My Graduation Project Final Report 1h433f

Jordan University of Science and Technology Electrical Engineering Department

Graduation Project EE 592 Car's Blind-Spot Collision Avoidance System using Ultrasonic Sensors and PIC Microcontroller Prepared By:

Rami Moh'd Zaghal ID # 20010024035 E-mail: [email protected]

January 2007

Supervisor:

Bassam El-Asir, Assoc. Prof.

To my loving parents You are all the reasons I am what I am…

To Richard Bandler You made up NLP… It changed my life!

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Acknowledgments First, I want to thank Dr. Bassam El-Asir for supervising my graduation project. His continuous and consultation provided great help during the progress of the project. He has not only been an excellent teacher and a caring father, but also a long-lasting mentor to me… and he will remain… I also want to thank Jordan University of Science and Technology for completely funding my project. Without their funding, none of this could have been accomplished. Finally, my special thanks and gratitude go to all the people on the Internet (EDAboard, MicroChip Forum, and MELabs PICBASIC Forums) who answered my technical questions and provided invaluable information without even knowing me.

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Abstract The Blind-Spot collision voidance system is an integrated automobile system designed to assist drivers when changing lanes. On busy highways, changing lanes can be very hazardous. There is region called “blind spot” which is a problem for every car driver since it is not covered by the driver’s mirrors. Relying solely on the mirrors while changing lane can lead to a collision with another vehicle. It is proposed to implement the collision avoidance system to address these problems and provide a cost-effective solution that eases the process of changing lanes. The system employs ultrasonic sensors for the detection of objects in the blind spot. The sensors are mounted to car's left and right bumpers and the distance from the bumper of the automobile to another car is continuously updated to the driver on an LCD display located in the cabin of the automobile. A PIC microcontroller is used to control the sensors and the LCD.

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Contents Acknowledgments --------------------------------------------------------------------------------------------------------------------- 2 Abstract ------------------------------------------------------------------------------------------------------------------------------------ 3 Contents ----------------------------------------------------------------------------------------------------------------------------------- 4 Chapter 1: Introduction ---------------------------------------------------------------------------------------- 6 1.1 The Modern Car ---------------------------------------------------------------------------------------------------------- 6 1.1.1 Present and Future Car Technologies Overview -----------------------------------------------6 1.1.2 The Parking Space Finder Service-----------------------------------------------------------------7 1.1.3 Parking Assistant Systems --------------------------------------------------------------------------7 1.1.4 No-Hands Parking System--------------------------------------------------------------------------8 1.2 Blind-Spot Detection System----------------------------------------------------------------------------------------- 9 1.3.1 System Overview -------------------------------------------------------------------------------------9 1.3.2 Features and Benefits ------------------------------------------------------------------------------ 11 1.3.3 Technical Specifications--------------------------------------------------------------------------- 11 1.4 Project Objectives Summary --------------------------------------------------------------------------------------- 11 Chapter 2: Ultrasonic Waves and Sensors------------------------------------------------------------------12 2.1 Introduction to Acoustics and Ultrasonics-------------------------------------------------------------------- 12 2.1.1 Sound Propagation --------------------------------------------------------------------------------- 12 2.1.2 Sound Waves properties--------------------------------------------------------------------------- 13 2.1.2.1 Amplitude and Frequency ------------------------------------------------------------------ 13 2.1.2.2 Wavelength and Attenuation--------------------------------------------------------------- 13 2.1.2.3 Speed of Propagation ------------------------------------------------------------------------ 15 2.2 Ultrasonic Sensors------------------------------------------------------------------------------------------------------ 15 2.2.1 Types of Ultrasonic Sensors ---------------------------------------------------------------------- 15 2.2.1.1 Magnetostrictive Ultrasonic Sensors ------------------------------------------------------ 16 2.2.1.2 Piezoelectric Ultrasonic Sensors ----------------------------------------------------------- 16 2.2.2 Pro-Wave 40 kHz Piezoelectric Ultrasonic Sensors------------------------------------------ 16 2.3 Sensor Radiation Pattern--------------------------------------------------------------------------------------------- 18 2.3.1 Transmitter Sensor Excitation -------------------------------------------------------------------- 19 2.4 How Far The Sensor Could Reach? ----------------------------------------------------------------------------- 20 2.5 Sensor Equivalent Circuit ------------------------------------------------------------------------------------------- 21 2.6 Environmental Factors and Sensors ----------------------------------------------------------------------------- 23 2.7 Applications of Ultrasonic Sensors ------------------------------------------------------------------------------ 24 2.7.1 Special Applications--------------------------------------------------------------------------------- 25 Chapter 3: Microcontrollers ----------------------------------------------------------------------------------26 3.1 Introduction -------------------------------------------------------------------------------------------------------------- 26 3.1.1 What is a Microcontroller? ----------------------------------------------------------------------- 26 3.1.2 MicroChip PIC Microcontrollers---------------------------------------------------------------- 28 3.2 The PIC16F877A Microcontroller------------------------------------------------------------------------------- 29 3.2.1 PIC16F87X → PIC16F87XA Migration------------------------------------------------------- 29 3.2.2 PIC16F877A Hardware and Features ---------------------------------------------------------- 29 3.2.3 PIC16F877A Pin-out Description --------------------------------------------------------------- 30 3.3 PIC16F877A Subsystems in Use --------------------------------------------------------------------------------- 32 3.3.1 I/O Ports --------------------------------------------------------------------------------------------- 32 3.3.2 Timer1 ------------------------------------------------------------------------------------------------ 33 3.3.3 Comparator Module ------------------------------------------------------------------------------- 34 3.3.4 Comparator's Voltage Reference Module ------------------------------------------------------ 36 4

Chapter 4: Ultrasonic Ranging Systems --------------------------------------------------------------------37 4.1 Overview of Echo Ranging ----------------------------------------------------------------------------------------- 37 4.2 Pro-Wave Sonar Ranging Module ------------------------------------------------------------------------------- 38 4.3 Distance Calculation using the Microcontroller ------------------------------------------------------------ 40 Chapter 5: Design Details and Circuit Explanation ------------------------------------------------------41 5.1 The Overall System ---------------------------------------------------------------------------------------------------- 41 5.1.1 System Block Diagram ---------------------------------------------------------------------------- 41 5.1.2 System Circuit Schematic ------------------------------------------------------------------------- 42 5.1.3 Transmitter-Receiver Separation ---------------------------------------------------------------- 43 5.2 The Transmitter --------------------------------------------------------------------------------------------------------- 43 5.2.1 Design Explanation -------------------------------------------------------------------------------- 43 5.2.2 Simulation Results---------------------------------------------------------------------------------- 45 5.3 The Receiver ------------------------------------------------------------------------------------------------------------- 45 5.3.1 Design Explanation -------------------------------------------------------------------------------- 45 5.3.2 Simulation Results---------------------------------------------------------------------------------- 47 5.4 The Microcontroller --------------------------------------------------------------------------------------------------- 49 5.4.1 Biasing the PIC-------------------------------------------------------------------------------------- 49 5.4.2 Resetting the PIC ----------------------------------------------------------------------------------- 50 5.4.3 PIC Clock Frequency ------------------------------------------------------------------------------ 50 5.4.4 PIC Ports and Pins --------------------------------------------------------------------------------- 50 5.5 The Switches ------------------------------------------------------------------------------------------------------------- 50 5.5.1 The Manual SPDT Switch------------------------------------------------------------------------ 50 5.5.2 IC Electronic Switch ------------------------------------------------------------------------------- 50 5.6 The Alphanumeric LCD Module -------------------------------------------------------------------------------- 51 Chapter 6: PIC Programming and Interfacing -------------------------------------------------------------53 6.1 Programming Language --------------------------------------------------------------------------------------------- 53 6.2 PIC Programmer-------------------------------------------------------------------------------------------------------- 53 6.3 PIC Program Code----------------------------------------------------------------------------------------------------- 54 6.3.1 Code Flow ------------------------------------------------------------------------------------------- 54 6.3.2 Code Analysis --------------------------------------------------------------------------------------- 56 Chapter 7: Conclusions ----------------------------------------------------------------------------------------59 7.1 Challenges----------------------------------------------------------------------------------------------------------------- 59 7.2 Future Work-------------------------------------------------------------------------------------------------------------- 59 7.3 Recommendations ----------------------------------------------------------------------------------------------------- 60 7.4 Final Comments -------------------------------------------------------------------------------------------------------- 60 References and Readings --------------------------------------------------------------------------------------61 Web Resources --------------------------------------------------------------------------------------------------62 Appendix A ------------------------------------------------------------------------------------------------------63 List of Components Used in the Project --------------------------------------------------------------------------------- 63 Appendix B ------------------------------------------------------------------------------------------------------64 Sensors and Modules Purchase Order ------------------------------------------------------------------------------------ 64 Appendix C ------------------------------------------------------------------------------------------------------65 Selected Data Sheets------------------------------------------------------------------------------------------------------------- 65

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Chapter 1: Introduction 1.1 The Modern Car 1.1.1

Present and Future Car Technologies Overview

As the technology advances day-after-day, cars manufacturers and developers provide us with more sophisticated, high technology cars and vehicles. We are living in the smart car era. Figure 1.1 illustrates features available in a typical modern car. This car utilizes an engine control system that optimizes performance and fuel combustion, a system that detects collisions and activate the airbags in the event of a crash, a system that regulates the interior climate based on enger preferences and exterior climate conditions, a system that controls the braking system for maximum efficiency, a GPS navigation system to aid driver approach his destination in most efficient ways, and much more. In fact, modern car - nowadays - may contain up to a 100 microprocessor and microcontroller systems that together manifest all these features. According to statistics, vehicle accidents cause 40,000 deaths and 3.5 million injuries annually. In a given two-hour period, 1,600 accidents, 800 injuries, and 10 deaths will occur on U.S. highways. The ultimate goal of cars manufacturers is to come up with safe, driver-friendly add-on systems to ensure the safety of drivers, engers and pedestrians. This may, in some way or another minimizes car accidents and injuries.

Figure 1.1: Example of features of a modern car.

Safe driving systems are starting to appear on vehicles including adaptive cruise control (ACC) systems that maintain safe distance between you and the vehicle ahead, lane keep (LKS) systems that prevent drivers from departing lane, and pre-crash brake systems that automatically tighten seat belts, activate air-bags and apply brakes if a collision cannot be avoided. Ultrasonic, Millimeter-wave and Infrared Radars and image processing cameras are the environment sensors with the key roles of recognizing and deciding what action to take in these safe driving systems. These sensors must incorporate intelligent recognition technologies considering various complex external factors they might encounter in the real world: pedestrians darting out into the road, other vehicles cutting-in in front of you, poor visibility due to adverse weather conditions, etc. Symbols and signals in a car must provide the driver with accurate information about the car’s status, and with clear warnings of critical situations. The visual aspect frequently dominates in convenience functions. A graphical icon or symbol, for instance, may clearly demonstrate available options and appropriate actions the driver can take to back into a parking space or to change into 6

new lane. In addition, acoustic (audible) signals can denote the start and finish of required steering, backing-up and braking actions. Figure 1.2 illustrates ACC and LKS systems.

Figure 1.2: Examples of safe driving systems.

1.1.2

The Parking Space Finder Service

This is one of the most promising (hot) schemes in the field. The objective of the PSF service is to use feeds from cameras installed in parking lots in a metropolitan area and allow s to make queries about the availability of parking spots at a particular location. The microcomputers used in this service processes the webcam feed and recognize whether the parking spots are empty or full. s specify a destination and constraints of their desired spot. The PSF service returns the driving directions (using the Yahoo Maps service) to the empty parking spot that satisfies the constraints and is the nearest to their destination.

1.1.3

Parking Assistant Systems

With increasing traffic density, especially in urban areas, parking can be a tricky maneuver and an error can be costly, in the event of with other parked cars or hidden obstacles. Such accident repairs are more and more frequent and expensive. Drivers can prevent such costly, time consuming and stressful situations by selecting an Ultrasonic Park Assist (UPA) system when buying a new vehicle or installing any of the commercially available kits as post-equipment, both of which cost less than the average accident repair. UPA is available for rear applications using two to six sensors mounted discreetly behind the rear bumper or a combined front and rear system using eight to twelve sensors. Figure 1.3 shows a typical four-sensor reverse parking aid. Figure 1.4 shows - from three different views - how the system is installed and highlights the range covered by the three sensors. This system provides a visual or acoustic warning, which alerts the driver of the presence of, and distance to any obstacles to the rear or front of the vehicle. Various display and audio options are available.

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Figure 1.3: Rear-bumper sensors (Blue) used to detect the distance from behind cars and walls.

Figure 1.4: Installation diagram and sensing range of a 3-sensor parking assistant.

