave or bridge rectifier or bridge rectifier is 48% such high

percentages of ripples is not acceptable for most of the applications. Ripples can be

removed by one of the following methods of filtering:

(a) A capacitor, in parallel to the load, provides an easier bypass for the ripples voltagethough it due to low impedance. At ripple frequency and leave the d.c to appear the load.

(b) An inductor, in series with the load, prevents the passage of the ripple current (due to

high impedance at ripple frequency) while allowing the d.c (due to low resistance to d.c)

(c) Various combinations of capacitor and inductor, such as L-section filter section

filter, multiple section filter etc. which make use of both the properties mentioned in (a)

and (b) above. Two cases of capacitor filter, one applied on half wave rectifier and

another with full wave rectifier.

Filtering is performed by a large value electrolytic capacitor connected across the

DC supply to act as a reservoir, supplying current to the output when the varying DC

voltage from the rectifier is falling. The capacitor charges quickly near the Peak of the

varying DC, and then discharges as it supplies current to the output.

Filtering significantly increases the average DC voltage to almost the peak value

(1.4 RMS value). To calculate the value of capacitor(C).


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REGULATOR:

Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or variable

output voltages. The maximum current they can pass also rates them. Negative voltage

regulators are available, mainly for use in dual supplies. Most regulators include some

automatic protection from excessive current ('overload protection') and overheating

('thermal protection'). Many of the fixed voltage regulator ICs has 3 leads and look like

power transistors, such as the 7805 +5V 1A regulator shown on the right. The LM7805 is

simple to use. You simply connect the positive lead of your unregulated DC power

supply (anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to

the Common pin and then when you turn on the power, you get a 5 volt supply from the

output pin.

A Three Terminal Voltage Regulator


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78XX:

The Bay Linear LM78XX is integrated linear positive regulator with three

terminals. The LM78XX offer several fixed output voltages making them useful in wide

range of applications. When used as a zener diode/resistor combination replacement, the

LM78XX usually results in an effective output impedance improvement of two orders of

magnitude, lower quiescent current. The LM78XX is available in the TO-252, TO-220 &

TO-263packages,

Features:

Output Current of 1.5A

Output Voltage Tolerance of 5%

Internal thermal overload protection

Internal Short-Circuit Limited

No External Component

Output Voltage 5.0V, 6V, 8V, 9V, 10V, 12V, 15V, 18V, 24V

Offer in plastic TO-252, TO-220 & TO-263

Direct Replacement for LM78XX


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Diodes

Diodes is a P-N junction semi-conductor unilateral device, in the

for ward bias. The depletion layer width is reduced majority carries can

cross the junction. Thus the junction resistance is reduced current flows.

In the reverse bias. The width of the depletion layer increase due to this

resistance increases and current does not flow.


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Forward Biased P-N junction:

When external voltage applied to the junction is cancels the

potential barrier. Thus permitting flow of current. It is called forward

biasing.

Suppose positive battery terminal is connected to P-region of a

semiconductor and the negative battery terminal to the N-region as

shown in Fig is called bias. Forward bias permits easy flow of current

across the junction. The current flow may be explained as the following

ways.

As soon as the battery connections are made, holes are repelled bythe positive battery terminal ad electronics are repellld by the negative

battery terminal with the holes are driven to wards the junction. This

movement of electronics and holes constitutes a large current flow

through the semiconductor. The diode offers low resistance in forwards

direction.

The applied forward voltage reduced the height of potentialbarrie4r at the junction. It allows more caries cross the junction, more


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current to flow across the junction. Forward bias reduced the thickness

of depletion layer.

Reverse Biased P-N junction:

When the external voltage applied to the junction is in such a

direction that potential barrier is increased. It is called reverse biasing.


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Suppose a negative terminal of the battery is connected to P-

region of the diode and the positive battery terminal the N-region as

shown in Fig is called reverse bias. In this case holes are attracted by the

negative battery terminal and electrons by the positive terminal so that

both holes and electronics move away from the junction since there is no

current flow and the junction offers high resistance. The applied reverse

voltage V increase the potential barrier there by blocking the flow of

majority carries. The rever4se bias increases the thickness of depletion

layer.

Although under reverse bias condition, there is practically no

current due to majority carries, yet there is a small amount of current due

to flow of minority carries. This current is called reverse saturation

current lo.


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Since, minority carriers are thermally generated lo is

extremely temperature dependent lo found to double to every 100C rise

extremely temperature dependent. lo is found to double to every 100C

rise for germanium and for every 60

C rise in silicon. L0 is in order of

mA for germanium and nH for silicon.

If reverse voltage is increased continuously the kinetic energy of

minority electronics will become high enough to knockout electronic

from the semiconductor atom. At this stage break down of the junction

occurs, characterized by a sudden rise of reverse current and a sudden

fall of the resistance of barrier region. This may destroy the junction

permanently.

CAPACITORS


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Introduction:

A capacitor or condenser is a passive electronic component

considering of at least two conduction surfaces separated by on

insulation medium called dielectric. The conduction surfaces may be in

the from of circular or rectangular or cylindrical in shape the most

common dielectric material used in capacitors are Mica, air, paper,

ceramic, etc,. the kind of dielectric material used names the type of

capacitor, like resister, capacitors are also available in fixed andvariable types.


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Behavior of a Capacitor:

The process of storing electric charge in a capacitor is know as

charging and the release of stored energy is known as discharge.

Properties of Capacitor:

It is a two terminal passive element. It stores electric charge. it allows AC and blocks DC in the CKT. It opposes the instantaneous charge of voltage in the CKT.

