09-05-2010, 04:21 PM
[attachment=3486]
Wireless GSM Based Electronic Notice Board
Presented By:
Mrs. S.P.Gaikwad , Manikeshwari Shahdeo , Meghna Priya , Prashant Kr. Raghav
Department Of Electronics Bharati Vidyapeeth College Of Engineering, Pune India
Abstract- GSM based electronic notice display system is presented in this paper, this is the model for displaying notices in college on electronic notice board by sending messages in form of SMS through mobile, it is a wireless transmission system which has very less errors and maintenance. The hardware board contains microcontroller 89c51 at the heart of the system. The microcontroller is interfaced with PC via MAX232 level convertor. It is used to convert RS232 voltage levels to TTL voltage levels and vice versa. We use PC's serial port to interface microcontroller. The hardware also has a 64K EEPROM chip AT24C64. This EEPROM is used to store the timings and messages to be displayed. Hardware also contains a real time clock DS1307 to maintain track of time. Both these ICs are interfaced with microcontroller using I2C interface. The keypad is used to set/reset parameters directly. A 4x4 keypad is attached using Row Column configuration. A 16x2 Character LCD display is attached in byte mode to port 1 of microcontroller. This display will be used to display the messages / advertisements. Microcontroller coding will be done using Embedded C and Kiel. PC Coding will be done using VB.
Nokia PC Connectivity SDK is a tool used in VB for GSM
Modem interfacing, this project implementation will save time, also cost efficient. a single person can handle all the work with just a message. We can use a PC with administrator for ease of message sending and keeping records.
I. INTRODUCTION Market research analysts are predicting that the wireless
technologies will eventually become more widespread than the various wired solutions. The wireless communications present the ideal solution for the home network .This increasing demand of getting wireless can be seen not only in the field communication but also in the transferring information and data. The cell phones which are the best example of wireless data and voice transfer can be used for many other purposes that can replace the traditional system. One simple way of using this wireless communication is to use a simple cell phone for sending messages. Our administrator uses a simple GSM based handset for sending messages to different display stations which are located far away from him. The GSM modem used at the receiver end is used to receive the messages and LCD to display them. As we are using mobile for sending messages, its easy to handle and operate. As it's a wireless transmission the system has very less errors and maintenance. With greater efficiency we can display the messages at various places like public transports, crowded cities and advertisement of chain restaurants. We can use this displaying system at distant area where our wire or manpower can go easily.GSM and GPRS based designs have developed another innovative and Public Utility Product for mass communication. This is a Wireless Scrolling Message Electronic Display Board, which displays the messages, received as SMS or GPRS Packets.
II. BLOCK DIAGRAM DESCRIPTION
The hardware board contains microcontroller 89c51 at the heart of the system. The microcontroller is interfaced with PC via MAX232 level convertor. It is used to convert RS232 voltage to TTL voltage levels and vice versa. We use PC's serial port to interface microcontroller. The hardware also has a 64K EEPROM chip AT24C64. This EEPROM is used
to store the timings and messages to be displayed. Hardware also contains a real time clock DS1307 to maintain track of time. Both these ICs are interfaced with microcontroller using I2C interface. The keypad is used to set/reset parameters directly. A 4x4 keypad is attached using Row Column configuration. A 16x2 Character LCD display is attached in byte mode to port 1 of microcontroller. This display will be used to display the messages / advertisements. Microcontroller coding will be done using Embedded C and Kiel. PC Coding will be done using VB. Nokia PC Connectivity SDK is a tool used in VB for GSM Modem interfacing. BLock diagram FOR Wireless GSM based electronic notice display is shown in figure 1.
and GSM modem.
Features:
¢ 80C51 Central Processing Unit
¢ On-chip FLASH Program Memory
¢ Speed up to 33 MHz
¢ Full static operation
¢ RAM expandable externally to 64 k bytes
¢ 4 level priority interrupt
¢ 6 interrupt sources
¢ Four 8-bit I/O ports
¢ Full-duplex enhanced UART
- Framing error detection
- Automatic address recognition
¢ Power control modes
- Clock can be stopped and resumed
- Idle mode
- Power down mode
¢ Programmable clock out
¢ Second DPTR register
¢ Asynchronous port reset Low EMI (inhibit ALE)
¢ 3 16-bit timers
¢ Wake up from power down by an external interrupt
Description:
The AT89C5WD is a low-power, high-performance CMOS 8-bit microcontroller with20K bytes of Flash programmable read only memory and 256 bytes of RAM. The device is manufactured using Atmel's high-density nonvolatile memory technology and is compatible with the industry standard 80C51 and 80C52 instruction set and pinout. The on-chip Flash allows the program memory to be user programmed by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C59WD is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The AT89C59WD provides the following standard features: 20K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector, two-level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C59WD is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next external interrupt or hardware reset.
