ABSTRACT

The microcontroller based Ultrasonic distance meter or Ultrasonic proximity meter is a non contact and non loading displacement measuring device. This device can be used to even large displacement with pin point accuracy.The heart of this distance meter is the microcontroller AT89C2051. This system potentially has very large applications not only in various industries, the luxury automobile sector but also in the armed force where accuracy and durability is of primary importance.

TABLE OF CONTENTS Abstract1: Introduction2: Ultrasonic Principles3: Basic Block Diagram 4: Circuit Diagram & Description5: PCB Layout 6:Various Components involved in the circuit7: Flow chart 8:Assembly Language Program 9: Applications of ultrasonic distance meter10: Conclusion and future scope11: Reference

INTRODUCTIONThere are several ways to measure distance. Ultrasonic distance meter is one such non contact method, it measures distance without any mechanical coupling with the object and is hence non loading as well.The heart of the circuit is the microcontroller AT89C2051. The microcontroller based Ultrasonic distance meter consists of 6 major components other than the microcontroller itself, the 40Khz ultrasonic transmitter, 40Khz Ultrasonic receiver , CD4049 Fairchild Hex inverting buffer, LM324 Low power quad operational-amplifier, ULN2003 current buffer and four LTS542 common anode seven segment display.The microcontroller is used to generate 40 kHz sound pulses. These sound pulses are used to excite the ultrasonic transmitter thereby transmitting these waves, and expect an echo from the object whose distance is to be measured.These waves travels to the object in the air and is reflected back when they fall on the object, this echo signal is picked up by another ultrasonic transducer unit, the Receiver, also a 40Khz pre-tuned unit. These signals received are weak, they are further amplified several times in the receiver circuit before being read by the micro controller and microcontroller finds the time taken in microseconds for the to-and-fro travel of the sound waves. Using the velocity of 333 m/sec, the speed of sound at 25 degree Celsius ambient temperature, the micro controller does the calculations and finally displays the distance of the object from the device on the four seven segment display.

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ULTRASONIC PRINCIPLESUltrasonic is the study and application of high-frequency sound waves, usually in excess of 20 KHz (20,000 cycles per second). Ultrasonic generators use piezo-electric materials such as zinc or lead zirconium tartrates or quartz crystal. The material thickness decides the resonant frequency when mounted and excited by electrodes attached on either side of it.The medical scanners used for abdomen or heart ultrasound are designed at 2.5 MHz Modern ultrasonic generators can produce frequencies as high as several gigahertz ( several billion cycles per second) by transforming alternating electric currents into mechanical oscillations, and scientists have produced ultrasound with frequencies up to about 10Ghz. There maybe an upper limit to the frequency of usable ultrasound, but it is not yet known.Higher frequencies have shorter wavelengths, which allow them to reflect from objects more readily and to provide better information about those objects. However extremely high frequencies are difficult to generate and measure. Detection and measurement of ultrasonic waves is accomplished mainly through the use of piezoelectric receivers or by optical means. The latter is possible because ultrasonic waves are rendered visible by the diffraction of light.Ultrasound is far above the human auditory range, which is only about 20Hz to 18 KHz. However, some mammals can hear well above this. For example, bats and whales use a phenomenon called echo location for easy navigation that can reach frequencies in excess of 100 KHz.With an ultrasonic transducer, the waves propagate out from the transducer face with a circular wave front, these waves travel through the medium until they encounter any obstacles in its path, owing to their shorter wavelength, they are readily reflected back by these obstacles , these reflected waves are picked up by the receiver circuit, these signals are amplified several times . Weak echoes also occur due to the signals being received directly through the side lobes. These maybe ignored as the real information regarding the proximity and nature of the obstacle.3.1 CIRCUIT DIAGRAM

