REPORT

On

Remote control using Mobile Phone

Partial fulfillment of the requirements for the Diploma inDepartment of Electronics

Submitted by:Manish Kumar Sharma

Roll No. 153302098270Under the guidance of:INDUSTRIAL GUIDE:

COLLEGE GUIDE

Er. PRAMENDRA SINGH

MS. WSEETI MISHRAS. Manager (Videocon Lucknow)

BNCETSubmitted to :

B.N. College of Engineering & TechnologyBakshi Ka Talab, Sitapur Road,

Lucknow, Uttar Pradesh 226201CERTIFICATEI hereby declare that the project work entitled Remote control using Mobile Phone submitted by Manish Kumar Sharma to the Electronics Engineering department of BNCET for the award of the Diploma in Electronic is a genuine record of the work carried out by them during the period of .04 Jun 2015 to 10 July 2015.It is further certified that this project has been developed in original and has been the result of their personal efforts with little assistance wherever required.

Supervised by:

Er. PRAMENDRA SINGH

S. Manager (Videocon Lucknow)

ACKNOWLEDGEMENT

We are thankful to Er. PRAMENDRA SINGH, S. Manager (Videocon Lucknow) for providing us an opportunity to work on this project and also guided us throughout the project. We thank him for his support and inspiration, without which, understanding the intricacies of the site would have been very difficult.

Our special thanks to our family and friends who have continuously encouraged and motivated us during the course of development of the site.

Manish Kumar Sharma

Roll No. 153302098270INDEX

S.NO.

TOPIC

PAGE NO.

1.INTRODUCTION

52.BLOCK DIAGRAM OF REMOTE CONTROL USING MOBILE PHONE 63.FEATURES OF REMOTE CONTROL USING MOBILE PHONE 7 4.WHAT IS DTMF?

8-125.CIRCUIT DIAGRAM

13

6.LIST OF COMPONENTS

14

7.CIRCUIT DESCRIPTION

15-428.PCB DESIGNING

43-449. SOLDERING TECHNIQUE

44-46 10.EAGLE SOFTWARE

46-5811. APPLICATION OF THE CIRCUIT

59

12. CONCLUSION

60 13.BIBLIOGRAPHY

61INTRODUCTION

In our day-to-day life, sometimes, it is required to operate electric appliances from a distance. The main aim is to save TIME as well as POWER. Here, we need to develop a system, which enables switching an appliance from any distance overcoming the limited range of infrared and radio remote controls. This Project uses two mobile phones, One as a transmitter and the other as a receiver. The receiver mobile is connected to the kit through which the appliances to be switched can be connected.

The main purpose of the project is to develop control mechanism through mobile phones. In todays fast life, we often forget to switch off home appliances (Bulbs, Tube lights, fans, music system, etc), this project provides facility to switch any device using mobile phones.BLOCK DIAGRAM OF REMOTE CONTROL USING MOBILE PHONE

FEATURES OF REMOTE CONTROL USING MOBILE PHONERemote control through the mobile phone is an interesting proposition, and it became more popular with the introduction of dual tone multiple frequency (DTMF) mode of dialing. Single chip DTMF encoder/decoder is available today, which make the designing of such systems easy and reliable.

The remote control system described here has the following main features:

The control-application may vary from simple on/off operation to complex operation.

To perform any operation through the mobile phone, the user only needs to dial the required mobile number.

Receiver unit is connected to DTMF Decoder 8870.

DTMF decoder detects the incoming dual tone signal and decodes it into BCD code. 4028 BCD Decimal decoder converts the BCD code into decimal code.

The 4017 decade counter has ten outputs which go HIGH in sequence when a source of pulses is connected to the CLOCK input and when suitable logic levels are applied to the RESET and ENABLE inputs.

Electrical appliances to be controlled are connected to decade counter. The system is very economical and doesnt require complex devices such as microprocessors and other programmable devices. It is best suited to home and factory applications.

WHAT IS DTMF?

DUAL TONE MULTI FREQUENCY (DTMF)

In a rotary dial telephone it takes about 12 seconds to dial a 7 digits number. From the subscriber point of view a faster dialing rate is desirable. A more convenient method so signaling than rotary dialing is preferable from the point of view of 1-iLirrian factors. These considerations led to development of touch-tone dial telephone in the 1950s, which were introduced first in 1064 after field trails. They are increasingly replacing rotary dial telephone all over the world.

The touch-tone dialing scheme is shown below.

Design considerations

The need of touch tone signaling frequencies to be in the voice band bring with it the problem of vulnerability to talk-off which means that the speech signals may be mistaken for touch tone signals and unwanted control actions such as terminating a call may occur. Another aspect of talk-off is that happens to talk, while signaling is being attempted. The main design considerations for touch-tone signaling stems from the need for protection against talk-off and include the following factors:

1. Choice of code

2. Band separation

3. Choice of frequencies

4. Choice of power levels

5. Signaling duration

In addition to these human factors and mechanical aspects also require consideration.

The choice of code for touchtone signaling should be Such that imitation of code signals by speech and music should be difficult. Simple single frequency structures are prone to east imitation as they occur frequently in speech Or Music. Hence some form of multi frequency code is required. Such codes are easily derived by selecting as set of N frequencies and restricting them in a binary fashion to being either present or absent in a code combination. However some of the 2n combinations are not useful as they contain only one frequency. Transmitting Simultaneously N frequencies invoicing N-fold sharing of restricted amplitude range, and hence it is desirable to keep as small as possible the number of frequencies to be transmitted simultaneously.

It is also advantageous to keep fixed the number of frequencies to be transmitted for any valid code word. These factors lead to the consideration of p out of N code. Here a combination of P frequencies out of N frequencies constitutes a code word. The code yields N! P! (N-P)! Code words.

Prior to touch-tone, P out of N Multi frequency signaling known as multi frequency key pulsing (MFKP) was used between telephone exchanges by the operators. Here 2 out of 6 codes were used. This code is known to give a talk off performance of less than I in 5000. However this degree to talk off performance is inadequate for subscriber level signaling. In order to improve the performance, two measures are adopted. Firstly while retaining P as two N is chosen to be seven or eight, depending upon the number of code words desired. Secondly the chosen frequencies are placed in two separate bands, and a restriction is applied such that one frequency from each band is chosen to from a code word. When multiple frequencies are presented in speech signals they are closely spaced. Band separation of touch-tone frequencies reduces the probability of speech being able to produce touch-tone combinations. The number o valid combination is now limited to N1*N2 where N1 & N2 represent the number of frequencies in each band. With seven frequencies, four in one band and three in the other we have 12 distinct signals as represented in the above fig. With eight frequencies four in each band, we have 16 possible combinations. Since two frequencies are mixed from a set of seven or eight frequencies, CCIT refers t touch tone scheme by the name dual tone multi-frequencies has the following advantages:

Band separation of two frequencies has the following advantages:

1. Before attempting to determine the two specific frequencies at the receiver end, band filtering can be sued to separate the frequency groups. This renders determination of specific frequencies simpler.

