This study represents the scanning supersonic sensing system, which includes supersonic detector SRF05, microcontroller PIC16F877, temperature compensator DS18B20, 16A-2 LCD show, standard servo motor and connection to Personal computer. The supersonic and temperature detectors contribute to bring forthing cherished distance values for micro chip. And the servo motor is used to revolve the supersonic detector on a regular basis. Finally, these values are all transmitted to the LCD to expose. The circuit design, simulation and practical consequences show this system is capable of the needed aims, which is possible to be attached onto a wheeled auto or a automaton to give navigational AIDSs.
Contentss 3
1 Introduction and Research 4
1.1 Background of Ultrasonic Detection System 4
1.1.1 History of supersonic sensing 4
1.1.2 Review of background research 5
1.2 The Requirement for Ultrasonic sensing system 8
1.3 Error Analysis of Ultrasonic Detection and Scanning System 9
1.4 Previous Work 12
2 Function and Specification 13
3 Aims 18
3.1 Major Aims 18
3.2 Minor Aims 19
3.3 Minimum Aims 20
4 Main Components 20
4.1 Ultrasonic Sensor 20
4.2 LCD Module 22
4.3 Rotation Motor 24
4.4 Temperature Sensor 26
4.5 Microcontroller 30
5 Circuit Introduction 33
5.1 Undertaking System Circuit 33
5.1 power supply 37
5.2 Ultrasonic Sensor Module 38
5.3 LCD faculty 41
5.4 temperature detector faculty 43
5.4 Connection to Computer 43
1 Introduction and Research
1.1 Background of Ultrasonic Detection System
1.1.1 History of supersonic sensing
Man uses acoustic energy of lower frequences as a critical agency of communicating while mahimahis and chiropterans use acoustic energy of higher frequences, i.e. supersonic moving ridges, for acquiring their environmental information. [ 1 ]
The being of ultrasound was foremost noticed by Lazzaro Spallanzani in 1794. Since so, ultrasonics, the survey of sound propagated at frequences beyond the scope hearable to people ( i.e. above 20 kilohertz ) has been a new topic. [ 2 ]
The existent discovery took topographic point after that Pierre and Jacques Currie discovered of the “ Piezo-electric Consequence ” in certain crystals in 1880. This led to the development of ultrasound transducer. [ 1 ]
The possibility of the usage of an supersonic reverberation method for the sensing of submersed obstructions at sea, such as icebergs or wrecks, appears to hold been suggested by L.F. Richardson at the clip of the Titanic catastrophe in April 1912. After the 1914-1918 War the piezoelectric effect and its reverse consequence were foremost successfully applied in the sensing and coevals of ultrasound. The original application was to the sensing of enemy pigboats. And a feasible system was developed by P. Langevin. A beam of ultrasound is propagated vertically downwards in the sea, is reflected at the sea bed, or by some other object such as a pigboat above the sea bed, and returns to the generator/detector. By entering the going of the original pulsation and the reaching of the reverberation, the theodolite clip T for the return journey over a distance of 2d can be determined. Therefore, presuming the velocity degree Celsius of ultrasound in sea H2O is known, the deepness vitamin D can be calculated from. [ 3 ]
In 1935, the rule of supersonic sensing was applied into wireless sensing and ranging, utilizing electromagnetic moving ridges alternatively, which called Radar besides. [ 2 ]
However, the development of radio detection and ranging, during the Second War, resulted in many betterments in electronic engineering. These developments in bend wholly revolutionized the sensing system by presenting the possibility of utilizing arrays of transducers, enabling sector-scanning to be introduced, and by bettering ocular show systems. [ 3 ]
1.1.2 Review of background research
A distance sensor, besides called as a scope happening setup is one installing that determines and detects the distance between the mark and the sensing device, for the intent of appraising, finding focal point in picture taking, or accurately taking a arm. Some devices are applied utilizing active methods to mensurate ( such as ultrasound, optical maser, or radio detection and ranging ) , while others obtain the mensural distance utilizing trigonometry ( stadia metric scope finders and parallax, or cut-image scope finders ) . These methodological analysiss use a set of known information, normally distances or mark sizes, to do the measuring, and have been in regular usage since the 18th century. [ 1 ]
Since distance measuring has played an of import function in no affair the day-to-day life or working sphere, assorted types of range finders have been created to run into a assortment of demands.