A. MICROCONTROLLER
Microcontroller is the heart of the system. It is used for interfacing the display, memory with GSM modem. With the help of AT-commands we can interface the microcontroller
B. GSM MODULE WITH RS232
Full Type Approved Quad Band Embedded GSM Module (GSM 850/900 1800/1900) with AT command set and
RS232 interface on CMOS level shown in figure 2. This GSM wireless data module is the ready a solution for remote wireless applications, machine to machine or user to machine and remote data communications in all vertical market applications. A range of dual band GSM radio modems, which give compatible mobile devices wireless connectivity using the GSM900/1800 cellular networks. Each modem interfaces to the host via a Universal Synchronous/Asynchronous Serial Receiver-Transmitter (USART), which is automatically detected by the operating system and easily configured using standard operating system drivers.The modems are controlled by industry standard AT commands
¢ 10 general purposes I/O ports and serial bi¬directional bus on CMOS 2,8 V
¢ External SIM
¢ Analog audio for microphone, speaker and hands free set plus digital voice interface
¢ RS232 on CMOS 2,8 V (One RS232 (2,8V) with flow control (RX, TX, CTS, RTS, CTS, DTR, DSR, DCD, RI), baud rate 300 - 115.200 bps, auto
bauding 1200 - 57.600 bps
¢ 50 Ohm antenna connector
The GSM module offers the advantages as below :
¢ Ultra small size (22x22x3 mm), lightweight (3.2 g) and easy to integrate
¢ Low power consumption
¢ R&TTE type approval plus CE, GCF, FCC, PTCRB, IC
¢ Full RS232 on CMOS level with flow control (RX, TX, CTS, RTS, CTS, DTR, DSR, DCD, RI)
¢ High performance on low price
Product Features :
¢ E-GSM 900/1800 MHz and GSM 1800/1900 with GSM Phase 2 / 2+
¢ Control via AT commands (ITU, GSM, GPRS and
manufacturer supplementary)
¢ Supply Voltage range: 3.22 V - 4.2 V, nominal:3.8V
¢ Power consumption: Idle mode: <1.8 mA, speech mode: 200 mA (average)
Interfaces :
¢ Power supply nominal 3,8 V
C. DISPLAY UNIT
LCD modules are available in a wide range like 8x1, 8x2, 16x1, 16x2, 20x2, 20x4, 40x4. Here we have used 16x2- that means 2 rows of 16 characters. It is a Hitachi HD44780 compatible module, having 16 pins including 2 pins for backlight. To program the LCD module, first we have to initialize the LCD by sending some control words. RS should be low and E should be high when we send control. R/W pin 0 mean write data or control to LCD and R/W pin 1 means read data from the LCD. To send a data to LCD, make RS high, R/W low, place the data in pins 7 to 14 and make pin E high and low once. You can understand exact method after seeing the code, later in this tutorial. To make this let us first build a circuit. we are going to write on the LCD module and not reading back. So, R/W is connected to ground directly. We need not have to input any data through, so all output pins are used in our application. Data pins of LCD are connected to data pins of the port. Strobe signal (Pin 1 of D25 connector) is given to E (Pin 6 of LCD), Select printer (Pin 17 of D25) is connected to RS (pin 4 of the
LCD)
.Main display unit contains LED DISPLAY which is a ALPHANUMERIC display shown in figure 3.This display unit can display 32 alphabet at a time. Many functions as Rolling or still message display , speed variation , manage time for display is also added to the display board. Refreshing circuitry is also available in display board.