Capacitance:

Capacitance is the property exhibited by a capacitor and may bedefined as ability of a capacitor to store electric charge per unit

operatically difference. It is represented by the letter C. the unit of

capacitor is per paired and is CKT symbol is

It has been observed that quantity of charge a is proportional to the

applied voltage V in volt.0


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Q = CV

C = Q/V

Hence one served is defined as the capacitance of a capacitor

which requires a charge a one coulomb to establish aspect one volt

between its plates.

1Farad=1Coloumb/1Volt

The unit of capacitance farad is two large for practical purpose.Hence much smaller like F and picoF are qeheraly. Employed

CLASSIFICATION OF CAPACITORS:

According to the physical construction Fixed capacitor:

Whose capacitance volume cannot be varied mechanically or by one

other external means.

Variable capacitor:Whose capacitance value can be varied quite frequently or

Less frequency.

Ex: Tuning capacitor, and trimming capacitor.


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According to the Polarization: Polarized:Used in PC application.

Ex: Aluminum, tantalum, electrolytic capacitor.

Non Polarized:Used in AC application.

Ex: Aluminum, tantalum, electrolytic capacitor.

(Mica, Ceramic)

According to Voltage Rating:Low voltage capacitors (100V)

Ex: mica, glass, ceramic, capacitor.

Specifications of Capacitors:

Capacitor value. Dielectric constant Dielectric strength Power factor


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Tolerance Insulation resistance Temperature rang Frequency rang and Stability.

FIXED CAPACITOR

Paper capacitor:

These are two types 1. Impregnated paper capacitor,

2. Metalised paper capacitors.

Properties:

They are usually high-voltage (7100V) capacitors. Their capacitance value is usually between 0.0024F and

0.05F

They are mechanically very strong.

They are very cheap. They are quick balky.


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They have poor high frequency characteristics.Applications:

Used as R.F suppression capacitors in CKF where noiseinterference from R.F. sources can occur.

Used as by pass capacitors in amplifiers. Used in high voltage DCCKF. Used in communicating CKF of SCR.\

Mica Capacitors:

These are two types

Stacked mica capacitors Severed mica capacitors.

Properties:

Mica capacitors have good mechanical strength. They can be operated to temperatures as high a 9000C. They can with stand very high frequency operation. They are suitable for very high frequency operation.


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The capacitance value is generally between 5.3300PF. The capacitance value is highly stable. They are cheaper than polyester capacitors.

Applications:

Used as high-voltage capacitors in low frequency powerapplications.

Used as high voltage R.F. capacitors. Used as high voltage transmitter capacitors.

LIGHT-EMITTING DIODE (LED)

Light-emitting diodes are elements for light signalization in electronics. They are

manufactured in different shapes, colors and sizes. For their low price, low consumption andsimple use, they have almost completely pushed aside other light sources- bulbs at first place.

They perform similar to common diodes with the difference that they emit light when current

flows through them.

Fig LED Interfacing with 89C51 Microcontroller


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It is important to know that each diode will be immediately destroyed unless its current is

limited. This means that a conductor must be connected in parallel to a diode. In order tocorrectly determine value of this conductor, it is necessary to know diodes voltage drop inforward direction, which depends on what material a diode is made of and what color it is. There

are three main types of LEDs. Standard ones get full brightness at current of 20mA. Low Current

diodes get full brightness at ten times lower current while Super Bright diodes produce moreintensive light than Standard ones.

Since the 8051 microcontrollers can provide only low input current and since their pins are

configured as outputs when voltage level on them is equal to 0, direct connecting to LEDs is

carried out as it is shown on fig 3.3.1(Low Current LED, cathode is connected to out pin of

89C51)

LED INTERFACING WITH THE MICROCONTROLLER:

LED stands for Light Emitting Diode. LEDs are the most widely used input/outputdevices of the 8051.Microcontroller port pins cannot drive these LEDs as these require high

currents to switch on. Thus the positive terminal of LED is directly connected to Vcc, power

supply and the negative terminal is connected to port pin through a current limiting resistor. This

current limiting resistor is connected to protect the port pins from sudden flow of high currents

from the power supply.

Thus in order to glow the LED, first there should be a current flow through the LED. In order to

have a current flow, a voltage difference should exist between the LED terminals. To ensure the

voltage difference between the terminals and as the positive terminal of LED is connected to

power supply Vcc, the negative terminal has to be connected to ground. Thus this ground valueis provided by the microcontroller port pin. This can be achieved by writing an instruction CLRP1.0. With this, the port pin P1.0 is initialized to zero and thus now a voltage difference isestablished between the LED terminals and accordingly, current flows and therefore the LED

glows. LED and switches can be connected to any one of the four port pins.

P1.0

Vcc


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Fig LED Interfacing with 89C51

In this project, LEDS are used as the display units to indicate the level of the petrochemical

liquid in the processor container which is to be purified, motor running indication and the relay

on condition.

MICROCONTROLLERS

INTRODUCTION:

Microprocessors and microcontrollers are widely used in embedded systems

products. Microcontroller is a programmable device. A microcontroller has a CPU in

addition to a fixed amount of RAM, ROM, I/O ports and a timer embedded all on a single

chip. The fixed amount of on-chip ROM, RAM and number of I/O ports in

microcontrollers makes them ideal for many applications in which cost and space are

critical.

The Intel 8051 is Harvard architecture, single chip microcontroller (C) which

was developed by Intel in 1980 for use in embedded systems. It was popular in the 1980s

and early 1990s, but today it has largely been superseded by a vast range of enhanced

devices with 8051-compatible processor cores that are manufactured by more than 20independent manufacturers including Atmel, Infineon Technologies and Maxim

Integrated Products.

