CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

During the transmission microcontroller encodes the signal and transmits through the

Ultrasonic transmitter. The Ultrasonic transmitter converts the electrical signal to pulse.

During this time the time set is zero. Ultrasonic transducer emits a burst of 12 pulses at a

frequency, which is roughly identical with resonance frequency of the two

transducers.After the burst has been emitted the unit is switched to reception. The

sensitivity of the receiver is a function of time. When these pulses hits any object they

are reflected back and are received by ultrasonic receiver. The number of clock pulses

counted between onsets of the emission the burst and the sensing of echo is equal to

distance between two objects. The microcontroller calculates distance by using time. The

time taken to detect the target is helpful for finding the distance of the objects. The

measured distance or height is displayed on LCD. The senility of the receiver is a

function of time. When these pulses hits any object they are reflected back and are

received by ultrasonic receiver. The number of clock pulses counted between onsets of

the emission the burst and the sensing of echo is equal to distance between two objects.

1

CHAPTER 2

BLOCK DIAGRAM

2.1 BLOCK DIAGRAMOF ULTRASONIC DISTANCE METER

Fig2.1 Block diagram of ultrasonic distance meter

2

2.2 COMPONENT DESCRIPTION

The microcontroller and other devices get power supply from AC to Dc adapter through

voltage regulator. The adapter output voltage will be 12V DC non regulated. The 7805

voltage regulators are used to convert 12 V to 5VDC.

Fig.2.2IC 7805 INPUT & OUTPUT

Vital role of power supply in ‘ultra sonic distance meter’ The adapter output voltage will be 12V

DC non regulated. The 7805/7812 voltage regulators are used to convert 12 V to 5V/12V DC.

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of

in-system programmable Flash memory.

2.3 Features: 8K Bytes of In-System Programmable (ISP) Flash Memory

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Full Duplex UART Serial Channel

Fully Static Operation: 0 Hz to 33 MHz

Vital role of microcontroller in ‘ultra sonic distance meter’

This is main part of this project. It is used to control all the interfaces like LCD, RTC and

ultrasonic transducer. During the transmission it sets the time in RTC is zero and

transmits the signal through the ultrasonic transducer. During the reception it gets the

signal from ultrasonic transducer. It decodes the signal and calculates distance by getting

time from RTC.

3

LCD (LIQUID CRYSTAL DISPLAY)

LCD’s can add a lot to your application in terms of providing a useful interface for the user,

debugging an application or just giving it a "professional" look.

The most common type of LCD controller is the Hitatchi 44780 which provides a relatively

simple interface between a processor and an LCD.

Using this interface is often not attempted by inexperienced designers and programmers because

it is difficult to find good documentation on the interface, initializing the interface can be a

problem and the displays themselves are expensive.

Vital role of LCD in ‘ultra sonic distance meter’

LCD has single line display, Two-line display, four line display. Every line has 16

characters. This is used to display the operation of the system in written form.

Buzzer

The buzzer subsystem produces a 2 KHz audible tone when powered.

The buzzer will sound when the signal coming into the driver is high. It must be

connected to a transistor, Darlington or transducer driver subsystem.

The buzzer is connected between the supply rail (+V) and the input signal. This acts as

load on the driver.

When the input signal coming into the buzzer subsystem is low, a potential difference

across the buzzer causes current to flow.

It is this flow of current that causes the buzzer to sound.

Vital role of Buzzer in ‘ultra sonic distance meter’

This is used to indicate the extreme condition system.

4

Features of Ultrasonic distance meter

Fast & easy access.

Long distance communication.

Wireless communication

2.4 Applications

For scientists.

For colleges.

For radar.

5

CHAPTER 3

3.1CIRCUIT DIAGRAM

Fig3.1 circuit diagram

6

7

3.2 CIRCUIT DISCRIPTION

The circuit of the microcontroller-based distance meter. The 40 kHz pulse bursts from the

microcontroller are amplify by transistor t5. Inverting buff- er cd4049 drives the ultrasonic

sensor used as the transmitter. Three inverters (n1, n2 and n3) are con- netted in parallel to

increase the transmitted power. This inverted out- put is fed to an- other set of three inverters

(n4, n5 and n6). Outputs of both sets of par- allele inverters are applied as a push- pull drive to

the ultrasonic trans- meter.