D. PULL UP RESISTORS:
Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected. Pull-up resistors shown in figure 4 may also be used at the interface between two different types of logic devices, possibly operating at different power supply voltages. The idea of a pull-up resistor is that it weakly "pulls" the voltage of the wire it's connected to towards 5V (or whatever voltage represents a logic "high"). However, the resistor is intentionally weak (high-resistance) enough that, if something else strongly pulls the wire toward 0V, the wire will go to 0V. An example of something that would strongly pull a wire to 0V would be the transistor in an open-collector output.Similarly, pull-down resistors are used to hold the input to a zero (low) value when no other component is driving the input. They are used less often than pull-up resistors. Pull-down resistors can safely be used with CMOS logic gates because the inputs are voltage-controlled. TTL logic inputs that are left un¬connected inherently float high, thus they require a much lower valued pull-down resistor to force the input low. This also consumes more current. For that reason, pull-up resistors are preferred in TTL circuits. Pull-up resistors may be discrete devices mounted on the same circuit board as the logic devices. Many microcontrollers intended for embedded control applications have internal, programmable pull-up resistors for logic inputs so that minimal external components are needed.Some disadvantages of pull-up resistors are the extra power consumed when current is drawn through the resistor, and the reduced speed of a pull-up compared to an active current source. Certain logic
families
are
susceptible to power supply transients
introduced into logic inputs through pull-up resistors, which may force the use of a separate filtered power source for the pull-ups. PC requires pull-up resistors on its clock (SCL) and data line (SDA) because the pins on the chips are of open-collector design.5V power supply for digital circuits.This circuit is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers 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
FIGURE 4: A circuit showing a pull-up resistor (R2) and a pull-down resistor (R1)
E. POWER SUPPLY
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 therminal protection.
S-18U 15 On A
Pouer Supp I y
FIGURE 5: 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 veroboard
F. MAX232, MAX232I
DUAL EIA-232 DRIVERS/RECEIVERS
¢ Meet or Exceed TIA/EIA-232-F and ITU Recommendation V.28
¢ Operate With Single 5-V Power Supply
¢ Operate Up to 120 kbit/s
¢ Two Drivers and Two Receivers
¢ ±30-V Input Levels
¢ Low Supply Current . . . 8 mA Typical
¢ Designed to be Interchangeable With Maxim
MAX232
¢ ESD Protection Exceeds JESD 22- 2000-V Human-Body Model (A114-A)
The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply EIA-232 voltage levels from a single 5-V supply. Each receiver converts EIA-232 inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V and a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into EIA-232 levels. The driver, receiver, and voltage-generator functions are available as cells in the Texas Instruments LinASIC library.
III. SOFTWARES USED
A. EXPRESS PCB
Express PCB is a free PCB software and is a snap to learn and use. For the first time, designing circuit boards is simple for the beginner and efficient for the professional. The board manufacturing service makes top quality two and four layer
PCBs.
B. Embedded C
Use of embedded processors in passenger cars, mobile phones, medical equipment, aerospace systems and defense systems is widespread, and even everyday domestic appliances such as dish washers, televisions, washing machines and video recorders now include at least one such device. There is a large - and growing - international demand for programmers with 'embedded' skills, and many desktop developers are starting to move into this important area.Because most embedded projects have severe cost constraints, they tend to use low-cost processors like the 8051 family of devices considered in this book. These popular chips have very limited resources available: most such devices have around 256 bytes (not megabytes!) of
RAM, and the available processor power is around 1000 times less than that of a desktop processor. As a result, developing embedded software presents significant new challenges, even for experienced desktop programmers.
C. KEIL
Keil development tools for the 8051 Microcontroller Architecture support every level of software developer from the professional applications engineer to the student just learning about embedded software development. The industry-standard Keil C Compilers, Macro Assemblers, Debuggers, Real-time Kernels, Single-board Computers, and Emulators support all 8051 derivatives and help you get your projects completed on schedule.
FIGURE 6: KEIL DEVELOPMENT KIT
The Keil 8051 Development Tools are designed to solve the complex problems facing embedded software developers.
¢ When starting a new project, simply select the microcontroller you use from the Device Database and the LI Vision IDE sets all compiler, assembler, linker, and memory options for you.
¢ Numerous example programs are included to help you get started with the most popular embedded 8051 devices.
¢ The Keil LiVision Debugger accurately simulates on-chip peripherals (PC, CAN, UART, SPI, Interrupts, I/O Ports, A/D Converter, D/A Converter, and PWM Modules) of your 8051 device. Simulation helps you understand hardware configurations and avoids time wasted on setup problems. Additionally, with simulation, you can write and test applications before target hardware
is available.