1.1.4

No-Hands Parking System

Also referred to as “Autonomous Parallel Parking System”. It is very similar to the well-known aircraft's auto-pilot system. It helps drivers park their cars in tight spaces between other cars along the street (parallel parking). This system would be an option (although probably not a cheap one!) that a car buyer could purchase with a new car in the very soon future. Figure 1.5 demonstrates the operation of the No-Hands Parking System. Although not yet applied to real-life cars, the same idea is applied in Robot Homing Systems, where a pre-programmed autonomous robot moves in a prescribed path to reach its final destination with an intelligent capability to adjust its route in case some obstacle "popped-up" and encountered its way. However, my project is concerned only in one of safe driving systems, namely, the Blind-Spot Collision Avoidance System. The next section will deal in-detail with this system.

Figure 1.5: Autonomous Parallel Parking System.

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1.2 Blind-Spot Detection System 1.3.1

System Overview

It is every driver's nightmare: you change lanes suddenly, glancing in the rearview mirror without looking over your shoulder... and you merge directly into a car hidden in one of your car's blind spots. Yes, that is true. Every car has a blind spot; the area behind the car where cannot be seen from driver seat. According to recent statistics, more than 800,000 vehicles are involved in lane-change blind-spot collisions annually. Furthermore, the U.S. National Highway Traffic Safety istration says that "lane change situations" are involved in 4 to 10 percent of all car crashes. So, we are talking about a serious problem here! To solve this problem and maintain car's safety, the driver must make sure that the blind-spots of the vehicle are clear before he attempts to change lanes. My design goal is to implement a system that would detect objects present within the blind-spot, on either side of the vehicle (left/right), and appropriately warn the driver if the turn signal was on. The warning mechanism can be audio warning by a buzzer, or beeper. In addition, we wanted to display the distance measurement of the object present in the blind-spot on an LCD. The system will detect the presence of vehicles within the detection zone, as shown in Figure 1.6 by use of sensors. The detection zone is fixed. The zone extends from one to three and a half meters to the side of the vehicle to allow for traffic in the adjacent lane of traffic. The zone does not extend more than two meters back from the rear of the car. Objects detected will not be limited to cars, as vehicles such as motorcycles will be present in some situations. Sensors employed in design are so sensitive that they ensure the detection of an object the size of a pole or broom's handle!

Figure 1.6: Blind-Spot detection region.

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During initial design stages, various design alternatives were explored. The Blind Spot Detection system can be realized in two ways: Scheme Alternative 1: Always On The first scheme involves continuous monitoring of the rear blind spots on both sides of the vehicle. When a vehicle is present in either blind spot, for example, an overtaking vehicle, the driver is alerted to this potential hazard by a visible icon displayed in the door rear view mirror or a warning buzzer goes off when the distance becomes less than certain critical value to warn the driver of a possible collision. Scheme Alternative 2: Instant On The second scheme is illustrated in figure 1.7. When the driver gives the turn signal for a lane change to either left or right side, vibroactuators mounted on the wheel actuate the related sensor (left or right). The system uses microcontrollers to calculate the distance and indicate whether the car can turn left or right. The driver can be warned by means similar to those in scheme 1. I chosen this scheme over the first one because it saves power (only one sensor is activated) and electronic circuitry (the timer, transmitter and receiver can be shared between the two sensors).

Figure 1.7: Functional Block Diagram of the Blind-spot Detection System (Scheme 2).

One sensor or array of sensors During my initial research to find the best possible sensor for this application, I considered whether to get one sensor or an array of sensors. I had initially thought that we would require an array of sensors to cover all the detection region of Figure 1.6. Later on, I found one sensor that covered the entire detection region. Hence, at the end, I decided to go for one sensor since it also made controlling it much easier compared to controlling an array of sensors. Details on sensors radiation patterns, beam width and coverage area will be explained later in Section 2.3.

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1.3.2

Features and Benefits • The device will warn the driver of the presence of an object within the blind spot of the vehicle when the driver gives the turn signal for a lane change (Scheme 2). • The system will provide measurements of the object’s distance relative to the vehicle to the driver. • The system will decrease the probability of an accident occurring due to any reason related changing lanes. • The system will help the driver focus on road by taking care of his blind spot region. • The device will only notify the driver when the turn signal is activated (Scheme 2). • The device should withstand typical weather conditions. • The device will not significantly alter the outward appearance of the vehicle.

1.3.3

Technical Specifications Operating voltage: 12 V (from car's battery). Operating frequency: 40 kHz. Range: 25 to 225 cm. Resolution: 1 mm. Microcontroller clock (speed): 20 MHz. Wide operating temperature range.

1.4 Project Objectives Summary: Building a reliable, accurate, robust ultrasonic blind-spot collision warning system. Having sufficient number of sensors and ranging modules (ICs) available at the beginning of summer course. Operating and evaluating various types of ultrasonic sensors, for research's sake. Building a high-speed, fast-response system by minimizing stages delays and optimizing microcontroller's software code. Reducing the number of sensors used by replacing transmitter-receiver pair with a single transceiver. Reducing the power consumption of the overall system to minimum. Implementing the final system using PCB technology. Reducing the number of used microcontrollers to minimum. Deg a compact system with minimum size (area). Installing and testing the system board and sensors on a miniature remote-controlled car. Not exceeding the available funding budget (low-cost system). 11

Chapter 2: Ultrasonic Waves and Sensors There are several ways to measure distance without . Some products have infrared light emitters and receivers that determine an object’s distance by implementing the optical triangulation method. Other devices have laser-based systems that increase accuracy and precision. For electrically conductive metal objects, the eddy current method is an option, and capacitive sensors that are independent of the metal used in the measured objects can be used. I decided to use ultrasonic sensors. This chapter discusses ultrasonic waves and sensors with details.

2.1 Introduction to Acoustics and Ultrasonics Ultrasonics is the science of sound waves above the limits of human audibility. The frequency of a sound wave determines its tone or pitch. Low frequencies produce low or bass tones. High frequencies produce high or treble tones. Ultrasound is a sound with a pitch so high that it can not be heard by the human ear. Frequencies above 18 kHz are usually considered to be ultrasonic. The frequencies used for ultrasonic cleaning range from 20,000 cycles per second or kilohertz to over 100,000 kHz. Although ultrasound behaves in a similar manner to audible sound, it has a much shorter wavelength. This means it can be reflected off very small surfaces such as defects inside materials. This very property makes ultrasound useful for nondestructive testing of materials, and hence can be used in distance measurement systems. The Acoustic Spectrum in Figure 2.1 breaks down sound into 3 ranges of frequencies. The Ultrasonic Range is then broken down further into three subsections. I am interested in the frequency band (20-100 kHz) as the operating frequency is 40 kHz. Figure 2.1: Acoustic Spectrum.

2.1.1

Sound Propagation

In order to easily illustrate the generation and propagation of sound waves, I'll make use of the resemblance of sound waves propagation through transmission media and mechanical waves traveling through a spring as depicted in Figure 2.2. The source of the sound in the model is at the left. The compression generated by the sound source as it moves propagates down the length of the spring as each adjacent coil of the spring pushes against its neighbor. It is important to note that, although the wave travels from one end of the spring to the other, the individual coils remain in their same relative positions, being displaced first one way and then the other as the sound wave es. As a result, each coil is first part of a compression as it is pushed toward the next coil and then part of a rarefaction as it recedes from the adjacent coil. In much the same way, any point in a sound conducting medium is alternately subjected to compression and then rarefaction. At a point in the area of a compression, the pressure in the medium is positive (as indicated by the meter under the spring). At a point in the area of a rarefaction, the pressure in the medium is negative (as indicated by the meter under the spring). 12

Figure 2.2: The Nature of Sound Waves.

2.1.2 2.1.2.1

Sound Waves properties Amplitude and Frequency

Amplitude is very important property of sound waves. The illustrations below in Figure 2.3 demonstrate amplitude and frequency using the spring model introduced earlier. If “A” is the reference sound wave, “B” with less displacement of the media (less intense compression and rarefaction) as the wave front es, represents a sound wave of less amplitude or “loudness”. “C” represents a sound wave of higher frequency indicated by more wave fronts ing a given point within a given period of time.

Figure 2.3: Illustration of frequency and amplitude properties of sound waves.

2.1.2.2

Wavelength and Attenuation

The wavelength of sound changes as a function of both speed of sound and frequency, as shown by the well-known expression:

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As the sound travels, the amplitude of the sound pressure is reduced due to friction losses in the transmission medium. The attenuation (also known as absorption) of sound in air increases as the frequency increases, and at any given frequency the attenuation varies as a function of humidity. The value of humidity that produces the maximum attenuation is not the same for all frequencies. For example, above 125 kHz the maximum attenuation occurs at 100% relative humidity; however, at 40 kHz the maximum attenuation occurs at 50% relative humidity. Since an ultrasonic sensor usually is required to operate at all possible humidities, target range calculations should use the largest value of attenuation. A good estimate for the maximum attenuation in air at room temperature over all humidities for frequencies up to 50 kHz is given by:

For frequencies between 50 kHz and 300 kHz, the maximum attenuation over all humidities is:

I will take the first equation into when calculation maximum detectable distance as the nominal operating frequency is 40 kHz. Substituting 40 in the first equation gives: α(40) = 0.4 dB/ft = 0.1886 dB/m This value will be used in Section 2.4 in some important calculations. Figure 2.4 depicts the relation between sound waves absorption and frequency. Calculating the attenuation at 40 kHz using the curve gives the same result as the equation.

Figure 2.4: Sound Waves Absorption (Attenuation) due to distance traveled.

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2.1.2.3

Speed of Propagation

The speed of sound waves propagation depends on many factors including temperature and the nature of the medium itself (gas type). For an ideal gas, the speed of sound is mainly a function of temperature. At 0° C, the speed of sound is 13,044 in /s (332 m/s). At other temperatures, the speed is given by: C=

γ×R×T

Where: C = Speed of sound in meters per second γ = Ratio of specific heats. R = Gas constant. T = Absolute temperature (Kelvin), where 0˚C = 273.16 K For dry air (as in my case): γ = 1.4 (non-dimensional) R = 286.9 N.m/(kg.K) Therefore, the speed of sound at room temperature (22˚C) is: C = 1.4 × (22 + 273.16) × 286.9 = 344.31 meters per second (m/s) This calculated value will be used in distance measurement formula in later chapter.

2.2 Ultrasonic Sensors A transducer or sensor, by definition, is any device that converts one form of energy to another. An ultrasonic transducer converts electrical energy to mechanical energy, in the form of sound, and vice versa. When operating as transmitters, ultrasonic transducers transform electrical energy into acoustic energy that propagates through a medium, which is usually air or water. When operating as receivers, they transform the acoustical energy into electrical energy. The main components of ultrasonic sensors are the active element, backing, and wear plate. The active element can be piezo- or ferro-electric material. The most commonly used materials are polarized ceramics, which can be cut in a variety of manners to produce different wave modes. Recently, new materials such as piezo polymers and composites are also being employed for applications where they provide benefit to transducer and system performance. The operating frequency of an ultrasonic transducer, f, is predetermined by mechanical design. It should be selected after considering a number of factors such as transducer size, measurement resolution, background noise and attenuation, and the range to the receiving transducer.

2.2.1 Types of Ultrasonic Sensors The variations of the employed active element material give rise to two general types of ultrasonic transducers in use today: Magnetostrictive and Piezoelectric.

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2.2.1.1

Magnetostrictive Ultrasonic Sensors

Magnetostrictive transducers (also known as Ferroelectric transducers) utilize the principle of magnetostriction in which certain materials expand and contract when placed in an alternating magnetic field. Alternating electrical energy from the ultrasonic generator is first converted into an alternating magnetic field through the use of a coil of wire. The alternating magnetic field is then used to induce mechanical vibrations at the ultrasonic frequency in strips of nickel or other magnetostrictive material which are attached to the surface to be vibrated. Because magnetostrictive materials behave identically to a magnetic field of either polarity, the frequency of the electrical energy applied to the transducer is ½ of the desired output frequency. Magnetostrictive transducers were first to supply a robust source of ultrasonic vibrations for high power applications such as ultrasonic cleaning. Because of inherent mechanical constraints on the physical size of the hardware as well as electrical and magnetic complications, high power magnetostrictive transducers seldom operate at frequencies much above 20 kHz. Piezoelectric transducers, on the other hand, can easily operate well into the megahertz range. 2.2.1.2

Piezoelectric Ultrasonic Sensors

Piezoelectric ultrasonic sensors are known for what are called the piezoelectric and reverse piezoelectric effects. The piezoelectric effect causes a crystal to produce an electrical potential when it is subjected to mechanical vibration. In contrast, the reverse piezoelectric effect causes the crystal to produce vibration when it is placed in an electric field. Of piezoelectric materials, Rochelle salt and quartz have long been known as single-crystal piezoelectric substances. However, these substances have had a relatively limited application range chiefly because of the poor crystal stability of Rochelle salt and the limited degree of freedom in the characteristics of quartz. Later, barium titanate (BaTiO3), a piezoelectric ceramic, was introduced for applications in ultrasonic transducers, mainly for fish finders. More recently, a lead titanate, lead zirconate system (PbTiO3.PbZrO3) appeared, which has electromechanical transformation efficiency and stability (including temperature characteristics) far superior to existing substances. It has dramatically broadened the application range of piezoelectric ceramics. Magnetostrictive transducers are generally less efficient than their piezoelectric counterparts are. This is due primarily to the fact that the magnetostrictive transducer requires a dual energy conversion from electrical to magnetic and then from magnetic to mechanical. Some efficiency is lost in each conversion. Hysteresis effects also detract from the efficiency of the magnetostrictive transducer. I am willing to use piezoelectric transducers in my project. As a result, all subsequent discussion and analysis is concerned only with piezoelectric ceramic ultrasonic transducers.