2. Each frequency component can be amplitude regulated separately.

3. Extreme instantaneous limiters, which are capable of providing substantial guard action, can be used for each Frequency separately to reduce the probability of false response to speech or other unwanted signals.

The choice of frequencies for touch-tone signaling is dictated by the attenuation and delay distortion characteristics of telephone network circuits for the voice band frequencies (300Hz-340Hz). Frequencies in the range of 700-2200 hz. Both the lower and the upper frequency band are defined in this range.

Having decided on the frequency band and the spacing, the specific Values of frequencies can be so chosen as to avoid simple harmonic relationships like 1:2&2:3 between adjacent two frequencies in the same band and between pairs of frequencies III two different bands, respectively. Such a selection improves talk off performance. As mentioned earlier, sounds composed of a multiplicity of frequencies at comparable levels are not likely to produce talk off because of limiter and selector design. Such sounds are produced by consonants.

However vowels are single frequency sound with a series of harmonic components present in them. Susceptibility to talk off due to vowels can be reduced by choosing the specific frequencies appropriately.

The adjacent frequencies in the same band have a fixed ratio of 21: 19, I.e. only the 21 and 19t harmonic components have the same frequency value. Across the bands, the frequency that lie along the diagonals in above fig have ratio of 59:34. Thus chosen frequency values are such that they almost eliminate talk off possibility due to harmonics.

Since signaling information does not bear the redundancy of spoken words and sentences it is desirable that the signals power be as large as possible. A nominal value of 1 db above 1m W is provided for at telephone set for the combined signal power of the two frequencies.

A major advantage of touch-tone dialing is the potential for data transmission and remote control. The powerful application touch-tone dialing is data in voice answer (DIVA) system.

The control unit can work in conjunction with either the signal from a remote FM transmitter or a remote telephone. When a telephones, acts as the remote control unit, the, telephone-line interfacing circuit come into operation as soon as ring is detected. It consists of a ring detector that detects the ring form the exchange and triggers a timing circuit. The output of the timer is given to a relay driver circuit in order to simulate off-hook condition. The timer circuit maintains the telephone line in the off-hook state for 1.5 minutes on detecting a ring from the exchange and connects the telephone line to the DTMF decoding section though energized contacts of the relay.

The DTMF decoder uses IC MT8870, which forms a vital part of the circuit. It converts the dual tones to corresponding binary outputs. The 4-bit binary output of the DTMF of the DTMF decoder by a BCD-to-7-segment LED. A 4-to-16-line decoder (74LS154) is used t convert the 4-0bit binary into 16 individual lines.

The output of the 4-to-16 line decoder is applied to the appliance on/off control circuit that consists of AND gates and D flip-flops. The output of the on/off control circuit is sued to control the required devices with the help of relays.

This circuit also provides a device status output that is used to enable a tone generator. The short duration tone thus generated is transmitted through the telephone line by the line interfacing circuit to inform the user about the resulting states of the controlled device/appliance.

DTMF signaling:

AC register signaling is used in DTMF telephone. Here, tone rather then make/break pulses, are use for dialing. Each dialed digit is unique represented by a pair of sine wave tone. These tones (one form low ground for row and another from high group column) are sent to the exchange when a digit is dialed by pushing the key. These tones lie within the speech band 300 to 340Ohz, and are chosen so as minimize the possibility of any valid frequency pair existing in the normal speech simultaneously. Actually, this minimization is made possible by forming pairs with one tone from the higher group and the other from lower group frequency. The DTMF spectrum is shown in fig.

A valid DTMF signal is the sum of the tones, one from a lower group (697 Hz) and the other form a higher group (1209-1663 Hz). Each group constrains one individual tone. The DTMF dialing scheme is shown in fig. This scheme allows unique combination. Ten of these represent digits I through 9 and 0. The remaining 6 digit are reserved fro special-purpose dialing.

Tones in DTMF dialing are so choose that none of the tones is harmonic of another tone. Therefore there is no chance of distortion caused by harmonics. This tone is sent as long as the key remains pressed.

The DTMF coding scheme ensures that each signal contains only one component form each of the low and high groups. This significantly simplifies decoding because the composite DTMF signals may be separated with band-pass filters into single frequency component, each of which may be handled individually. As a result, the DTMF coding scheme is a flexible signaling scheme with high reliability, hence motivating innovative and competitive decoder design.

CIRCUIT DIAGRAM

LIST OF COMPONENTS Semiconductor devices:IC1

- 8870 DTMF BCD converter

IC2

-4028 BCD-DECIMAL ConverterIC3, IC4, IC5

-4017 DECADE CounterT1, T2, T3

- 2N222 A NPN Transistors

D1,D2, D3, D4 - 1N4001 Diodes

Resistors (all watt, ( 5% carbon)R1, R2

-100k

R3 -330k

R4, R5, R6

-470k Capacitors:

C1

- 0.47 (F, C2,C3

-0.47(FC4

- 0.1(F Miscellaneous:

Crystal Oscillator

- 3.58 MHzCIRCUIT DESCRIPTIONIC-M-8870 (DTMF Receiver)

DescriptionThe M-8870 is a full DTMF Receiver that integrates both band split filter and decoder functions into a single 18-pin DIP or SOIC package. Manufactured using CMOS Process technology, the M-8870 offers low power consumption (35 mW max) and precise data handling. Its filter section uses switched capacitor technology for both the high and low group filters and for dial tone rejection. Its decoder uses digital counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code. External component count is minimized by provision of an on-chip differential input amplifier, clock generator, and latched tri-state interface bus. Minimal external components required include a low-cost 3.579545 MHz color burst crystal, a timing resistor, and a timing capacitor.The M-8870-02 provides a power-down option which, when enabled, drops consumption to less than 0.5 mW. The M-8870-02 can also inhibit thedecoding of fourth column digits.Features Low Power Consumption

Adjustable Acquisition and Release Times

Central Office Quality and Performance

Power-down and Inhibit Modes (-02 only)

Inexpensive 3.58 MHz Time Base

Single 5 Volt Power Supply

Dial Tone Suppression

Applications Telephone switch equipment

Remote data entry

Paging systems

Personal computers

Credit card systemsPin diagram:

Pin NameDescription

1IN+(Non-inverting input)Connections to the front-end differential amplifier.

2IN-(Inverting input)Gives access to output of front-end amplifier for connection of feedback resistor.

3GS(Gain select)Gives access to output of front-end amplifier for connection of feedback resistor.

4VREFReference voltage output (nominally VDD/2). May be used to bias the inputs at mid-rail.

5INH*Inhibits detection of tones representing keys A, B, C, and D.