3.2 CIRCUIT DESCRIPTIONThe figure shows the circuit of the micro-controller based ultrasonic distance meter. The 40Khz pulse bursts from the microcontroller are amplified by transistor T5. Inverting buffer CD4049 drives the ultrasonic sensor used as the transmitter. Three inverters (N1,N2,N3) are connected in parallel to increase the transmitted power. This inverted output is fed to another set of three inverters (N4,N5,N6). Outputs of both sets of parallel inverters are applied as a push-pull drive to the ultrasonic transmitter.The positive going pulse is applied to one of the terminals of the ultrasonic sensor and the same pulse after 180-degree phase shift is applied to another terminal. Thus the transmitted power is increased for increased range.The echo signal received by the receiver sensor after reflection is very weak. It is amplified by quad operational amplifier LM324. The first stage (A1) is a buffer with unity gain. The received signal is directly fed to the to the non-inverting input (pin3) of A1 and coupled to the second stage by a 3.3nF capacitor. The second stage of the inverting amplifier uses a 2-mega-ohm resistor for feedback. The third stage is a precision rectifier amplifier with a gain of 10.The rectifier functions, unlike a simple diode, even for a signal voltage of less than 0.6V. The output is filtered to accept 40Khz frequencies and fed to pin12 of microcontroller AT89C2051, which is an analog comparator. Pin13 is the other pin of the comparator used for level adjustment using preset VR1.The ultrasonic transducer outputs a beam of sound waves, which has more energy on the main lobe and less energy (60dB below the main lobe) on the side lobes. Even this low side-lobe signals are picked up by the ultrasonic receiver unit. So the transmitter and receiver units are spaced 5cm apart.pins P1.7 through P1.2 connected to input pins 1 through 7 of IC2(IC ULN2003) respectively. These pins are pulled up with a 10-kilo-ohm resistor network. They drive all the segments of the 7-segment display with the help of the and port-3 pin P3.7 are Microcontroller AT89C2051 is at the heart of the circuit. Port-1 inverting buffer (ULN 2003).Port-3 pins P3.0 through P3.3 of the microcontroller are connected to the base of transistor T1 through T4 to provide the supply to the four 7-segment displays. Pin P3.0 of microcontroller IC1 goes low to drive transistor T1 into saturation, which provides supply to the common-anode pin of the first 7-segment display. Similarly, Transistor T2 through T4 provides anode currents to other three 7-segment displays.Microcontroller IC1 provides the segment data and display-enable signal simultaneously in time-division multiplexed mode for displaying a particular number on the 7-segment display unit.Segment data and display enable pulse for the display are refreshed every 5ms. Thus the display appears to be continuous, even though the individual LEDs used in it light up one by one.Using switch S1 you can manually reset the microcontroller. While the power-on reset signal for the microcontroller is derived from the combination of capacitor C4 and resistor R8. A 12Mhz crystal is used to generate the basic clock frequency for the microcontroller. Resistor R16 connected to pin 5 of 7-segment 2 enables the decimal point.The comparator is inbuilt in the microcontroller. The echo signal will make port-3 pin P3.6 low when it goes above the level set on pin13. This status is sensed by the microcontroller as programmed.When port-3 pin P3.6 goes high, we know that the signal has arrived; the timer is read and the 16-bit number is divided by twice the velocity of sound and then converted into decimal format as a 4-digit number.

3.3 POWER SUPPLY CIRCUITThe 230V AC main is stepped down by the transformer to deliver the secondary power of 15V-0-15V, 500mA. The transformer output is rectified by a full wave rectifier comprising of four diodes (IN4001),filtered by a capacitors C8 and C9and then regulated by ICs 7815(IC5), 7915(IC6),7805(IC7). Regulators 7815, 7915 and 7805 provide +15V, -15V and +5V regulated supply respectively. The capacitors C10, C11, C12 bypasses the ripples present in the regulated supply.

