CHAPTER 1 INTRODUCTION

Transcription

1 CHAPTER 1 INTRODUCTION 1.1 OVERVIEW There are lots of efforts being made by public transport corporations to improve public vehicle occupancy by requesting the public to use public transport over other modes of transportation. It can be noted that if the passenger knows with high confidence that the bus is going to come, he/she will definitely wait rather than opting for other modes of transportation. Efficient information can therefore help the users to choose faster and easier connections, which saves their time. Trends in wireless technology like Global System for Mobile communication (GSM) and RF Technology have resulted in easier and faster communication. Thus, this Project provides a very cost-effective solution as compared to existing technologies for tracking public vehicles. 1.2 BACKGROUND One of the possible reasons for people preferring private vehicles to public vehicles are that a passenger normally does not have exact information about the public vehicle arrival timing at their stops. By providing reliable public vehicle arrival information to the passengers at predefined stops, public vehicle occupancy can be improved. This is beneficial to both the passengers and public transport corporations. Tracking of a vehicle can be expressed as continuously monitoring of a vehicle. Tracking of buses can be useful for the automation of existing transportation systems. By the use of tracking the information about bus-arrival timing can be easily provided to passengers. 1

2 The different wireless technologies available today have resulted in the reliable and faster communication. GSM is an open, digital cellular technology used for transmitting mobile voice and data services. GSM has become the world s fastest growing mobile communication standard. GSM networks operate in a number of different carrier frequency ranges (separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G), with most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. The GSM network is structured into a number of discrete sections: (i) The Base Station Subsystem (the base stations and their controllers). (ii) The Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network. (iii) The GPRS Core Network (the optional part that allows packet based Internet connections). (iv) Operation Support System (OSS) for maintenance of the network. Radio-Frequency Transceiver is a wireless sensor technology, which is based on the detection of electromagnetic signals. There is emission of radio waves from the transmitter, which can reach up to 100 feet or more, depending on its power output and the radio frequency used. 2

3 2.1 BLOCK DIAGRAM CHAPTER 2 DESIGN AND DESCRIPTION BUS STOP RF TRANSMITTER BUS RF RECEIVER + CONTROLLER + GSM MODEM + LCD DISPLAY GSM NETWORK BUS STOP 3 BUS STOP 2 BUS STOP 1 Fig 2.1 Block Diagram 3

4 2.2 BASIC DESCRIPTION The basic block diagram of the bidirectional visitor counter with automatic light controller is shown in the above figure. Mainly this block diagram consists of the following essential blocks RF Transmitter and Receiver PIC Microcontroller GSM Modem LCD Display RF Transmitter and Receiver The RF module, as the name suggests, operates at Radio Frequency. The corresponding frequency range varies between 30 khz & 300 GHz. In this RF system, the digital data is represented as variations in the amplitude of carrier wave. This kind of modulation is known as Amplitude Shift Keying (ASK) PIC Microcontroller PIC is a family of modified Harvard Architecture made by Microchip Technology and PIC referred to as Peripheral Interface Controller. PIC devices are popular with both industrial developers and hobbyists due to their low cost, wide availability, large user base, extensive collection of application notes, availability of low cost or free development tools, serial programming, and re-programmable Flash-memory capability. 4

5 2.2.3 GSM Modem A GSM modem is a specialized type of modem, which accepts a SIM card, and operates over a subscription to a mobile operator, just like a mobile phone. When a GSM modem is connected to a computer, this allows the computer to use the GSM modem to communicate over the mobile network. While these GSM modems are most frequently used to provide mobile internet connectivity, many of them can also be used for sending and receiving SMS and MMS messages LCD Display A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments), animations and so on. 5