6PD*Power down. Logic high powers down the device and inhibits the oscillator. Internal pull down.

7OSC1(Clock input)3.579545 MHz crystal connected between these pins completes the internal oscillator.

8OSC2(Clock input)3.579545 MHz crystal connected between these pins completes the internal oscillator.

9VSSNegative power supply (normally connected to 0 V).

10OETri-statable output enable (input). Logic high enables the outputs Q1 - Q4. Internal pullup.

11-14Q1,Q2

Q3,Q4Tri-statable data outputs. When enabled by OE, provides the code corresponding to the last valid tone pair received.

15StDDelayed steering output. Presents a logic high when a received tone pair has

been registered and the output latch is updated. Returns to logic low when the voltage on St/GT falls

below VTSt.

16EStEarly steering output. Presents a logic high immediately when the digital

algorithm detects a recognizable tone pair.

Any momentary loss of signal condition will cause ESt to return to a logic low.

17St/GTSteering input/guard time output (bidirectional). A voltage greater than VTSt detected at St causes the device to register the detected tone pair and update the output latch. A voltage less than VTSt frees the device to accept a new tone pair. The GT output acts to reset the external steering time constant, and its state is a function of ESt and the voltage on St.

18VDDPositive power supply. (Normally connected to +5V.)

Timing Diagram

Explanation of Events

Tone bursts detected, tone duration invalid, outputs not updated.

Tone #n detected, tone duration valid, tone decoded and latched in outputs.

End of tone #n detected, tone absent duration valid, outputs remain latched until next valid tone.

Outputs switched to high impedance state.

Tone #n + 1 detected, tone duration valid, tone decoded and latched in outputs (currently high impedance).

Acceptable dropout of tone #n + 1, tone absent duration invalid, outputs remain latched.

(G) End of tone #n + 1 detected, tone absent duration valid, outputs remain latched until next valid tone.

Explanation of Symbols

VINDTMF composite input signal.

EStEarly steering output. Indicates detection of valid tone

frequencies.

St/GT Steering input/guard time output. Drives external RC timing

circuit.

Q1 - Q44-bit decoded tone output.

StD Delayed steering output. Indicates that valid frequencies have been present/absent for the required guard time , thus constituting a valid signal.

OEOutput enable (input). A low level shifts Q1 - Q4 to its high impedance state.

tRECMaximum DTMF signal duration not detected as valid. tRECMinimum DTMF signal duration required for valid

recognition.

tID Minimum time between valid DTMF signals.

Tdo Maximum allowable dropout during valid DTMF

signal.

tDP Time to detect the presence of valid DTMF

signals. tDA Time to detect the absence of valid DTMF

signals.

TGTPGuard time, tone present.

TGTAGuard time, tone absent.

IC4028 (BCD Decimal decoder)

The MC14028B decoder is constructed so that an 8421 BCD code on the four inputs provides a decimal (oneoften) decoded output, while a 3bit binary input provides a decoded octal (oneofeight) code output with D forced to logic 0. Expanded decoding such as binarytohexadecimal (oneof16), etc., can be achieved by using other MC14028B devices. The part is useful for code conversion, address decoding, and memory selection

control, demultiplexing, or readout decoding.

Diode Protection on All Inputs

Supply Voltage Range = 3.0 Vdc to 18 Vdc

Capable of Driving Two Lowpower TTL Loads or One Lowpower Schottky TTL Load Over the Rated Temperature Range

Positive Logic Design

Low Outputs on All Illegal Input Combinations

Similar to CD4028B.

HEF4017B

1. General descriptionThe HEF4017B is a 5-stage Johnson decade counter with ten spike-free decoded active HIGH outputs (Q0 to Q9), an active LOW carry output from the most significant flip-flop (Q5-9), active HIGH and active LOW clock inputs (CP0, CP1) and an overriding asynchronous master reset input (MR).

The counter is advanced by either a LOW-to-HIGH transition at CP0 while CP1 is LOW or a HIGH-to-LOW transition at CP1 while CP0 is HIGH.

When cascading counters, the Q5-9 output, which is LOW while the counter is in states 5, 6, 7, 8, and 9, can be used to drive the CP0 input of the next counter. A HIGH on MR resets the counter to zero (Q0 = Q5-9 = HIGH; Q1 to Q9 = LOW) independent of the clock inputs (CP0, CP1).

Automatic counter code correction is provided by an internal circuit: following any illegal code the counter returns to a proper counting mode within 11 clock pulses. Schmitt trigger action makes the clock inputs highly tolerant of slower rise and fall times. It operates over a recommended VDD power supply range of 3 V to 15 V referenced to VSS (usually ground). Unused inputs must be connected to VDD, VSS, or another input. It is also suitable for use over both the industrial (40 C to +85 C) and automotive (40 C to+125 C) temperature ranges.2. Features

Automatic counter correction

Tolerant of slow clock rise and fall times

Fully static operation

5 V, 10 V, and 15 V parametric ratings

Standardized symmetrical output characteristics

Operates across the automotive temperature range 40 C to +125 C

Complies with JEDEC standard JESD 13-B

3. Applications

Industrial and automotive

4. Ordering information

All types operate from 40 C to +125 C

Type number Package

Name Description Version

HEF4017B DIP16 plastic dual in-line package; 16-leads (300 mil)SOT38-4

HEF4017BT SO16 plastic small outline package; 16 leads; body width 3.9 mm SOT109-1Functional diagram

SHAPE \* MERGEFORMAT

Logic diagram:

logic symbol IEE LOGIC S.

6. Pin Configuration information6.1 Pin diagram

6.2 Pin descriptionSymbol Pin Description

Q0 to Q9 3, 2, 4, 7, 10, 1, 5, 6, 9, 11 decoded output

VSS 8 ground supply voltage

Q5-9 12 carry output (active LOW)

CP1 13 clock input (HIGH-to-LOW edge-triggered)CP0 14 clock input (LOW-to-HIGH edge-triggered)

MR 15 master reset input

VDD 16 supply voltage7. Functional description

Function table

MR CP0 CP1 Operation

H X X Q0 = Q5-9 = H; Q1 to Q9 =

L H counter advances

L L counter advances

L L X no change

L X H no change

L H no changeL L no change[1] H = HIGH voltage level; L = LOW voltage level; X = dont care;

= positive-going transition; = negative-going transition.

Timing diagram:

8. Limiting valuesIn accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol Parameter Conditions Min Max Unit

VDD supply voltage 0.5 +18 V

IIK input clamping current VI < 0.5 V or VI > VDD + 0.5 V - 10 mA

VI input voltage 0.5 VDD + 0.5 V

IDD supply current - 50 mA

Tstg storage temperature 65 +150 C

Tamb ambient temperature 40 +125 CP power dissipation per output - 100 mW9. Recommended operating conditionsSymbol Parameter Conditions Min Typ Max Unit

VDD supply voltage 3 - 15 V

VI input voltage 0 - VDD V

Tamb ambient temperature in free air 40 - +125 C

t/V input transition rise and fall rate

VDD = 5 V - - 3.75 ns/V

VDD = 10 V - - 0.5 ns/V

VDD = 15 V - - 0.08 . 10.Dynamic power dissipation PD

PD can be calculated from the formulas shown. VSS = 0 V; tr = tf 20 ns; Tamb = 25 C.