2.2.2 Pro-Wave 40 kHz Piezoelectric Ultrasonic Sensors The most important part of this project is to choose and buy necessary sensors. Unfortunately, their availability is limited in the Jordanian market. I spent lot of time searching for suitable sensors that can be shipped with the limited quantity we need. That was a quite difficult task. Here are all the cited manufacturers: 1. Mobicon Electronic Components. 2. MuRata Corp. 16

3. 4. 5. 6. 7. 8. 9.

PANASONIC. Sanwa. Pro-Wave Electronics Corp. SensComp. Quantelec. KOBITONE. Sencera and Kwang Hwa Elect. Material.

Pro-Wave Electronics Corp. provides various sensor solutions for all applications (some shown in Figure 2.5) and they were ready to ship us the quantity we want (refer to Appendix: B for more details) by their middle east distributor, Farnell. Ultrasonic piezoelectric ceramic transducers come in different types. They are: • Open-type Transmitter. • Open-type Receiver. • Open-type Transceiver. • Enclosed-type Transceiver. The “open” type ultrasonic transducer design exposes the piezo bender bonded with a metal conical cone behind a protective screen. The “enclosed” type transducer design has the piezo bender mounted directly on the underside of the top of the case which is then machined to resonant at the desired frequency. The “PT and EP” type transducer has more internal damper for minimizing “ringing”, which usually operates as a transceiver, oscillating in a short period and then switching to receiving mode. The later type is used in my project and the maximum ringing duration plays an essential role in determining the minimum measurable distance by the sensor and the system. When compared to the enclosed transducer, the open type receiver will develop more electrical output at a given sound pressure level (high sensitivity) and exhibit less reduction in output as the operating frequency deviates from normal resonant frequency (greater bandwidth). The open type transmitter will produce more output for a specific drive level (more efficient). The enclosed type transducer is designed for very dusty or outdoor applications. The face of the transducer must be kept clean and free of damage to prevent losses. Pro-Wave and other manufacturer provide different Housing Materials as well. This include: • Natural Aluminum Housing (Silver Color). • White Painted Plastic Housing. • Black Aluminum Housing. • Black Painted Plastic Housing.

Figure 2.5: Various 40 kHz piezoelectric ultrasonic sensors manufactured by Pro-Wave Corp.

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2.3 Sensor Radiation Pattern The acoustic radiation pattern, or beam pattern, is the relative sensitivity of a transducer as a function of spatial angle. This pattern is determined by factors such as the frequency of operation and the size, shape and acoustic phase characteristics of the vibrating surface. The beam patterns of transducers are reciprocal, which means that the beam will be the same whether the transducer is used as a transmitter or as a receiver. Transducers can be designed to radiate sound in many different types of patterns, from omnidirectional to very narrow beams. For a transducer with a circular radiating surface vibrating in phase, as is most commonly used in ultrasonic sensor applications, the narrowness of the beam pattern is a function of the ratio of the diameter of the radiating surface to the wavelength of sound at the operating frequency. The larger the diameter of the transducer as compared to a wavelength of sound, the narrower the sound beam. As can be seen in Figure 2.6, the sensor produces a narrow conical beam and a number of secondary lobes of reduced amplitude separated by nulls. Even though the beam is called conical, it does not have straight sides and a flat top as the word "conical" may imply. The beam angle, alpha (α), is usually defined as the measurement of the total angle where the sound pressure level of the main beam has been reduced by 3 dB (half its peak value) on both sides of the on-axis peak. However, the transducer still has the sensitivity at greater angles, both in the main beam and in the secondary lobes.

Figure 2.6: Directivity Plot.

When describing the beam patterns of transducers, two-dimensional plots are most commonly used. They show the relative sensitivity of the transducer vs. angle in a single plane cut through the three-dimensional beam pattern. For a symmetrical conical pattern, such as that shown in Figure 2.7a, a simple single two-dimensional plot will describe the entire three-dimensional pattern. Figure 2.7b shows an asymmetric beam pattern. Two perpendicular 2-D beam plots are required to fully describe its directivity. One of which is along the narrow angle and the other is along the wide angle. When using transducers, it is important to be aware that nearby unwanted targets that are beyond the beam angle can inadvertently be detected, because the transducers are still sensitive at angles greater than the beam angle. Some transducers used in sensing applications are specially designed to minimize or eliminate the secondary lobes to avoid detecting unwanted targets. Narrow beam angle systems are also less susceptible to background ultrasonic noise, and the systems will also operate over a greater range.

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(a) (b) Figure 2.7: (a) Symmetric Beam Pattern for 400EP18A sensor. (b) Asymmetric Beam Pattern for 400EP14D sensor.

2.3.1 Transmitter Sensor Excitation 1. Continuous Excitation: A sine wave drive should be used to minimize harmonics that may excite the transducer in an overtone mode (vibrate at a multiple of the resonant frequency). For most models, the maximum amplitude of the drive waveform varies between to 50 - 140 V p-p. The transmitter dissipation must be limited to an effective or average level of 200 mW by reducing the duty cycle when the transmitter is dissipating more than 200 mW. This type of excitation can be used in TX-RX pair system. 2. Pulse Excitation: The ultrasonic transmitters may also be driven with a pulse waveform. Application of a DC Pulse of 10 – 20 volts will cause the transducer to “ring” at the selected resonant frequency. The ultrasonic output will be a damped ringing waveform as illustrated in Figure 2.8. This type of excitation can be used in single-sensor (transceiver) system.

(a)

(b)

Figure 2.8: (a) Pulse Wave Excitation of Sensor (b) A waveform: Periodic generates a short pulse that drives the transmitter into conduction. B waveform: A 40 kHz short burst emitted by transducer.

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2.4 How Far The Sensor Could Reach? One of the most frequently asked questions is “How far the sensor could reach?”. This question can be answered by a simple calculation that is based on the published specifications in the Ultrasonic Ceramic Transducer Data Sheets. The basic procedure is to first determine the minimum sound pressure level (S.P.L.) developed at the front end of the receiver for a specific transmitter driving voltage and distance between the transmitter and receiver (transceiver has double distance between reflect target). This SPL must then be converted “Pa” (Pascal) or “μbar” (microbar) units. The sensitivity of the receiver must then be converted from a dB reference to an absolute mV/Pa or μbar level present to obtain the final output. Assume a 400PT160 transmitter is driven at a level of 8.49 Vrms (12 Vp-p periodic pulses) and a 400PT160 receiver is located 4.5 meters from the transmitter and loaded with a 100KΩ resistor (loaded resistor value varies receiver sensitivity, see Figure 2.9). 4.5 meter separation between TX-RX is equal to 2.25 meters from the target/object in echo ranging. Figure 2.9: 400PT160 Sensor's Sensitivity Variation vs. Loaded Resistor.

Under the above conditions, I am going to perform the worst-case analysis to find the level of output voltage from the receiver for maximum detectable distance in my design specification. Worstcase analysis includes the minimum values of S.P.L. and sensitivity for transmitter and receiver, respectively. Data sheet of 400PT160 (refer to Appendix: C) states the following: 1. Transmitting Sound Pressure Level at 40.0kKHz is 117dB min (0dB corresponding to 0.0002μbar per 10Vrms at 30cm). 2. Receiving Sensitivity at 40.0kHz is –65dB min (0dB = 1 volt/μbar). Determining S.P.L. at the front end of Receiver S.P.L. Gain for 8.49Vrms (12Vp-p) driving voltage = 20 × log (8.49V / 10V) = –1.422 dB S.P.L. Reduction at 4.5 meters (maximum distance) = 20 × log (30 cm / 450 cm) = –23.522 dB Wave absorption (refer to Figure 2.4) = 0.1886 dB/m × 4.5m = 0.8487 dB The S.P.L. at 4.5 meters becomes = 117 – 1.422 – 23.522 – 0.8487 = 91.207 dB Converting S.P.L. to μbar: 91.207 dB = 20 × log (X / 0.0002 μbar) X = 7.268 μbar Determining Receiver Sensitivity in Volts/μbar Converting Sensitivity to Volt/μbar: -65 dB = 20 × log (X / 1 Volt/μbar) X = 0.56 mV/μbar Voltage generated under 7.268 μbar = 0.56 × 7.268 = 4.07 mV This calculated voltage developed under the assumed conditions is output voltage from the receiver sensor for maximum measurable distance. Of course, it needs to be amplified before processing. The actual voltage output will be varied depending on the environmental conditions and absorption or reflection characteristics of target materials. 20

The previous two sections (2.3 and 2.4) revealed the comparative characteristics of piezo-electric ultrasonic transducers. They are: 1. Transmitter Sound Pressure Level: The higher, the better. (e.g. 118 dB S.P.L. is better than 100 dB) 2. Receiving Sensitivity: The higher, the better. (e.g. -78 dB sensitivity is better than -85 dB) 3. Total Beam Angle: Application dependent. The narrower the beam, the more directional the transducer. A compromise (tradeoff) should be made when desiring high S.P.L, sensitivity and wide coverage (wide beam). The designer, then, have to judge whether this receiving voltage level is large enough for electronic processing.

2.5 Sensor Equivalent Circuit The equivalent circuit of piezoelectric ceramic ultrasonic transducer is similar as the well-known crystal, which is composed of a series branch of Ls, Cs and Rs and a parallel branch of Cd as shown in Figure 2.10, where: Cd: Clamping Capacity, measured at the frequency far away from resonant frequency, which approximates to static capacity. Cs: Equivalent Inductor = 1/(4π2 fs2 Cs) Ls: Equivalent Capacity = Cd × [(fp2/fs2) – 1] Rs: Real part of the impedance at resonant frequency The values can be simply obtained from calculation of the impedance data. Figure 2.10: Equivalent circuit of a crystal.

400PT160 Open-Type Transceiver Equivalent Circuit: A transducer of model 400PT160 has impedance characters shown as below.

Figure 2.11: 400SPT160 Sensor's Impedance/Phase Angle vs. Frequency.

fs = 39.0 kHz fp = 40.6 kHz Zfs = 900 Ω 21

θfs = -46.5° Zfp = 1200 Ω Cd = 2400 pF (From Data Sheet) Impedance (Z∟θ) at resonant frequency of 39.0 kHz is (900∟-46.5°). Cs = 2400 × [(40.62/39.02) – 1] = 188.17 pF Ls = 1/[4 × 3.142 × 390002 × (188.17 × 10-12)] = 88.59 mH Rs = 900 × cos (-46.5°) = 619.5 Ω These values are used in the simulation of transmitter circuit (refer to Section 5.2 for results) 400ST120 Open-Type Transmitter Equivalent Circuit: A transducer of model 400ST/R120 has impedance characters shown as below. The equivalent circuit parameters of 400ST120 (Transmitter) are calculated below.

Figure 2.12: 400ST/R120 Sensor's Impedance/Phase Angle vs. Frequency.

fs = 40.25 kHz fp = 41.50 kHz Zfs = 510 Ω θfs = -33.0° Zfp = 1330 Ω Cd = 2400 pF (From Data Sheet) Impedance (Z∟θ) at resonant frequency of 40.25 kHz is (510∟-33.0°). Cs = 2400 × [(41.502/40.252) – 1] = 151.38 pF Ls = 1/[4 × 3.142 × 402502 × (151.38 × 10-12)] = 103.39 mH Rs = 510 × cos (-33.0°) = 427.7 Ω From Figures 2.11 and 2.12, one can infer that ultrasonic transmitter impedance characteristics vary with operating frequency and temperature in complex manner that is different for each construction. In general, for frequencies approximately 0.1 octave on either side of the resonant frequency, the transmitter looks like a capacitor. The current through the transmitter will lead the voltage developed across the transmitter by 90 degrees. As the resonant frequency is approached, the voltage drop across the transmitter will decrease to a minimum at the resonant frequency (minimum series impedance) and the current will increase proportionally. The phase lead to this current relative to the voltage will decrease to zero near the resonant frequency and the transmitter will then appear to be a pure resistance. As the frequency is increased above the resonant point, the current may now 22

lag the voltage by an increasing amount (maximum of 90 degrees) as the voltage across the transmitter climbs to a peak, which is defined as the anti-resonant frequency. During this transition, the transmitter appears to have an inductive characteristic.