8051 is an 8-bit processor, meaning that the CPU can work on only 8 bits of data

at a time. Data larger than 8 bits has to be broken into 8-bit pieces to be processed by the


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CPU. 8051 is available in different memory types such as UV-EPROM, Flash and NV-

RAM.

The microcontroller used in this project is At89s52. Atmel Corporation introduced

this at89s52 microcontroller. This microcontroller belongs to 8051 family. This

microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one serial

port and four ports (each 8-bits wide) all on a single chip. At89s52 is Flash type 8051.

The present project is implemented on Keil Uvision. In order to program the

device, proload tool has been used to burn the program onto the microcontroller.

The features, pin description of the microcontroller and the software tools used are

discussed in the following sections.

3.2 FEATURES OF At89s52:

4K Bytes of Re-programmable Flash Memory.

RAM is 128 bytes.

2.7V to 6V Operating Range. Fully Static Operation: 0 Hz to 24 MHz. Two-level Program Memory Lock. 128 x 8-bit Internal RAM. 32 Programmable I/O Lines. Two 16-bit Timer/Counters.


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Six Interrupt Sources. Programmable Serial UART Channel. Low-power Idle and Power-down Modes.

DESCRIPTION:

The At89s52 is a low-voltage, high-performance CMOS 8-bit microcomputer with

4K bytes of Flash programmable memory. The device is manufactured using Atmels

high-density nonvolatile memory technology and is compatible with the industry-

standard MCS-51 instruction set. By combining a versatile 8-bit CPU with Flash on a

monolithic chip, the Atmel At89s52 is a powerful microcomputer, which provides a

highly flexible and cost-effective solution to many embedded control applications.

In addition, the At89s52 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes. The Idle Mode

stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system

to continue functioning. The power-down mode saves the RAM contents but freezes the

oscillator disabling all other chip functions until the next hardware reset.


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PIN DIAGRAM


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Fig 4.2.1: Pin diagram


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Fig :Block diagram of at89s52


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PIN DESCRIPTION:

VCC: Pin 40 provides supply voltage to the chip. The voltage source is +5V.

GND: Pin 20 is the ground.

XTAL1 and XTAL2:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting

amplifier that can be configured for use as an on-chip oscillator, as shown in Figure 11.

Either a quartz crystal or ceramic resonator may be used. To drive the device from an

external clock source, XTAL2 should be left unconnected while XTAL1 is driven, as

shown in the below figure. There are no requirements on the duty cycle of the external

clock signal, since the input to the internal clocking circuitry is through a divide-by-two

flip-flop, but minimum and maximum voltage high and low time specifications must be

observed.

Fig : Oscillator Connections


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C1, C2 = 30 pF 10 pF for Crystals

= 40 pF 10 pF for Ceramic Resonators

Fig : External Clock Drive Configuration

RESET:

Pin9 is the reset pin. It is an input and is active high. Upon applying a high pulseto this pin, the microcontroller will reset and terminate all the activities. This is often

referred to as a power-on reset.


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EA (External access):

Pin 31 is EA. It is an active low signal. It is an input pin and must be connected to

either Vcc or GND but it cannot be left unconnected.

The 8051 family members all come with on-chip ROM to store programs. In such

cases, the EA pin is connected to Vcc. If the code is stored on an external ROM, the EA

pin must be connected to GND to indicate that the code is stored externally.

PSEN (Program store enable):

This is an output pin.

ALE (Address latch enable):

This is an output pin and is active high.

PORTS 0, 1, 2 & 3:

The four ports P0, P1, P2 and P3 each use 8 pins, making them 8-bit ports. All theports upon RESET are configured as input, since P0-P3 have value FFH on them.

PORT 0(P0):


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Port 0 is also designated as AD0-AD7, allowing it to be used for both address and

data. ALE indicates if P0 has address or data. When ALE=0, it provides data D0-D7, but

when ALE=1, it has address A0-A7. Therefore, ALE is used for demultiplexing address

and data with the help of an internal latch.

When there is no external memory connection, the pins of P0 must be connected

to a 10K-ohm pull-up resistor. This is due to the fact that P0 is an open drain. With

external pull-up resistors connected to P0, it can be used as a simple I/O, just like P1 and

P2. But the ports P1, P2 and P3 do not need any pull-up resistors since they already have

pull-up resistors internally. Upon reset, ports P1, P2 and P3 are configured as input ports.

PORT 1 & PORT 2:

With no external memory connection, both P1 and P2 are used as simple I/O.

With external memory connections, port 2 must be used along with P0 to provide the 16-

bit address for the external memory. Port 2 is designated as A8-A15 indicating its dual

function. While P0 provides the lower 8 bits via A0-A7, it is the job of P2 to provide bits

A8-A15 of the address.

PORT 3:


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Port 3 occupies a total of 8 pins, pins 10 through 17. It can be used as input or

output. P3 does not need any pull-up resistors, the same as port 1 and port 2. Port 3 has an

additional function of providing some extremely important signals such as interrupts.

Table: Port 3 Alternate Functions

Addressing Modes:

While operating, processor processes data according to the program instructions.Each instruction consists of two parts. One part describes what should be done and

another part indicates what to use to do it. This later part can be data (binary number) or

address where the data is stored. All 8051 microcontrollers use two ways of addressing

depending on which part of memory should be accessed:


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Direct Addressing:

On direct addressing, a value is obtained from a memory location while the

address of that location is specified in instruction. Only after that, the instruction can

process data (how depends on the type of instruction: addition, subtraction, copy).