These device types vary each other harmonizing to their public presentation in different fortunes, every bit good as the cost, where public presentation is determined by truth, easiness of usage, sensing scope, etc. [ 4 ]
In recent yearss, three chief types of distance sensing faculty are 1s utilizing infrared, ultrasound and laser severally.
Hereinto, scanning supersonic sensing system is the type utilizing supersonic detectors.
Supersonic detectors are normally used for non-contact, propinquity or distance measuring applications. These devices typically transmit a short pulsation moving ridge to the mark, which reflects the sound back to the supersonic detectors. The system so mensurate the echo clip of the moving ridge returning to the detector and work out the distance to the mark with the velocity of sound. [ 5 ]
The basic regulation for the usage of ultrasound as a measuring tool is the time-of-flight technique, of which this pulse-echo method is one illustration.
As shown in figure 1.
Figure 1. Basic Illustration Of Ultrasonic Detection — Transducer Generates Ultrasonic Waves And Then Listens To Repeat
Therefore, the rule of supersonic sensing system is given as followers:
If the speed of supersonic moving ridges extension has been known, mensurate the period between the clip of its launch and contemplation back from an obstruction, so that the practical distance between launch point and obstruction can be determined, which is similar to the rule of radio detection and ranging.
Frequently, the equation is given as: . ( 1 )
Where, d represents the magnitude of distance, C equals to supersonic extension speed in the air and T is the time-lag which normally amounts to the entire clip from launch and response. [ 6 ]
1.2 The Requirement for Ultrasonic sensing system
In recent yearss, there are assorted types of distance measurement detectors, like infrared, supersonic and optical maser range finders.
They differ each other in tonss of facets: truth, scope, size, weight etc.
Infrared
Supersonic
Laser
Accuracy
Typically 0.1m
Typically at centimeters
Typically at millimeters
Detection moving ridge
Electromagnetic moving ridge ( unseeable radiation )
Sound wave
Electromagnetic moving ridge ( several sorts )
Costing
i??6.83 ~ i??17.89 [ 7 ]
i??9.99 ~ i??70.79 [ 8 ]
i??870 ~ i??3485 [ 9 ]
Usual usage juncture
Small refractile index ( go through other stuff ) , good for long distance sensing [ 10 ]
Insensitive to dust, soil and fog, good for utilizing under serious environment state of affairs [ 11 ]
High preciseness, good for high-accuracy demand state of affairs [ 12 ]
Problems
Low preciseness, worse way control [ 10 ]
Preciseness influenced by temperature, humidness, force per unit area etc. [ 11 ]
Not safe to human in some state of affairs, optical system must be clean to observe [ 12 ]
Table.1: Comparison among Three Types of Detection Systems Using Infrared, Ultrasound and Laser Respectively
Harmonizing to the tabular array above, the infrared detectors have cheaper monetary value and shorter response clip than supersonic detectors, but have hapless preciseness, way control and rely strongly on good coefficient of reflection belongingss.
In footings of optical maser scope finder, it owns high preciseness but besides has high monetary value and hard operating, in common instances it is used in military kingdom.
In the usual instances, the supersonic sensor is more equal for day-to-day utilizing or extended utilizing for industrial or societal occasions for its moderate monetary value, stable capableness and acceptable truth.
The lone job for supersonic sensing system is its preciseness in some particular occasions like remote-controlled cars or endorsing for autos which require more cherished distance consequences.
1.3 Error Analysis of Ultrasonic Detection and Scanning System
For the intent of the supersonic sensing and scanning system, supersonic is one of the active countries of research and development. Supersonic detectors are good known for their public presentations in debatable environment where other detectors are non capable to be used. The rule is based on time-of-flight ( TOF ) theory, as illustrated antecedently, the clip of flight is the period of clip that travelled to and bounced back from the mark object. Use the look ( 1 ) , the distance can be determined.
However, the extension speed of supersonic moving ridge is affected by the temperature, force per unit area, humidness, air turbulency and gas composing.
But the most of import factor that affects the sound velocity is the temperature. The approximative velocity of sound in dry ( 0 % humidness ) air, in metres per second ( ) , at temperatures near 0 A°C, can be calculated from:
( 2 )
Where I? is the temperature in grades Celsius ( A°C ) . [ 13 ]
Give the undermentioned fluctuations in the velocity of sound utilizing the criterion ambiance.