2.6 Environmental Factors and Sensors Since the sensors will be mounted outside the vehicle, they have to be such that they can withstand the changes in the surrounding environment. Many environmental factors affect the performance of an ultrasonic sensor such as temperature, humidity, atmospheric pressure, acoustic interference, air turbulence and convection currents. Each of these factors is discussed briefly. Temperature Temperature is an important factor since it can negatively affect the performance of an ultrasonic sensor. For example, the speed of the sound through air changes 0.18% for every Celsius degree. So at a target distance of 1 meter, a 25°C change in air temperature throws off the reading by 4.5 cm. However, most modern ultrasonic sensors have a built-in temperature compensator to solve this problem, and I can use one of these sensors. Figure 2.13 Illustrates an ultrasonic transmitter and receiver performance for wide temperature range.

Figure 2.13: 400ST/R120 Temperature characteristics: (Left) Sensitivity Variation vs. Temperature (Right) SPL Variation vs. Temperature.

Air Turbulence and Convection Currents A particular temperature problem is posed by convection currents that contain many bands of varying temperature. If these bands between the sensor and the target, they will abruptly change the speed of sound while present. No type of temperature compensation (either temperature measurement or reference target) will provide complete high-resolution correction at all times under these circumstances. In some applications it may be desirable to install shielding around the sound beam to reduce or eliminate variations due to convection currents. Averaging the return times from a number of echoes will also help reduce the random effect of convection currents. s addressing applications requiring high accuracy and resolution should evaluate these suggestions carefully. Temperature variations and wind produce air turbulence that has various effects on the total performance of any ultrasonic sensing system, causing bending and distortion of the sound waves. The narrower the angle of the sound beam and the greater the distance to the target, the greater the turbulence. Additional signal processing may be able to filter data under high turbulence conditions to improve ranging information.

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Atmospheric Pressure Normal changes in atmospheric pressure will have little effect on measurement accuracy. Reliable operation will deteriorates however, in areas of unusually low air pressure, approaching a vacuum. Humidity Humidity does not significantly affect the operation of an ultrasonic measuring system. Changes in humidity do have a slight effect, however, on the absorption of sound. If the humidity produces condensation, sensors designed to operate when wet must be used (enclosed-type). Since the used ultrasonic sensor is required to operate almost at all possible humidity conditions, target range calculations should use the largest value of attenuation.

Acoustic Interference Special consideration must be given to environments that contain background noise in the ultrasonic frequency spectrum. For example, air forced through a nozzle, such as air jets used for cleaning machines, generates a whistling sound with harmonics in the ultrasonic range. When in close proximity to a sensor, whether directed at the sensor or not, ultrasonic noise at or around the sensor's frequency may affect system operation. Typically, the level of background noise is lower at higher frequencies, and narrower beam angles work best in areas with a high ultrasonic background noise level. Often a baffle around the noise source will eliminate the problem. Because each application differs, testing for interference is suggested.

2.7 Applications of Ultrasonic Sensors Ultrasonic sensors are not ideal and do have drawbacks. The emitted pulse has a nonideal cone shape and it is not possible to discern between small objects, such as a broomstick, and large objects such as a chair or wall for this reason as both will return an echo. Also, The broad ultrasonic beam leads to inaccurate echoes. These drawbacks can be overcome by using multiple or rotating sensors. Other disadvantages are there because ultrasonic sensors produce inaccurate measurements due to acoustic drift in the open air. Moreover, The operating range becomes restricted when it is foggy. The range is approx. 1.5 times the human vision. Nonetheless, Ultrasonic Sensors found their way into industry and are used in a wide variety of applications, such as: • Car parking and reversing. • Blind-spot detection. • Pre-crash detection. • Occupant position and motion sensing. • Cruise control and collision avoidance. • Remote control equipments. • Range Finders. • Automatic doors. • Water (liquid) level measurements. • Intrusion alarms. • Tape measurements. … And much more! 24

2.7.1 Special Applications Ultrasonic Cleansing All hermetically sealed and wash-proof components can be cleaned using standard aqueous and solvent based cleaning methods. Units with tuning holes, open covers and other openings should not be soaked or cleaned in an environment where the cleaning solution can penetrate the openings. Exceptions are units that are designed for wash-through and are clearly marked or specified as such. Ultrasonic cleaners use low frequencies (< 20kHz) and typically do not cause damage. Robotics Ultrasonic Sensors are the eyes by which Robots can see and find their paths. Ultrasonic Eyes or Ultrasonic Vision is applied widely to various autonomous robots and in Robot Homing schemes. Crane collision avoidance In crane applications, the distance between traveling cranes running on the same tracks is estimated by crane-operating staff. Accidents can often occur, particularly where cranes have to be moved in restricted areas. At present, ultrasonic and microwave sensors are used.

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Chapter 3: Microcontrollers 3.1 Introduction The microcontroller is the intelligent part of the system and its most important component that integrates the transmitter and receiver together. The microcontroller is a very common component in modern electronics control systems. It consists of a processor, memory, input/output ports, timers, PWM and analog to digital converter. This configuration facilitates the widespread of using microcontrollers in many applications such as: Engine management systems in automobiles. Keyboard of a PC. Electronic measurement instruments (such as digital multi-meters, frequency synthesizers, and oscilloscopes). Printers. Mobile phones. Televisions, radios, CD players, tape recording equipment. Hearing aids. Security alarm systems, fire alarm systems, and building services systems. … And much more! As a matter of fact, we are living in the Microcontrollers era!

3.1.1 What is a Microcontroller? Basically, a microcontroller is a device, which integrates a number of the components of a microprocessor system onto a single microchip (System On-Chip, or SoC). So a microcontroller combines onto the same microchip: •

The U core

•

Memory (both ROM and RAM)

•

Some parallel digital I/O

Most microcontrollers will also combine other devices such as: •

A timer module to allow the microcontroller to perform tasks for certain time periods.

•

A serial I/O port to allow data to flow between the microcontroller and other devices such as a PC or another microcontroller.

•

An Analog to Digital Converter (ADC) to allow the microcontroller to accept anaput data for processing.

•

PWM, or formally pulse width modulation, creates a square wave with duty cycle and frequency depending on demand.

Figure 3.1 illustrates a typical microcontroller device and the different sub units integrated onto the microcontroller microchip. Where the heart of the microcontroller is the U core.

26

Figure 3.1: A single chip microcontroller.

U Core in microcontroller In the past this has traditionally been based on an 8-bit microprocessor unit. For example, Motorola uses a basic 6800 microprocessor core in their 6805/6808 microcontroller devices. In recent years, microcontrollers have been developed around specifically designed U cores. For example, the 10-Bit Microchip PIC range of microcontrollers. Memory in a microcontroller The amount of memory contained within a microcontroller varies between different microcontrollers. Some may not even have any integrated memory. However, most modern microcontrollers will have integrated memory. The memory will be divided up into ROM and RAM, with typically more ROM than RAM. Typically, the amount of ROM type memory will vary between around 512 bytes and 4096 bytes, although nowadays we can see microcontrollers with more ROM memory. ROM type memory is used to store the program code. ROM memory can be classified into three types: •

ROM: memory is manufactured containing program that cannot be erased or programmed so program code must be stable that’s why ROM is least expensive.

•

EPROM (Erasable Programmable Read Only Memory): here we have Ceramic package has quartz window. The microcontroller can be erased using an ultraviolet eraser and reprogrammed many times typical erase times range between 5 and 30 minutes. EPROM is the most expensive version of program memory due the high cost of the windowed ceramic package.

•

EEPROM (FLASH): Electrically Erasable Programmable Read Only Memory provides the ultimate flexibility because it can be electrically erased by a programmer in just a few seconds and reprogrammed. Devices such as the PIC16F77 and PIC16F877 use FLASH program memory, and are denoted with an “F” in the part number.

The amount of RAM memory is usually somewhat smaller, typically ranging between 25 bytes to 4 Kbytes. RAM is used for data storage and stack management tasks. It is also used for stacks (as in the microchip PIC range of microcontrollers). 27

3.1.2 MicroChip PIC Microcontrollers There is a large variety of microcontrollers on the market. Selection the most suitable microcontroller was crucial and time-consuming. The most popular manufacturers are: 1. Micochip's PIC. 2. Atmel's AVR. 3. Intel's 80xx. 4. Motorola's MCxxx. 5. Cypress PSoC. Most of them more than one programming language, such as Assembly Language, Pascal, C Language, and Basic Language. I went for Microchip's PIC microcontrollers. Microchip provides solutions for the entire performance range of 8-bit and 16-bit microcontrollers, with a powerful architecture, flexible memory technologies, comprehensive easyto-use development tools, complete technical documentation and post de through a global sales and distribution network. Benefits realized by selecting Microchip’s microcontroller solutions are: ● Easy migration across product families. ● Low-risk product development and faster time to market. ● Lower total system cost. ● Excellent product and programming services. ● Certified quality. ● Microchip is #1 in worldwide 8-bit microcontroller shipment serving 50000+ customers. Figure 3.2 shows Microchip's PIC MCU and dsPIC families. In the early 1980s, the term PIC stood for Peripheral Interface Controller. Microchip's microcontroller solutions come in different IC packaging and pin numbers such as 8-, 14-, 18-, 28-, 40-, 64-, 68-, or 84-Pin IC.

Figure 3.2

Generally speaking, developing a PIC-based project takes only six easy steps: 1. Type in the program. 2. Assemble the program into a binary file. 3. Simulate the program and debug it. 4. Load the binary program into the PIC’s memory. 5. Wire up the circuit. 6. Switch on and test. 28

3.2 The PIC16F877A Microcontroller From all Microchip's PICmicro products, I decided to use PIC16F877A in my project. Many reasons stand behind that choice, most importantly the availability of its programmer device in the lab. Others factors will be revealed in the following paragraphs.

3.2.1 PIC16F87X → PIC16F87XA Migration This is the title of an application note released by Microchip. This document is intended to describe the functional differences and the electrical specification differences present when migrating from one device to the next. Simply put, PIC16F877A is a newer version of PIC16F877, which is obsolete now. PIC16F877A is designed to be pin-to-pin, and functionally compatible with the PIC16F877 product family. As a result, all information in PIC16F877 applies to PIC16F877A. Many improvements and updates were added by Microchip in the migration from PIC16F877 to PIC16F877A. To me, the most important are the new comparator and comparator voltage reference modules in PIC16F877A.

3.2.2 PIC16F877A Hardware and Features The hardware specification of the PIC16F877A is: • • • • • • •

The program memory is 8K Words RAM memory is 368 bytes. EEPROM is 256 bytes. Three kinds of timers. Analog Digital converter. Hardware PWM. Flash memory is used for PIC16F877A. So, the PIC programmer can easily rewrite the program.

The PIC16F877A microcontroller core features are: • • • • • • • • • • • • • • • • • •

High performance Reduced Instruction Simplified Computer (RISC) U. Only 35 single word instructions to learn. Operating speed: 20 MHz clock input. Up to “8 K X 14” words of FLASH Program memory. Up to “368 X 8” bytes of Data Memory (RAM). Up to “256 X 8” bytes of EEPROM Data Memory. Interrupt capability (up to 14 sources). Eight level hardware stack. Direct, indirect and relative addressing modes. Power-on Reset (POR). Power-up Timer (PWRT) and Oscillator Start-up Timer (OST). Watchdog Timer (WDT) with its own on-chip. RC oscillator for reliable operation. Programmable code protection. Power saving SLEEP mode. Selectable oscillator options. Low power, high speed CMOS FLASH/EEPROM technology. In-Circuit Serial Programming (ICSP) via two pins. 29

• • • • • • •

Single 5V In-Circuit Serial Programming capability. In-Circuit Debugging (ICD) via two pins. Processor read/write access to program memory. Wide operating voltage range: 2.0V to 5.5V. High Sink/Source Current: 25mA. Commercial, Industrial and Extended temperature ranges. Low-power consumption: 1- < 0.6 mA typical @ 3V, 4 MHz 2- 20 μA typical @ 3V, 32 kHz 3- < 1μA typical standby current.

Figure 3.3 illustrates PIC16F877A's block diagram.

Figure 3.3: PIC16F877A block diagram.

3.2.3 PIC16F877A Pin-out Description Figure 3.4 illustrates PIC16F877A's pin configuration. While Table 3.1 shows PIC16F877A's pinout configuration (description). every pin is based depends on: its name, its order on the chip, its type (P-power, I-input, and O-output), Buffer type (ST-Schmitt trigger, TTL, CMOS), and brief description. Every pin may be multiplexed with more than one input or output. Its state can be controlled by defining the special related to.