Obviously, a number being changed during operating a variable can reside at that

specified address. For example: Since the address is only one byte in size ( the greatest

number is 255), this is how only the first 255 locations in RAM can be accessed in this

case the first half of the basic RAM is intended to be used freely, while another half is

reserved for the SFRs.

Indirect Addressing:

On indirect addressing, a register which contains address of another register is

specified in the instruction. A value used in operating process resides in that another

register. For example:

Only RAM locations available for use are accessed by indirect addressing (never

in the SFRs). For all latest versions of the microcontrollers with additional memory block

(those 128 locations in Data Memory), this is the only way of accessing them. Simply,

when during operating, the instruction including @ sign is encountered and if the

specified address is higher than 128 (7F hex.), the processor knows that indirect

addressing is used and jumps over memory space reserved for the SFRs.

MACHINE CYCLE FOR 8051:

The CPU takes a certain number of clock cycles to execute an instruction. In the

8051 family, these clock cycles are referred to as machine cycles. The length of the

machine cycle depends on the frequency of the crystal oscillator. The crystal oscillator,

along with on-chip circuitry, provides the clock source for the 8051 CPU.


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The frequency can vary from 4 MHz to 30 MHz, depending upon the chip rating

and manufacturer. But the exact frequency of 11.0592 MHz crystal oscillator is used to

make the 8051 based system compatible with the serial port of the IBM PC.

In the original version of 8051, one machine cycle lasts 12 oscillator periods.

Therefore, to calculate the machine cycle for the 8051, the calculation is made as 1/12 of

the crystal frequency and its inverse is taken.

The assembly language program is written and this program has to be dumped into

the microcontroller for the hardware kit to function according to the software. The

program dumped in the microcontroller is stored in the Flash memory in the

microcontroller. Before that, this Flash memory has to be programmed and is discussed

in the next section.

PROGRAMMING THE FLASH

The At89s52 is normally shipped with the on-chip Flash memory array in the

erased state (that is, contents = FFH) and ready to be programmed. The programming

interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable

signal. The low-voltage programming mode provides a convenient way to program the

At89s52 inside the users system, while the high-voltage programming mode is

compatible with conventional third party Flash or EPROM programmers. The At89s52 is

shipped with either the high-voltage or low-voltage programming mode enabled. The

respective top-side marking and device signature codes are listed in the following table.

Table 4.3.1: Top side marking & Device Signature codes


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The At89s52 code memory array is programmed byte-byte in either programming

mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory

must be erased using the Chip Erase Mode.

Programming Algorithm:

Before programming the At89s52, the address, data and control signals should be

set up according to the Flash programming mode table. To program the At89s52, the

following steps should be considered:

1. Input the desired memory location on the address lines.

2. Input the appropriate data byte on the data lines.

3. Activate the correct combination of control signals.

4. Raise EA/VPP to 12V for the high-voltage programming mode.

5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-

write cycle is self-timed and typically takes no more than 1.5 ms.


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Repeat steps 1 through 5, changing the address and data for the entire array or until the

end of the object file is reached.

Data Polling:

The At89s52 features Data Polling to indicate the end of a write cycle. During a

write cycle, an attempted read of the last byte written will result in the complement of the

written datum on PO.7. Once the write cycle has been completed, true data are valid on

all outputs, and the next cycle may begin. Data Polling may begin any time after a write

cycle has been initiated.

Ready/Busy:

The progress of byte programming can also be monitored by the RDY/BSY outputsignal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY.

P3.4 is pulled high again when programming is done to indicate READY.

Chip Erase:

The entire Flash array is erased electrically by using the proper combination of

control signals and by holding ALE/PROG low for 10 ms. The code array is written with

all 1s. The chip erase operation must be executed before the code memory can be re-

programmed.

Reading the Signature Bytes:


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The signature bytes are read by the same procedure as a normal verification of

locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low.

The values returned are as follows.

(030H) = 1EH indicates manufactured by Atmel

(031H) = 51H indicates at89s52

(032H) = FFH indicates 12V programming

(032H) = 05H indicates 5V programming

Programming Interface:

Every code byte in the Flash array can be written and the entire array can be

erased by using the appropriate combination of control signals. The write operation cycle

is self timed and once initiated, will automatically time itself to completion. All major

programming vendors offer worldwide support for the Atmel microcontroller series.

Table: Flash Programming Mode


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Fig: Programming the Flash


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PROGRAM OF MICROCONTROLLER OF RF:

org 0h

mov p1,#00h

mov p2,#0ffh

start:

jnb p2.0,l1

jnb p2.1,l2

jnb p2.2,l3

jnb p2.3,l4

sjmp start

l1:

mov p1,#00001100b

acall del

mov p1,#00000110b

acall del

mov p1,#00000011b

acall del

mov p1,#00001001b

acall del

sjmp l1

l2:

mov p1,#00001001b

acall del


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mov p1,#00000011b

acall del

mov p1,#00000110b

acall del

mov p1,#00001100b

acall del

sjmp l2

l3:

mov p1,#00001000b

acall del

mov p1,#00001100b

acall del

mov p1,#00000100b

acall del

mov p1,#00000110b

acall del

mov p1,#00000010b

acall del

mov p1,#00000011b

acall del

mov p1,#00000001b

acall del

mov p1,#00001001b

acall del

sjmp l3


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l4:

mov p1,#00001001b

acall del

mov p1,#00000001b

acall del

mov p1,#00000011b

acall del

mov p1,#00000010b

acall del

mov p1,#00000110b

acall del

mov p1,#00000100b

acall del

mov p1,#00001100b

acall del

mov p1,#00001000b

acall del

sjmp l4

del:

mov r0,#6

h3:mov r1,#10

h2:mov r2,#250

h1:djnz r2,h1

djnz r1,h2

djnz r0,h3


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ret

end

RELAYS

Relay is an electrically operated switch.