6 6 2.3 CIRCUIT DIAGRAM Fig 2.2 Circuit Diagram RA0/AN0 2 RA1/AN1 3 RA2/AN2/VREF-/CVREF 4 RA4/T0CKI/C1OUT 6 RA5/AN4/SS/C2OUT 7 RE0/AN5/RD 8 RE1/AN6/WR 9 RE2/AN7/CS 10 OSC1/CLKIN 13 OSC2/CLKOUT 14 RC1/T1OSI/CCP2 16 RC2/CCP1 17 RC3/SCK/SCL 18 RD0/PSP0 19 RD1/PSP1 20 RB7/PGD 40 RB6/PGC 39 RB5 38 RB4 37 RB3/PGM 36 RB2 35 RB1 34 RB0/INT 33 RD7/PSP7 30 RD6/PSP6 29 RD5/PSP5 28 RD4/PSP4 27 RD3/PSP3 22 RD2/PSP2 21 RC7/RX/DT 26 RC6/TX/CK 25 RC5/SDO 24 RC4/SDI/SDA 23 RA3/AN3/VREF+ 5 RC0/T1OSO/T1CKI 15 MCLR/Vpp/THV 1 U1 PIC16F877A D7 14 D6 13 D5 12 D4 11 D3 10 D2 9 D1 8 D0 7 E 6 RW 5 RS 4 VSS 1 VDD 2 VEE 3 LCD1 LM016L RF Receiver RF Transmitter 5V GSM Modem Rx Tx D1 D2

7 2.3.1 Circuit Diagram Explanation Transmitter in the bus is programmed to send RF signal carrying the bus details. When the bus approaches the bus stop, the (always-on) RF transmitter (which is pre-programmed) sends RF signal carrying the details of the bus number, route and its time of arrival. The always-on RF receiver at the bus stop receives the transmitted signal and it is decoded using 16F877A microcontroller. Then, using GSM modem, the decoded bus details are sent to some selected bus stops on the route. At Bus stops, GSM SIM card receives the information and the bus details are displayed at the bus stop using a LCD monitor that is interfaced to the microcontroller. 7

8 CHAPTER 3 HARDWARE DESCRIPTIONS 3.1 PIC16F877A MICROCONTROLLER PIC 16F877 is one of the most advanced microcontroller from Microchip. This controller is widely used for experimental and modern applications because of its low price, wide application range, high quality and ease of availability. It is ideal for applications such as machine control applications, measurement devices, study purpose and so on. The PIC 16F877 features all the components which modern microcontrollers normally have. The picture of a PIC16F877 chip is shown below. Fig 3.1 PIC IC Features of PIC16F877 The features of PIC16F877A are given below Special Features 100,000 erase/write cycle Enhanced Flash Program Memory Self-reprogrammable under software control Single-supply 5V In-Circuit Serial Programming 8

9 Watchdog Timer (WDT) with its own on-chip RC oscillator Programmable Code Protection Peripheral Features Two 8-bit (TMR0, TMR2) timer/counter with pre-scalar One 16-bit timer/counter Parallel Slave Port (PSP): 40/44 pin-device only High performance RISC CPU: Only 35 single-word instructions to learn DC-20MHz clock input Fig 3.2 PIC Pin Configuration 9

10 3.2 RF TRANSMITTER The TWS-434 is small, and is excellent for applications requiring shortrange RF remote controls. The transmitter module is only 1/3 the size of a standard postage stamp, and can easily be placed inside a small plastic enclosure. TWS-434: The transmitter output is up to 8mW at MHz with a range of approximately 400-foot (open area) outdoors. Indoors, the range is approximately 200 foot, and will go through most walls. The TWS-434 transmitter accepts both linear and digital inputs can operate from 1.5 to 12 Volts-DC, and makes building a miniature hand-held RF transmitter very easy. The TWS-434 is approximately the size of a standard postage stamp. Fig 3.3 RF Transmitter IC 10

11 3.2.1 PIN Descriptions Table 3.1 RF Transmitter PIN Descriptions Pin No Function Name 1 Ground (0V) Ground 2 Serial data input pin Data 3 Supply voltage; 5V Vcc 4 Antenna output pin ANT 3.3 HT640 ENCODER The 3 encoders are a series of CMOS LSIs for remote control system applications. They are capable of encoding 18 bits of information, which consists of N address bits, and 18_N data bits. Each address/data input is externally ternary programmable if bonded out. It is otherwise set floating internally. Fig 3.4 HT640 Encoder IC General Description Various packages of the 3 encoders offer flexible combinations of programmable address/data to meet various application needs. The 11