30

Figure 3.4: PIC16F877A pin configuration. Pin Name

DIP Pin#

I/O/P Type

Buffer Type

Description

OSC1/CLKIN OSC2/CLKOUT

13 14

I O

ST/CMOS(4)

MCLR/VPP

1

I/P

ST

RA0/AN0 RA1/AN1 RA2/AN2/VREF-

2 3 4

I/O I/O I/O

TTL TTL TTL

RA3/AN3/VREF+

5

I/O

TTL

RA4/T0CKI

6

I/O

ST

RA5/SS/AN4

7

I/O

TTL

RB0/INT RB1 RB2 RB3/PGM RB4 RB5 RB6/PGC

33 34 35 36 37 38 39

I/O I/O I/O I/O I/O I/O I/O

TTL/ST(1) TTL TTL TTL TTL TTL TTL/ST(2)

Oscillator crystal input/external clock source input. Oscillator crystal output. Connects to crystal or resonator in crystal oscillator mode. In RC mode, OSC2 pin outputs CLKOUT which has 1/4 the frequency of OSC1, and denotes the instruction cycle rate. Master Clear (Reset) input or programming voltage input. This pin is an active low RESET to the device. PORTA is a bi-directional I/O port. RA0 can also be anaput0. RA1 can also be anaput1. RA2 can also be anaput2 or negative analog reference voltage. RA3 can also be anaput3 or positive analog reference voltage. RA4 can also be the clock input to the Timer0 timer/counter. Output is open drain type. RA5 can also be anaput4 or the slave select for the synchronous serial port. PORTB is a bi-directional I/O port. PORTB can be software programmed for internal weak pull-up on all inputs. RB0 can also be the external interrupt pin.

RB7/PGD

40

I/O

TTL/ST(2)

RC0/T1OSO/T1CKI

15

I/O

ST

RC1/T1OSI/C2

16

I/O

ST

RC2/C1

17

I/O

ST

RC3/SCK/SCL

18

I/O

ST

RC4/SDI/SDA

23

I/O

ST

RC5/SDO

24

I/O

ST

RC6/TX/CK

25

I/O

ST

RC7/RX/DT

26

I/O

ST

—

RB3 can also be the low voltage programming input. Interrupt/on/change pin. Interrupt/on/change pin. Interrupt-on-change pin or In-Circuit Debugger pin. Serial programming clock. Interrupt-on-change pin or In-Circuit Debugger pin. Serial programming data. RC0 can also be the Timer1 oscillator output or a Timer1 clock input. RC1 can also be the Timer1 oscillator input or Capture2 input/Compare2 output/PWM2 output. RC2 can also be the Capture1 input/Compare1 output/PWM1 output. RC3 can also be the synchronous serial clock input/output for both SPI and I2C modes. RC4 can also be the SPI Data In (SPI mode) or data I/O (I2C mode). RC5 can also be the SPI Data Out (SPI mode). RC6 can also be the USART Asynchronous Transmit or Synchronous Clock. RC7 can also be the USART Asynchronous Receive or Synchronous Data.

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Pin Name

Dip Pin#

I/O/P Type

Buffer Type

RD0/PSP0 RD1/PSP1 RD2/PSP2 RD3/PSP3 RD4/PSP4 RD5/PSP5 RD6/PSP6 RD7/PSP7

19 20 21 22 27 28 29 30

I/O I/O I/O I/O I/O I/O I/O I/O

ST/TTL(3) ST/TTL(3) ST/TTL(3) ST/TTL(3) ST/TTL(3) ST/TTL(3) ST/TTL(3) ST/TTL(3)

RE0/RD/AN5

8

I/O

ST/TTL(3)

RE1/WR/AN6

9

I/O

ST/TTL(3)

RE2/CS/AN7

10

I/O

ST/TTL(3)

VSS VDD NC

12,31 11,32 —

P P

— — —

Description

PORTD is a bi-directional I/O port or parallel slave port when interfacing to a microprocessor bus.

PORTE is a bi-directional I/O port. RE0 can also be read control for the parallel slave port, or anaput5. RE1 can also be write control for the parallel slave port, or anaput6. RE2 can also be select control for the parallel slave port, or anaput7. Ground reference for logic and I/O pins. Positive supply for logic and I/O pins. These pins are not internally connected. These pins should be left unconnected.

Table 3.1: PIC16F877A Pinout Configuration. Legend: I = input — = Not used

O = output TTL = TTL input

I/O = input/output ST = Schmitt Trigger input

P = power

* Notes:

1- This buffer is a Schmitt Trigger input when configured as an external interrupt. 2- This buffer is a Schmitt Trigger input when used in Serial Programming mode. 3- This buffer is a Schmitt Trigger input when configured as general purpose I/O and a TTL input when used in the Parallel Slave Port mode (for interfacing to a microprocessor bus). 4- This buffer is a Schmitt Trigger input when configured in RC oscillator mode and a CMOS input otherwise.

3.3 PIC16F877A Subsystems in Use PIC16F877A contains several independent subsystems and modules for various applications. For this project, I only used some of these subsystems. The employed modules are described in what follows.

3.3.1 I/O Ports The digital/analog I/O ports are the means by which the PIC microcontroller interfaces to the environment. Usually, I/O tends to be grouped into byte wide ports (8 digital bits) that can be configured as either input bits or output bits by defining the special related to the port. The PIC16F877A microcontroller ports are: 1. 2. 3. 4. 5.

Port A: has 6 bits/pins. Port B: has 8 bits/pins. Port C: has 8 bits/pins. Port D: has 8 bits/pins. Port E: has 3 bits/pins.

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3.3.2 Timer1 PIC16F877A has three timers Timer0, Timer1 and Timer2. Each one of these timers has its own properties and specifications. All three timers can be used in the same time in one application or any one can be used depending on the application requirement. After a thorough study of each timer, I decided to use Time1 in my design. The Timer1 module is a 16-bit timer/counter having the following features: • Two 8-bit s (TMR1H and TMR1L). • Readable and writable • 8-bit software programmable prescaler • Internal or external clock select • Interrupt on overflow from FFFFh to 0000h • Edge select for external clock • (TMR1H: TMR1L) increments from 0000h to FFFFh and rolls over to 0000h Timer1 can operate in one of two modes: as a timer, or as a counter. The operating mode is determined by the clock select bit, TMR1CS (T1CON<1>). In Timer mode, Timer1 increments every instruction cycle. In Counter mode, it increments on every rising edge of the external clock input. Timer1 can be enabled/disabled by setting/clearing control bit TMR1ON (T1CON<0>). 3.1 shows the Timer1 control . Since Timer1 is a 16-bit timer, when the timer overflows, it reaches a count of 65535 (216–1). Different prescaler ratios can also be attached to Timer1 allowing it to increment on every 1, 2, 4, or 8 instruction cycles. If 1:1 prescaler was assigned to it, this means that the Timer1 will increment on every instruction cycle (FOSC/4). If 20 MHz crystal was used as clock: FOSC/4 = 5 MHz Increment = (5 MHz)-1 = 200 ns This means that each count of Timer1 using 1:1 prescalar ratio and 20 MHz clock equals to 200 ns. In other words, Timer1 can count up to (200 ns × 65535) 13.107 ms. Table 3.2 includes Timer1 maximum timing and the equivalent measured distance for each prescalar ratio (using 20 MHz clock). Thus, 1:1 prescalar ratio is suitable to my design.

Prescaler Ratio 1:1 1:2 1:4 1:8

Timer1 Maximum Timing (ms) 13.107 26.214 52.428 104.85

Equivalent Distance (m) 4.5088 9.0176 18.035 36.070

Table 3.2: Timer1 full time and equivalent distance for different prescaler ratios.

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3.1: Timer1 control .

3.3.3 Comparator Module The comparator module contains two analog comparators. The inputs to the comparators are multiplexed with I/O port pins RA0 through RA3, while the outputs are multiplexed to pins RA3 and RA4. The on-chip Voltage Reference (described in the next section) can also be an input to the comparators. The CMCON ( 3.2) controls the comparator input and output multiplexors. A block diagram of the various comparator configurations is shown in Appendix C. A single comparator is shown in Figure 3.5, along with the relationship between the anaput levels and the digital output. When the anaput at VIN+ is less than the anaput VIN-, the output of the comparator is a digital low level. When the anaput at VIN+ is greater than the anaput VIN-, the output of the comparator is a digital high level. The shaded areas of the output of the comparator in Figure 3.5 represent the uncertainty due to input offsets and response time.

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3.2: Comparator control .

Figure 3.5: Comparator Operation.

35

3.3.4 Comparator's Voltage Reference Module The comparator voltage reference generator is a 16-tap resistor ladder network that provides a fixed voltage reference when the comparators are in mode ‘010’. A programmable controls the function of the reference generator. 3.3 lists the bit functions of the CVRCON . The comparator reference supply voltage (also referred to as CVRSRC) comes directly from VDD. It should be noted, however, that the voltage at the top of the ladder is (CVRSRC – VSAT) where VSAT is the saturation switch transistor. The output of the reference connected to the RA2/AN2/CVREF/VREF- pin. This can be used as a simple D/A function by high impedance load is used. The primary function is to provide a test reference generator function.

3.3: Voltage reference control .

For example, using the high range of the D/A, i.e.: CVREF = (¼ × CVRSRC) + (VR3:VR0/32 × CVRSRC) And assuming CVRSRC = 4.8 V (this means that VSAT = 0.2 V) gives: For VR3:VR0 = 0110 → CVREF = 2.10 V For VR3:VR0 = 0111 → CVREF = 2.25 V For VR3:VR0 = 1000 → CVREF = 2.40 V 36

Chapter 4: Ultrasonic Ranging Systems 4.1 Overview of Echo Ranging Ultrasonic ranging systems are used to determine the distance to an object by measuring the time required for an ultrasonic wave to travel to the object and return to the source. This technique is frequently referred to as “echo ranging”. Figure 4.1 illustrates the reflection principle. The transmitter is designed to have low impedance at the resonant frequency to obtain high mechanical efficiency. The receiver is constructed to maximize the impedance at the specified anti-resonant frequency to provide high electrical efficiency. The amplitude of the reflected wave is directly proportional to how much surface is available on the object for coherent reflection. Surface size, shape and orientation (normal or oblique incidence), are major factors contributing to the strength of the reflected signal. Material composition of the object is a decisive factor too. A part of the wave landing on the surface of the material is reflected, while a part of the wave penetrates the material and is eventually reflected of any surface boundaries encountered while traveling within the material (delayed reflection). Figure 4.1: Reflection of ultrasonic waves is used in distance measurements systems.

Any ranging system should contain a timer to estimate the Time-of-Flight (TOF), that is, the time required for the ultrasonic wave to hit the target/object, reflect, and reach the receiver back. TOF is equivalent to double the distance between the distance sensor and the target. This should be taken into consideration. The past few years witnessed an increased use of ultrasonic sensors in ranging and distance measurement applications. This popularity made the manufacturers to extend their products to include a complete ultrasonic system consisting of transmitter, receiver, and sensor. These ranging modules became widely used by designers, since they save the efforts to design the transmitter and receiver electronic circuits, and interface it to the sensor. The whole system is integrated into one board using PCB technology. All what the have to do is to connect the ranging module to MCU (Microprocessor Control Unit) such as a microcontroller. The 's focus is more concentrated on the programming of the microcontroller (task becomes more software oriented). Commercial modules such as Devantech Sonic RangeFinder (SRF04, SRF08, and SRF10), SensComp 6500 Ranging Module (Polaroid), and Pro-Wave Sonar Ranging Module (SRM400) are available in the market. I chose Pro-Wave's Sonar Ranging Modules (SRM400) for my project. Unfortunately, they have not arrived yet! This was a turning point in the progress of my project, since I was forced to design my own transmitter and receiver sensor-compatible circuits.

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4.2 Pro-Wave Sonar Ranging Module Pro-Wave's Sonar Ranging Module (SRM400) in Figure 4.2 is being discussed in what follows: The SRM400 is a sonar ranging module utilizing our new developed Sonar Ranging IC, PW-0268, which can work with all our PT or EP type transducers. SRM400 provides as a shortcut to develop car reversing systems or some other distance measurement systems for design engineers who are not very familiar with analog circuit and/or the operation of ultrasonic transducers. By using this module engineers can focus firstly on the other fields of digital circuit and software designs as well as some other mechanical issues. After first stage then you can either design your own analog circuit based on the module construction or consult with factory for making your own module for your special needs.

Figure 4.2: Pro-Waves' Sonar Ranging Module.

Features: Operating Voltage: 6 – 10Vdc single source Operating Frequency: broadband output ranging up to 250KHz Built-in variable RC oscillator matching transducers with different frequencies High Gain Amplifier: varies with time over 32 steps Integrated Band Filter: reduces external component count, Bi-direction I/O Pin: simplifies the control function for transmitting a pulse and receiving an echo An adjustable System Clock: enables the control of, the number of pulses transmitted, the slope of the variable gain amplifier, and the pulse repetition rate Board size: 27.9 * 18 mm (L*W)

Table 4.1: SMR400 Specifications.