Current flowing through the coil of the relay

creates a magnetic field which attracts a lever

and changes the switch contacts. The coil current can be on or off so

relays have two switch positions and they are double throw

(changeover) switches.

Relays allow one circuit to switch a second circuit which

can be completely separate from the first. For example a low voltage

battery circuit can use a relay to switch a 230V AC mains circuit. There

is no electrical connection inside the relay between the two circuits; the

link is magnetic and mechanical.


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The coil of a relay passes a relatively large current, typically 30mA

for a 12V relay, but it can be as much as 100mA for relays designed to

operate from lower voltages. Most ICs (chips) cannot provide this

current and a transistor is usually used to amplify the small IC current to

the larger value required for the relay coil. The maximum output current

for the popular 555 timer IC is 200mA so these devices can supply relay

coils directly without amplification.

Relays are usually SPDT or DPDT but they can have many more

sets of switch contacts, for example relays with 4 sets of changeover

contacts are readily available. For further information about switch

contacts and the terms used to describe them please see the page on

switches.


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Most relays are designed for PCB mounting but you can solder

wires directly to the pins providing you take care to avoid melting the

plastic case of the relay. The supplier's catalogue should show you the

relay's connections. The coil will be obvious and it may be connected

either way round. Relay coils produce brief high voltage 'spikes' when

they are switched off and this can destroy transistors and ICs in the

circuit. To prevent damage you must connect a protection diode across

the relay coil.

The animated picture shows a working relay with its coil and

switch contacts. You can see a lever on the left being attracted by

magnetism when the coil is switched on. This lever moves the switch

contacts. There is one set of contacts (SPDT) in the foreground and

another behind them, making the relay DPDT.
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The relay's switch connections are usually labelled COM, NC and NO:

COM = Common, always connect to this, it is the moving part ofthe switch.

NC = Normally Closed, COM is connected to this when the relaycoil is off.

NO = Normally Open, COM is connected to this when the relaycoil is on.

Connect to COM and NO if you want the switched circuit to be onwhen the relay coil is on.

Connect to COM and NC if you want the switched circuit to be onwhen the relay coil is off.

Choosing a relay

You need to consider several features when choosing a relay:

1.Physical size and pin arrangement If you are choosing a relay foran existing PCB you will need to ensure that its dimensions and

pin arrangement are suitable. You should find this information in

the supplier's catalogue.

2.Coil voltage the relay's coil voltage rating and resistance must suitthe circuit powering the relay coil. Many relays have a coil rated

for a 12V supply but 5V and 24V relays are also readily available.


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Some relays operate perfectly well with a supply voltage which is

a little lower than their rated value.

3.Coil resistance the circuit must be able to supply the currentrequired by the relay coil. You can use Ohm's law to calculate the

current:

Relay coil current =

supply voltage

coil resistance

4.For example: A 12V supply relay with a coil resistance of 400passes a current of 30mA. This is OK for a 555 timer IC

(maximum output current 200mA), but it is too much for most ICs

and they will require a transistor to amplify the current.

5.Switch ratings (voltage and current) the relay's switch contactsmust be suitable for the circuit they are to control. You will need to

check the voltage and current ratings. Note that the voltage rating

is usually higher for AC, for example: "5A at 24V DC or 125V

AC".

6.Switch contact arrangement (SPDT, DPDT etc).Most relays are SPDT or DPDT which are often described as

"single pole changeover" (SPCO) or "double pole changeover"

(DPCO). For further information please see the page on switches

Protection diodes for relays
http://www.kpsec.freeuk.com/ohmslaw.htmhttp://www.kpsec.freeuk.com/trancirc.htm#chiphttp://www.kpsec.freeuk.com/trancirc.htm#chiphttp://www.kpsec.freeuk.com/ohmslaw.htm


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Transistors and ICs (chips) must be protected from the brief high voltage

'spike' produced when the relay coil is switched off. The diagram shows

how a signal diode (eg 1N4148) is connected across the relay coil to

provide this protection. Note that the diode is connected 'backwards' so

that it will normally not conduct. Conduction only occurs when the relay

coil is switched off, at this moment current tries to continue flowing

through the coil and it is harmlessly diverted through the diode. Without

the diode no current could flow and the coil would produce a damaging

high voltage 'spike' in its attempt to keep the current flowing.

Reed relays

Reed relays consist of a coil surrounding a reed

switch. Reed switches are normally operated with a magnet, but in a

reed relay current flows through the coil to create a magnetic field and

close the reed switch.

Reed relays generally have higher coil resistances than standard

relays (1000 for example) and a wide range of supply voltages (9-20V

for example). They are capable of switching much more rapidly than


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standard relays, up to several hundred times per second; but they can

only switch low currents (500mA maximum for example).

Relays and transistors compared:

Like relays, transistors can be used as an electrically operated

switch. For switching small DC currents (< 1A) at low voltage they are

usually a better choice than a relay. However transistors cannot switch

AC or high voltages (such as mains electricity) and they are not usually

a good choice for switching large currents (> 5A). In these cases a relay

will be needed, but note that a low power transistor may still be needed

to switch the current for the relay's coil! The main advantages and

disadvantages of relays are listed below:

Advantages of relays:

Relays can switch AC and DC, transistors can only switch DC. Relays can switch high voltages, transistors cannot. Relays are a better choice for switching large currents (> 5A). Relays can switch many contacts at once.

Disadvantages of relays:

Relays are bulkier than transistors for switching small currents.
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Relays cannot switch rapidly (except reed relays), transistors canswitch many times per second.