12 programmable address/ data is transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal. The capability to select a TE trigger type or a DATA trigger type further enhances the application flexibility of the 3 18 series of encoders Block diagram Fig 3.5 HT640 Encoder Block Diagram Features Operating voltage: 2.4V~12V Low power and high noise immunity CMOS technology Low standby current Three words transmission Built-in oscillator needs only 5% resistor Easy interface with an RF or infrared transmission media Minimal external components 3.4 RF RECEIVER The receiver needs between 4.5V and 5.5V to power up. The receiver will send any data it receives through Pin 2, which is labeled "Digital Data Output". It is connected to the microcontroller for decoding. 12

13 Pin 3, labeled "Linear Output/Test" is for testing the receiver, and we will not be using it at all. It takes the receiver around 30 milliseconds to start up. Fig 3.6 RF Receiver IC PIN Description Table 3.2 PIN Configurations Pin No Function Name 1 Ground (0V) Ground 2 Serial data output pin Data 3 Linear output pin; not connected NC 4 Supply voltage; 5V Vcc 5 Supply voltage; 5V Vcc 6 Ground (0V) Ground 7 Ground (0V) Ground 8 Antenna input pin ANT 13

14 3.5 HT648 DECODER The 3 decoders are a series of CMOS LSIs for remote control system applications. They are paired with the 3 series of encoders. For proper operation a pair of encoder/decoder pair with the same number of address and data format should be selected General Description The 318 series of decoders receives serial address and data from that series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. It then compares the serial input data twice continuously with its local address. If no errors or unmatched codes are encountered, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission. The 3 18 decoders are capable of decoding 18 bits of information that consists of N bits of address and 18 N bits of data. To meet various applications they are arranged to provide a number of data pins whose range is from 0 to 8 and an address pin whose range is from 8 to 18. In addition, the 318 decoders provide various combinations of address/data number in different packages. Fig 3.7 HT648 Decoder Block Diagram 14

15 3.5.2 Features Operating voltage: 2.4V~12V Low power and high noise immunity CMOS technology Low standby current Capable of decoding 18 bits of information Pairs with HOLTEK s 318 series of encoders 8~18 address pins 0~8 data pins Ternary address setting Two times of receiving check Built-in oscillator needs only a 5% resistor Valid transmission indictor Easily interface with an RF or an infrared transmission medium Minimal external components 3.6 GSM MODEM A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves. A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer. 15

16 Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate. Both GSM modems and dial-up modems support a common set of standard AT commands. You can use a GSM modem just like a dial-up modem. In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. With the extended AT commands, you can do things like: Reading, writing and deleting SMS messages. Sending SMS messages. Monitoring the signal strength. Monitoring the charging status and charge level of the battery. Reading, writing and searching phone book entries. The number of SMS messages that can be processed by a GSM modem per minute is very low only about six to ten SMS messages per minute GSM Modem Characteristics Triband GSM GPRS modem (EGSM 900/1800 / 1900 MHz) Designed for GPRS, data, fax, SMS and voice applications GPRS multi-slot class 10 GPRS mobile station class B Designed for GPRS, data, fax, SMS and voice applications Fully compliant with GSM Phase 2/2+ specifications Built-in TCP/IP Protocol Built-in RTC in the module. 16

17 3.6.2 Specifications for SMS via GSM Point-to-point MO & MT SMS cell Broadcast Text & PDU mode Power supply Use AC DC Power Adaptor with following ratings Input AC Voltage: 230V Output DC Voltage: 12V Output DC Current: 2A Polarity: Centre +ve & Outside ve PIC Interfacing with GSM PIC MICROCONTROLLER MAX232 GSM MODEM Fig 3.8 GSM Interface Block Diagram 17

