Construction of microcontroller-based Vehicle Speed Alarm
Chapter One
THE AIM AND OBJECTIVE OF THE PROJECT
- To design a digital
- Incorporate a speed monitor with respect to set
CHAPTER TWO:
LITERATURE REVIEW
HISTORICAL BACKGROUND
A speedometer is a gauge that measures and displays the instantaneous speed of a land vehicle. Now universally fitted to motor vehicles, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards.[1] Speedometers for other vehicles have specific names and use other means of sensing speed. For a boat, this is a pit log. For an aircraft, this is an airspeed indicator.
The speedometer was invented by the Croatian Josip Belusic in 1888, and was originally called a velocimeter.
The eddy current speedometer has been used for over a century and is still in use. Until the 1980s and the appearance of electronic speedometers it was the only type commonly used.
Originally patented by a German, Otto Schulze on 7 October 1902, it uses a rotating flexible cable usually driven by gearing linked to the output of the vehicle’s transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.
When the car or motorcycle is in motion, a speedometer gear assembly will turn a speedometer cable which then turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with a small aluminum cup (called a speed cup) attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the changing magnetic field produces eddy currents in the cup, which themselves produce another magnetic field. The effect is that the magnet exerts a torque on the cup, “dragging” it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them.
The pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet (which is driven by the car’s transmission). Thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the eddy currents on the cup is balanced by the opposing torque of the spring, and then stop. Since the torque on the cup is exactly proportional to the car’s speed, and the spring’s deflection is proportional to the torque, the angle of the pointer is also proportional to the speed. At a given speed the pointer will remain motionless and pointing to the appropriate number on the speedometer’s dial.
The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tail shaft gears that drive the flexible cable, the final drive ratio in the differential, and the diameter of the driven tires.
SPEEDOMETERS
Many modern speedometers are electronic. In designs derived from earlier eddy- current models, a rotation sensor mounted in the transmission delivers a series of electronic pulses whose frequency corresponds to the (average) rotational speed of the driveshaft, and therefore the vehicle’s speed, assuming the wheels have full traction. The sensor is typically a set of one or more magnets mounted on the output shaft or (in transaxles) differential crown wheel or a toothed metal disk positioned between a magnet and a magnetic field sensor. As the part in question turns, the magnets or teeth pass beneath the sensor, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring. Alternatively, in more recent designs, some manufactures rely on pulses coming from the ABS wheel sensors.
A computer converts the pulses to a speed and displays this speed on an electronically-controlled, analog-style needle or a digital display. Pulse information is also used for a variety of other purposes by the ECU or full-vehicle control system, e.g. triggering ABS or traction control, calculating average trip speed, or more mundanely to increment the odometer in place of it being turned directly by the speedometer cable.
Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsate driven by the car’s wheel or transmission. The watch mechanism endeavors to push the speedometer pointer toward zero, while the vehicle-driven pulsation tries to push it toward infinity. The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms. The illustration above boil up in the implementation of the hall-effect technique, the induced voltage as its result is converted to digital using the analog to digital conversion technique.
Hall Effect is an electrical effect that occurs under certain conditions when an electrical conductor is subject to a magnetic field or a region of space influenced by a magnet or other magnetizing objects (see Magnetism). Studies of the Hall Effect have led to a better understanding of the electronic properties of solids, such as conduction in metals and semiconductors, which are materials that conduct electricity better than electrical insulators but not as well as electrical conductors.
The Hall Effect occurs when a conductor or semiconductor carrying an electric current is placed in a magnetic field. A voltage, called the Hall voltage, is created across the conductor or semiconductor perpendicular to both the current and the magnetic field. This voltage arises because the magnetic field distorts the flow of electrons or other charge carriers that constitute the current, pushing the charged particles to one side of the conductor.
The Hall voltage is proportional to the current and magnetic field and inversely proportional to the number of electrons or other charged particles. For instance, the Hall voltage across a metal is much smaller than across a semiconductor carrying the same current in the same magnetic field because the metal contains more charged particles than the semiconductor.
This effect was discovered in 1879 by American physicist Edwin Hall. German physicist Klaus-Olaf von Klitzing won the 1985 Nobel Prize in physics for his discovery of the quantum Hall effect, which helps explain electrical movements in atoms. The Hall Effect is useful in the study of plasmas a state of matter in which some or all of the atoms or molecules are separated into ions, or particles with net electric charges and the study of magneto hydrodynamics, the interaction between magnetic fields and conducting liquids. The function of a variety of electric meters and measuring instruments, such as ammeters, wattmeter’s, magnetic compasses, and position sensing devices, as well as power-transforming solid-state devices known as transducers, are based on the Hall Effect.
CHAPTER THREE:
SYSTEM OPERATION
BLOCK DIAGRAM OF THE PROJECT
The flow chart of the project really helped me in actualization of it. Below is the flow chart for the system designing and construction approach, the flow chart is in the next page.