The positive- going pulse is ap- plied to one of the terminals of the ultrasonic sensor and the

same pulse after 180-degree phase shift is ap- plied to another terminal.

Thus the transmitter power is increased for in- creasing the range. If you want to increase the

range up to 5 metres, use a ferrite-core step- up pulse transformer, which steps-up the transmitter

output to 60v (peak- to-peak). The echo signal received by the receiver sensor after reflections

very weak. It is amplified by quad opera-(a1) is a buffer with unity gain.

The received signal is directly fed to the non-inverting input (pin 3) of a1 and coupled to the

second stage by a 3.3nf (small-value) capacitor. If you use the ubiquitous 0.01µf capacitor for

coupling, there will be enormous hum at the output.

The second stage of the (a1) is a buffer with unity gain. The received signal is directly fed to the

non-inverting input (pin 3) of a1 and coupled to the second stage by a 3.3nf (small-value)

capacitor. If you use the ubiquitous 0.01µf capacitor for coupling, there will be enormous hum at

the output. 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 signal voltage of less than 0.6v.

The output is faltered to accept 40 kHz frequencies and fed to pin 12 of microcontroller

at89c2051, which is an analogue comparator. Pin 13 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. (60 db below the main lobe)Even this low side-lobe signal is directly

picked up by the receiver unit. So you have to space the transmitter and receiver units about 5

cm apart. The two units are fixed by cello tape onto a cardboard, with the analogue circuit at one

end. Microcontroller at89c2051 is at the heart of the circuit.

8

Port-1 pins p1.7 through p1.2, and port-3 pin p3.7 are connected to input pins 1 through 7 of ic2

(ic uln2003), respectively. These pins are pulled up with a 10-kilo-ohm resistor network

rnw1.They drive all the segments of the 7-segment display with the help of inverting buffer ic2.

Port-3 pins p3.0 through p3.3 of the microcontroller are connected to the base of transistors t1

through t4 to provide the supply to displays dis1 through dis4, respectively. Pin p3.0 of

microcontroller ic1 goes low to drive transistor t1 into saturation, which provides supply to the

com- non-anode pin (either pin 3 or 8) of display dis1.

Outputs of both sets of par- allele inverters are applied as a push- pull drive to the ultrasonic

trans- meter. The positive- going pulse is ap- plied to one of the terminals of the ultrasonic

sensor and the same pulse after 180-degree phase shift is ap- plied to another terminal.

Thus the transmitter power is increased for in- creasing the range. If you want to increase the

range up to 5 metres, use a ferrite-core step- up pulse transformer, which steps-up the transmitter

output to 60v (peak- to-peak). The echo signal received by the receiver sensor after reflections

very weak. It is amplified by quad opera-(a1) is a buffer with unity gain.

The received signal is directly fed to the non-inverting input (pin 3) of a1 and coupled to the

second stage by a 3.3nf (small-value) capacitor. If you use the ubiquitous 0.01µf capacitor for

coupling, there will be enormous hum at the output. The second stage of the (a1) is a buffer with

unity gain. The received signal is directly fed to the non-inverting input (pin 3) of a1 and

coupled to the second stage by a 3.3nf (small-value) capacitor.

If you use the ubiquitous 0.01µf capacitor for coupling, there will be enormous hum at the

output.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 signal voltage of less than 0.6v.The output is faltered to accept 40khz

frequencies and fed to pin 12 of microcontroller at89c2051, which is an analogue

comparator.Pin 13 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. (60 db below the main lobe)

9

Even this low side-lobe signal is directly picked up by the receiver unit. So you have to space the

transmitter and receiver units about 5 cm apart.

The two units are fixed by cello tape onto a cardboard, with the analogue circuit at one end.

Microcontroller at89c2051 is at the heart of the circuit. Port-1 pins p1.7 through p1.2, and port-3 pin p3.7

are connected to input pins 1 through 7 of ic2 (ic uln2003), respectively. These pins are pulled up with a

10-kilo-ohm resistor network rnw1. They drive all the segments of the 7-segment display with the help of

inverting buffer ic2. Port-3 pins p3.0 through p3.3 of the microcontroller are connected to the base of

transistors t1 through t4 to provide the supply to displays dis1 through dis4, respectively.