18 The 16F877A has a built in serial port that makes it very easy to communicate with the PC's serial port but the 16F877A outputs are 0 and 5 volts and we need +10 and -10 volts to meet the RS232 serial port standard. The easiest way to get these values is to use the MAX232. The MAX232 acts as a buffer driver for the processor. It accepts the standard digital logic values of 0 and 5 volts and converts them to the RS232 standard of +10 and -10 volts. It also helps protect the processor from possible damage from static that may come from people handling the serial port connectors. The MAX232 requires 5 external 1uF capacitors. The internal charge pump to create +10 volts and -10 volts uses these. The MAX232 is an electronic circuit that converts signals from a serial port to signals suitable for usage in e.g. microprocessor circuits. A standard serial interfacing for PC, RS232C, requires negative logic, i.e., logic '1' is -3V to -12V and logic '0' is +3V to +12V. To convert a TTL logic, say, TxD and RxD pins of the uc chips, thus need a converter chip. The MAX232 is a four-channel driver; it amplifies/lowers RX,TX, CTX and RTS signals. The voltage discrepancy (up to V from RS232 to 3.3V TTL) is generated by capacitors (typically 10 nf. An MAX232 has a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept ±30-V inputs. The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply TIA/EIA-232-F voltage levels from a single 5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresiof 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels 18

19 Fig 3.9 MAX232 Functional Diagram For the first capacitor, the negative leg goes to ground and the positive leg goes to pin 16. For the second capacitor, the negative leg goes to 5 volts and the positive leg goes to pin 2. For the third capacitor, the negative leg goes to pin 3 and the positive leg goes to pin 1. For the fourth capacitor, the negative leg goes to pin 5 and the positive leg goes to pin 4. For the fifth capacitor, the negative leg goes to pin 6 and the positive leg goes to ground. 19

20 The MAX232 includes 2 receivers and 2 transmitters so two serial ports can be used with a single chip. We will only use one transmitter for this project. The only connection that must be made to the 2051 is one jumper from pin 3 of the 2051 to pin 11 of the MAX232. To power the MAX232 Connect pin 16 to 5 volts. Connect pin 15 to ground. The only thing left is that we need some sort of connector to connect to the serial port. The sample code below is written for Comm1 and most computers use a 9-pin DB9 male connector for Comm1 so a 9 pin female connector is included for this project. You may also want to buy a DB9 extension cable (Shown on order form as DB9 to DB9 cable) to make the connection easier. There should be 3 wires soldered to the DB9 connector pins 2, 3 and 5. Connect the wire from pin 5 of the connector to ground on the breadboard. Connect the wire from pin 2 of the connector to pin 14 of the MAX232. The serial communications are used for transferring data over long distances, because parallel communications requires too many wires. Serial data received from a modem or other devices are converted to parallel so that it can be transferred to the PC bus. The serial communications equipment can be divided into simplex, halfduplex and full duplex. A simplex serial communication sends information only in one direction (i.e. a commercial radio station). 20

21 Half-duplex means that data can be send in either direction between two systems, but only in one direction at a time. In a full-duplex transmission each system can send and receive data at the same time. There are two ways to transmit serial data: synchronously or asynchronously. In a synchronous transmission data is sent in blocks, one or more special characters called sync characters synchronize the transmitter and the receiver. The serial port of the PC is an asynchronous device, so we will describe this kind of systems. For asynchronous transmission, a bit identifies its start and 1 or 2 bits identify its end, don't need any synchronization. The data bits are sent to the receiver after the start bit. The least significant bit is transmitted first. A data character usually consists of 7 or 8 bits. Depending on the configuration of the transmission a parity bit is send after each data bit. It is used to check errors in the data characters. Finally 1 or 2 stop bits are send RS-232 pin out DB-9 pin Fig 3.10 PIN Connection and Block Diagram 21

22 PIN Signal Description: 1 PGND Protective Ground 2 TXD Transmit Data 3 RXD Receive Data 4 RTS Ready To Send 5 CTS Clear To Send 6 DSR Data Set Ready 7 SG Signal Ground 8 CD Carrier Detect 20 DTR Data Terminal Ready 22 RI Ring Indicators RS-232 Interface RS-232 (EIA Std.) Applicable to the 25 pin interconnection of Data Terminal Equipment (DTE) and Data Communication Equipments (DCE) using Serial Binary Data. Fig 3.11 RS232 Interface Connection 22