Relays use more power due to the current flowing through theircoil.

Relaysrequire more current than many chips can provide, so a lowpower transistor may be needed to switch the current for the relay's

coil.

RF- MODULE:

The RF Module 3.5a is an optional package that

extends the COMSOL Multiphysics modeling environment with

customized user interfaces and functionality optimized for the

analysis of electromagnetic waves.

This particular module solves problems in thegeneral field of electromagnetic waves, such as RF and microwave

applications, optics, and photonics. The application modes included

here are fully multiphysics enabled, making it possible to couple them

to any other physics application mode in COMSOL Multiphysics or

the other modules. For example, to analyze stress-optical effects in a

waveguide, you would first do a plane strain analysis using the

Structural Mechanics Module followed by an optical mode analysis

show the resulting split of the fundamental modes.

The underlying equations for electromagnetics

are automatically available in all of the application modesa featureunique to COMSOL Multiphysics. This also makes nonstandard

modeling easily accessible.


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The documentation set for the RF Module consists of theRF Module

Users Guide, theRF Module Model Library, and the book you are

reading, theRF Module Reference Guide.


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ULN2003 (MOTOR DRIVE)

DEFINITION:

Motor drivers are essentially little current amplifiers; their

function is to take a low-current control signal, and turn it into a

proportionally higher-current signal that can drive a motor. Stepper

motor also has a motor driver circuit to drive it.uln 2003 is one of the

motor driver circuit.

INTERNAL DESCRIPTION OF ULN2003:

The ULN2003 is a monolithic high voltage and high current

Darlington transistor arrays. It consists of seven NPN Darlington pairs


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that feature high-voltage outputs with common-cathode clamp diode for

switching inductive loads.

The collector-current rating of a single Darlington pair is 500mA.

The Darlington pairs may be paralleled for higher current capability.

Applications include relay drivers, hammer drivers, lamp drivers,

display drivers (LED gas discharge), line drivers, and logic buffers.

pair for operation directly with TTL or 5V CMOS Devices.

WORKING OF ULN 2003:

Motor are used for the motion of any body for example to move a robot,

to move gate near the railway gates etc. generally motor work on the

12volts or the 5volts during the interface of the any motor to the micro

controller we need to have a motor driver circuit.

Motor driver is used as the amplifier to which contains transistor

connected in the form of the Darlington pair. The Darlington transistor

(often called a Darlington pair) is a compound structure consisting of

twobipolar transistors(either integrated or separated devices) connected

in such a way that the current amplified by the first transistor is

amplified further by the second one. This configuration gives a much

highercurrentgainthan each transistor taken separately and, in the case

of integrated devices, can take less space than two individual transistors

because they can use a sharedcollector. Integrated Darlington pairscome packaged singly in transistor-like packages or as an array of

devices (usually eight) in anintegrated circuit.
http://en.wikipedia.org/wiki/Bipolar_transistorhttp://en.wikipedia.org/wiki/Bipolar_transistorhttp://en.wikipedia.org/wiki/Bipolar_transistorhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Bipolar_transistor


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So the motor driver circuit I placed in middle of the micro controller and

the motor what we are using, the below figure explains ULN driver to

motor connection. We have the connection of micro controller to the

driver and the driver to the motor. By this the motor can rotate in its

individual direction. Motor has the clock wise direction and anti clock

wise direction depend upon the application. Micro controller works on

5volts has the motor needs the 12v or the 5v

Interfacing uln2803 to micro controller:


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FEATURES OF ULN2003:

Output current (single output): 500 mA max High sustaining voltage output: 50 V min Inputs compatible with various types of logic Package Type-APG: DIP-16pin

DC MOTOR:

A DC motor is anelectric motorthat runs ondirect current(DC)

electricity. DC motors were used to run machinery, often eliminating theneed for a local steam engine or internal combustion engine. DC motors

can operate directly from rechargeable batteries, providing the motive

power for the first electric vehicles. Today DC motors are still found in

applications as small as toys and disk drives, or in large sizes to operate

steel rolling mills and paper machines. Modern DC motors are nearly

always operated in conjunction with power electronic devices.

Types of motors

Permanent-magnet electric motors

A permanent-magnet motor does not have a field winding on the

stator frame, instead relying on permanent magnets to provide the

magnetic field against which the rotor field interacts to produce torque.
http://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Permanent-magnet_electric_motorhttp://en.wikipedia.org/wiki/Permanent-magnet_electric_motorhttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Electric_motor


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Compensating windings in series with the armature may be used on

large motors to improve commutation under load. Because this field is

fixed, it cannot be adjusted for speed control. Permanent-magnet fields

(stators) are convenient in miniature motors to eliminate the powerconsumption of the field winding. Most larger DC motors are of the

"dynamo" type, which have stator windings. Historically, permanent

magnets could not be made to retain high flux if they were

disassembled; field windings were more practical to obtain the needed

amount of flux. However, large permanent magnets are costly, as well as

dangerous and difficult to assemble; this favors wound fields for large

machines.

Brushed DC electric motor

Workings of a brushed electric motor with a two-pole rotor and

permanent-magnet stator. ("N" and "S" designate polarities on the inside

faces of the magnets; the outside faces have opposite polarities.)

DC motors have AC in a wound rotor also called anarmature, with

a split ringcommutator, and either a wound or permanent magnet stator.