As shown in table 2 below.
Temperature ( A°C )
Sound velocity ( m/s )
-20
318.89
-10
325.16
0
331.30
10
337.33
20
343.26
25
346.18
30
349.08
Table.2: Relationship between Temperature and Sound Speed
So for a sensing system that does non hold temperature detector, if the practical distance is 3m, the clip of flight distance is 6m. And presume ever to utilize the velocity value at temperature 20 A°C, which is 343.26 m/s. But in fact, when the temperature alterations, the practical velocity of sound value can besides be different.
Assume the temperature changes into -10 degree Celsius, and so harmonizing to the table.2, practical velocity of sound is 325.16 metres per second, that is, the practical mensural clip of flight should be
.
But if the microcontroller still uses the sound velocity at 20 A°C, practical measured distance could be
,
This outputs
mistake.
That is to state, in this instance, under temperature -10 grade Celsius, one metre long distance may hold about 5.57 centimeters mistake, which is a comparatively large mistake in some alone juncture such as remote-controlled vehicle or the unsighted pilotage and will ensue in serious jobs.
Because of that, a temperature compensation step should be taken to heighten the truth of this supersonic distance sensing system.
1.4 Previous Work
There are many supersonic distance metres in markets, having different features. Here gives several typical 1s:
Merchandise
Features
Supersonic Distance Meter
aˆ? Features a liquid crystal show with 12mm figures
aˆ?Can cipher the surface and the contents.
aˆ? Range of 61cm ( 2ft ) to 14.5m ( 48.3ft )
aˆ? Accuracy of A±0.5 %
aˆ? requires 2×3.0V CR2032 batteries
aˆ? Dimensions ( wxH ) : 66x130mm [ 14 ]
Silverline 255664 Digital Range Measure
aˆ?Laser sight for accurate targeting
aˆ?automatically performs computations of country and volume.
aˆ?backlit digital show for easy reading
aˆ?Metric and Imperial, with measurement verification and mistake bleeper
aˆ?Range 0.6 – 15m ( 2′-50 ‘ ) .
aˆ?Accuracy 1 % .
aˆ?Requires 1 x 9v battery. [ 14 ]
Parallax – Sensor Sampler Kit
aˆ?Motion Detection
aˆ?Angle and G-force detectors
aˆ?Distance/ Range sensor
aˆ?Sensirion Temperature and Humidity Sensor
aˆ?Compass pilotage [ 15 ]
SensComp Series 6500 Sonar Ranging Module # 615078
aˆ?Accurate Sonar Ranging from 6 inches to 35 pess
aˆ?Drives a 50 kilohertz Electrostatic Transducer Without an Extra Interface
aˆ?Operates from a Single Power Supply Source
aˆ?Accurate Clock Output Provided for External Use
aˆ?Selective Echo Exclusion
aˆ?Integrated Transducer Cable [ 16 ]
Table.3: Comparison of several typical supersonic sensing system
2 Function and Specification
The Scanning Ultrasonic Detection System is designed for automaton pilotage, remote-controlled vehicle, and obstacle-proof auto. The system contains microcontroller, supersonic detector, temperature detector, Liquid Crystal Display ( LCD ) , rotary motion motor and connection to Personal computer.
Figure.2: conventional for scanning supersonic sensing system
Here is a study map for this system shown in figure.2. Each portion will be specified as followers.
Microcontroller: processing unit of the system
Generate driven moving ridges to supersonic detector for supersonic sensing.
Receive signals from temperature detector and supersonic detector, and procedure informations.
Procedure signals to drive rotary motion motor.
Output distance, temperature and angular informations to LCD.
Datas transmitted with computing machine utilizing RS232 protocol.
Liquid crystal display: liquid crystal show, this unit is used for:
Display acquired signals
Backlight support for utilizing in the dark
Supersonic detector: this unit is used to observe the obstruction:
Generate supersonic sensing moving ridges and so listen to the reverberation.
Give signal back to microcontroller.
Temperature detector: this unit is to observe temperature surrounding:
Detect temperature and so roll up it to binary codification.
Transmit informations back to microcontroller.
Rotation motor: this unit contribute to revolving angle:
Receive signal from microcontroller and so revolve a relevant angle
Put supersonic detector on it to observe obstructions within a sector.