3.4 COMPONENT LISTSEMICONDUCTORS:1. IC1 - AT89C2051 microcontroller2. IC2 - ULN2003 current buffer3. IC3 - CD4049 hex inverting buffer4. IC4 - LM324 quad operational amplifier5. IC5 - 7815, 15V regulator6. IC6 - 7915, -15V regulator7. IC7 - 7805, 5V regulator8. T1-T4 - BC557 pnp transistor9. T5 - 2N2222 npn transistor10. D1, D2 - 1N4148 switching diode11. D3-D6 - 1N4007 rectifier diode12. DIS1-DIS4 - LTS 542 common-anode seven segment display

RESISTORS (all -watt, 5% carbon):1. R1,R2-2-mega-ohm2. R1, R2 - 2-mega-ohm3. R3 - 82-kilo-ohm4. R4, R7-R10 - 10-kilo-ohm5. R5 - 33-kilo-ohm6. R6 - 100-kilo-ohm7. R11 - 1-kilo-ohm8. R12-R15 - 1.2-kilo-ohm9. R16 - 220-ohm10. RNW1 - 10-kilo-ohm resistornetwork11. VR1 - 1-kilo-ohm presetCAPACITORS:1. C8, C9 - 1000F, 50V electrolytic2. C1, C2 - 3.3nF ceramic disk3. C7, C10-C12 - 0.1F ceramic disk4. C3 - 2.2nF ceramic disk5. C4 - 10F, 16V electrolytic6. C5, C6 - 22pF ceramic disk

MISCLLANEOUS:

1. X1- 230V AC primary to secondary transformer2. XTAL - 12MHz crystal3. S1 - Push-to-on switch4. S2 - On/off switch5. TX1 - 40kHz ultrasonic transmitter6. RX1 - 40kHz ultrasonic receiver

COMPONENT DISCRIPTION4.1 SEMICONDUCTORS4.1.1 AT89C2051 MICROCONTROLLER:

Fig.4.1.1: AT89C2051 MicrocontrollerThe AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with 2K Bytes of Flash programmable and erasable read only memory (PEROM). 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 AT89C2051 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.

Features :1. Compatible with MCS-51 Products2. 2K Bytes of Reprogrammable Flash Memory3. 2.7 to 6V Operating Range4. Fully Static Operation: 0 Hz to 24 MHz5. Two-level Program Memory Lock6. 128 x 8-bit Internal RAM7. 15 Programmable I/O Lines8. Two 16-bit Timer/Counters9. Six Interrupt Sources10. Programmable Serial UART Channel11. Direct LED Drive Outputs12. On-chip Analog Comparator13. Low-power Idle and Power-down Modes14. 20-pin DIP

Pin Diagram AT89C2051 :

Fig 4.1.2:Pin Diagram AT89C2051

Pin Description :Pin Number

Description

1RESET Reset

2P3.0 Port 3 RXD

3P3.1 Port 3 TXD

4XTAL2 Crystal

5XTAL1 Crystal

6P3.2 Port 3 INT0

7P3.3 Port 3 INT1

8P3.4 Port 3 TO

9P3.5 Port 3 T1

10GND Ground

11P3.7 Port 3

12P1.0 Port 1 AIN0

13P1.1 Port 1 A1N1

14P1.2 Port 1

15P1.3 Port 1

16P1.4 Port 1

17P1.5 Port 1

18P1.6 Port 1

19P1.7 Port 1

20Vcc Positive Power Supply

Fig.4.1.3 Pin description

4.2 IC7 7805 5V regulator:7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear voltage regulator Ics. The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide. 7805 provides +5V regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels.Pin Diagram:

Figure 4.2.1: Pin Diagram ofIC 7805Pin Description:Pin NoFunctionName

1 .Input voltage (5V-18V)Input

2 .Ground (0V)Ground

3 .Regulated output; 5V (4.8V-5.2V)Output

Table 4.2.2: Pin Description of IC 7805

The7805 voltage regulatorsemploy built-in current limiting, thermal shutdown, and safe-operating area protection which makes them virtually immune to damage from output overloads. 7805 is a three-terminal positive voltage regulator.With adequate heatsinking, it can deliver in excess of 0.5A output current. Typical applications would include local (on-card) regulators which can eliminate the noise and degraded performance associated with single-point regulation.7805 regulator comes from the 78xx family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is a very popular choice for many electronic circuits which require a regulated power supply, due to their ease of use and relative cheapness. When specifying individual Ics within this family, the xx is replaced with a two-digit number, which indicates the output voltage the particular device is designed to provide (for example, the 7805 voltage regulator has a 5 volt output, while the 7812 produces 12 volts). The 78xx line are positive voltage regulators, meaning that they are designed to produce a voltage that is positive relative to a common ground. There is a related line of 79xx devices which are complementary negative voltage regulators. 78xx and 79xx Ics can beused in combination to provide both positive and negative supply voltages in the same circuit, if necessary.7805 Ics have three terminals and are most commonly found in the TO220 form factor, although smaller surface-mount and larger TO3 packages are also available from some manufacturers. These devices typically support an input voltage which can be anywhere from a couple of volts over the intended output voltage, up to a maximum of 35 or 40 volts, and can typically provide up to around 1 or 1.5 amps of current (though smaller or larger packages may have a lower or higher current rating).The 7805 series has several key advantages over many other voltage regulator circuits which have resulted in its popularity:7805 series Ics do not require any additional components to provide a constant, regulated source of power, making them easy to use, as well as economical, and also efficient uses of circuit board real estate. By contrast, most other voltage regulators require several additional components to set the output voltage level, or to assist in the regulation process. Some other designs (such as a switching power supply) can require not only a large number of components but also substantial engineering expertise to implement correctly as well.7805 series Ics have built-in protection against a circuit drawing too much power. They also have protection against overheating and short-circuits, making them quite robust in most applications. In some cases, the current-limiting features of the 7805 devices can provide protection not only for the 7805 itself, but also for other parts of the circuit it is used in, preventing other components from being damaged as well.7805 Voltage Regulator Pinout :

Figure 4.2.3: 7805 Voltage Regulator Pin out

7805 Regulator Circuit:

Figure 4.2.4: 7805 Regulator Circuit4.3 CD4049 HEX INVERTING BUFFER:The CD4049 hex buffer is a monolithic complementary MOS (CMOS) integrated circuit, manufactured by Fairchild semiconductor, constructed with N channel enhancement mode transistors. This device feature logic level conversion using only one supply voltage (VDD). The input signal high level (VIH) can exceed the VDD supply voltage when the devices are used for logic level conversions. The device is intended for use as hex buffers, CMOS to DTL/ TTL converters, or as CMOS current drivers, and at VDD = 5.0V, they can drive directly two DTL/TTL loads over the full operating temperature range. 4.4 LM324 QUAD OPERATIONAL AMPLIFIER:The LM124 series consists of four independent, high gain, internal frequency compensated operational amplifiers which designed specifically to operate a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current is independent of the of the power supply voltage. Application areas include transducer amplifiers,DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM124 series can be directly operated off of the standard 5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional 15V power supplies. 4.5 ULN2003 CURRENT BUFFER:Ideally suited for interfacing between low-level logic circuitry and multiple peripheral power loads, the Series ULN20xxA/L high-voltage, high-current Darlington arrays feature continuous load current ratings to 500 mA for each of the seven drivers. At an appropriate duty cycle depending on ambient temperature and number of drivers turned ON simultaneously, typical power loads totaling over 230 W (350 mA x 7, 95 V) can be controlled. Typical loads include relays, solenoids, stepping motors, magnetic print hammers, multiplexed LED and incandescent displays, and heaters. All devices feature open-collector outputs with integral clamp diodes.4.6 D1 - 1N4007 rectifier diode