Pin p3.0 of microcontroller ic1 goes low to drive transistor t1 into saturation, which provides supply to

the com- non-anode pin (either pin 3 or 8) of display dis1.

10

CHAPTER 4THEORY AND APPLICATION

4.1ULTRASOUND THEORY

Ultrasound is a cyclic sound pressure wave with a frequency greater than the upper limit of the

human hearing range.

Ultrasound is thus not separated from "normal" (audible) sound based on differences in physical

properties, only the fact that humans cannot hear it. Although this limit varies from person to

person, it is approximately 20 kilohertz (20,000 hertz) in healthy, young adults. Ultrasound

devices operate with frequencies from 20 kHz up to several gigahertz

Fig 4.1 1PRINCIPLE OF AN ACTIVE SONAR

Fig 4.2 2PRINCIPLE OF FLAW DETECTION WITH ULTRASOUND

11

The results obtained from this work are summarized as follows:

Noncontact ultrasonic imaging system was developed for the visualization of ultrasonic

waves propagating on opaque media.

This imaging system provides propagation image, amplitude image, arrival time image,

trajectory image and velocity image.

By use of this visualization method can produce a series of successive images as an

animation of wave propagation.

This technique is applicable to non-destructive inspection and materials characterization.

Ultrasonic sensors (also known as transceivers when they both send and receive) work on

a principle similar to radar or sonar which evaluate attributes of a target by interpreting

the echoes from radio or sound waves respectively.

Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is

received back by the sensor. Sensors calculate the time interval between sending the

signal and receiving the echo to determine the distance to an object.

This technology can be used for measuring: wind speed and direction (anemometer),

fullness of a tank and speed through air or water. For measuring speed or direction a

device uses multiple detectors and calculates the speed from the relative distances to

particulates in the air or water.

To measure the amount of liquid in a tank, the sensor measures the distance to the

surface of the fluid.

Further applications include: humidifiers, sonar, medical ultrasonography, burglar alarms

and non-destructive testing.

Systems typically use a transducer which generates sound waves in the ultrasonic range,

above 18,000 hertz, by turning electrical energy into sound, then upon receiving the echo

turn the sound waves into electrical energy which can be measured and displayed.

An ultrasonic transducer is a device that converts energy into ultrasound, or sound waves

above the normal range of human hearing.

12

While technically a dog whistle is an ultrasonic transducer that converts mechanical

energy in the form of air pressure into ultrasonic sound waves, the term is more apt to be

used to refer to piezoelectric transducers that convert electrical energy into sound.

Piezoelectric crystals have the property of changing size when a voltage is applied, thus

applying an alternating current (AC) across them

4.2 Applications

In Industries

Cavitations is probably the most interesting (and potent) effect - the shock waves

generated by tiny implosions of vapour bubbles can be devastating at close range.

The bubbles are so tiny that they can penetrate even the smallest crevices, making the

process ideal for parts which could not be cleaned by other methods.

Note also that the process must be well controlled to minimise erosion of the surfaces of

the parts being cleaned.

The standard test of ultrasonic intensity in a cleaning bath is to immerse a standard foil

strip for a set time, then remove it and count the number of holes!Traditionally the

transducers were fitted around the walls of the cleaning bath, but some modern

equipment uses an external transducer attached to a resonant probe which transmits the

vibrations to the fluid.

The ultrasonic’s may affect the cleaning process in several ways. Rapid movement in the

fluid can help to de-wet surfaces, overcoming surface tension, and may also help to

dislodge dirt particles and carry them away from the surface.

Cavitations is probably the most interesting (and potent) effect - the shock waves

generated by tiny implosions of vapour bubbles can be devastating at close range.

The bubbles are so tiny that they can penetrate even the smallest crevices, making the

process ideal for parts which could not be cleaned by other methods.

Note also that the process must be well controlled to minimise erosion of the surfaces of

the parts being cleaned.