23 Table 3.3 RS232 Pin Explanations 3.7 LCD DISPLAY In recent years the LCD is finding widespread use replacing LEDs (sevensegment LEDs or other multi segment LEDs). This is due to the following reasons The declining prices of LCDs. The ability to display numbers, characters, and graphics. This is in contrast to LEDs, which are limited to numbers and a few characters. 23

24 Incorporation of a refreshing controller into the LCD, thereby relieving the CPU of the task of refreshing the LCD. In contrast, the LED must be refreshed by the CPU (or in some other way) to keep displaying the data. Ease of programming for characters and graphics LCD pin descriptions The LCD discussed in this section has 16 pins. The function of each pin Fig 3.12 LCD Pin Description V CC, V SS, and V EE While V CC and V SS provide +5V and ground, respectively, V EE is used for controlling LCD contrast. RS, Register Select There are two very important registers inside the LCD. The RS pin is used for their selection as follows. If RS=0, the instruction command code register is selected, allowing the user to send a command such as clear display, cursor at home, etc. If RS=1 the data register is selected, allowing the user to send data to be displayed on the LCD. 24

25 R/W, Read/Write R/W input allows the user to write information to the LCD or read information from it. R/W=1 when reading; R/W=0 when writing. E, Enable The LCD to latch information presented to its data pins uses the enable pin. When data is supplied to data pins, a high-to-low pulse must be applied to this pin in order for the LCD to latch in the data present at the data pins. This pulse must be a minimum of 450ns wide. D0-D7 The 8-bit data pins, D0-D7, are used to send information to the LCD or read the contents of the LCD s internal registers. To display letters and numbers, we send ASCII codes for the letters A-Z, a- z, and numbers 0-9 to these pins while making RS=1. There are also instruction command codes that can be sent to the LCD to clear the display or force the cursor to the home position or blink the cursor. 3.8 POWER SUPPLY A power supply provides a constant output regardless of voltage variations. "Fixed" three-terminal linear regulators are commonly available to generate fixed voltages of plus 3 V, and plus or minus 5 V, 9 V, 12 V, or 15 V when the load is less than about 7 amperes. The "78xx" series (7805, 7812, etc.) regulate positive voltages while the "79xx" series (7905, 7912, etc.) regulate negative voltages. Often, the last two digits of the device number are the output voltage; e.g., a 7805 is a +5 V regulator, while a 7915 is a -15 V regulator. The 78xx series ICs can supply up to 1.5 Amperes depending on the model. 25

26 3.8.1 Features 1. Output Current up to 1A 2. Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, Thermal Overload Protection 4. Short Circuit Protection 5. Output Transistor Safe Operating Area Protection When you have a requirement for a project of say 12V, or even 5V if it's a digital project, then these are the types you use or 7812 are the types. There are of course negative voltage regulators with the numbers 79XX which are substantially the same as those discussed here excepting they are negative. We will not consider them further. Assume your project calls for a basic fixed 12V D.C. to operate. Looking back to our earlier tutorial we apply all the same principles. Look at the original schematic. Fig 3.13 Basic power supply diagram In a typical linear power supply, AC line voltage is first down-converted to a smaller peak voltage using a transformer, which is then rectified using a full wave bridge rectifier circuit. A capacitor filter is then used to smoothen the 26

27 obtained sinusoidal signal. The residual periodic variation or ripple in this filtered signal is eliminated using an active regulator. To obtain a DC power supply with both positive and negative output voltages, a center-tapped transformer is used, where a third wire is attached to the middle of the secondary winding and it is taken as the common ground point. Then voltages from the opposite ends of the winding will be positive or negative with respect to this point Summary of circuit features Brief description of operation: Gives out well regulated +5V output, output current capability of 100 ma Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot Circuit complexity: Very simple and easy to build Circuit performance: Very stable +5V output voltage, reliable operation Availability of components: Easy to get, uses only very common basic components Applications: Part of electronics devices, small laboratory power supply Power supply voltage: Unregulated DC 8-18V power supply Power supply current: Needed output current + 5 ma Component costs: Few dollars for the electronics components + the input transformer cost 27