Connection to computing machine and monitoring package:
Transmit day of the month of distance, temperature and angle to computing machine utilizing HyperTerminal package. [ 17 ]
Be possible to be applied into echography, to expose graph on the proctor ( by taking advantage of some specific package ) . [ 18 ]
In the practical application of counsel for wheeled little auto or automaton, the whole system should be installed onto the bearer, frequently with a switch and battery to command and drive it.
Put the supersonic detector onto the rotary motion motor, to do the supersonic detector detect object in a sector, here from 0 grade to 180 grade.
Once bend on the system, the microcontroller starts to give directives to the rotary motion motor to do it revolve to the initial angle, 0 degree way. And so do the supersonic starts to run, bring forth supersonic moving ridges and so listen to the reverberation. Harmonizing to the signal moving ridges received from the supersonic detector, the microcontroller starts to cipher the distance value, taking proper velocity of sound value by utilizing the temperature compensation measuring. After the computation is done, the values are transmitted into LCD and show on it to state the obstruction distance at relevant angle and temperature. Each clip when the objects on the way at cherished angle have been detected or there are no objects, the microcontroller will give directives to do the rotary motion motor rotate into the following angle. For case, each clip the rotary motion motor is ordered to revolve 20 grade, ab initio, it starts from 0 grade, when the sensing on this way has been done, it rotate 20 grade, once more to make the sensing, and following, it rotate 20 grade into the way of 40 grade, to make the sensing, as the entire 9 times rotary motion is done, the rotary motion motor turns back into its initial angle 0 grade to re-start the sector scanning sensing.
Here is a flow chart to demo the system work processs:
The initial way
Detection objects
Calculation and temperature compensation
Display informations on LCD
Rotate angle ( illustration as 20 grade )
The followers are the same as earlier. Each clip the sensing is done, revolve another 20 grade. After entire nine times rotary motion, the rotary motion motor attached under supersonic detector returns back into the initial place.
Harmonizing to the information detected, it is possible to be used for the wheeled auto or automaton to make up one’s mind where to travel and how to avoid obstructions.
3 Aims
3.1 Major Aims
Design a system which detects the presence of objects utilizing a revolving supersonic scanner.
The power of micro chip, LCD, rotary motion motor, supersonic detector and temperature detector is supplied by 5V beginning.
The frequence to drive the supersonic detector should be 40 kilohertz.
Once the power is on, the microcontroller will enable the supersonic detector to bring forth moving ridges. And the feedback signals will be transmitted back to the microcontroller for processing.
Once the echo signal is processed, the temperature detector will offer temperature compensation for sound velocity.
After power is on, the rotary motion motor is driven to initial angle place and starts to revolve from 0 grade to 180 grade, rotate one time by a certain angle when each clip the sensing is done.
Each clip the sensing is done, the LCD will expose the information about it including distance, temperature and comparative angle, like “ 86.5cm 23a„? 90A° “ .
Once the sensing is done, the information will be transmitted to computing machine and show on the proctor utilizing hyperterminal package.
All the detectors and devices are connected to the microcontroller utilizing wires.
3.2 Minor Aims
Design the 5V beginning utilizing a electromotive force regulator attached on a 9V battery within a battery bearer.
Attach the supersonic detector onto the rotary motion motor to do it possible to observing a sector.
Develop a PCB for circuit of microcontroller, supersonic detector, temperature detector, servo motor, LCD and connection to computing machine.
Design a wadding for seting PCB into it.
3.3 Minimum Aims
Complete the existent circuit on bread board.
Accomplish scheduling codifications for the whole system.
Imitate the map and run into the major aims utilizing relevant package.
4 Main Components
4.1 Ultrasonic Sensor
There are some sorts of supersonic detectors. The chiefly used two theoretical accounts are SRF04 and SRF05 because their comparative lower monetary value and moderate public presentation. Here is a comparing between them.
SRF04
Voltage: 5V merely needed
Current: 30mA typical 50mA soap
Frequency: 40 kilohertz
Scope: from 3cm to 3m.