¢ When you are ready to begin testing your software application with target hardware, use the MON51, MON390, MONADI, or FlashMON51 Target Monitors, the ISD51 In-System Debugger, or the ULINK USB-JTAG Adapter to download and test program code on your target system.
IV. CIRCUIT DIAGRAM
V. CONCLUSION
By introducing the concept of wireless technology in the field of communication we can make our communication more efficient and faster , with greater efficiency we can display the messages and with less errors and maintenance. This model can be used very efficiently in establishments like chain restaurants wherein the order and special discounts can be displayed at all branches simultaneously, in colleges wherein students and staves can be informed simultaneously in no time. It can be set up at public transport places like railways , bus station , airport and also at roadside for traffic control and in emergency situations, it is cost efficient system and very easy to handle, a single person can handle all the work with just a message. PC with administrator has been used for ease of message sending and keeping record
ACKNOWLEDGMENT
This seminar report would not have seen the light of the day without Mrs Gaikwad ma' am, our project guide. We are highly grateful and obliged for her guidance and instructions which made this report possible. Had it not been her concern and help at every stage of the preparation of the seminars, we would not have been able to come to the conclusion of the seminar report. it was because of her help and support that we could successfully complete this report.
REFERENCES
[1] Books: The 8051 Microcontroller and
System
- Janice Gillispie Mazidi
- Rolin D. McKinlay
- Muhammad Ali Mazidi
[2] Books: ]GSM and Personal Communications Handbook
- Siegmund Redl,
- Matthias Weber
- Malcolm W. Oliphant
[3] Web Site - http://burnsidetelecomwhitepapers/gsm.pdf [4] Web site - http://cisco.com [5] Web site - http:// alldatasheets.com [6] Web Site - http:// atmel dyn/resources/prod
_documents/doc0265.pdf [7] Web Site - http://robotroomAlphanumericDisplay.html [8] Web Site - http://pdfserv.maxim-icen/an/AN83.pdf [9] Web Site - http://beyondlogicserial/serial.pdf [10] Web Site - http:// directindustry. com/industrial [11pdf - Philips semiconductors/80c51 8 bit microcontroller data sheets
Wireless GSM Based Electronic Notice Board
Presented By:
Mrs. S.P.Gaikwad , Manikeshwari Shahdeo , Meghna Priya , Prashant Kr. Raghav
Department Of Electronics Bharati Vidyapeeth College Of Engineering, Pune India
Abstract- GSM based electronic notice display system is presented in this paper, this is the model for displaying notices in college on electronic notice board by sending messages in form of SMS through mobile, it is a wireless transmission system which has very less errors and maintenance. The hardware board contains microcontroller 89c51 at the heart of the system. The microcontroller is interfaced with PC via MAX232 level convertor. It is used to convert RS232 voltage levels to TTL voltage levels and vice versa. We use PC's serial port to interface microcontroller. The hardware also has a 64K EEPROM chip AT24C64. This EEPROM is used to store the timings and messages to be displayed. Hardware also contains a real time clock DS1307 to maintain track of time. Both these ICs are interfaced with microcontroller using I2C interface. The keypad is used to set/reset parameters directly. A 4x4 keypad is attached using Row Column configuration. A 16x2 Character LCD display is attached in byte mode to port 1 of microcontroller. This display will be used to display the messages / advertisements. Microcontroller coding will be done using Embedded C and Kiel. PC Coding will be done using VB.
Nokia PC Connectivity SDK is a tool used in VB for GSM
Modem interfacing, this project implementation will save time, also cost efficient. a single person can handle all the work with just a message. We can use a PC with administrator for ease of message sending and keeping records.
I. INTRODUCTION Market research analysts are predicting that the wireless
technologies will eventually become more widespread than the various wired solutions. The wireless communications present the ideal solution for the home network .This increasing demand of getting wireless can be seen not only in the field communication but also in the transferring information and data. The cell phones which are the best example of wireless data and voice transfer can be used for many other purposes that can replace the traditional system. One simple way of using this wireless communication is to use a simple cell phone for sending messages. Our administrator uses a simple GSM based handset for sending messages to different display stations which are located far away from him. The GSM modem used at the receiver end is used to receive the messages and LCD to display them. As we are using mobile for sending messages, its easy to handle and operate. As it's a wireless transmission the system has very less errors and maintenance. With greater efficiency we can display the messages at various places like public transports, crowded cities and advertisement of chain restaurants. We can use this displaying system at distant area where our wire or manpower can go easily.GSM and GPRS based designs have developed another innovative and Public Utility Product for mass communication. This is a Wireless Scrolling Message Electronic Display Board, which displays the messages, received as SMS or GPRS Packets.