Fig4.6.1:1N4007 Diode The 1N4007 has a blocking voltage of 1000V and is typically supplied in an axial-leaded DO-41 package.The 1N4007 is a 1 Amp (1A) general purpose rectifier diode commonly used in power applications.Currently the 1N4007 is sourced from manufacturers such as Comchip Technology Corporation, DAICO Industries Inc., Diodes Incorporated, EIC Semiconductor, Fairchild Semiconductor, Micro Commercial Components (MCC), Microsemi Corporation, NTE Electronics, ON Semiconductor, SPC Technology, and Vishay Semiconductors.Related parts, primarily varying in blocking voltage include: 1N4001, 1N4002, 1N4003, 1N4004, 1N4005 and 1N4006.

1N4007 Features:1. Current Rating: 1A2. Blocking Voltage: 1000V3. Packages: DO-41 (Axial Leaded), DO-20 (Axial Leaded)1N4007 Applications:1. General Purpose2. AC Adaptors3. Household Appliances

1N4007 Circuit Diagram :

Figure 4.9:1N4007 Circuit Diagram 4.2 CAPACITORS4.2.1 C8,C9 - 1000F, 50V electrolytic

Figure 4.11 : 1000F, 50V electrolytic capacitorSpecifications of 1000F, 50V electrolytic capacitorCategoryCapacitors

FamilyAluminum

SeriesFC

Capacitance1000F

Voltage Rating25V

Tolerance20%

Lifetime @ Temp.5000 Hrs @ 105C

Operating Temperature-55C ~ 105C

FeaturesGeneral Purpose

Ripple Current1.655A

ESR (Equivalent Series Resistance)-

Impedance38 mOhm

Mounting TypeThrough Hole

Package / CaseRadial, Can

Size / Dimension0.492" Dia (12.50mm)

Height - Seated (Max)0.787" (20.00mm)

Lead Spacing0.197" (5.00mm)

Surface Mount Land Size-

PackagingBulk

Catalog Page1689 (US2011 Interactive)1689 (US2011 PDF)

Other NamesEEUFC1E102P10278

4.2.2 C7,C10-C12 - 0.1F ceramic

Fig 4.2.1: C3 0.1f ceramic

Specifications Of C3 0.1f ceramic CAPACITOR CERAMIC 0.1UF, 50V, Y5V, RAD

CapacitanceCapacitance ToleranceVoltage RatingCapacitor MountingCapacitor TerminalsLead SpacingRoHS Compliant0.1F 20%50VThrough HoleRadial Leaded2.54mmYes

4.3 MISCELLANEOUS

4.3.1S2 - SPST on/off switch:Specifications:1. Supply Power: +5v @ 100mA / -5V @ 60Ma2. Logic Input High (2.5~5V, 1mA max) : On3. Logic Input Low (0~0.6V, 3mA max) : OffElectronics specification and abbreviationExpansionofabbreviationBritishmainswiringnameAmericanelectricalwiringnameDescriptionSymbol

SPSTSingle pole, single throwOne-wayTwo-wayA simple on-off switch: The two terminals are either connected together or disconnected from each other. An example is alight switch.