Symbol Parameter VDD Typical formula for PD (W)

PD dynamic power 5 V PD = 500 fi + (fo CL) VDD

dissipation

10 V PD = 2200 fi + (fo CL) VDD

15 V PD = 6000 fi + (fo CL) VDD

where:

fi = input frequency in MHz;

fo = output frequency in MHz;

CL = output load capacitance in pF;

VDD = supply voltage in V;

(CL fo) = sum of the outputs.11. Waveforms

Conditions: CP1 = LOW, while CP0 triggers on a LOW-to-HIGH transition. CP1 triggers on a HIGH-to-LOW transition;

The shaded areas indicate where the output state is set by the input count.Waveforms showing the propagation delays for CP0, CP1 to Qn, Q5-9 outputs and the output transition times.

12. Application information

Decade counter with decimal decoding

1 out of n decoding counter (when cascaded)

Sequential controller

Timer

13. Abbreviations

Acronym Description

DUT Device under Test

ESD Electro Static Discharge

HBM Human Body Model

MM Machine ModelRelays A relay is an electrical switch that opens and closes under the control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts.

Pole and throwCircuit symbols of relays. "C" denotes the common terminal in SPDT and DPDT types. A relay will switch one or more poles, each of whose contacts can be thrown by energizing the coil in one of three ways:

Normally-open (NO) contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive. It is also called a Form A contact or "make" contact.

Normally-closed (NC) contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive. It is also called a Form B contact or "break" contact.

Change-over (CO), or double-throw (DT), contacts control two circuits: one normally-open contact and one normally-closed contact with a common terminal. It is also called a Form C contact or "transfer" contact ("break before make"). If this type of contact utilizesmake before break" functionality, then it is called a Form D contact.

The following designations are commonly encounteredSPST - Single Pole Single Throw. These have two terminals which can be connected or disconnected. Including two for the coil, such a relay has four terminals in total. It is ambiguous whether the pole is normally open or normally closed. The terminology "SPNO" and "SPNC" is sometimes used to resolve the ambiguity.

SPDT - Single Pole Double Throw. A common terminal connects to either of two others. Including two for the coil, such a relay has five terminals in total.

DPST - Double Pole Single Throw. These have two pairs of terminals. Equivalent to two SPST switches or relays actuated by a single coil. Including two for the coil, such a relay has six terminals in total. The poles may be Form A or Form B (or one of each).

DPDT - Double Pole Double Throw. These have two rows of change-over terminals. Equivalent to two SPDT switches or relays actuated by a single coil. Such a relay has eight terminals, including the coil.

The "S" or "D" may be replaced with a number, indicating multiple switches connected to a single actuator. For example 4PDT indicates a four pole double throw relay (with 14 terminals).

In industrial application we need to isolate one circuit electrically from another, while still allowing the first circuit to control the second. The way of providing electrical isolation between two circuits is to place a relay between them.A relay consists of a coil, which may be energized by the low-voltage circuit, and one or more sets of switch contacts, which may be connected to the high-voltage circuit.

HOW RELAYS WORK:

When a relay is off, the metal arm is at its rest position and so there is contact between the Normally Closed (N.C.) switch contact and the common switch contact.

If a current is passed through the coil, the resulting magnetic field attracts the metal arm and there is now contact between the Normally Open (N.O.) switch contact and the common switch contact.

ADVANTAGES OF RELAYS:

The complete electrical isolation improves safety by ensuring that high voltages and current cannot appear where there should not be.

Relays come in all shapes and sizes for different applications and they have various switch contact configurations. Double Pole Double Throw (DPDT) relays are common and even 4-pole types are available. You can there after control several circuits with one relay or use one relay to control the direction of a motor.

It is easy to tell when a relay is operating you can hear a click as the relay switches on and off and you can sometimes see the contacts moving.

Disadvantages of Relays:

Being mechanical through, relays do have some disadvantage over other methods of electrical isolation

Their parts can wear out as the switch contacts become dirty high voltages and currents cause sparks between the contacts.

They cannot be switched on and off at high speeds because they have a slow response and the switch contacts will rapidly wear out due to the sparking.

Their coils need a fairly high current to energize, which means some micro-electronic circuits cant drive them directly without additional circuitry.

The back-emf created when the relay coil switches off can damage the components that are driving the coil. To avoid this, a mode ran be place across the relay coil as will be seen in any Electronics in Mecca no circuits that use relays with sensitive components.

Choosing A Relay:

When choosing a relay to use in a circuit, it is needed to bear in mind properties of both the coil and the switch contacts.

Firstly, it is needed to find a relay that has the required number of switch poles for your application. You then need to make sure that the switch contacts can cope with the voltage and current you intend to use for example, if you were using the relay to switch a 60W mains lamp, on and off, the switch contacts would need to be rated for at least 250mA at 240V AC.

Also of importance is the material that the switch contacts are made of gold is good for low-voltages, whereas tungsten is suitable for switching high voltage and currents.

Finally, a relay chosen that has a coil that can be energized by your low-voltage control circuit. Relay coils are generally rated by their voltage and resistance, so you can work out their current consumption using Ohms Law. You will need to make sure that the circuit powering the coil can supply enough current; otherwise the relay will not operate properly.

Crystal Oscillators It is often required to produce a signal whose frequency or pulse rate is very stable and exactly known. This is important in any application where anything to do with time or exact measurement is crucial. It is relatively simple to make an oscillator that produces some sort of a signal, but another matter to produce one of relatively precise frequency and stability. AM radio stations must have a carrier frequency accurate within 10Hz of its assigned frequency, which may be from 530 to 1710 kHz. SSB radio systems used in the HF range (2-30 MHz) must be within 50 Hz of channel frequency for acceptable voice quality, and within 10 Hz for best results. Some digital modes used in weak signal communication may require frequency stability of less than 1 Hz within a period of several minutes. The carrier frequency must be known to fractions of a hertz in some cases. An ordinary quartz watch must have an oscillator accurate to better than a few parts per million. One part per million will result in an error of slightly less than one half second a day, which would be about 3 minutes a year. This might not sound like much, but an error of

10 parts per million would result in an error of about a half an hour per year. A clock such as this would need resetting about once a month, and more often if you are the punctual type. A programmed VCR with a clock this far off could miss the recording of part of a TV show. Narrow band SSB communications at VHF and UHF frequencies still need 50 Hz frequency accuracy. At 440 MHz, this is slightly more than 0.1 part per million.