II. BLOCK DIAGRAM DESCRIPTION
The hardware board contains microcontroller 89c51 at the heart of the system. The microcontroller is interfaced with PC via MAX232 level convertor. It is used to convert RS232 voltage to TTL voltage levels and vice versa. We use PC's serial port to interface microcontroller. The hardware also has a 64K EEPROM chip AT24C64. This EEPROM is used
to store the timings and messages to be displayed. Hardware also contains a real time clock DS1307 to maintain track of time. Both these ICs are interfaced with microcontroller using I2C interface. The keypad is used to set/reset parameters directly. A 4x4 keypad is attached using Row Column configuration. A 16x2 Character LCD display is attached in byte mode to port 1 of microcontroller. This display will be used to display the messages / advertisements. Microcontroller coding will be done using Embedded C and Kiel. PC Coding will be done using VB. Nokia PC Connectivity SDK is a tool used in VB for GSM Modem interfacing. BLock diagram FOR Wireless GSM based electronic notice display is shown in figure 1.
and GSM modem.
Features:
¢ 80C51 Central Processing Unit
¢ On-chip FLASH Program Memory
¢ Speed up to 33 MHz
¢ Full static operation
¢ RAM expandable externally to 64 k bytes
¢ 4 level priority interrupt
¢ 6 interrupt sources
¢ Four 8-bit I/O ports
¢ Full-duplex enhanced UART
- Framing error detection
- Automatic address recognition
¢ Power control modes
- Clock can be stopped and resumed
- Idle mode
- Power down mode
¢ Programmable clock out
¢ Second DPTR register
¢ Asynchronous port reset Low EMI (inhibit ALE)
¢ 3 16-bit timers
¢ Wake up from power down by an external interrupt
Description:
The AT89C5WD is a low-power, high-performance CMOS 8-bit microcontroller with20K bytes of Flash programmable read only memory and 256 bytes of RAM. The device is manufactured using Atmel's high-density nonvolatile memory technology and is compatible with the industry standard 80C51 and 80C52 instruction set and pinout. The on-chip Flash allows the program memory to be user programmed by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C59WD is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The AT89C59WD provides the following standard features: 20K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector, two-level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C59WD is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next external interrupt or hardware reset.
A. MICROCONTROLLER
Microcontroller is the heart of the system. It is used for interfacing the display, memory with GSM modem. With the help of AT-commands we can interface the microcontroller
B. GSM MODULE WITH RS232
Full Type Approved Quad Band Embedded GSM Module (GSM 850/900 1800/1900) with AT command set and
RS232 interface on CMOS level shown in figure 2. This GSM wireless data module is the ready a solution for remote wireless applications, machine to machine or user to machine and remote data communications in all vertical market applications. A range of dual band GSM radio modems, which give compatible mobile devices wireless connectivity using the GSM900/1800 cellular networks. Each modem interfaces to the host via a Universal Synchronous/Asynchronous Serial Receiver-Transmitter (USART), which is automatically detected by the operating system and easily configured using standard operating system drivers.The modems are controlled by industry standard AT commands
¢ 10 general purposes I/O ports and serial bi¬directional bus on CMOS 2,8 V
¢ External SIM
¢ Analog audio for microphone, speaker and hands free set plus digital voice interface
¢ RS232 on CMOS 2,8 V (One RS232 (2,8V) with flow control (RX, TX, CTS, RTS, CTS, DTR, DSR, DCD, RI), baud rate 300 - 115.200 bps, auto
bauding 1200 - 57.600 bps
¢ 50 Ohm antenna connector
The GSM module offers the advantages as below :
¢ Ultra small size (22x22x3 mm), lightweight (3.2 g) and easy to integrate
¢ Low power consumption
¢ R&TTE type approval plus CE, GCF, FCC, PTCRB, IC
¢ Full RS232 on CMOS level with flow control (RX, TX, CTS, RTS, CTS, DTR, DSR, DCD, RI)
¢ High performance on low price
Product Features :
¢ E-GSM 900/1800 MHz and GSM 1800/1900 with GSM Phase 2 / 2+
¢ Control via AT commands (ITU, GSM, GPRS and
manufacturer supplementary)
¢ Supply Voltage range: 3.22 V - 4.2 V, nominal:3.8V
¢ Power consumption: Idle mode: <1.8 mA, speech mode: 200 mA (average)
Interfaces :
¢ Power supply nominal 3,8 V
C. DISPLAY UNIT