SOFTWARE DEVELOPMENT5.1 SOFTWARE5.2 MICROCONTROLLER PROGRAMMINGORG 0HAJMP 30HORG 0BH ;TIMER 0 INTERRUPT VECTOR; AJMP TIMER0ISR ;Timer 0 Interruptservice routine addressORG 30HMOV SP,#60H ;set stack pointerMOV P3,#0FFH ;set all port 3 bits highto enable inputs alsoMOV P1,#03 ;set port 1 to all zeros expect bits 0,1MOV TMOD,#01100001B ;TIMER 1 - MODE 2COUNTER,TIMR-0 TO MODE 1BEG: MOV TH0,#0H ;TIMER REG.0 IS SET TO0, GIVES 64msMOV TL0,#0 ; timer low reg. is also so;TOTAL CYCLE TIME IS 64.6ms ,350m/sgives 0.35mx65=22.5m; up and down 10 metres say! .35 m/ms,.35 mm/us, 1mm per 3 micros; up and down .35/2 mm/us = 1/6 mm/us; VELOCITY OF SOUND IN AIR IS 350 M/S; AFTER 100 TIMES, WE HAVE TO STOPTRANSMITTING FOR A TIME OF ABOUT .1 S; SO WE STOP FOR THIS AMOUNT OF TIMEand expect an echo.mov r2,#25 ; 25 pulses 26 us =.53 ms(343m/s*.5ms=17cm)pulse: setb p3.4 ;generates 40KHzmov r1,#5djnz r1,$clr p3.4mov r1,#5djnz r1,$ ;wait for 13 usdjnz r2, pulse ;20pulsessetb tr0 ;start timermov r2,#10djnz r2,$ ;wait 20 uscheck_echo:jnb p3.6,checktimeoutMOV 40h,TL0 ; read timer countMOV 41h,TH0mov r0,40hmov r1,41hmov r3,#0mov r2,#6call UDIV16 ;divide by 6mov 40h,r0mov 41h,r1mov 50h,#25disp: call disp1 ; show the value onLEDdjnz 50h,disp ; so many times for avisible time limitjmp begchecktimeout: mov a,th0cjne a,#0c0h,check_echo ;upto 4 metresjmp beg;subroutine UDIV16;16 bit/16bit unsigned divide;input r1,r0 =dividend X;input r3,r2 =divisor Y;output r1,r0 =quottient q of x/y;output r3,r2 = remainder; alters acc,r4-47,flags,dptrUDIV16: mov r7,#0 ;clear partial remaindermov r6,#0 ;mov B,#16 ;set loop countdiv_loop: clrC ;clear carry flagmov a,r0 ; shift the highest bit ofdividend intorlc amov r0,amov a,r1rlc amov r1,amov a,r6 ;... the lowest bit of partialremainderrlc amov r6,amov a,r7rlc amov r7,amov a,r6clr Csubb a,r2movdpl,amov a,r7subb a,r3movdph,acpl Cjnc div_1 ;update partial reaminderif borrowmov r7,dphmov r6,dpl ; update parital reminderdiv_1: mov a,r4rlc amov r4,amov a,r5rlc amov r5,adjnzB,div_loopmov a,r5mov r1,a ; put qt. in r0,r1mov a,r4mov r0,amov a,r7 ;get rem. saved before themov r3,a ;last subtraction.mov a,r6mov r2,aret;16 Bit Hex to BCD Conversion for 8051Microcontroller; This routine is for 16 bit Hex to BCDconversion;;Accepts a 16 bit binary number inR1,R2 and returns 5 digit BCD in;R7,R6,R5,R4,R3(upto 64K )Hex2BCD: ;r1=high byte ;r7 most significantS4: ACALL DELAY1 ; let it burnfor some timeMOV A,#0ffH ; extinguishthe digit after that timeMOV P3,A ; to prevent shadows6: RETledcode:DB 7EH,0CH,0B6H,9EH,0CCH,0DAH,0FAHDB 0EH,0FEH,0CEH,0EEH,0F8H,72H,0BCH,0F6H,0E2H;these are code forthe numbers 0 to 9 and A to FDELAY1: MOV R1,#0ffHN: NOPDJNZ R1,NRETEND

FLOWCHART

PCB LAYOUT6.1 Etching Process

PCB is printed circuit board which is of insulating base with layer of thin copper-foil .The etching process was carried out in this manner :The PCB is cleaned with the thinner , so that the dust on the PCB is removed and we get a shiny surface .Then we inserted our PCB in the DIPCOAT that is negative photoresistive material and expose the PCB for 5 to 10 seconds so that the negative photoresistive material should dry .