28 3.8.3 Circuit description This circuit is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall transformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily available, but usually their voltage regulation is very poor, which makes then not very usable for digital circuit experimenter unless a better regulation can be achieved in some way. The following circuit is the answer to the problem. This circuit can give +5V output at about 150 ma current, but it can be increased to 1 A when good cooling is added to 7805 regulator chip. The circuit has over overload and terminal protection. Fig 3.14 Circuit diagram of the power supply. The capacitors must have enough high voltage rating to safely handle the input voltage feed to circuit. The circuit is very easy to build for example into a piece of Vero board. 28

29 Fig 3.15 Voltage Regulator Pin Diagram Pin out of the 7805 regulator IC. 1. Unregulated voltage in 2. Ground 3. Regulated voltage out Component list 7805 regulator IC 100 uf electrolytic capacitor, at least 25V voltage rating 10 uf electrolytic capacitor, at least 6V voltage rating 100 nf ceramic or polyester capacitor 7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs. The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide provides +5V regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels. 29

30 3.8.5 Voltage Regulator Features Output Current up to 1A Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V Thermal Overload Protection Short Circuit Protection Output Transistor Safe Operating Area Protection 3.9 BUZZER A buzzer or beeper is a signaling device, usually electronic, typically used in automobiles, household appliances such as a microwave oven, or game shows. It most commonly consists of a number of switches or sensors connected to a control unit that determines if and which button was pushed or a preset time has lapsed, and usually illuminates a light on the appropriate button or control panel, and sounds a warning in the form of a continuous or intermittent buzzing or beeping sound. Initially this device was based on an electromechanical system, which was identical to an electric bell without the metal gong (which makes the ringing noise). Often these units were anchored to a wall or ceiling and used the ceiling or wall as a sounding board. Another implementation with some AC-connected devices was to implement a circuit to make the AC current into a noise loud enough to drive a loudspeaker and hook this circuit up to a cheap 8-ohm speaker. Nowadays, it is more popular to use a ceramic-based piezoelectric sounder which makes 30

31 a high-pitched tone. Usually these were hooked up to "driver" circuits, which varied the pitch of the sound or pulsed the sound on and off. Fig 3.16 Buzzer In game shows it is also known as a "lockout system," because when oneperson signals ("buzzes in"), all others are locked out from signaling. Several game shows have large buzzer buttons, which are identified as "plungers. The word "buzzer" comes from the rasping noise that buzzers made when they were electromechanical devices, operated from steppeddown AC line voltage at 50 or 60 cycles. Other sounds commonly used to indicate that a button has been pressed are a ring or a beep RELAY A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field, which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and they are double throw (changeover) switches. Relays allow one circuit to switch a second circuit, which can be completely separate from 31

32 the first. For example, a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits; the link is magnetic and mechanical. The coil of a relay passes a relatively large current; typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to the larger value required for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices can supply relay coils directly without amplification. Fig 3.17 Relay Relays are usually SPDT or DPDT but they can have many more sets of switch contacts, for example relays with 4 sets of changeover contacts are readily available. Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay. The animated picture shows a working relay with its coil and switch contacts. You can see a lever on the left being attracted by magnetism when the coil is switched on. This lever moves the switch 32

33 contacts. There is one set of contacts (SPDT) in the foreground and another behind them, making the relay DPDT. Fig 3.18 Relay Working Diagram The relay's switch connections are usually labeled COM, NC and NO: COM = Common, always connect to this; it is the moving part of the switch. NC = Normally Closed, COM is connected to this when the relay coil is off. NO = Normally Open, COM is connected to this when the relay coil is on. 33

34 CHAPTER 4 SOFTWARE DESCRIPTIONS 4.1 DEVELOPMENT TOOLS The Development Systems product categories are: Compilers Emulators In Circuit Debuggers MPLAB Compiler Compiler is a computer program (or set of programs) that translates text written in a computer language (the source language) into another computer language (the target language). The original sequence is usually called the source code and the output called object code Emulator Emulator is a device it has the ability of a computer program or electronic device to imitate another program or device In Circuit Debugger Microchip's in-circuit debugger for the flash PIC16F87x family only utilizes the in-circuit Debugging capability of the PIC16F87X along with in-circuit Serial Programming (ICSP) protocol to provide cost-effective in-circuit flash programming and debugging from the graphical user interface of the MPLAB MPLAB IDE MPLAB X IDE is a software program that is used to develop applications for Microchip microcontrollers and digital signal controllers. This development tool is called an Integrated Development Environment, or IDE, because it provides a single integrated environment to develop code. 34