13

The standard test of ultrasonic intensity in a cleaning bath is to immerse a standard foil

strip for a set time, then remove it and count the number of holes!

In cleaning

Cleaning was one of the earliest industrial applications of ultrasonics. Objects to be

cleaned are placed in a bath of fluid which is violently agitated by a number of ultrasonic

transducers.

The fluid may be water or solvent based, depending on the application.

In cutting

Imagine a knife which moves itself backwards and forwards in a sawing action, thirty

thousand times a second.

True the distance moved is very small but the acceleration is so high that nothing can

move with the blade or stick to it. Ultrasonic scalpels are used by surgeons

where they want to cut without exerting any pressure.

In industry ultrasonic cutting tools are used for products that are difficult to cut by other

means.

The heat generated by the ultrasonic vibrations can also be useful.

Some man-made fabrics are cut and simultaneously sealed using ultrasonic knives

toprevent fraying.

METAL FORMING

My own experience of power ultrasonic is mainly in this field. CarnaudMetalbox R&D

(now a part of Crown Cork and Seal - the biggest packaging company in the world) and

Loughborough University developed a new aerosol can using a number of novel metal-

forming processes, starting with ultrasonic necking (i.e. reducing the diameter of the can

at one end).

14

The advantage of using ultrasonic in this case was to minimise friction between the can and

the die, thus reducing the forming force. Without ultrasonics the force was so high that the

can body would buckle and collapse during the necking process.

With ultrasonic a 30% reduction in can diameter could be achieved in a single operation (in

conventional necking processes the maximum is typically about 5%).

The ultrasonic were only effective when the vibrations were perpendicular to the surface -

for a cylindrical can this meant developing a round die that would vibrate in the radial

direction. As with other high-power applications, all tooling had to be resonant, so the

desired mode of resonance was a uniform hoop expansion / contraction.

We quickly found that while it was fairly easy to design a die to resonate in this mode at the

frequency of the ultrasonic equipment, excluding other modes of vibration was a major

challeng

Another difficulty was that with the whole die expanding and contracting there was no

convenient nodal (stationary) point which could be used for mouning it.

This was solved by the use of a tubular mounting system which was itself resonant at the

same frequency as the die.

The ultrasonic forming process went into production making small-diameter aerosol cans in

a UK factory.

The production line still runs intermittently, making promotional packaging for several

prominent customers. One of its products ("Flexures de Paris" parfumdeospray can) won

silver in the 1997 Metal Packaging Manufacturers Association awards.

METAL WELDING

Ultrasonic can be used to weld different metals together, without solder and flux or special

preparation.

The process is different to plastic welding in that the two components are vibrated parallel to the

interface.

This is a more intuitively logical method of generating friction between them, but frictional

heating is not thought to be the prime mechanism of the process - the temperature needed to melt

(or even soften) most metals would be very difficult to achieve. Instead the mechanism is

15

thought to be diffusion-bonding: atoms of each part diffuse into the other when the two surfaces

are brought together in close contact.

The ultrasonic’s promotes this close contact by breaking down the surface oxide layers,

allowing the "raw" metals to make contact. The process has some limitations. It is only

suitable for relatively small components (a prime example is welding connectors to car

battery leads) since the power required to weld larger parts would be higher than can

practically supplied by this method.

Also the process tends to mark and deform the components, since high clamping forces

and sonotrodes with serrated working faces must be used to grip the workpiece firmly.

PLASTIC WELDING

Plastic welding is used for a huge variety of products ranging from blister packs,

cartons andsmall consumer goods up to car fuel tanks and dashboards.

It works by generating heat exactly where it is needed - at the interface between the

components to be joined. The

Components are clamped between a vibrating sonotrode and a fixed mounting.

Strangely, the vibrations are usually applied perpendicular to the contact surface,

although much of this vibration may be converted to in-plane movement.

This also has the advantage that the clamping pressure will keep the sonotrode in

contact with the component - serrated surfaces are generally not required. Best results

are achieved when the components are clamped close to the interface ("near-field"

welding) but if this is not possible then the process can still work at a distance ("far-

field").