Ordinary L-C oscillators using conventional inductors and capacitors can achieve typically 0.01 to

0.1 percent frequency stability, about 100 to 1000 Hz at 1 MHz. This is OK for AM and FM broadcast receiver applications and in other low-end analog receivers not requiring high tuning accuracy. By careful design and component selection, and with rugged mechanical construction, .01 to 0.001%, or even better

(.0005%) stability can be achieved. The better figures will undoubtedly employ temperature compensation components and regulated power supplies, together with environmental control (good ventilation and ambient temperature regulation) and battleship mechanical construction. This has been done in some communications receivers used by the military and commercial HF communication receivers built in the1950-1965 era, before the widespread use of digital frequency synthesis. But these receivers were extremely expensive, large, and heavy. Many modern consumer grade AM, FM, and shortwave receivers employing crystal controlled digital frequency synthesis will do as well or better from a frequency stability standpoint.

An oscillator is basically an amplifier and a frequency selective feedback network (Fig 1). When, at a particular frequency, the loop gain is unity or more, and the total phase shift at this frequency is zero, or some multiple of 360 degrees, the condition for oscillation is satisfied, and the circuit will produce a periodic waveform of this frequency. This is usually a sine wave, or square wave, but triangles, impulses, or other waveforms can be produced. In fact, several different waveforms often are simultaneously produced by the same circuit, at different points. It is also possible to have several frequencies produced as well, although this is generally undesirable.

In an oscillator, the feedback network determines the frequency and stability of the generated signal. Frequency is of course the number of cycles per unit time produced and is generally specified in Hz, kHz (1000 Hz), MHz (1 million Hz), or even GHz (1 billion Hz). Stability is another matter. What we are trying to express is how much the oscillator frequency will change in a certain amount of time. The key here is the length of time. Long term stability is generally expressed in frequency drift (delta F or F) per unit time or specified time interval. Long term drift is caused by component aging due to electrical, thermal, physical, and chemical changes in components over a relatively long (100 hours or more) time period. This is generally, but not always, permanent. This is generally compensated for by readjustment of circuit parameters, either manually or automatically. electrical and mechanical. Generally time periods here are minutes to an hour or so. This is often temporary and tends to follow a pattern, but can be random due to cyclic temperature changes, etc. Even shorter term frequency drift involving periods of a few seconds down to millisecond intervals is caused by circuit noise and mechanical factors (shock and vibration). As the time interval gets shorter, we run into random frequency fluctuations caused by noise in the amplifier and circuit components, as well as naturally occurring thermal noise generated in resistances. This noise is generally called phase noise as it appears as random noise modulation in AM, FM, and phase modulation (They are mathematically all related) on the generated signal. This noise is generally measured in a given bandwidth at some specified frequency away from the main carrier. This is done with a spectrum analyzer and notch filters to notch out the main carrier. Note that the main carrier is often 60-120 dB higher in amplitude than the noise level we are trying to measure. This measurement is then converted to a figure expressed in decibels per Hz of bandwidth with respect to the main carrier and expressed as dBc. One often sees oscillator phase noise measurements given in specs for oscillator circuits and prepackaged oscillators. It is hard to say what a good figure is as it depends on application. Low phase noise is important in radio receivers and communications systems. It is less important in applications such as computer clocks, and noncritical timing oscillators used in digital systems and circuits. An oscillator that has high phase noise is said to be dirty.

The key component in determining oscillator stability is the feedback network, assuming the amplifier portion has relatively good noise performance. In the amplifier, a low noise transistor or other active device should be employed. The more stable oscillators tend to have better noise specs. Phase noise and drift are manifestations of frequency instability on different time scales. The stability of an oscillator, all other things equal, can be related to the rate of change of feedback network phase shift versus frequency. This, in plain English, implies something with very high selectivity and therefore high Q, the higher the better. These devices include quartz crystals, ceramic resonators, resonant cavities (UHF and microwave only), and other exotic devices.

The quartz crystal is the most widely used frequency-determining element. It is relatively cheap, widely available, and comes in frequencies from audio to low UHF. Frequencies in the HF range (2-30

MHz) are most common. Distributors generally stock commonly used frequencies as microprocessor crystals. Since these are manufactured in large quantities, they are often available for less than a dollar. Custom frequencies specially manufactured are generally several times as costly. By varying the way the crystal is cut and its size, the resonant frequency and temperature characteristics can be controlled. There are many different cuts that are specified by the way the crystal is oriented and cut from the mother crystal

(AT, BT, SC, etc). AT crystal cuts are generally used above 1 MHz. Crystals can be operated in a mode called overtone mode. Third overtone, and fifth overtone crystals are commonly used in the lower VHF range 30 to 150 MHz. Seventh and ninth overtone crystals are also used, and can operate up to a few hundred MHz. Most fundamental crystals can be operated on their third and often fifth overtone, and higher order overtone crystals can be operated on their lower order overtones and fundamental as well. Also, spurious modes may exist in many crystals, particularly higher overtone types, which can be totally unrelated mathematically to any legal overtones or frequencies. The circuit designer must be aware of these effects and may have to design in certain circuit features to ensure oscillator operation on expected oscillator and crystal frequency. This may involve extra tuned circuits and components to suppress unwanted modes.

Fig 2 is an approximate equivalent circuit of a crystal. This circuit is a pretty good approximation near the crystal resonant frequency. It has two fundamental resonances, one series, the other parallel (anti- resonant). The crystal behaves as an inductor at certain frequencies as well. In many crystals, the effective series inductance may be measured in henries, while the capacitance is a small fraction of a picofarad, and the resistance is in the 20 to 100 range. Since the Q value of a series resonant circuit is 2fL/R, if the frequency is 1 Mhz, the series effective capacitance C1 = .025 pf, the inductance L1 = 1 henry, and resistance Rs = 50 ohms, the circuit Q is 125,600. The shunt capacitance C2 is usually a few pf. This resonator would have a bandwidth of about 8 Hz at 1 MHz center frequency. Contrast this with a typical Q of 100 at 1 MHz with a 10 kHz bandwidth obtainable using conventional small size coils and capacitors. The crystal gives a 1250 times improvement in this example. Crystals may be purchased for series or parallel operation. Parallel crystals are usually specified with a circuit capacitance (Usually 18, 20 or 32 pF) load. This capacitance is that with which the crystal will operate on its marked frequency. Series crystals do not have this specification. Commonly parallel crystals are fundamental types and series crystals overtone types, but there are many exceptions to this rule, so no reliable data can be assumed for any crystal. Either a series or parallel crystal usually will work in a given circuit, but the oscillation frequency may be not as marked. This discrepancy could be several kHz, with inability to adjust the frequency to specs. The crystal should be placed in a suitable test circuit and measurements made to obtain reliable data