35 MPLAB IDE Development Tools: MPLAB IDE integrates several tools to provide a complete development environment. MPLAB Project Manager Use the Project Manager to create a project and work with the specific files related to the project. When using a project, you can rebuild source code and download it to the simulator or emulator with a single mouse Click. MPLAB Editor Use the MPLAB Editor to create and edit text files such as source files, code, and linker script files. MPLAB ICD In-Circuit Debugger The MPLAB ICD In-Circuit Debugger is a powerful, low-cost development and evaluation kit for many PICmicro MCU FLASH devices. MPLAB SIM Simulator The software simulator models the instruction execution and I/O of the PICmicro MCUs. MPLAB ICE 2000 In-Circuit Emulator The MPLAB ICE 2000 emulator uses hardware to provide real-time emulation of PICmicro MCUs, either with or without a target system. MPASM Assembler/MPLINK Linker/MPLIB Librarian The MPASM assembler allows source code to be assembled without leaving MPLAB IDE. The MPLINK linker creates the final application by linking reloadable modules from MPASM, MPLAB C17 and MPLAB C18 C Compilers. The MPLIB librarian manages custom libraries for maximum code reuse. MPLAB CXX C Compilers The MPLAB C17 and MPLAB C18 C Compilers provide ANSI-based high level source code solutions. Complex projects can use a combination of C 35

36 and assembly source files to obtain the maximum benefits of speed and maintainability. PRO MATE II and PICSTART Plus Programmers Develop code with the simulator or an emulator, assemble or compile it, then use one of these tools to program devices. This can all be accomplished with MPLAB IDE. Although the PRO MATE II programmer does not require MPLAB IDE to operate, programming is easier using MPLAB IDE. PICMASTER and PICMASTER CE Emulators MPLAB IDE provides legacy support for the PICMASTER and PICMASTER CE emulators. Steps to create firmware for an embedded system using MPLAB Open the MPLAB 6.43 from the Startà Programsà Microchip MPLAB IDEàMPLAB IDE. Select Project Wizard from the Project menu. This wizard helps you to create and configure a new MPLAB project. Click Next. Select a device. For example: PIC16F877A. Select a Language Tool suite. For example: Microchip MPASM Tool suite. Name your project and select a project directory. Add any existing file to your project (optional). Click Finish to create a new project. A new Workspace will be created and the new project added to that workspace. To write a source file for your project, select Fileà New option. A new text editor is created for entering the assembly language or C language code. 36

37 After completion of entering the code, save it with the extension <file name>.asm (for assembly language) or <file name>.c (for C language). Add source code to your project by selecting Add Files to Project option from the Project menu. Assemble or compile the project by choosing Build All option from the Project menu. If you have written your program without errors you will get a message Build Succeeded else build Failed along with errors and their types. A hexadecimal file of your project is created with the extension.hex 37

38 CHAPTER 5 APPENDIX 5.1 CODE #include <16f877a.h> #device PASS_STRINGS=IN_RAM ADC=10 #include <string.h> #use delay( clock= ) #fuses NOWDT, HS, NOPROTECT, NOBROWNOUT, NOPUT, NOLVP #use rs232(baud=9600, xmit=pin_c6,rcv=pin_c7,errors) #zero_ram #BYTE PORTB = 0X06 #BYTE TRISB = 0X86 #BIT RF_Receive1 = 0X06.0 #BIT RF_Receive2 = 0X06.1 #include"lcdo.h" void Display(); char Data; char tempdata; #INT_RDA void Data_Received() { tempdata=getc(); if(tempdata=='@') { 38