Fig.6.1:DipcoatThen the photoresistive material ( liquid ) should be made hard on the PCB for which the PCB is kept in the oven ( protocure ) for four minutes .After the liquid is made hard on the PCB it is kept in the PCB exposure for two minutes. .In the PCB exposure the circuit is kept with its layout . The ultraviolet rays are passed through the PCB.

Fig.6.2 :PCB Exposure Then we have to expose our PCB to the nail polish remover solution which is also called as developer liquid .As a result of this an impression of tracks is formed on the PCB .Put the PCB in a oven ( protocure ) to make the impression hard . The PCB is kept in oven for four minutes .After removing the PCB from the oven , the tracks on the PCB will be developed .After this the PCB is dipped into the PROTO- ETCH for five minutes . The solution used in the PROTO-ETCH is ferric chloride , due this the tracks now are fully developed on the PCB . Then the PCB is washed in water by hand and cleaned by the cloth .Thus the etching process is completed to mount the components on the PCB we need to drill the PCB according to the layout . we did the drilling in our IPR lab under the guidance of the lab incharge.

.2.3 Component Placement :

6.3 Soldering

For soldering of any joints first the terminal to be soldered are cleaned to remove oxide film or dirt on it. If required flux is applied on the points to be soldered.

Now the joint to be soldered is heated with the help of soldering iron heat applied should be such that when solder wire is touched to joint , it must melt quickly.

The joint and the soldering iron is held such that molten solder should flow smoothly over the joint .When joint is completely covered with molten solder , the soldering iron is removed .The joint is allowed to cool, without any movement .The bright shining solder indicates good soldering .In case of dry solder joint, a air gap remains in between the solder material and the joint. it means that soldering is improper .this is removed and soldering is done.

Thus in this way all the components are soldered on PCB .

Calculations Anoscilloscope(also known as ascope,CRO,DSOor, anO-scope) is a type ofelectronic test instrumentthat allows observation of constantly varying signalvoltages. Oscilloscopes are commonly used to observe the exactwave shapeof an electrical signal. In addition to the amplitude of the signal, an oscilloscope can show distortion, the time between two events (such as pulse width, period, or rise time) and relative timing of two related signals.

APPLICATIONS OF THE ULTRASONIC DISTANCEMETER:a) Ultrasonic distance meters are being increasingly used in various industries to measure critical parameters like fluid height, thickness of materialsetc with very high accuracy.b) Various luxury cars are equipped with state-of-the-art ultrasonic distance meters as part of its parking assist system.c) A technology pretty similar to this, Patented by Mercedes and Co. is being used in their next generation luxury cars in what they call the ACCIDENT PREVENTION SYSTEM.d) Ultrasonic distance meters can be potentially used in rifles and war planes for target assessment by the armed force. It is already a part of several military surveillance equipments.e) The same hardware system, with slight change in the microcontroller program can be made to detect moving objects and find their range and speed, which maybe used in speed guns to measure the speed of vehicles.

CONCLUSION AND FUTURE SCOPE:The unit can successfully used to measure distance with a very high degree of accuracy.The range of this ultrasonic distance meter can be increased further than 2.5m by using a higher pulse excitation voltage or a better transducer.The same unit can be made to detect movement of objects such as cars racing on the street and find their range and speed.It can also be used with suitable additional software as a burglar alarm unit for homes and office.

REFERENCES

Books:

1. Principles of Electronics by V.K.Meheta.2. Electronic Instrumentation by H.S. Kalsi.3. 8051 Microcontroller and Embedded System by Mazidi and Mazidi.4. A textbook of Applied Electronics by R.S.Sedha.

Websites:1. www.geocities.com2. www.yahoo.com3. http://olimp.infomir.kiev.ua/docs/PDF/AT89C20514. http://www.efy.com5. www.8051projects.net6. www.wikipedia.com7. www.electronicsforu.com8. www.ieee.org9. www.crazyengineers.com10. www.electronics4everyday.com

Software Used :1. Eagle Software - For PCB2. ASEM-51.exe - Assembler3. Keil Execution.

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