Sensitivity: 3cm at 2m, 1.5 %
Input trigger: 10 uS Min. TTL degree pulsation
Echo pulsation: positive TTL degree signal, width proportional to run
Small size: 43mm x 20mm ten 17mm tallness
Monetary value: i??14.50 ( Inc. VAT i??17.40 )
SRF05
Voltage: 5V merely needed
Low Current: 4mA Typical
Frequency: 40 kilohertz
Max Range: 4m
Min Range: 1cm
Mode1: Single pin for trigger/echo
Mode2: 2 Pin SRF04 compatible
Input Trigger: 10uS Min. TTL degree pulsation
Echo Pulse: Positive TTL signal
Size: 43 x 20 ten 17h ( millimeter )
Monetary value: i??11.50 ( Inc. VAT i??13.80 )
Table.4: comparing between two supersonic detectors
Comparing the characteristics of two supersonic detectors, they are all capable to complete this undertaking. But eventually the determination is made to SRF05. And the grounds are listed as followers.
Although they portion the equal electromotive force demand, SRF05 merely require much lower current. Therefore, utilizing SRF05 will necessitate smaller power to drive. It is more energy-saving.
They both need 40 kilohertzs to drive, which meet the demand of this undertaking. But SRF05 has a scope from 1cm to 4m, which is larger than SRF04, whose scope is 3cm to 3m. For the demand of more accurate and larger-scale sensing, the SRF05 is better for this undertaking.
SRF05 has two manners for taking, one is single-pin for both trigger and reverberation, the other one is compatible to SRF04, two-pin for trigger or reverberation. So SRF05 can salvage 1 pin if usage mode1, but besides be used as SRF04 if usage mode2.
Harmonizing to the monetary value listed, SRF05 has a lower monetary value than SRF04.
4.2 LCD Module
In this undertaking, the LCD is used for exposing information of obstructions and environment in environing country. Harmonizing to this, the demand of LCD faculty should be:
The LCD faculty is capable to expose numerical values, English alphabets and some measurement units.
The LCD screen is large or long plenty to demo full information.
The LCD screen should be seen in dark topographic point so it may hold a backlight map.
The LCD faculty does hold interface to microcontroller for their transmittal.
The LCD faculty is easy to run.
The LCD should hold a comparatively inexpensive monetary value.
Harmonizing to the demands, here is the determination: VERBOUQUET -ALPHANUMERIC, 2X16, STN LCD MODULE,
Here is the specification of this LCD faculty:
LCD MODULE, ALPHANUMERIC, 2X16, STN
No. of Digits / Alpha: 32
Character Count x Line: 16 tens 2
Character Size: 5.56mm
Supply Voltage: 5V
Display Mode: Brooding
Display Area Width: 64.5mm
Display Area Height: 16mm
Operating Temperature Range: 0A°C to +50A°C
External Depth: 10mm
External Length / Height: 44mm
External Width: 84mm
Active Area Height: 16mm
Active Area Width: 64.5mm
Background Colour: Yellow
Fictional character Height: 4.86mm
Character Type: Dot Matrix + Cursor
Character Width: 2.96mm
Connector Type: B, 1 ten 14
Display Polarization: Brooding
Display Technology: STN
Font Colour: Green
Interface Type: Analogue
No. of Colours: 1
No. of Digits / Alpha: 16
No. of Lines: 2
Resolution: 5 x 7 Dots + Cursor
Storage Temperature Max: +70A°C
Storage Temperature Min: -20A°C
Supply Voltage Max: 6V
Supply Voltage VDC: 5V
Monetary value: i??7.06
Table.5: specification of selected LCD faculty
4.3 Rotation Motor
In this undertaking, the rotary motion motor should run into there demands:
The microcontroller straight controls the rotary motion motor to revolve and make up one’s mind the angle value.
The rotary motion motor has the shaft to be installed on with supersonic detector.
The truth demand to be ensured.
The monetary value is non high.
Compared to these demands, here are two types of motors: hoofer motor and servo motor. Here is a comparing between these two types utilizing typical theoretical accounts:
Stepper motor
Bipolar 48mm Stepper
Measure Angle: 0.9A°
Measure Accuracy: 5 %
Keeping Torsion: 4800g-cm / 66.66 oz-in
Coil Resistance: 10hm
Rated Current: 2.4A
Motor Length: 48mm
Mounting Plate Size: NEMA-17
Shaft Diameter: 5mm
Weight: 362g
Number of Leads: 4
Monetary value: i??14.55
Servo motor
Parallax ( Futaba ) Standard Servo
Holds any place between 0 and 180 grades
43.1 oz-in torsion at 6 V
Accepts four mounting prison guards
High preciseness cogwheel made of the POM ( polyacetal ) rosin makes the operation smooth doing no recoil
Power Requirements: 4 to 6 VDC
Communication: Pulse-width transition
Dimensions: 2.2 x 0.8 ten 1.6 in ( 55.8x 19 ten 406 millimeter ) excepting servo horn
Operating temp scope: +14 to +144 A°F ( -10 to +50 A°C )
Monetary value: i??10.79
Table.6: comparing between typical hoofer motor and servo motor
Harmonizing to the comparing, it can be concluded that the servo motor is more appropriate for this undertaking because these grounds:
When servo motor receives a pulsation, it can end product a pulsation back to the microcontroller to give feedback, which is good to command the truth of the angle. Its truth can maintain up to 0.001mm, more precise than stepper motor.