Crystal oscillator circuits are similar to L-C oscillator circuits, often substituting the crystal for L- C components. In some circuits the crystal is used as a series resonator, in others as a parallel inductor or resonator. The main difference is that in an L-C oscillator we can employ a tapped or multi-winding inductance. Since we cannot install taps on a crystal, capacitance divider techniques and configurations are used instead. It is no trick at all to get stability an order of magnitude better than the best L-C oscillators from a crystal oscillator. A few parts in a million (ppm) would be typical. (One ppm = .0001%) With careful design, proper choice of crystal cut, and the use of temperature compensation, 1 part in ten million is achievable over a reasonably wide (50 degrees C) range without too much trouble. These circuits are called temperature compensated crystal oscillators (TCXOs). With solid state components the entire crystal and associated circuitry can be placed in an oven heated by a watt or less of power, and the internal temperature maintained at a specified figure (60 to 85 deg C typically). Stabilities of another order of magnitude (1 part in 100 million) can result. These are called oven controlled crystal oscillators (OCXOs) and can be obtained as prepackaged assemblies. There are circuits in which the amplitude of oscillation is also regulated with automatic gain control, keeping the amplitude of oscillation within the linear region of the circuitry. It is also possible to do this with L-C and crystal oscillators, rather than depending on circuit nonlinearity for amplitude limiting. The Wein Bridge oscillator is an example of an R-C oscillator that uses a tungsten lamp filament or a thermistor to do this. This improves noise performance, waveform purity, and frequency stability, as it minimizes drive to the crystal. This helps to keep thermal frequency drift to a minimum.

POWER SUPPLY

Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others.

Circuit diagram

PCB DESIGNING

Any circuit is fabricated on PCB. With the help of PCB the circuit size became very small and simple in making the PCB is generally abbreviated as the PCB the material PCB can be making by two processes.

(I) Lab method.

(II) Commercial method

We used lab method for preparing the PCB.

LAB method:

This method is used for making PCB at small scale. In this method the following items are used.

(I) Copper clay board

(II) Paint

(III) Graph paper

(IV) Tracing paper

(V) Carbon paper

(VI) Ferric chloride acid

(VII) Thinner

(VIII) Hand drill machine and drill bit of 9mm dia.

Procedure:

The procedure of making of PCB consist of following steps

(I) Drawing of the lay out.

(II) Printing of PCB

(III) Etching of PCB

Drawing of the layout:

With the circuit diagram and the entire component at hand, we draw a complete lay out plan on a graph paper. We should care regarding location shape utilization and we keep the line on the other side as for as possible, we trace the complete layout on a trace paper.

Printing of PCB:

We cut the referred size of PCB using hawk saw and file. Now we put carbon paper on it with it 11~ICIIIO carbon surface and we put tracing paper on the carbon paper. Since the tracing paper transparent we can now reproduced a carbon paint over the carbon surface by using ball pen over the

SOLDERING TECHNIQUE

Soldering:

Soldering is a process for the jointing metal parts with the add of solder where the melting temperature is solvated below that of material joined.

Selection of Proper Soldering, Iron:There should be a proper soldering iron for each type of job, as we know that metal is a very good conductor of neat therefore when soldering on a metal; chasis of heavy iron is used.

But it will not practical to use such type of iron on a PCB used in project because heat dissipation on the other side could damage a PCB a low wattages (35w) soldering iron is used for this purpose.

Selection of solder:

Selection of proper solder wire for the job is the major consideration in the making of good soldering connections it should be of low melting temperature metal consisting basically of fin and load with varying amount of other metal such as a antimony and cadmium to give alloys various physical purpose in the process of joining of two metal together the solder detach a small amount of surface of each at temperature below there melting point the action of melting solder on metal is similar to the action of water on salt generally the composition used fro the solder in 60% tin and 40% lead.

Flux:

The application of a proper flux is a necessary link in the soldering chain the metal we commonly used in electronics is usually converted with a fine non-metallic film called oxide.The main function of the flux is to deal with the metal oxide.

Soldering procedure:

1. Proper iron should be selected or a special job. A side tipped, high voltage is necessary when soldering on a metal chassis pen. For PCB repairing a low wattage pencil iron should be recommended tip of which should be narrow.

2. The iron tip should be kept clean, when iron is used continuously. It is exposed to air and the tip may become oxidized oxidization can be prevented by keeping the tip may clean at all the time.

3. When the iron is turned, the tip should be whipped removed any excessive metal solder. A ray should never be used to write the tip because it may have small deposit of carbon instead of a commercial tip cleaner.

4. The area to be soldered should clean at all the time. It may look clean. A thin oxide film may be present and prevent proper soldering only or greasily deposit or small bit or large material should be cleaned, that may be embedded on the surface to be soldered purpose.

5. A flat face of a well-sheeted iron should be applied against the surface to be soldered. This should be heated to a high temperature enough to melt the solder.

6. The solder should be removed first and when the iron on junction should be distributed or more any portion of it.

7. When the surface is sufficiently heated, the solder is applied to the deposit and not to melt and flow freely towards the iron.

8. The area around the junction should be checked to any excess solder on tinning plate, which can cause shorts.

The excess of solder should be removed and cleaned.

Applications

Automotive

Data terminals

Instrumentation

Medical electronics

Alarm system

Industrial electronics

Remote metering

Computers

EAGLE SOFTWARE

The Control Panel

The Control Panel normally appears after starting EAGLE, and this is the program's control center. All the files specific to EAGLE are managed here,

and some basic settings can be made. It is similar to the familiar file managers used by a wide variety of applications and operating systems. Each

EAGLE file is displayed in the tree view by means of a small symbol.

A context menu is opened by clicking with the mouse on an entry in the tree

view. This allows you, depending on the object, to carry out a variety of

actions (rename, copy, print, open, create new etc.).The Control Panel supports Drag & Drop. This can also be done between different programs. You can, for instance, copy files, move them, or create links on the desktop. User Language programs or script files that are pulled with the aid of the mouse out of the Control Panel and into an editor window are started automatically. If, for instance, you pull a board file with the mouse into the Layout Editor, the file is opened. The tree structure provides a quick overview of the libraries, Design Rules, User Language programs, script files, CAM jobs and projects. Special libraries, text, manufacturing and documentation files can belong to a project as well as schematic diagrams and layouts.

The first time it is called, the Control Panel will appear very much as shown in the following diagram. If an object is selected in the tree view, further relevant information is displayed in the right hand part of the window.Simply click onto various folders and files in order to experiment with the Control Panel's facilities.

Drag & Drop. If it has more than one Package version, the ADD dialog opens

automatically, so that the desired Package can be selected.

The green marker behind the library entry indicates that this library is in use.

This means that it can be used in the current project. Devices in this library

will be examined by the search function in the ADD dialog of the schematic

diagram or of the layout. This makes them available for the project. The

library will not be examined if the marking is gray.