SRM400 includes: 1. Module board 2. 400EP14D enclosed type transducer of asymmetrical beam patterns. 3. Detail electrical schematic

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Figure 4.3: Electronic Circuit Diagram.

Figure 4.4: Waveforms and Operations of SRM400.

Waveforms at different test points: Figure 3.7 (above) shows how the module works with transducer model 400EP14D against a hard target of size of 20cmL×20cmW×1cmT at distance of 50cm.

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4.3 Distance Calculation using the Microcontroller The electrical parameter in this system is time and is proportional to the distance separating the object from the source (car in my case). It is straightforward to trigger a timer (stopwatch) when the ultrasonic burst is transmitted and stop the timer when the transmitted burst is received. The distance traveled is related to time-of-flight and speed by the well-known relation: Distance = (Time-of-Flight / 2) × Speed Or using mathematical notation: D = 0.5 × C × (T1 - T0) Where: D = Distance to Object C = Speed of Sound in transmission medium T0 = Time at which ultrasonic wave is transmitted T1 = Time at which ultrasonic wave is received PIC16F877A's Timer1 is used as a stopwatch. It was shown in Section 3.3.2 that Timer1 can be incremented once every 200 nanoseconds. In Section 2.1.2.3, the speed of sound waves in dry air in rooms temperature was found to be 344.31 meters per second. The value stored in the two 8-bit s of Timer1 represents the time-of-flight. Thus: D(in mm) = ½ × Timer1 value × 200 (ns) × 344310 (mm/s) With some mathematical manipulations, the formula becomes: D(in mm) = Timer1 value ÷ 29.04 (mm-1) ≈

TimerV alue 29

This is the formula used in PIC16F877A to calculate distance in millimeters. Instrument's Resolution is the smallest change in the measured value to which the instrument will respond. Using the last formula to evaluate the distance produces a resolution of one millimeter for the designed ranging system.

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Chapter 5: Design Details and Circuit Explanation 5.1 The Overall System The car's blind-spot collision avoidance system was described in Section 1.2 in of design requirements, technical specifications, and general overview. This chapter deals with design details and circuit schematic, and hardware implementation of the system. The most important advantage of ultrasonic sensors will become evident. That is, their ease of interface to electronic circuitry (digital and analog).

5.1.1 System Block Diagram Unlike the simplified, functional block diagram of the blind-spot collision avoidance system presented in Figure 1.7, the block diagram in Figure 5.1 is detailed gives a closer look to the system details. As shown in the block diagram, the microcontroller is the brain of the system that controls and coordinates between the other parts. The switch is controlled by the driver's turning signal when he decides to change lane. The appropriate sensor is selected (left or right) and connected to the transmitter and receiver. The state of the switch is known to the microcontroller so the correct sensor side is displayed on the LCD.

Figure 5.1: System's Block Diagram.

Throughout my design, I adapted a modular approach towards the development and building of the system. After testing and ing the operation of each module (subsystem) alone, all modules are connected and interfaced together to give the complete system. 41

5.1.2 System Circuit Schematic Figure 5.2 shows the complete system schematic drawn using PREOTEUS ISIS Professional, version 6.9 SP3. Figure 5.3 shows a photo of the system realized on solderless breadboard.

Figure 5.2: Complete System Schematic.

From Figure 5.2, one can notice that the implemented system consists mainly from these components: 1. Transmitter (has red wires). 2. Receiver (has blue wires). 3. Microcontroller (the largest block). 4. Switches (have green wires). 5. LCD (has purple wires). Each of these components will be explained in detail in the following sections.

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Figure 5.3: System Implementation on Test Board.

5.1.3 Transmitter-Receiver Separation The use of a single transceiver sensor instead of using a dedicated transmitter and receiver sensors means that the sensor will be connected directly to the both the transmitter and receiver circuits. Some sort of physical separation between these two circuits is required. This was done by use of diodes (1N4148 small-signal diode). Figure 5.4 illustrates the separating action of the two groups pf parallel-opposite diodes. On the receiver side: These diodes just limit (clip) any transmitted signal to prevent receiver circuit damage. Any input signal to the receiver's circuit is limited to ± 0.6 V (the threshold "ON" voltage of the diode). On the transmitter side: Since the received signal voltage is very small, (about few milliVolts) the diodes' dynamic impedance is very high and they separate the transmitter circuit from the receiver. Figure 5.4: Diodes configuration to separate the receiver from the transmitter.

5.2 The Transmitter 5.2.1 Design Explanation The generation of 40 kHz signal is done by the PIC. An output pin goes high and low continuously. The output pulses have 5V amplitude. We need to transmit as large a signal as possible in order to carry enough energy (large S.P.L.) to have a portion of it reflected back to the receiver. This can be achieved via a transistor, which switches a larger power supply, jacking up the voltage to the supply voltage instead of the 5V. 43

The transmitter circuit design shown in Figure 5.2 (with red connections) or in Figure 5.3 was inspired from the well-known TTL to CMOS interface circuit which converts the voltage levels (0-5) to (0-10). The transmitter circuit operation explanation follows:

Figure 5.5: Ultrasonic transmitter schematic.

1. When RB2 (or F.G. output) is at logic low (0V): The NPN transistor Q1 is OFF (BE1 junction is reverse biased VBE < VBE ON) and is taken out of the circuit. The PNP transistor Q2 is OFF too (EB2 is also reverse biased VEB < VEB ON) and is taken out of the circuit. This means that VC2 is zero. 2. When RB2 (or F.G. output) is at logic high (5V): The NPN transistor Q1 will be in SAT mode if IB1 > IB1(EOS). Assuming that Q1 is SAT (this results in VC1= VCE1 SAT =0.3 V)

V C 2 V CC −V EC 2SAT 12 − 0.3 = = = 4.3 mA RC 1 2.7k RC 1 4.3m IC 2SAT IB2(EOS) = = = 53.75 μA β 80 V B 2 −V C 1 V CC −V EB 2ONACT −V C 1 12 − 0.6 − 0.3 = = = 4.1 mA IB2 = 2.7 k RB 1 RB 1 Since IB2 > IB2(EOS) → Q2 is SAT. IC2 SAT =

V CC −V CE 1SAT 12 − 0.3 + IB2 = + 4.1 m = 8.4 mA RC 1 2.7 k IC 1SAT 8.4m IB1(EOS) = = = 112.6 μA 75 β 5 −V BE 1ONACT V BE 1ON ACT 5 − 0.6 0.6 IB1 = – = – = 2 mA 2.7 k 2.7 k 2.7 k 2.7 k Since IB1 > IB1(EOS) → Q1 is SAT. My assumption is verified correct! So, VC2 equals 11.7 V

IC1 SAT =

The analysis above has shown that 5V pulses entering the circuit becomes approximately 12V pulses. Transistors data was taken from their data sheets (refer to Appendix: C for more data). 44

5.2.2 Simulation Results The simulation circuit of Figure 5.5 was drawn using Electronics Workbench MultiSim version 9 Power-Pro. The Agilent function generator simulates the pulses produced by the PIC pin RB2 in Figure 5.2. Agilent two-channel oscilloscope displays the input and the output of the transmitter circuit. These waveforms are shown in Figure 5.6. The waveform in purple color is input signal generated by PIC while the waveform in red color shows the output, which is the input to the transmitting ultrasonic sensor.

Figure 5.6: Transmitter operation simulation using EWB MultiSim.

5.3 The Receiver 5.3.1 Design Explanation The signal picked up from the ultrasonic transducer is extremely small and has a large fluctuation depending on the size, angle, surface shape, moving speed, distance of the reflector body for the receiver. Therefore, in order to be of any use it needs quite a significant amount of amplification. In fact, every enhancement in the amplification gives increment to the detection range (distance) and more sensitivity to smaller bodies. Unlike other receivers, a typical ultrasonic receiver does not require filtering before the amplification stage, because the receiver unit is a resonator itself. As a result, it oscillates only at a certain frequency (40 kHz), and it filters out other frequencies. In other words, the receiver sensor is naturally sensitive to signals around 40 kHz only. Using a single operational amplifier with large voltage gain will be very problematic. Any amplification of more that 50 V/V may introduce noise to the 40 kHz signal, and sophisticated filtering is required. I had to split amplification into two cascaded stages. The overall gain is the

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product of each individual gains. The gain value usually depends on the sensor type and detection range that a designer needs for his application. Figure 5.7 below shows the ultrasonic receiver schematic. It is very simple, consisting of two main components; amplifier and comparator. The receiver sensor is loaded with a 100kΩ resistor to provide a direct signal path to ground and to increase (improve) the receiver's sensitivity as the curve in Figure 2.9 in Section 2.4 indicates.

Figure 5.7: Ultrasonic receiver schematic.

R2, R3 and R7 10kΩ potentiometer form a voltage divider that supplies the op-amps with about half the 5V-regulated voltage. The reason for this is that the input signal is true AC, and the operational amplifier has a single positive power supply (5V-regulated). This commonly named "floating ground" eliminates the need for a negative supply by lifting the input signal up. C1 is used for ripple suppression. Each of the operational amplifiers along with its negative input terminal series capacitor and resistor, and the resistor is essentially a "high-" filter. The first active high- filter has cut-off frequency (2πR1C2)-1 Hz and high-frequency gain (R6/ R1) V/V. The same analogy applies to the second Op-Amp. The output of U1B is now sufficiently large enough to be useful, but is not suitable for interfacing directly to the PICmicro microcontroller. The PICmicro expects a clean high or low on its IO pin, but the output of the Op-Amp is an amplified AC signal with a midpoint DC voltage in the range 1.67V to 3.33 V depending on the potentiometer position. This is were the use of some sort of wave shaping comes in. In order to convert the AC signal into discernable highs and lows, I use PIC16F877A built-in comparator (which is simulated by the LM393 comparator IC in Figure 5.7). PIC16F877A comparator's operation was illustrated by Figure 3.5 in Section 3.3.3. Without any input signal to the two-stage amplifier, the output of U1B will be a steady DC voltage. This is fed directly to the negative input of the PIC16F877A comparator. The positive input of the comparator is connected to the PIC16F877A voltage reference module (which is simulated by the 2.2V voltage source Figure 5.7).

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Initially, the potentiometer's position will be set to produce about 2.5V DC level "floating ground" to the amplified AC signal. Therefore, when there is no reflected wave (no obstacle/object state) the voltage on the negative input is slightly higher than the positive input, and the output of the comparator is low. When an echo is received, an amplified version of the signal appears on the output of U1B and is fed to the negative input of the comparator, which now goes both higher and lower than before as the AC signal is super-imposed on the original 2.5 DC voltage. So, if the received signal on the negative input should go lower than the voltage on the positive input, the comparator output will go high, and hence, the output from the comparator will be a series of positive going pulses that can be recognized by the PICmicro processor. By adjusting 10kΩ potentiometer, the voltage difference varies between the positive and negative inputs of the comparator and makes it more or less sensitive. Higher DC voltages set by the potentiometer makes the receiver less sensitive.

5.3.2 Simulation Results The LM358 IC is a low noise high gain dual operational amplifier that needs a single positive supply to work. Referring to the data sheet, I found its gain bandwidth product (also known as "unity gain") equals to 1 MHz. This means that for 40 kHz signal input, the maximum attainable gain from the amplifier is: GainMax = (Unity Gain)/(signal frequency) = 1M/40K = 25 V/V (27.96 dB) In other words, if the ratio of the resistor to the negative input terminal resistor, i.e., (R6/ R1) or (R10/ R4) is more than 25, the actual voltage gain is reduced to 25. Once again, simulation was done using Electronics Workbench MultiSim version 9 Power-Pro. In the first case shown by Figure 5.7, the SPDT switch is closed enabling a 40 kHz signal from the function generator to enter the circuit (The receiving sensor is modeled by an AC voltage source represented by the F.G.). Worst-case analysis was performed in Section 2.4 where the minimum detectable signal has 8 mVp-p amplitude. This signal is generated by the F.G. in Figure 5.7. Tektronix four-channel oscilloscope displays the input AC signal, the output of first amplifier, the output of second amplifier, and the output of comparator as in Figure 5.8. The results were as expected theoretically, the gain of the first stage is 25V/V, while the second stage gives gain of 10V/V. Detection is confirmed by the PIC when the comparator's output becomes high. Being high for about 12.5 μs is enough to be recognized by the PIC. Notice the 4.7k pull-up resistor at the output of LM393 in Figure 5.7. This is because its output is open collector requiring a pull-up resistor. The second case when there's no received signal is shown in Figure 5.9. The simulation results for the four channels are displayed simultaneously on the scope screen in Figure 5.10 and they are expected.

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(a)

(b)

(c)

(d)

Figure 5.8: Receiver operation simulation using EWB MultiSim (Switch is closed): (a) Input signal (b) Output of first amplifier (c) Output of second amplifier (d) Output of comparator

Receiver's practical experimentation and measurements in the lab gave the following results: G1 G2 Gtot

= VO1/VIN1 = 370m/19.75m = 18.73 V/V (25.45 dB) = VO2/VIN2 = 2.935/370m = 7.93 V/V (17.98 dB) = G1×G2 = 18.73 × 7.93 = 148.53 V/V (43.44 dB)

The actual results are close to the computer simulation results.