LCD modules are available in a wide range like 8x1, 8x2, 16x1, 16x2, 20x2, 20x4, 40x4. Here we have used 16x2- that means 2 rows of 16 characters. It is a Hitachi HD44780 compatible module, having 16 pins including 2 pins for backlight. To program the LCD module, first we have to initialize the LCD by sending some control words. RS should be low and E should be high when we send control. R/W pin 0 mean write data or control to LCD and R/W pin 1 means read data from the LCD. To send a data to LCD, make RS high, R/W low, place the data in pins 7 to 14 and make pin E high and low once. You can understand exact method after seeing the code, later in this tutorial. To make this let us first build a circuit. we are going to write on the LCD module and not reading back. So, R/W is connected to ground directly. We need not have to input any data through, so all output pins are used in our application. Data pins of LCD are connected to data pins of the port. Strobe signal (Pin 1 of D25 connector) is given to E (Pin 6 of LCD), Select printer (Pin 17 of D25) is connected to RS (pin 4 of the
LCD)
.Main display unit contains LED DISPLAY which is a ALPHANUMERIC display shown in figure 3.This display unit can display 32 alphabet at a time. Many functions as Rolling or still message display , speed variation , manage time for display is also added to the display board. Refreshing circuitry is also available in display board.
D. PULL UP RESISTORS:
Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected. Pull-up resistors shown in figure 4 may also be used at the interface between two different types of logic devices, possibly operating at different power supply voltages. The idea of a pull-up resistor is that it weakly "pulls" the voltage of the wire it's connected to towards 5V (or whatever voltage represents a logic "high"). However, the resistor is intentionally weak (high-resistance) enough that, if something else strongly pulls the wire toward 0V, the wire will go to 0V. An example of something that would strongly pull a wire to 0V would be the transistor in an open-collector output.Similarly, pull-down resistors are used to hold the input to a zero (low) value when no other component is driving the input. They are used less often than pull-up resistors. Pull-down resistors can safely be used with CMOS logic gates because the inputs are voltage-controlled. TTL logic inputs that are left un¬connected inherently float high, thus they require a much lower valued pull-down resistor to force the input low. This also consumes more current. For that reason, pull-up resistors are preferred in TTL circuits. Pull-up resistors may be discrete devices mounted on the same circuit board as the logic devices. Many microcontrollers intended for embedded control applications have internal, programmable pull-up resistors for logic inputs so that minimal external components are needed.Some disadvantages of pull-up resistors are the extra power consumed when current is drawn through the resistor, and the reduced speed of a pull-up compared to an active current source. Certain logic
families
are
susceptible to power supply transients
introduced into logic inputs through pull-up resistors, which may force the use of a separate filtered power source for the pull-ups. PC requires pull-up resistors on its clock (SCL) and data line (SDA) because the pins on the chips are of open-collector design.5V power supply for digital circuits.This circuit is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers 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
FIGURE 4: A circuit showing a pull-up resistor (R2) and a pull-down resistor (R1)
E. POWER SUPPLY
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 therminal protection.
S-18U 15 On A
Pouer Supp I y
FIGURE 5: 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 veroboard
F. MAX232, MAX232I
DUAL EIA-232 DRIVERS/RECEIVERS
¢ Meet or Exceed TIA/EIA-232-F and ITU Recommendation V.28
¢ Operate With Single 5-V Power Supply
¢ Operate Up to 120 kbit/s
¢ Two Drivers and Two Receivers
¢ ±30-V Input Levels
¢ Low Supply Current . . . 8 mA Typical
¢ Designed to be Interchangeable With Maxim
MAX232
¢ ESD Protection Exceeds JESD 22- 2000-V Human-Body Model (A114-A)
The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply EIA-232 voltage levels from a single 5-V supply. Each receiver converts EIA-232 inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V and a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into EIA-232 levels. The driver, receiver, and voltage-generator functions are available as cells in the Texas Instruments LinASIC library.