If starting EAGLE without a project (no eagle.epf file is read, the project has

been closed before exiting EAGLE last time) and creating a new project

( File/New/Project) all libraries will be in use automatically. However,

opening an already existing project, where only certain libraries are in use

before creating the new project, will adopt this selection.

If the Library Editor window is open you can Drag&Drop a complete Device

set or Package definition from the Control Panel into the library window.

This way you can copy it from one library into another.

The Schematic Editor Window

The Schematic Editor window opens when we load an existing schematic or

create a new one. There are several ways of opening files in EAGLE.

We can, for instance, load a schematic diagram by means of the File/Open/Schematic menu in the Control Panel. Alternatively we can double click onto a schematic diagram file in the tree view.

If we want to create a new schematic diagram, select the menu File/New/Schematic. This will open a schematic with the name untitled.sch in the current project directory.If you want to create a schematic diagram straight away in a new project,

you may for example click with the right mouse button onto a project in the

Projects entry of the tree view, and select the New project option from the context menu. The new project receives a name. Then click onto this entry

with the right mouse button. Now select New/Schematic from the context

menu.The Layout Editor Window

The Layout Editor window opens when we open an existing board file or

create a new board. If we own the Schematic Editor we will normally draw

a schematic first and then generate the board file with the BOARD command,

or by clicking the Board icon.

The Layout Editor window appears very much like the Schematic Editor

window.

Descriptions of commands that cannot be reached through the command

toolbar are also to be found in the section concerning the Schematic Editor

window. All of the commands can also be reached through the pulldown

menus in the menu bar. This also applies, of course, to the Schematic and

Layout Editor windows.

The CAM Processor

Manufacturing data is generated by means of the CAM Processor. A number

of drivers for the data output are available. The drivers are defined in the file

eagle.def, which can be edited with any Text Editor.

Output to matrix printers, however, is not created with the CAM Processor

but with a PRINT command. The EAGLE license conditions allows to give the CAM Processor to board manufacturer. To do this,supply them with a copy of

the EAGLE Freeware. The CAM Processor can run without limitation with the

Freeware. Alternatively, board manufacturer can order the EAGLE

Freeware directly from CadSoft.

The Library Editor Window

The Library Editor window opens when we load a library for creating or

editing components. A library normally has three different elements:

Packages, Symbols and Devices.

A Package is a Device's housing, as will be used in the Layout Editor

(on the board).

The Symbol contains the way in which the Device will be shown in

the schematic.

The Device represents the link between one (or more) Symbol(s) and

a Package. Here we define the connection between a pin of a Symbol

and the referring pad of the Package.

We call it a Device set if the component exists in more than one Package and/or technology variant.

A library need not contain only real components. Ground or supply symbols

as well as drawing frames can also be stored as Devices in a library. These

Symbols do not normally contain any pins.

There are also libraries that only contain Packages. These libraries can only

be used in the Layout Editor.

When a library is loaded the following window appears first:

The Text Editor Window

EAGLE contains a simple Text Editor.

We can use it to edit script files, User Language programs or any other text

file. The EAGLE Text Editor stores its files with UTF8 encoding.The menus brings to a variety of functions, such as commands for printing, copying and cutting, searching, replacing (with support of Regular Expressions), changing font and size, and so on.

The keyboard shortcuts in the EAGLE Text Editor follow the platform specific

standards.

When in the Text Editor, the right mouse button calls up a context menu.

Creating the Schematic DiagramDevices are taken from existing libraries and placed on the drawing area.

The connecting points (pins) on the Devices are then joined by nets(electrical connections). Nets can have any name, and can be assigned to various classes. Power supply voltages are generally connected automatically. In order to document all the supply voltages in the schematic diagram it is necessary to place at least one so called supply symbol for each voltage. Schematic diagrams can consist of a number of pages (but not in the Light edition). Nets are connected across all the pages if they have the same name.

It is assumed that libraries containing the required components are available.

It is possible at any time to create a layout with the BOARD command or with the Board icon. As soon as a layout exists, both files must always be loaded at the same time. This is necessary for the association of the schematic diagram and the board to function.

Open the Schematic Diagram

First start the Control Panel. From here open a new or existing

schematic diagram, for instance by means of the File/Open or the File/New

menus, or with a double click on a schematic diagram file in the directory

tree. The schematic diagram editor appears.

Create more schematic sheets if needed. For that purpose, open the combo

box in the action toolbar with a mouse click, and select the New. A new sheet

will be generated (see page 50). Another way to get a second sheet is to type

in EDIT .S2

on the command line. If, however page is not required, the

entire sheet is deleted with REMOVE .S2

Set the Grid

The grid of schematic diagrams should always be 0.1 inch, i.e. 2.54 mm.

Nets and Symbol connection points (pins) must lie on this common grid.

Otherwise connections will not be created between nets and pins.

Place Symbols

First we have to make available the libraries we want to take elements from

with the USE command. Only libraries which are in use will be recognized by

the ADD command and its search function.

Load Drawing Frame

It is helpful first to place a frame. The ADD command is used to select

Devices from the libraries. When the ADD icon is clicked, the ADD dialog opens .It shows all the libraries that are made available with the USE command,

first. You can expand the library entries for searching elements manually or

you can use the search function.

A letter format frame is to be used. Enter the search key letter in the Search

line at the lower left, and press the Enter key. The search result shows a number of entries from frames.lbr. If one of the entries is selected, a preview is shown on the right, provided the Preview option is active. Disabling the option Description excludes the part's descriptive texts.

Clicking OK closes the ADD window, and return to the schematic diagram editor. The frame is now hanging from the mouse, and it can be put down. The bottom left hand corner of the frame is usually at the coordinate origin .

Library names, Device names and terms from the Device description can be

used as search keys. Wildcards such as * or ? are allowed. A number of search keys, separated by spaces, can be used.

Place Circuit Symbols (Gates)

Decide a Package variant at this early stage. It can easily be changed later if it should turn out that a different Package form is used in the layout. If we have placed a Device with ADD, and then want to return to the ADD Dialogue in order to choose a new Device, press the Esc key or click the ADD icon again. Give the Devices names and values (NAME, VALUE).

If the text for the name or the value is located awkwardly, separate them from the Device with SMASH, and then move them to whatever position with MOVE. Clicking with DELETE on either of the texts makes it invisible. Use the Shift key with SMASH to get the texts at their original positions. The texts are now no longer separated from the Device (unsmash). The same effect has Deleting the remaining text or deactivating the Smashed option in the context menu's Properties window.

MOVE relocates elements, and DELETE removes them. With INFO or SHOW

information about an element is displayed on the screen.

ROTATE turns gates by 90. The same can be done with a right mouse click

while the MOVE command is active.