39 Data=getc(); } if(data=='1') { Data='\0'; tempdata='\0'; Clr_Screen(); sprintf(lcd_dispdata,"a1 Bus Reached: "); LCD_Cmd(0X80); LCDData_Write(); sprintf(lcd_dispdata,"gandhipuram "); LCD_Cmd(0XC0); LCDData_Write(); delay_ms(100); fputs("at+cmgda=\"del ALL\""); delay_ms(100); fputs("at+cmgda=\"del ALL\""); delay_ms(10000); Display(); } if(data=='2') { Data='\0'; tempdata='\0'; Clr_Screen(); sprintf(lcd_dispdata,"a2 Bus Reached: "); LCD_Cmd(0X80); LCDData_Write(); 39

40 } sprintf(lcd_dispdata,"gandhipuram "); LCD_Cmd(0XC0); LCDData_Write(); delay_ms(100); fputs("at+cmgda=\"del ALL\""); delay_ms(100); fputs("at+cmgda=\"del ALL\""); delay_ms(10000); Display(); } void main() { TRISB=0XFF; LCD_Initialization(); Display(); delay_ms(5000); fputs("at"); delay_ms(1000); fputs("at+cmgf=1"); delay_ms(1000); fputs("ate0"); delay_ms(1000); fputs("at+cnmi=1,2,0,0,0"); delay_ms(1000); 40

41 fputs("at+cmgr=1"); delay_ms(1000); fputs("at+cmgda=\"del ALL\""); delay_ms(100); fputs("at+cmgda=\"del ALL\""); delay_ms(1000); enable_interrupts(global); enable_interrupts(int_rda); while(true) { if(rf_receive1==1) { puts("at+cmgs=\" \""); // // putc(0x0d); delay_ms(500); puts("@1"); delay_ms(500); putc(0x1a); delay_ms(100); } if(rf_receive2==1) { puts("at+cmgs=\" \""); putc(0x0d); delay_ms(500); 41

42 delay_ms(500); putc(0x1a); delay_ms(100); } } } void Display() { Clr_Screen(); sprintf(lcd_dispdata," Bus "); LCD_Cmd(0X80); LCDData_Write(); sprintf(lcd_dispdata," Monitoring "); LCD_Cmd(0XC0); LCDData_Write(); delay_ms(100); } 42

43 6.1 RF TRANSMITTER SECTION CHAPTER 6 RESULTS When the bus approaches the bus stop, a unique number assigned to it is sent to the same through RF Transmitter Fig 6.1 RF Transmitter Section 6.2 RF RECEIVER AND GSM SECTION RF Receiver receives the RF signal, PIC Microcontroller decodes the signal and process for corresponding bus information and then the details of bus are sent to other selected bus stops through GSM modem. 43

44 Fig 6.2 RF Receiver and GSM Section 6.3 LCD OUTPUT The bus details are shown at other bus stops using LCD Fig 6.3 LCD Output 44

45 CHAPTER 7 ADVANTAGES Use of GSM technology as compared to other existing techniques used for tracking makes it more cost efficient and innovative Use of GSM technology allows tracking in high density urban areas Low cost system opens up a new segment of the market Real time monitoring 45

46 CHAPTER 8 CONCLUSION The key feature of this system is its relatively simple mode of communication. The tracking of different local buses can be done easily using this system. The project involves the use of GSM and RF technology, which is used to send and receive information for locating vehicles. The use of GSM technology as compared to other existing techniques used for tracking makes it more cost efficient and innovative. Our system design has an open architecture that can be easily expanded to other applications. This system can be easily extended for central tracking system to keep track of all the public vehicles. Thus, the proposed system is beneficial for both passengers and the bus operators. 46

47 CHAPTER 9 REFERENCES [1]. Asaad M. J. Al-Hindawi, Ibraheem Talib, Experimentally Evaluation of GPS/GSM Based System Design, Journal of Electronic Systems, Volume 2 Number, 2 June, [2]. Kane, L., Verma, B., Jain, S., Vehicle tracking in public transport domain and associated spatio-temporal query processing, Elsevier: Computer Communications, v.31 n.12, p (2008). [3]. Oberli, C et al (2010). Performance Evaluation of UHF RFID technologies for Real Time passenger Recognition in Intelligent Public transportation systems, IEEE Transactions on Intelligent Transport Systems, Vol.11(3), pp [4]. PIC Microcontroller- [5]. GSM -Wikipedia, the free encyclopedia ( [6]. Basics Reference- 47