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Figure 5.9: Ultrasonic receiver schematic.

Figure 5.10: Receiver operation simulation using EWB MultiSim (Switch is open).

5.4 The Microcontroller 5.4.1 Biasing the PIC PIC16F877A has wide operating voltage range: 2.0V to 5.5V. However, the available voltage is 12 V from car's battery. Voltage level step-down is performed by the voltage regulator IC LM7805 (U3 in Figure 5.2). The 7805 takes a 12V input and convert it to 5V output suitable for PIC. These five volts are fed to one of PIC's VDD pins (11 or 32). They are internally connected. Ground (0V) connection is required to any of PIC's VSS pins (12 or 31). The Two capacitors, C4 and C5, suppress high- and low-frequency noise on the 5-V supply line, respectively.

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5.4.2 Resetting the PIC PIC16F877A reset can be achieved via its MCLR pin (Master CLear Reset) numbered one. Being active low dictates the use of a 4.7 kΩ pull-up (current-limiting) resistor. Pressing the push-button makes the input "low" and resets the PIC.

5.4.3 PIC Clock Frequency For maximum processing speed, I used a 20 MHz crystal as a clock by connecting it across pins 13 and 14. This results in 200 ns instruction cycle.

5.4.4 PIC Ports and Pins PIC16F877A connection in Figure 5.2 uses 9 pins of the 33 available Ports pins. These are: RA1: Second amplifier output. RA4: Switch state. RB2: Transmitter drive. RD2: LCD Select line. RD3: LCD Enable line. RD4-RD7: LCD Data lines.

5.5 The Switches 5.5.1 The Manual SPDT Switch The left and right sensors are selected and switch using a Single-pole Double-through switch (SPDT). For car's application, this switch is controlled by the turning signal. Before changing lane, the driver should give a pre-turn signal, similar to the manual switching action. In Figure 5.2, the collector C3 is connected to the control input of the IC switch connected to the left sensor. While the Base B3 is connected to the control input of the IC switch connected to the right sensor. Thus, the electronic switch cannot be in the same state. One of them is ON (closed), while the other if OFF (open). When the SPDT SW is in the upper position, Q3 (inverter configuration) is in saturation mode. The signal fed into pin 13 of the 4066 IC switch is low and Switch A is closed. Switch B, on the other hand, is open and the left sensor is selected (connected to the transmitter-receiver side). When the SPDT SW is in the lower position, Q3 is off. The signal fed into pin 12 of the 4066 IC switch is low and Switch B is closed. Switch A, on the other hand, is open and the right sensor is selected (connected to the transmitter-receiver side).

5.5.2 IC Electronic Switch The CD4066 IC is a quad bilateral switch intended for the transmission or multiplexing of analog or digital signals. Each switch has three pins, input "X", output "Y", control "C". When the control signal is low, the switch is closed, otherwise it's open. This switch has many attractive features that made me consider it in my design. It has wide supply voltage range, extremely low "ON" resistance, high noise immunity, low crosstalk, and high degree linearity

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5.6 The Alphanumeric LCD Module One of the best solutions for devices that require visualizing the data is the Alphanumeric DotMatrix Liquid Crystal Display (LCD). I used the 16×2 LCD to display the distance to the driver. There are two main types of these LCDs, serial and parallel LCDs. The serial LCD requires uses one "serial" line for data transmission. However, it works on voltages of -10V and +10V but the output coming out of the PIC16F877A serial output port is the standard digital voltages of 0V and +5V. Voltage level conversion to standard TTL is required. This can be done by use of MAX232 chip. On the other hand, parallel LCD requires 4 to 8 "parallel" data pins to be connected to the PIC. The availability of parallel LCD modules in the lab and the fact that they do not need voltage level conversion made me decide on them. Figure 5.11 Shows the available LCDs. Its connection to PIC16F877A is shown in Figure 5.2.

Figure 5.11: Available LCD Modules.

The pin-out for standard parallel LCD is shown in table. Description of each pin's function is presented below. Pin No. Name 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Vss Vdd Vee RS R/W E D0 D1 D2 D3 D4 D5 D6 D7

Function Ground Positive Supply Contrast Select Read/Write Enable Data bit 0 Data bit 1 Data bit 2 Data bit 3 Data bit 4 Data bit 5 Data bit 6 Data bit 7

Table 5.1: Pin-out designation for most standard LCDs.

Pins 1 and 2 are power supply lines, Vss and Vdd. The Vdd pin should be connected to the positive supply, and Vss to the 0V supply or ground.

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Pin 3 is a control pin, Vee, which is used to alter the contrast of the display. ideally, this pin should be connected to a variable voltage supply. For simplicity, I connected it to the ground for maximum contrast. Pin 4 is the Select (RS) line, the first of the three-command control input. When this line is low, data bytes transferred to the display are treated as commands. By setting the RS line high, character data can be transferred to and from the module. Pin 5 is the Read/Write line. This line is pulled low in order to write commands or character data to the module because communication is one-way (toward LCD). Pin 6 is the Enable line this input is used to initiate the actual transfer of commands or character data between the module and the data lines. When writing to the display data is transfer only on the high to low transition of this signal. Pins 7 to 14 are the eight data bus lines (D0–D7).data can be transferred to and from the display, either as single 8-bit or as 4-bit. I decided to use 4-bit mode to save engaged pins in the PIC.

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Chapter 6: PIC Programming and Interfacing Programming PIC microcontrollers is a simple three-step process: Write the code, compile the code, and the code into a microcontroller. Following is discussion about the used programming language, compiler, programmer, and program code explanation.

6.1 Programming Language There are a number of compilers on the market that allow s to write programs (codes) in different high-level languages. High-level language frees the programmer from wrestling with and controlling the microcontroller’s s when writing code and accessing the different aspects of the microcontroller’s features and memory. There are various programming languages such as Assembly, BASIC, C, Pascal, …etc. The high-level language I used is a derivative of the BASIC language. It is called PicBasic. (The PicBasic and PicBasic Pro compilers used to write PicBasic programs are products and trademarks of microEngineering Labs, Inc.) PicBasic is similar to the PBasic language used in programming the Basic Stamp series. Programming microcontrollers directly using the PicBasic (or PicBasic Pro) compiler offer two major advantages over the Basic Stamp series of microcontrollers which use external serial EEPROM for memory storage, faster program execution speed, and reduced cost. When compared to other high-level languages, BASIC is still considered by many PC s to be the easiest programming language to use. It allows faster and much easier development of applications for PIC. I had to learn about 30 different instructions to write my program code. The compiler I used is "MicroCode Studio", which compiles PicBasiro (PBP) programming language. The program code is written and edited in MicroCode Studio window. Then it saves the work as PBP file (program.pbp). When compiled, the program.pbp file is converted to Assembly language code file (program.asm) and HEX file (program.hex). This file is the one that should be loaded to the PIC using its programmer. To accomplish this, an application called "IC-Prog" has to be used to interface the programmer to MS-Windows. It loads the hexadecimal file to the PIC's memory.

6.2 PIC Programmer Microcontroller Programmer is a circuit (hardware) by which HEX files (program code) are transferred (loaded) from a computer to the microcontroller's memory. The used programmer was already available in the lab. Its circuit is very simple and can be homemade (there are lot of ready-touse programmer schematics on he Internet). Figure 6.1 shows the circuit schematic for the programmer. Its photo is shown in Figure 6.2.

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Figure 6.1: Programmer computer interface diagram and circuit.

Figure 6.2: PIC Programmer.

6.3 PIC Program Code 6.3.1

Code Flow

The PicBasic program code shows the "big picture" of the whole system. The code flow diagram in Figure 6.3 tells the whole story of how distance is measured. The program starts by introducing the surrounding environment to the PIC microcontroller. The clock oscillator and the LCD are defined, along with the variables intended to be used later (so their memory locations are stored). Initial settings are set by storing correct values in the controlling s of Ports A and B (determine input and output pins), comparator module, and voltage

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reference module (D/A). A delay of half second allows the PIC to stabilize its clock and s. Then, the selected sensor is recognized by the PIC by checking the logic state of Port A's pin 4 (RA4).

Figure 6.3: Code Flow Diagram.

The program then calls the subroutine "Send40k" which transmits ten cycles of 40 kHz ultrasonic pulses. This is immediately followed by resetting and restating Timer1 which works as a stopwatch. Another delay (No operation) of 1.2 ms is required before staring the detection of any reflected waves to make sure that Ringing (residual vibrations) is over to avoid false detection. Before starting the detection loop, a check on the selected sensor state is made. If the selected sensor hasn't changed since its recognition at the beginning, the program starts the detection process, otherwise the new state is saved and the program returns to the transmitting phase. The detection loop aims to check the internal comparator's output repeatedly. When it goes high, detection of reflected wave is confirmed and Timer1 is stopped. The value in Timer1 s (low and high) is then divided by 29 to evaluate the distance in millimeters. The calculated value is then displayed on the LCD.

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If Timer1 overflows without any detection, an "out of range" message is displayed on the LCD. After displaying either the distance measured by the selected sensor or out of range messages on the LCD, the program returns to the beginning to send another cycles of ultrasonic waves. And so on.

6.3.2

Code Analysis

Now comes the actual PicBasic code. The comments (in blue) clarify each line of the code in detail. I wrote a self-explanatory code so there is no need to say more! '**************************************************************** '* Name : Documentation.BAS * '* Author : Rami M. Zaghal * '* Notice : Copyright (c) 2006 J.U.S.T. * '* : All Rights Reserved * '* Date : 09-Dec-06 * '* Version : 1.5 * '* Notes : * '* : * '**************************************************************** '' ------------ [ Includes / Defines ] ----------------------- '' define osc 20

'Inform PBP compiler that 20MHz is used as clock

DEFINE DEFINE DEFINE DEFINE DEFINE DEFINE DEFINE DEFINE DEFINE DEFINE

'Define 'Define 'Define 'Define 'Define 'Define 'Define 'Define 'Define 'Define

LCD_DREG PORTD LCD_DBIT 4 LCD_RSREG PORTD LCD_RSBIT 2 LCD_EREG PORTD LCD_EBIT 3 LCD_BITS 4 LCD_LINES 2 LCD_COMMANDUS 2000 LCD_DATAUS 50

PIC port used for LCD Data lines first pin of PORTD connected to LCD DB4 PIC port used for RS line of LCD PORTD pin used for RS connection PIC port used for E line of LCD PORTD pin used for E connection the 4 bit communication mode to LCD using a 2 line LCD delay between sending LCD commands delay time between data sent

'' ------------ [ Variables, Aliases and Constants ] --------- '' T1_LowerByte var word T1_UpperByte var word TOF var word Distance var word Sensor_old var byte Sensor_new var byte Loop_cnt var byte

'Variable used 'Variable used 'Variable used 'Variable used 'Variable used 'Variable used 'Variable used 'to be sent

to to to to to to to

store lower byte value of TIMER1 store upper byte value of TIMER1 store the whole word value of TIMER1 store current measured Distance value store initial value of PORTA4 (Sensor select) store new value of PORTA4 (Sensor select) determine the number of 40k ultrasonic cycles

'' ------------ [ Initialization ] --------------------------- '' TRISA = %11111011 TRISB = %00000000 CMCON = %00000101 CVRCON = %11000110

'Set PORTA to all input except RA2 'Set PORTB to all output 'Set Comparator Module to one independent comparator mode 'with its output not inverted 'Set Comparator Voltage Reference Module to generate about '2.15V at PORTA.2 (Comparator's positive terminal)

'' ------------ [ Main Code ] -------------------------------- '' INTCON = 0 LCDOUT $FE, 1 pause 500

'Make sure that all interrupts are OFF 'Clear display screen 'Wait for PICmicro to stabilize

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Main:

'Main program's loop

T1CON = %00000000 PIR1.0 = 0

'Stop TIMER1 'Make sure that TIMER1 overflow flag is clear

'If CMCON.7 = 0 then the Comparator's positive terminal voltage is less than the negative terminal (NO 'detection occurred! No echo!) 'If CMCON.7 = 1 then the Comparator's positive terminal voltage is greater than the negative terminal '(Detection occurred! Echo Received!) 'Make sure that Echo pin is initially high if CMCON.7 = 1 then PORTA.1 = 1 '"Comp. out is low" 'If PORTA.4 = 0 then the Right sensor is activated/chosen 'If PORTA.4 = 1 then the Left sensor is activated/chosen

Sensor_old = PORTA.4

'Store initial value of PORTA.4 (Initially 'selected sensor) 'Enable TIMER1 with Prescaler 1:1 'Start transmission of 40kHz ultrasonic waves 'Clear lower byte of TIMER1 and start TIMER1 'Clear upper byte of TIMER1 'Wait until Ringing finishes

T1CON = %00000001 Gosub Send40k TMR1L = 0 TMR1H = 0 pauseus 1200 Sensor_new = PORTA.4

'Store current value of PORTA.4 (Currently 'selected sensor) 'Check if selected sensor has changed and return 'to "Main" if it has

if Sensor_new != Sensor_old then Main repeat if CMCON.7 = 1 then T1CON = %00000000 goto Calculate_Dist endif until PIR1.0 = 1

'Loop until TIMER1 overflows 'If detection occurred: 'Stop TIMER1 'Then start distance calculation process

if PORTA.4 = 0 then LCDOUT $FE, 1, "Object is out of range

'Timeout if TIMER1 overflow flag is set "TIMER1 'overflowed" 'Check which sensor is currently selected from RIGHT sensor!" 'Clear display screen

and 'show "out of range" 'message

else LCDOUT $FE, 1, "Object is out of range from LEFT SENSOR!"