Servo motor can revolve an angle harmonizing to the pulsation transmitted from microcontroller within several msecs. But stepper motor can merely steps to the needed angle, frequently it will take 200~400 msecs.
Servo motor has a lower monetary value than stepper motor.
So, the determination is made to the servo motor, in this undertaking, utilize Parallax ( Futaba ) Standard Servo Motor for its standard public presentation and low monetary value.
4.4 Temperature Sensor
The temperature detector should hold some demands:
High truth to do certain of the preciseness of this undertaking.
Easy to run.
Low monetary value.
There are two chief ways to compose the temperature compensation system: parallel and digital. The table.7 below shows the two ways ‘ composing parts needed severally.
Method
Amplifier
Temperature detector
Variable resistances
ADC ( linear digital convertor )
Analogue
a?s
a?s
a?s
a?s
Digital
a?s
Table.7. Comparison between Two Temperature Technique, a?s Means the Part Is Needed
Here is a specific analysis for each type of temperature detector. And both the two types use typical devices to exemplify.
Analogue type uses LM35DZ as illustration and digital type uses DS18B20 as illustration. As shown below.
Analogue Temperature Sensor
Temperature detector
Amplifier
Microcontroller
Liquid crystal display
Figure.3: Block Diagram of Analogue Temperature Sensing System
As shown in figure.3, the temperature detector LM35DZ can be used in broad temperature scope -40 to 100 grade Celsius. It has an end product electromotive force which is linearly relative to the Celsius and has precise built-in standardization so that there is no demand to put any external standardization to offer typical truths of A±0.25a„? at room temperature and A±0.75a„? over a full temperature scope. As the temperature increases each one grade Celsius, the electromotive force from LM35DZ will increase 10mV. The Op-Amp CA3140 has working temperature scope from -55 to 125 grade Celsius. The operational amplifier is used as non-inverting amplifier. As the temperature increases, the LM35DZ increases 10mV, CA3140 Op-Amp will increase the electromotive force to 5 times.
Digital Temperature Sensor
Temperature detector
Microcontroller
Liquid crystal display
Figure.4: Block Diagram of Digital Temperature Sensing System
As it is shown in figure.4, temperature detector choose digital temperature detector DS18B20 which has feeling truth at A±0.5a„? and besides a broad temperature feeling scope from -55a„? to 125a„? , supply electromotive force is at a scope 3V to 5.5V, besides the declaration spots is 12 spots. The nucleus map of DS18B20 is its direct to digital temperature detector. The declaration of the temperature detector is user-configurable to 9, 10, 11 or 12 spots, matching to increases of 0.5, 0.25, 0.125 and 0.0625a„? severally.
Compared parallel feeling system with digital detection system, shown in table.8 as followers:
Analogue detection system
Digital detection system
Temperature detector
LM35DZ
DS18B20
Temperature scope
-40a„? ~ 100a„?
-55a„? ~ 125a„?
Accuracy
A±0.25a„? at room temperature
A±0.75a„? over all the scope
A±0.5a„?
Need for ADC
Yes
No
Resolution spots
10
12
Costing
Sensor + Op-amp + variable resistors=i??4.47
Merely sensor=i??3.27
Table.8: Comparison between Analogue and Digital Sensing System
In the table.8, the costing values are all based on the values and monetary values shown at Farnell website. Analogue detector LM35DZ, Op-Amp CA3140, variable resistances and digital detector DS18B20 are i??1.29, i??1.67, i??1.51 and i??3.27 severally.
Conclude the information given by the table.8, a simple and natural decision can be given that digital detector DS18B20 is somewhat or unusually superior to the parallel one.