III. SOFTWARES USED
A. EXPRESS PCB
Express PCB is a free PCB software and is a snap to learn and use. For the first time, designing circuit boards is simple for the beginner and efficient for the professional. The board manufacturing service makes top quality two and four layer
PCBs.
B. Embedded C
Use of embedded processors in passenger cars, mobile phones, medical equipment, aerospace systems and defense systems is widespread, and even everyday domestic appliances such as dish washers, televisions, washing machines and video recorders now include at least one such device. There is a large - and growing - international demand for programmers with 'embedded' skills, and many desktop developers are starting to move into this important area.Because most embedded projects have severe cost constraints, they tend to use low-cost processors like the 8051 family of devices considered in this book. These popular chips have very limited resources available: most such devices have around 256 bytes (not megabytes!) of
RAM, and the available processor power is around 1000 times less than that of a desktop processor. As a result, developing embedded software presents significant new challenges, even for experienced desktop programmers.
C. KEIL
Keil development tools for the 8051 Microcontroller Architecture support every level of software developer from the professional applications engineer to the student just learning about embedded software development. The industry-standard Keil C Compilers, Macro Assemblers, Debuggers, Real-time Kernels, Single-board Computers, and Emulators support all 8051 derivatives and help you get your projects completed on schedule.
FIGURE 6: KEIL DEVELOPMENT KIT
The Keil 8051 Development Tools are designed to solve the complex problems facing embedded software developers.
¢ When starting a new project, simply select the microcontroller you use from the Device Database and the LI Vision IDE sets all compiler, assembler, linker, and memory options for you.
¢ Numerous example programs are included to help you get started with the most popular embedded 8051 devices.
¢ The Keil LiVision Debugger accurately simulates on-chip peripherals (PC, CAN, UART, SPI, Interrupts, I/O Ports, A/D Converter, D/A Converter, and PWM Modules) of your 8051 device. Simulation helps you understand hardware configurations and avoids time wasted on setup problems. Additionally, with simulation, you can write and test applications before target hardware
is available.
¢ When you are ready to begin testing your software application with target hardware, use the MON51, MON390, MONADI, or FlashMON51 Target Monitors, the ISD51 In-System Debugger, or the ULINK USB-JTAG Adapter to download and test program code on your target system.
IV. CIRCUIT DIAGRAM
V. CONCLUSION
By introducing the concept of wireless technology in the field of communication we can make our communication more efficient and faster , with greater efficiency we can display the messages and with less errors and maintenance. This model can be used very efficiently in establishments like chain restaurants wherein the order and special discounts can be displayed at all branches simultaneously, in colleges wherein students and staves can be informed simultaneously in no time. It can be set up at public transport places like railways , bus station , airport and also at roadside for traffic control and in emergency situations, it is cost efficient system and very easy to handle, a single person can handle all the work with just a message. PC with administrator has been used for ease of message sending and keeping record
ACKNOWLEDGMENT
This seminar report would not have seen the light of the day without Mrs Gaikwad ma' am, our project guide. We are highly grateful and obliged for her guidance and instructions which made this report possible. Had it not been her concern and help at every stage of the preparation of the seminars, we would not have been able to come to the conclusion of the seminar report. it was because of her help and support that we could successfully complete this report.
REFERENCES
[1] Books: The 8051 Microcontroller and
System
- Janice Gillispie Mazidi
- Rolin D. McKinlay
- Muhammad Ali Mazidi
[2] Books: ]GSM and Personal Communications Handbook
- Siegmund Redl,
- Matthias Weber
- Malcolm W. Oliphant
[3] Web Site - http://burnsidetelecomwhitepapers/gsm.pdf [4] Web site - http://cisco.com [5] Web site - http:// alldatasheets.com [6] Web Site - http:// atmel dyn/resources/prod
_documents/doc0265.pdf [7] Web Site - http://robotroomAlphanumericDisplay.html [8] Web Site - http://pdfserv.maxim-icen/an/AN83.pdf [9] Web Site - http://beyondlogicserial/serial.pdf [10] Web Site - http:// directindustry. com/industrial [11pdf - Philips semiconductors/80c51 8 bit microcontroller data sheets