'Clear display screen

and 'show "out of range" 'message

endif pause 1000 Goto Main

'Wait 1 second "LCD Delay" 'Start a new program cycle

'Distance calculation process Calculate_Dist: T1_LowerByte = TMR1L 'Store lower byte value of TIMER1 in variable T1_UpperByte = TMR1H 'Store upper byte value of TIMER1 in variable TOF = T1_LowerByte + (T1_UpperByte * 256) 'Calculate total time of flight Distance = TOF/29 'Calculate distance in millimeters 'Check which sensor is currently selected if PORTA.4 = 0 then LCDout "DISTANCE from RIGHT sensor (in mm) = ", dec Distance 'Display decimal value 'of distance in 'millimeters on the 'screen

else LCDout "DISTANCE from LEFT sensor (in mm) = ", dec Distance

endif pause 1000 Goto Main

'Display decimal value 'of distance in 'millimeters on the 'screen

'Wait 1 second "LCD Delay" 'Start a new program cycle

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'' ------------ [ Subroutines ] ------------------------------ '' Send40k:

'Function that generates 10 cycles of 40kHz 'ultrasonic pulses at PORTB.2 'Count from 10 to 0 by 1 'First half of the cycle 'Create delay of 11 us (ON Time) 'Second half of the cycle 'Create delay of 10 us (OFF Time) 'Go back to and do next count

for Loop_cnt = 10 to 0 step -1 PORTB=%00000100 pauseus 11 PORTB=%00000000 pauseus 10 next Loop_cnt return

One last point worth mentioning here regards the subroutine "Send40k", you can notice that it's simply a loop that is repeated 10 times. The aim of each cycle in "Send40k" is to make PortB's pin 2 high for the first half cycle, and low for the second half. Duty cycle of 50% is very difficult to obtain using this technique. Instead, PortB.2 can be "high" for 12 μs, and "low" for 13 μs. That's a 40 kHz waveform of 48% duty cycle. From my experimentation, I found that the PAUSEUS command used in the “MicroCode Studio” compiler takes 1μs to be executed. This delay of 2 μs should be taken into . Extra delay is caused by the looping action, i.e., decrementing the loop counter, going back to the start, and checking that it did not reach zero value. This is approximately 2 μs delay. So, for the period to be 25 μs (40 kHz), The no-operation delay should be 11 μs and 10 μs for the ON and OFF times, respectively. That is: 1μs + 11μs + 1μs + 10μs + 2μs = 25μs

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Chapter 7: Conclusions 7.1 Challenges During my work on the project, I faced the following challenges: 1. Studying various microcontrollers to choose the most suitable one with no previous background. 2. Learning PIC programming from scratch. 3. Delay in arrival of ranging modules (SRM400) changed the course of the project significantly. I didn't see that coming!

7.2 Future Work This project can be a starting point for several other projects in distance measurement using ultrasonic sensors and microcontrollers area. Some modifications and improvements are suggested below: 1. The measurement process is based on a typical air temperature of 22°C. This can be limiting when the specific application involves a wide operating temperature range. It would be an improvement to implement an external integrated temperature sensor to measure the air temperature. 2. Serial LCD can be used instead of the parallel one with only one data input to the PIC. 3. LEDs with three or four levels or colors can be used to alert the driver. The LEDs flashes depending on the distance between the car and the obstacle/object in a pre-determined color convention. 4. With slight modifications, the system can be converted into a reverse parking assistant. 5. With slight modifications, the system can be converted into ultrasonic radar by simply mounting the sensor on a stepper motor that rotates to scan the required areas. 6. Improvement the PIC code could be achieved by implementing ISR (Interrupt Service Routine) using the interrupt-on-change-pin ed by PIC to switch (select) sensors. 7. The system can have the ability to increase the volume of the audible warning sound as the object distance decreases when turn signal is activated with the extra option to switch off the sound warning by the . Moreover, the distance range for sounding the audio warning may be changed or controlled by the . 8. The system can have the ability to change units of distance being displayed on LCD.

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7.3 Recommendations After completing the project, I realized that the following improvements could be made by the department of Electrical Engineering any future projects including microcontrollers: 1. Providing PIC Programmer and development Kits and boards for students working on projects involving PIC microcontrollers. Such kits have built-in LCD, ICD (In-Circuit Debugging) feature and much more. The programmer can program PIC chips with different pin numbers, which enhance the experimentation with PIC experience for the students. More information is available on MicroChip's and mikroelektronika websites. 2. Getting a licensed version of PICmicro Simulators and IDE (Integrated Development Environment) tools such as PROTEUS. Licensed fully functional versions of the well known C and BASIC programming languages compilers, such as mikroBasic, PICBASIC Pro, PICC, CCS PCWH, …etc. 3. Add an introductory course on microcontrollers in new plan for Electrical Engineering students.

7.4 Final Comments The work on this project was very challenging and entertaining. It involved precise selection of sensors and microcontroller, programming the microcontroller, deg ultrasonic transmitter and receiver circuits, simulating the designed circuits and written code, and finally, implementing the whole system and testing it. To sum up, my project involved all what it takes for a real electronics engineer or designer to build a reliable practical system. My Internet research skills have improved remarkably. I ed many internet forums & communities related to CAD simulation and microcontrollers. My reading speed even increased! Another advantage worth mentioning is the interaction with Dr. Bassam El-Asir (Project supervisor). It was my pleasure to work with him. This was the richest experience I had in my academic life. One of the most important lessons I learnt from this experience is the power of question, or let us call it "the power of courtesy". You must ask properly, precisely and in good timing about unknown or unclear things in order to get fulfilling useful answers. As they say, ask gently and you will be given. All in all, I was 95% satisfied with my graduation project. ☺

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References and Readings "Top 10 Tech Cars", IEEE Spectrum Magazine, April 2006, pp.24-33. J. David N. Cheeke, "Fundamentals and Applications of Ultrasonic Waves", CRC Press, 2002. F. Alton Everest, "The Master Handbook of Acoustics", Fourth Edition, McGraw-Hill, 2001. R. A. Serway and R. J. Beichner, "Physics for Scientists and Engineers, with Modern Physics", Fifth Edition, Saunders College Publishing, 2000. J. Borenstein, H.R. Everett and L. Feng, "Where Am I?, Sensors And Methods For Mobile Robot Positioning", The University of Michigan, April 1996. Donald Massa, "Part 2: Optimizing Sensor Selection", Sensors Magazine, March 1999. Ming C. Lin, "Efficient Collision Detection for Animation and Robotics", Department of Electrical Engineering and Computer Science, University of California, Berkeley, 1993. "PICmicro Mid-Range MCU Family Reference Manual", Microchip Technology Inc., 1997. "What’s A Microcontroller - Student Guide v2.2 ", Parallax Inc., 2004. Myke Predko, "PICmicro Microcontroller Pocket Reference", McGraw-Hill, 2001. John Iovine, "PIC Robotics - A Beginner’s Guide to Robotics Projects Using the PICmicro", McGraw-Hill, 2004. John Iovine, "PIC Microcontroller Project Book", McGraw-Hill, 2000. Fred Stevens, "Getting Started With PIC Microcontrollers", 1997. "PicBasic Pro Compiler", microEngineering Labs, Inc., 2004. Chuck Hellebuyck, "Programming PIC Microcontrollers with PicBasic", Newnes, Elsevier Science, 2003. Les Johnson, "Experimenting with the PICBasic Pro Compiler", CROWNHILL Associates Ltd, 2000. Adel Sedra and Kenneth Smith, "Microelectronic Circuits", Fifth Edition, Oxford University Press, 2004. K. "Gopal" Gopalan, "Introduction to Digital Microelectronic Circuits", Prentice-Hall. William Hayt, Jack Kemmerly and Steven Durbin, "Engineering Circuit Analysis", Sixth Edition, McGraw-Hill, 2002.

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Web Resources Pro-Wave Electronics Corp. application notes: http://www.prowave.com MuRata Corp. application notes: http://www.murata.com MicroChip Technology Inc. application notes: http://www.microchip.com MicroChip Forum: http://forum.microchip.com/ MELabs PICBASIC Forums: http://www.picbasic.co.uk/forum/ Basic Micro Forums: http://forums.basicmicro.net/Default.aspx Proton PICBASIC Development Forums: http://www.picbasic.org/forum/ mikroElektronika Forum: http://www.mikroe.com/forum/search.php?mode=results EDABoard: http://www.edaboard.com Farnell Distributor: http://www.farnell.com

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Appendix

A List of Components Used in the Project

♦ Resistors: 1. 2. 3. 4. 5. 6. 7.

100 Ω (× 1). 2.7 kΩ (× 5). 4.7 kΩ (× 3). 10 kΩ (× 4). 100 kΩ (× 2). 1 MΩ (× 1). 10 kΩ potentiometer (× 1).

♦ Capacitors: 1. 2. 3. 4. 5.

0.1 μ F radial electrolytic (× 1). 1 μ F radial electrolytic (× 1) 100 μ F radial electrolytic (× 1) 10 nF ceramic disc (× 2). 10 pF ceramic disc (× 2).

♦ Switches:

1. Manual SPDT-SW (× 1). 2. CD4066 quad bilateral switch (× 1). 3. Mini push-button (× 1).

♦ Sensors:

1. 400PT160 open-type transceiver ultrasonic sensor (× 2).

♦ Discrete Semiconductor Components: 1. 2. 3. 4.

1N4148 small-signal diode (× 4). 2N2222 NPN bipolar transistor (× 1). 2N2907 PNP bipolar transistor (× 1). 2N3904 NPN bipolar transistor (× 1).

♦ Integrated Circuits:

1. PIC16F877A Microcontroller (× 1). 2. LM358N dual operational amplifier (× 1). 3. LM7805 voltage regulator (× 1).

♦ Miscellaneous: 1. 2. 3. 4. 5.

20 MHz crystal (× 1). 16×2 standard parallel alphanumeric LCD (× 1). NEWSTAR voltage adapter [12V voltage source] (× 1). Solderless breadboard (× 3). Connection cords.

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Appendix

B Sensors and Modules Purchase Order

Manufacturer and Supplier Info: Manufacturer: Pro-Wave Electronics Corp. http://www.prowave.com Distributor: Farnell. http://www.farnell.com Agent (Dealer): Madhoun Electronics and Trade.

Order Details: Part Number

Part Description

Order Code

Unit Price

Qty

Total Cost

SRM400 PROWAVE

Sonar Ranging Module (Includes

1007370

39.76

4

159.04

Has not arrived yet!

PW0268 PROWAVE 400EP18A PROWAVE 400PT160 PROWAVE 400PT120 PROWAVE 400ST120 PROWAVE 400SR120 PROWAVE

Sonar Ranging SMT IC Ultrasonic Txr, Enc, 40kHz Ultrasonic Txr, Open, 40kHz Ultrasonic Txr, Open, 40kHz Ultrasonic Tx, Open, 40kHz Ultrasonic Rx, Open, 40kHz

1007371

5.70

2

11.40

Arrived

1007355

11.4

3

34.20

Arrived

1007353

7.15

3

21.45

Arrived

1007354

7.40

3

22.20

1007339

6.90

4

27.60

Has not arrived yet! Arrived

1007340

6.90

4

27.60

Arrived

303.49 48.56 352.05

Sub Total 16% Sales Tax Total

(JD)

(JD)

One 400EP14D)

64

Status

Appendix

C Selected Data Sheets

This appendix contains data sheets for the following components: 1. 400PT160 Ultrasonic Sensor 2. 400ST/R120 Ultrasonic Sensor 3. 400EP18A Ultrasonic Sensor 4. 400EP14D Ultrasonic Sensor 5. PIC16F877A Comparator Configuration 6. LM358N Dual Operational Amplifier 7. CD4066 Quad Bilateral Switch 8. 2N2222 NPN Bipolar Transistor 9. 2N2907 PNP Bipolar Transistor 10. 1N4148 Small-Signal Diode

65