4.5 Microcontroller
The microcontroller is the cardinal bosom of the whole undertaking system, but there are many types of microcontroller. And here are the two chief types which are used most widely: PIC micro chip and Maxim 8051 household.
Here is the specific comparing between these two types, here use PIC 16f87 series as illustration:
PIC micro chip ( 16f87 series )
Harvard architecture
High public presentation RISC CPU
All individual rhythm instructions except for plan
Operating velocity: DC – 20 MHz clock input
Up to 8K tens 14 words of FLASH Program Memory,
Pinout compatible to the PIC16C73B/74B/76/77
Interrupt capableness ( up to 14 beginnings )
Power-on Reset ( POR )
Power-up Timer ( PWRT ) and
Oscillator Start-up Timer ( OST )
Watchdog Timer ( WDT ) with its ain on-chip RC
Programmable codification protection
Power salvaging sleep manner
Selectable oscillator options
In-Circuit Debugging via two pins
Processor read/write entree to plan memory
Low-power ingestion:
Monetary value: i??5.38
Maxim 8051 household
Harvard architecture
Core Size: 8bit
RAM Memory Size: 256Byte
CPU Speed: 25MHz
Oscillator Type: External Merely
No. of Timers: 3
Supply Voltage Range: 4.5V to 5.5V
Operating Temperature Scope: -40A°C to +85A°C
Clock Frequency: 25MHz
Interface Type: UART
Memory Size: 256Byte
Memory Type: Random-access memory
No. of Spots: 8
RAM Size: 256Byte
Supply Voltage Max: 5.5V
Supply Voltage Min: 4.5V
Termination Type: Through Hole
Monetary value: i??8.56
Table.9: comparing between two types of microcontroller
By comparing the two typical devices of each type, both two types can do the undertaking successful, but the determination is made to PIC 16f87 household because these grounds listed below:
The PIC 16f87 series are more popular than Maxim 8051 series in UK.
The MPLAB package is compatible to PIC micro chips and utilize it can assist to imitate the assembly linguistic communication map and detect the registry and map codifications state of affairs.
The PIC 16f87 series has lower monetary value than Maxim 8051 series.
PIC 16f87 series includes 16F873, 16F874, 16F876, 16F877. Here is the pin diagram of them:
Figure.5: PIC16F87 series
Here is comparison among these 4 theoretical accounts in PIC 16f87 series:
Key Features
PIC16F873
PIC16F874
PIC16F876
PIC16F877
Operating Frequency
DC – 20 Megahertz
DC – 20 Megahertz
DC – 20 Megahertz
DC – 20 Megahertz
RESETS ( and Delays )
POR, BOR
( PWRT, OST )
POR, BOR
( PWRT, OST )
POR, BOR
( PWRT, OST )
POR, BOR
( PWRT, OST )
FLASH Program Memory ( 14-bit words )
4K
4K
8K
8K
Data Memory ( bytes )
192
192
368
368
EEPROM Data Memory
128
128
256
256
Interrupts
13
14
13
14
I/O Ports
Ports A, B, C
Ports A, B, C, D, E
Ports A, B, C
Ports A, B, C, D, E
Timers
3
3
3
3
Capture/Compare/PWM Modules
2
2
2
2
Consecutive Communicationss
MSSP, USART
MSSP, USART
MSSP, USART
MSSP, USART
Parallel Communications
–
PSP
–
PSP
10-bit Analogue-to-Digital Faculty
5 input channels
8 input channels
5 input channels
8 input channels
Direction Set
35 instructions
35 instructions
35 instructions
35 instructions
Table.10: comparing among 16f87 series
For this design, 33 I/O pins are required because of the other devices ‘ pin Numberss, sing the job of monetary value and size of bit, the concluding determination is made to PIC 16F877.
5 Circuit Introduction
5.1 Undertaking System Circuit
Block diagram
Here is the block diagram for this undertaking.
Figure.6: block diagram for the undertaking
The undertaking system includes LCD, supersonic detector, temperature detector, servo motor, connection to computing machine and one microcontroller PIC 16F877. The LCD and connection to computing machine are end products for the system, the temperature detector and servo motor transmit informations and signal between microcontroller and themselves. The supersonic detector sender is for conveying supersonic moving ridges and the supersonic detector receiving system is for having echo moving ridges. Here use 9V battery and one regulator to give the undertaking power beginning 5V.