The commutator and brushes are a long-life rotary switch. The rotorconsists of one or more coils of wire wound around a laminated "soft"

ferromagnetic core on a shaft; an electrical power source feeds the rotor

windings through the commutator and its brushes, temporarily

magnetizing the rotor core in a specific direction. The commutator
http://en.wikipedia.org/wiki/Brushed_DC_electric_motorhttp://en.wikipedia.org/wiki/Brushed_DC_electric_motorhttp://en.wikipedia.org/wiki/Armature_%28electrical_engineering%29http://en.wikipedia.org/wiki/Armature_%28electrical_engineering%29http://en.wikipedia.org/wiki/Armature_%28electrical_engineering%29http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Armature_%28electrical_engineering%29http://en.wikipedia.org/wiki/File:Electric_motor_cycle_2.pnghttp://en.wikipedia.org/wiki/Brushed_DC_electric_motor


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switches power to the coils as the rotor turns, keeping the magnetic poles

of the rotor from ever fully aligning with the magnetic poles of the stator

field, so that the rotor never stops (like a compass needle does), but

rather keeps rotating as long as power is applied.

Many of the limitations of the classiccommutatorDC motor are

due to the need for brushes to press against the commutator. This creates

friction. Sparks are created by the brushes making and breaking circuits

through the rotor coils as the brushes cross the insulating gaps between

commutator sections. Depending on the commutator design, this may

include the brushes shorting together adjacent sectionsand hence coil

endsmomentarily while crossing the gaps. Furthermore, theinductanceof the rotor coils causes the voltage across each to rise when

its circuit is opened, increasing the sparking of the brushes. This

sparking limits the maximum speed of the machine, as too-rapid

sparking will overheat, erode, or even melt the commutator. The current

density per unit area of the brushes, in combination with theirresistivity,

limits the output of the motor. The making and breaking of electric

contact also generateselectrical noise; sparking generatesRFI. Brusheseventually wear out and require replacement, and the commutator itself

is subject to wear and maintenance (on larger motors) or replacement

(on small motors). The commutator assembly on a large motor is a

costly element, requiring precision assembly of many parts. On small

motors, the commutator is usually permanently integrated into the rotor,

so replacing it usually requires replacing the whole rotor.

While most commutators are cylindrical, some are flat discs

consisting of several segments (typically, at least three) mounted on an

insulator.

Large brushes are desired for a larger brush contact area to maximize

motor output, but small brushes are desired for low mass to maximize
http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Electrical_noisehttp://en.wikipedia.org/wiki/Electrical_noisehttp://en.wikipedia.org/wiki/Electrical_noisehttp://en.wikipedia.org/wiki/Radio_frequency_interferencehttp://en.wikipedia.org/wiki/Radio_frequency_interferencehttp://en.wikipedia.org/wiki/Radio_frequency_interferencehttp://en.wikipedia.org/wiki/Radio_frequency_interferencehttp://en.wikipedia.org/wiki/Electrical_noisehttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Commutator_%28electric%29


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the speed at which the motor can run without the brushes excessively

bouncing and sparking (comparable to the problem of "valve float" in

internal combustion engines). (Small brushes are also desirable for lower

cost.) Stiffer brush springs can also be used to make brushes of a givenmass work at a higher speed, but at the cost of greater friction losses

(lower efficiency) and accelerated brush and commutator wear.

Therefore, DC motor brush design entails a trade-off between output

power, speed, and efficiency/wear.

Brushless DC electric motor

Some of the problems of the brushed DC motor are eliminated in

the brushless design. In this motor, the mechanical "rotating switch" or

commutator/brushgear assembly is replaced by an external electronic

switch synchronised to the rotor's position. Brushless motors are

typically 8590% efficient or more, efficiency for a brushless electricmotor, of up to 96.5% was reported

[19]whereas DC motors with

brushgear are typically 7580% efficient.

Brushless DC motors are commonly used where precise speed

control is necessary, as in computerdisk drivesor invideo cassette

recorders, the spindles withinCD,CD-ROM(etc.) drives, and

mechanisms within office products such asfans,laser printersand

photocopiers. They have several advantages over conventional motors:

Switched reluctance motor

The switched reluctance motor (SRM) has no brushes or

permanent magnets, and the rotor has no electric currents. Instead,torque comes from a slight mis-alignment of poles on the rotor with

poles on the stator. The rotor aligns itself with the magnetic field of the

stator, while the stator field stator windings are sequentially energized to

rotate the stator field.
http://en.wikipedia.org/wiki/Valve_floathttp://en.wikipedia.org/wiki/Brushless_DC_electric_motorhttp://en.wikipedia.org/wiki/Brushless_DC_electric_motorhttp://en.wikipedia.org/wiki/Electric_motor#cite_note-18http://en.wikipedia.org/wiki/Electric_motor#cite_note-18http://en.wikipedia.org/wiki/Disk_drivehttp://en.wikipedia.org/wiki/Disk_drivehttp://en.wikipedia.org/wiki/Disk_drivehttp://en.wikipedia.org/wiki/Video_cassette_recorderhttp://en.wikipedia.org/wiki/Video_cassette_recorderhttp://en.wikipedia.org/wiki/Video_cassette_recorderhttp://en.wikipedia.org/wiki/Video_cassette_recorderhttp://en.wikipedia.org/wiki/CDhttp://en.wikipedia.org/wiki/CDhttp://en.wikipedia.org/wiki/CDhttp://en.wikipedia.org/wiki/CD-ROMhttp://en.wikipedia.org/wiki/CD-ROMhttp://en.wikipedia.org/wiki/CD-ROMhttp://en.wikipedia.org/wiki/Fan_%28mechanical%29http://en.wikipedia.org/wiki/Fan_%28mechanical%29http://en.wikipedia.org/wiki/Fan_%28mechanical%29http://en.wikipedia.org/wiki/Laser_printerhttp://en.wikipedia.org/wiki/Laser_printerhttp://en.wikipedia.org/wiki/Laser_printerhttp://en.wikipedia.org/wiki/Photocopierhttp://en.wikipedia.org/wiki/Photocopierhttp://en.wikipedia.org/wiki/Switched_reluctance_motorhttp://en.wikipedia.org/wiki/Switched_reluctance_motorhttp://en.wikipedia.org/wiki/Switched_reluctance_motorhttp://en.wikipedia.org/wiki/Photocopierhttp://en.wikipedia.org/wiki/Laser_printerhttp://en.wikipedia.org/wiki/Fan_%28mechanical%29http://en.wikipedia.org/wiki/CD-ROMhttp://en.wikipedia.org/wiki/CDhttp://en.wikipedia.org/wiki/Video_cassette_recorderhttp://en.wikipedia.org/wiki/Video_cassette_recorderhttp://en.wikipedia.org/wiki/Disk_drivehttp://en.wikipedia.org/wiki/Electric_motor#cite_note-18http://en.wikipedia.org/wiki/Brushless_DC_electric_motorhttp://en.wikipedia.org/wiki/Valve_float