Staking, or insertion, is a variation of this process in which a metal part (generally a

threaded bush) is driven into a hole in a plastic component, which then solidifies

around it to form a permanent join.

This is a convenient method of producing strong tapped holes in a plastic part.

16

4.3 CONCLUSION

The integrated analog Comparator A, the 16-bit Timer A with hardware

capture/compareregisters, the Basic Timer1, and the LCD driver peripherals simplify this

ultrasonic distance measurement application design and provide a system-in-a-chip solution. The

average currentconsumed by the application is 1.3 mA during a 15-inch distance measurement.

This includesthe quiescent current of LDO U2, operational amplifier U3, and CMOS hex

inverter U4.Theoperational amplifier alone has a quiescent current of 1 mA and the remainder of

the circuit current consumption is 300 μA. The LED draws 5 mA while it is on. The MSP430

draws an average current of 2.1 μA with the LCD continuously active. This is made possible by

taking advantage of the ultralow-current features of the MSP430. The MSP430 sleeps in LPM3

mostof the time and the CPU resources used by this application are only 5.6%.

17

4.4 COMPONENT LIST

Components Value Quantity

IC1 AT89C52 microcontroller 1

IC2 7812 12V regulator 1

IC3 7805 5V regulator 1

IC4 LM324 quad Amplifier 1

IC5 7815, 15V regulator 1

IC6 7915, -15V regulator 1

IC7 7805, 5V regulator 1

T1-T4 BC557 pnp transistor 4

T5 2N2222 npn transistor 1

D1, D2 & D3-D6 N4007 rectifier diode 4

R1, R2 2-mega-ohm 2

R3 82-kilo-ohm 1

R4, R7-R10 10-kilo-ohm 3

R5 33-kilo-ohm 1

R6 100-kilo-ohm 1

R12- R15 12-kilo-ohm 4

C1, C2 3.3nF ceramic disk 2

R16 220-ohm 1

R11 1-kilo-ohm 1

C3 2.2nF ceramic disk 1

C4 10μF, 16V electrolytic 1

C5, C6 22pF ceramic disk 2

18

C8, C9 1000μF, 50V electrolytic 2

C7, C10-C12 0.1μF ceramic disk 3

X1 230V AC primary to15V-0-

15V, 500mAsecondary

transformer

1

XTAL 12MHz crystal 1

S1 Push-to-on switch 1

S2 On/off switch 1

VR1 1 KILO OHM PRESET 1

TX1 40kHz ultrasonic transmitter 1

DIS1-DIS4 LTS,7segment display 4

19

4.5 BLOCK DIAGRAM OF AT89C2051

20

4.6 Description

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K

Bytes of Flash programmable and erasable read only memory (FPEROM). The device

Is manufactured using Atmel’s high-density non-volatile memory technology and is

Compatible with the industry-standard 80C51 and 80C52 instruction set and pin out.

The on-chip Flash allows the program memory to be reprogrammed in-system or by a

conventional non-volatile memory programmer. By combining a versatile 8-bit CPU

With Flash on a monolithic chip, the Atmel AT89C52 is a powerful microcomputer

Which provides a highly-flexible and cost-effective solution to many embedded control

applications?

AT89C2051 PIN TABLE

P3.0 RXD (SERIAL INPUT PORT)

P3.1 TXD (SERIAL OUTPUT PORT)

P3.2 INT0‾ (EXTERNAL INTRUPT 0)

P3.3 INT1 (EXTERNAL INTRUPT 1)

P3.4 T0 (TIMER 0 EXTERNAL INPUT)

P3.5 T1 (TIMER 1EXTERNAL OUTPUT)

P3.6 WR‾

P3.7 RD‾

4.6 AT89C2051 PIN TABLE

21

4.7 PIN DIAGRAM OF AT89C52

.

22

4.7 PIN DISCRIPTION

XTAL1: Input to the inverting oscillator amplifier.

XTAL2: Output from the inverting oscillator amplifier.

Port 0: Port 0 is an 8-bit open drain bidirectional port. As an open drain output port, it

can sink eight LS TTL loads. Port 0 pins that have 1s written to them float, and in that

state will function as high impedance inputs. Port 0 is also the multiplexed low-order

address and data bus during accesses to external memory. In this application it uses

strong internal pull-ups when emitting 1s. Port 0 emits code bytes during program

verification. In this application, external pull-ups are required.

Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. Port 1 pins that

have 1s written to them are pulled high by the internal pull-ups, and in that state can be

used as inputs. As inputs, port 1 pins that are externally being pulled low will source

current because of the internal pull-ups.

Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2 emits the

high-order address byte during accesses to external memory that use 16-bit addresses. In

this application, it uses the strong internal pull-ups when emitting 1s.

Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. It also serves the

functions of various special features of the 80C51 Family as follows:

Port Pin Alternate Function

P3.0 RxD (serial input port)

P3.1 TxD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 1)

23

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 WR (external data memory write strobe)

P3.7 RD (external data memory read strobe)

VCC: Supply voltage

PSEN:

Program Store Enable is the read strobe to external program memory. When the

AT89C52 is executing code from external program memory, PSEN is activated twice

each machine cycle, except that two PSEN activations are skipped during each access to

external data memory.

EA/VPP:

External Access Enable. EA must be strapped to GND in order to enable the device to

fetch code from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, A will be internally latched on reset. A

should be strapped to VCC for internal program executions. This pin also receives the

12-volt programming enable voltage (VPP) during Flash programming when 12-volt

programming is selected.

24

4.8 PCB LAYOUT

25

4.9 IC 7805 5V regulator supply

Fig 4.9 pin of IC7805

FEATURES

Output Current up to 1A

Output Voltages of 5V fix

Thermal Overload Protection

Short Circuit Protection

Output Transistor Safe Operating Area Protection

26

7805 REGULATOR IC DESCRIPTION

The 7805 voltage regulators employ built-in current limiting, thermal shutdown, and safe-

operating area protection which make them virtually immune to damage from output overloads.

7805 is a three-terminal positive voltage regulator.

With adequate heat sinking, 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 is 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 be used 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.

27

4.10 CD4049 Hex Non-Inverting Buffer

General Description

The CD4049UBC and CD4050BC hex buffers are monolithic complementary MOS (CMOS)

integrated circuits constructed with N- and P-channel enhancement mode transistors.

These devices feature logic level conversion using only one supply voltage (VDD).

The input signal high level (VIH) can exceed the VDD supply voltage when these

devices are used for logic level conversions.

These devices are 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.

Features

Wide supply voltage range: 3.0V to 15V

Direct drive to 2 TTL loads at 5.0V over full temperature range High source and sink

current capability Special input protection permits input voltages greater than VDD

28

4.11 PHOTO OF ULTASONIC DISTANCE METER

4.11 PHOTO SHOUT OF ULTRASOIC DISTANCE METER

29

4.12 DESCRIPTION/ORDERING INFORMATION

These devices consist of four independent high-gain frequency-compensated operational

amplifiers that are designed specifically to operate from a single supply over a wide

range of voltages.

Operation from split supplies also is possible if the difference between the two supplies is

3 V to 32 V (3 V to 26 V for the LM2902), and VCC is at least-1.5 V more positive than

the input common-mode Applications include transducer amplifiers, dc amplification

blocks, and all the conventional operational-amplifier circuits that now can be more

easily implemented in single-supply-voltage systems.

For example, the LM124 can be operated directly from the standard 5-V supply that is

used in digital systems and provides the required interface electronics, without requiring

additional ±15-V supplies.

Similarly, transistors t2 through t4 provide anode currents to the other three 7-segment

displays. Microcontroller ic1 provides the segment data and display-enable sig- nil

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 5 ms. Thus the

display appears to be continuous, even though the individual lads 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 re-

sistor r8.

A 12MHz crystal is used to generate the basic clock frequency for the microcontroller.

Resistor r16 connected to pin 5 of dis2 enables the decimal point.

This status is sensed by the mi- controller as programmed. When port-3 pin p3.6 goes

high, we know that the echo 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.

30

REFERENCES:

The 8051 Microcontroller And Embedded Systems, Muhammad Ali Mazidi, Janice Gillis

pieMazidi

"8051-Basic Microcontrollers" by Jan Axelson 1994

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