Multiple used parts may be copied with the COPY command. COPY places

always a new part even if it consists of several gates and not all of them are

already used.

Repeated circuitry can be reproduced in the schematic diagram with the aid

of the GROUP, CUT and PASTE commands. First make sure that all the layers

are made visible (DISPLAY ALL).

Hidden Supply Gates

Some Devices are defined in the libraries in such a way that the power supply pins are not visible on the schematic diagram. Visibility is not necessary, since all the power pins with the same name are automatically connected, regardless of whether or not they are visible.

If we want to connect a net directly to one of the hidden pins, fetch the gate

into the schematic diagram with the aid of the INVOKE command. Click onto

the INVOKE icon, and then on the Device concerned, assuming that it is located on the same sheet of the schematic diagram. If the gate is to be placed on a different schematic diagram sheet, go to that sheet, activate INVOKE, and type the name of the Device on the command line. Select the desired Gate in the INVOKE window, then place it. Then join the supply gate to the desired net.

Devices with Several Gates

Some Devices consist not of one but of several Gates. These can normally be

placed onto the schematic diagram one after another with the ADD

command. To place a certain Gate you can use the Gate name directly.

Example: The Device 74*00 from the 74xxeu

library with Package variant N and in AC technology consists of for NAND gates named A to D and one power gate named P. If you want to place the Gate C first, use the Gate name with the ADD command: ADD 'IC1' 'C' 74AC00@74xx-eu.lbr

As soon as one Gate has been placed, the next one is attached to the mouse

(Add level is Next). Place one Gate after another on the diagram. When all

the Gates in one Device have been used, the next Device is brought in.

If the Gates in one Device are distributed over several sheets, place them first

with ADD, change to the other sheet of the schematic diagram, and type, for

example INVOKE IC1

on the command line. Select the desired Gate from the INVOKE window.Wiring the Schematic Diagram

Draw Nets (NET)

The NET command defines the connections between the pins. Nets begin and

end at the connection points of a pin. This is visible when layer 93, Pins, is

displayed (DISPLAY command).

Nets are always given an automatically generated name. This can be changed

by means of the NAME command. Nets with the same name are connected to

one another, regardless of whether or not they appear continuous on the

drawing. This applies even when they appear on different sheets.

If a net is taken to another net, a bus, or a pin connecting point, the net line

ends there and is connected. If no connection is made when the net is placed,

the net line continues to be attached to the mouse. This behavior can be

changed through the Options/Set/Misc menu (using the Auto end net and bus

option). Nets must end exactly at a pin connecting point in order to be joined. A net is not joined to the pin if it ends somewhere on the pin line. EAGLE will inform you about the resulting net name or offer a selection of possible names if you are connecting different nets. The JUNCTION command is used to mark connections on nets that cross one another. Junctions are placed by default. This option, (Auto set junction), can also be deactivated through the Options/Set/Misc menu. Nets must be drawn with the NET command, not with the WIRE command.

Do not copy net lines with the COPY command. If you do this, the new net

lines won't get new net names. This could result in unwanted connections.

If the MOVE command is used to move a net over another net, or over a pin,

no electrical connection is created.

To check this, you can click the net with the SHOW command. All the

connected pins and nets will be highlighted. If a Gate is moved, the nets

connected to it will be dragged along.

Defining Cross References for Nets

If a LABEL with active XREF option for a net is placed, a cross reference will be shown automatically. It points to the next sheet where the net occurs again. Depending on the rotation of the label the cross reference refers to a previous or a following schematic sheet. If the label itself goes towards the right or bottom border of the drawing, the cross reference shows the next

higher page number. If the label points to the left or top border, the previous pages are taken into consideration. In the case that the net is only available

on one sheet, this cross reference is shown, independently from the rotation

of the label.

Drawing a bus (BUS)

Buses receive names which determine which signals they include. A bus is a

drawing object. It does not create any electrical connections. These are always created by means of the nets and their names. The associated menu

function is a special feature of a bus. A menu opens if you click onto the bus

with NET. The contents of the menu are determined by the bus name. The name of the net that is to be placed is selected from here.

Power Supply

Pins defined as having the direction Pwr are automatically wired up. This is true, even if the associated power gate has not explicitly been fetched into the schematic. The name of the Pwr pin determines the name of the voltage line. This is already fixed by the definition of the Symbols in the library. If nets are connected to a Device's Pwr pins, then these pins are not automatically wired. They are joined instead to the connected net.

For every Pwr pin there must be at least one pin with the same name but the

direction Sup (a supply pin). There must be one on every sheet. These Sup pins are fetched into the schematic in the form of power supply symbols, and

are defined as Devices in a library .These Devices do not have a Package, since they do not represent components. They are used to represent the supply voltages in the schematic diagram, as is required by the Electrical Rule Check (ERC) for the purposes of its logical checks. Various supply voltages, such as 0 V or GND, which are to have the same potential (GND, let's say), can be connected by adding the corresponding supply symbols and connecting them with a net. This net is then given the name of that potential (e.g. GND).

ERC Check and Correct Schematic

A schematic diagram must be checked with the aid of the Electrical Rule Check (ERC), when the design of the schematic diagram has been completed,

if not before. It is actually a good idea to run the (ERC) many times during design process to catch errors immediately.To start the Electrical Rule Check click onto the ERC icon in the command menu or the entry Erc in the Tools menu. All the errors and warnings are listed in the ERC Error window. Errors are marked with a red icon, warnings with a yellow icon. In the case of a corresponding board file, the ERC also checks the consistency between schematic and board. If there are no differences, ERC reports Board and schematic are consistent. Otherwise the ERC Errors window contains a branch with Consistency errors.

APPLICATION OF THE PROJECT(a) Using the remote control using Mobile phone one can remotely control switching of up to ten appliances.

(b) Just by using dial keypad of remote telephone from where you are calling you can perform on/off (operation of the appliances. Theses appliances have to be connected to phone line through the kit at the called side.

(c) The ranges of appliances that are controlled depend upon the persons usage. Room heater, water heater, parking lights, music system or any other electrical/electronic appliance switching can be controlled once they are connect to kit.

CONCLUSION

Remote control is useful in many situations. Using the DTMF remote control system, we can turn on or off the water pump, washing machine, garden light, or any other electrical appliances in our house with just a mobile call. The system is particularly suitable for use at homes. It is simple to operate and is user friendly. Bibliography

Bigelow J. Stephen, Carr J. Joseph, Winder Steve, Understanding Telephone electronics, Newnes, Pages 49-124 Graf F. Rudolf, Sheets William, The encyclopedia of electronic circuits, McGraw-Hill, Pages 23-89.

Software Programs

Complete PCB design using EAGLE 5.3 , Eagle help Files.

Websites

DTMF Receiver, Relays, WWW.WIKIPEDIA.ORG Specification Sheets WWW.GOOGLE.COM4