Circuit diagram
Figure.7: circuit diagram for the undertaking system
Here is the circuit diagram designed by package Protues.
PCB design
Here is the PCB design designed by PCB Express. Show in Figure.8 and Figure.9.
Figure.8: PCB design manner
Figure.9: PCB design Real World Mode
Real Picture
Figure.10: existent image
5.1 power supply
In this undertaking, all the devices are based on 5V power supply. However, most common batteries do non back up this electromotive force value. So use 9V battery and electromotive force regulator to give a 5V electromotive force beginning.
Besides, here can add a switch to command the whole system to turn on or turn off.
Because it is needed to give a 5V beginning, so the electromotive force regulator determination is made to LM7805.
Here is the diagram for the power supply.
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Figure.11 schematic for power supply faculty
5.2 Ultrasonic Sensor Module
The supersonic detector faculty has two manners to take.
Mode 1: 2-pin Trigger/Echo Mode
This manner uses separate trigger and reverberation pins, and is the simplest manner to utilize. All codification illustrations for the SRF04 will work for the SRF05 in this manner. To utilize this manner, merely go forth the manner pin unconnected – the SRF05 has an internal pull up resistance on this pin.
Figure.12: connexions for 2-pin Trigger/Echo Mode
In this manner, the timing diagram is:
Small hold
Figure.13: SRF05 clocking diagram for manner 1
Here, the SRF05 includes a little hold before the reverberation pulsation to give slower accountants such as the Basic Stamp and Picaxe clip to put to death their pulsation in bids.
Mode 2: Single pin for both Trigger and Echo
This manner uses a individual pin for both Trigger and Echo signals, and is designed to salvage valuable pins on embedded accountants. To utilize this manner, connect the manner pin to the 0v Ground pin. The echo signal will look on the same pin as the trigger signal. The SRF05 will non raise the echo line until 700uS after the terminal of the trigger signal. You have that long to turn the trigger pin around and do it an input and to hold your pulsation mensurating codification ready. The PULSIN bid found on many popular accountants does this automatically.
Figure.14: connexion for individual pin trigger/echo manner
In this manner, the timing diagram is:
Figure.15: SRF05 clocking diagram for manner 2
In this undertaking, for there are 33 I/O pins for usage, there is no demand to utilize manner 2, so here use Mode 1 which is compatible to SRF04.
So here is the conventional for supersonic detector.
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Figure.16: conventional for supersonic detector faculty
5.3 LCD faculty
The Alphanumeric point Matrix LCD is the end product device of the undertaking system, which is used for exposing the direction and information to user.
Here is the mention image of the LCD faculty:
And here is the LCD ‘s pin connexion:
Pin figure
Pin symbol
Function
1
Volt
Land
2
Vdd
Power supply
3
Vo
Contrast adjust
4
R/S
Register Selection ( H: Data, L: Direction )
5
R/
Read/Homework help – Write Selection ( H: Read, L: Homework help – Write )
6
Tocopherol
Enable Signal
7~14
DB0~DB7
Data coach lines
15
A
Power supply for LED B.L. ( + )
16
K
Power supply for LED B.L. ( – )
Table.11: LCD pin connexions
Pin 3 is the contrast adjust for LCD, it should link 0-5V electromotive force depend on what brightness is required. Here use a potentiometer to set the electromotive force.
Pin 4 is an input pin for LCD faculty ; it is used as to command informations conveying or direction transmission. When it is connected to high electromotive force, any input information is regarded as informations, and low degree electromotive force is matching direction.
Pin 6 is an input pin for LCD faculty every bit good ; the LCD faculty ca n’t place any informations of direction until Pulse the E line being high.
Pin7- Pin14 are Data Bus lines, they can convey informations or instructions.
In this undertaking, PORTB0~B7 are connected to informations coach lines DB0~DB7. And the three map control pins RS, R/ and E are connected to RA0~RA2. The A and K temporarily blank but can be connected in possible use when backlight is needed.
Therefore, here is the conventional for LCD faculty:
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Figure.17: conventional for LCD faculty
5.4 temperature detector faculty
In this undertaking, the temperature detector is DS18B20.
Figure.18: DS18B20 pin diagram
Here is the pin diagram for this temperature detector, the pin 1 is connected to land, and pin 2 is the information line, pin 3 is connected to the power beginning.
5.4 Connection to Computer
Block diagram
figure.11: block diagram for connection to computing machine