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The magnetic flux created by the field windings follows the path of

least magnetic reluctance, meaning the flux will flow through poles of

the rotor that are closest to the energized poles of the stator, thereby

magnitizing those poles of the rotor and creating torque. As the rotorturns, different windings will be energized, keeping the rotor turning.

Coreless or ironless DC motors

Nothing in the principle of any of the motors described above

requires that the iron (steel) portions of the rotor actually rotate. If the

soft magnetic material of the rotor is made in the form of a cylinder, then

(except for the effect of hysteresis) torque is exerted only on the

windings of the electromagnets. Taking advantage of this fact is the

coreless or ironless DC motor, a specialized form of a brush or

brushless DC motor. Optimized for rapidacceleration, these motors have

a rotor that is constructed without any iron core. The rotor can take the

form of a winding-filled cylinder, or a self-supporting structure

comprising only the magnet wire and the bonding material. The rotor

can fit inside thestatormagnets; a magnetically soft stationary cylinder

inside the rotor provides a return path for the stator magnetic flux. Asecond arrangement has the rotor winding basket surrounding the stator

magnets. In that design, the rotor fits inside a magnetically soft cylinder

that can serve as the housing for the motor, and likewise provides a

return path for the flux.

Printed armature or pancake DC motors

A rather unusual motor design, the printed armature or pancake

motor has the windings shaped as a disc running between arrays of high-

flux magnets. The magnets are arranged in a circle facing the rotor with

space in between to form an axial air gap. This design is commonly

known as the pancake motor because of its extremely flat profile,
http://en.wikipedia.org/wiki/Accelerationhttp://en.wikipedia.org/wiki/Accelerationhttp://en.wikipedia.org/wiki/Accelerationhttp://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Acceleration


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although the technology has had many brand names since its inception,

such as ServoDisc.

The printed armature (originally formed on aprinted circuit board)

in a printed armature motor is made from punched copper sheets that are

laminated together using advanced composites to form a thin rigid disc.

The printed armature has a unique construction in the brushed motor

world in that it does not have a separate ring commutator. The brushes

run directly on the armature surface making the whole design very

compact.

Universal motorsModern low-cost universal motor, from avacuum cleaner. Field

windings are dark copper colored, toward the back, on both sides. The

rotor's laminated core is gray metallic, with dark slots for winding the

coils. The commutator (partly hidden) has become dark from use; it's

toward the front. The large brown molded-plastic piece in the

foreground supports the brush guides and brushes (both sides), as well as

the front motor bearing.

A series-wound motor is referred to as a universal motor when it

has been designed to operate on either AC or DC power. It can operate

well on AC because the current in both the field and the armature (and

hence the resultant magnetic fields) will alternate (reverse polarity) in

synchronism, and hence the resulting mechanical force will occur in a

constant direction of rotation.

Selection of motor :Among these above motors dc brushed motors are more preferable for

the demo project due to its low cost and high reliyability.
http://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Vacuum_cleanerhttp://en.wikipedia.org/wiki/Vacuum_cleanerhttp://en.wikipedia.org/wiki/Vacuum_cleanerhttp://en.wikipedia.org/wiki/Vacuum_cleanerhttp://en.wikipedia.org/wiki/Printed_circuit_board


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Brushed DC motors are one of the oldest motor topologies in

existence today. They use stationary brushes mounted to the stator frame

which rub against commutator segments on the rotor, which in turn are

connected to the rotating coil segments. As the rotor spins, differentrotor coils are connected and disconnected in such a way that the net

magnetic field produced by the rotor is stationary with respect to the

stator frame, and properly oriented with the stator magnetic field so as to

produce torque. As the commutator segments rotate past the brushes, the

electrical contacts to those particular rotor coil segments will be broken.

Since the rotor coils are inductive, and inductors oppose changes in their

current by generating a high flyback voltage, sparks are producedbetween the brushes and the disconnected commutator segments. These

sparks result in many negative consequences, such as electrical noise,

reduced efficiency, and in some cases, hazardous operation.

Furthermore, the brushes must be spring loaded against the commutator

segments in order to insure good electrical contact. This further reduces

efficiency, and requires periodic maintenance to replace the brushes.


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CONCLUSION


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CONCLUSION

The project has been successfully designed and tested. Integrating features of all

the hardware components used have developed it. Presence of every module has been

reasoned out and placed carefully thus contributing to the best working of the unit.

Secondly, using highly advanced ICs and with the help of growing technology the

project has been successfully implemented.


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Controlling of Electrical Equipments by Rf

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