CIRCUIT DIAGRAM AND OPERATION
The system comprises of few blocks which was illustrate as follows the power supply module, the control unit, the transistor switching module, hall-effect module, opt coupler module, keyboard module, display module, panic alarm module and analog to digital conversion (ADC) which help to simplify the hardware since the microcontroller contains it internally, all the unit are hardwired and tested as classified then were concatenated before generating the actual software the controls the system.
POWER SUPPLY UNIT
The power supply unit is built around a 12v automotive accumulator (car battery), then a voltage regulator is connected to tailor down the unregulated DC voltage to
+5volts dc via voltage regulator (78L05) These serves as the power supply. A decoupling capacitor is connected across the +5v and ground reference of the power to filter or reject the transient noise generated by the microcontroller and associate components in the circuit at run time.
THE DIODE
The diode (D1 in the figure below) used in the design is to protect the system from being damage whenever the battery polarity is altered or not properly connected. The protection lies on the characteristics and unique behavior of diode (semiconductor), since diodes allows current flow only in one direction when it attains its conducting voltage (this is maintained provided the applied voltage is below it break down voltage rating such info can be source from the detailed information of a given diode).
CHAPTER FOUR:
SYSTEM DESIGN AND CONSTRUCTION
The designing of the project was done complying with the basic rules in electronic designing and construction the components used had been described in the previous chapter. The construction is made in modules start from the power supply, then sensing part, the control part and the display unit.
SOFTWARE DESIGNING
There are hundreds of programming languages each was develop to solve a particular type of problem. Most traditional languages such as Basic, C, COBOL, FOTRAN, PL/I, AND PASCAL are procedural languages. That is, the program sequence determines the exact sequence of operations programming language is a free field language. Precedence of the operator determines the order of operation. Comments are used to document the software; preprocessor directives are special operations that occur first. Global declarations provide modular building blocks. Declarations are the basic operations .Function declarations allow for one routine to call another. Compound statements are the more complex operations. Global variables are permanent and can be shared. Local variables are temporary and are private Source files makes it easier to maintain large projects.
The software was designed using simple device C compiler (SDCC) C compiler which contains the header file of the Microcontroller (PIC16f88).It used virtual conventional C programming language keywords and syntax. The program environment is where the code are written, compile and debug .It will generate an Intel hex file (content of the system ROM) which is transfer into the microcontroller via a computer interfaced programming device.
CHAPTER FIVE:
TESTS OF RESULTS AND PACKAGING
TESTING OF THE INDIVIDUAL COMPONENTS
Components should be tested individually before fiddling with it so as to remove he bad ones .This test will be satisfied test measures for individual components which are basically used of the multi-meter (e.g. testing of transistor, diodes, LEDs are every other component that will be used in the project.
UNIT BY UNIT TESTING
These involve wiring up of circuitry and testing and satisfy its functions before soldering.
Examples are building of power supply stage of the project testing and confirming that is functional before soldering.
CHAPTER SIX:
CONCLUSON AND RECOMMENDATION
CONCLUSION
The design was actualized to using the basic rule in electrical and electronic designing and was implemented in real time; the design was installed in a vehicle and then the analog speedometer unit was replace with my designed project and it worked perfectly, thanks to my supervisor and o’mara.digiba both contributed immensely in the actualization of my goal.
PROBLEMS ENCOUNTERED AND SOLUTIONS
The buzzer was resetting the system which to troubleshooting that almost winding up my design, the problem was figured out when the buzzer was disconnected from the system power; solution an electrolytic capacitor was connected across the buzzer.
SUGGESTIONS FOR FURTHER IMPROVEMENTS
The transmission line cable should be eliminated and the hall-effect module be fabricated and attached directly to the gearbox but still detachable for easy maintenance, elimination of the hall-effect and introducing a wireless communication using GPS (global positioning satellite).
RECOMMENDATION
This project exhibit simplicity and power of the 8bit nano watt technology microcontroller (PIC16f88) from Microchip Inc., the use of the internal peripherals reduces the number of discrete components to be used thus increasing the performances and error prone.
Guided by findings, conclusions and output of this project the researcher feels obliged to make this situational recommendation as regard to the case study and construction, which the researcher belief if properly implemented by road users will minimize or eliminate the rate of road accident in the country.
BIBLIOGRAPHY
- Bannatyne R Prentice Hall, (1998). Speedometers 2nd edition UK: University Press (ISBN-13-840406-2)
- Jane Leavy (2010). The Last Boy: Mickey Mantle and the End of America’s Childhood. HarperCollins. Page 91.( ISBN 9780060883522)
- Letters Patent No. 79,965. Text accessed 26 February 2006 Microsoft Encarta 2009. © 1993-2008 Article on “Speedometers”
- John Wiley & sons New York (1977), Practical digital design 1st edition
- Paul Horowitz ,Winfield Hill. second edition: The art of electronics (ISBN 0-521-49846-5)
- Wray W.Greenfield J,b(1959), Using microprocessor and microcomputers
- Scherz, Paul (2006) “Practical Electronics for Inventors,” 589. McGraw-Hill/TAB Electronics. ISBN:978-0070580787.
