17-09-2014, 02:40 PM
Design and development of activation and controlling of home automation system via SMS through microcontroller Project Report
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INTRODUCTION
An embedded system is a combination of software and hardware to perform a dedicated task.
Some of the main devices used in embedded products are Microprocessors and Microcontrollers.
Microprocessors are commonly referred to as general purpose processors as they simply accept the inputs, process it and give the output.
In contrast, a microcontroller not only accepts the data as inputs but also manipulates it, interfaces the data with various devices, controls the data and thus finally gives the result.
ABSTRACT:
Nowadays there are various electronic equipment available for remote operation of grid control. However, the main disadvantage of these systems is that they can be operated only from short ranges and also less reliable. Thus, to overcome the above drawbacks, we are using one of the wireless communication technique i.e., GSM (Global System for Mobile communications) is a digital cellular communications system which has rapidly gained acceptance and market share worldwide.
The development of GSM is the first step towards a true personal communication system that will allow us to communication anywhere, anytime and with anyone
INTRODUCTION TO EMBEDDED SYSTEMS
An embedded system can be defined as a computing device that does a specific focused job. Appliances such as the air-conditioner, VCD player, DVD player, printer, fax machine, mobile phone etc. are examples of embedded systems. Each of these appliances will have a processor and special hardware to meet the specific requirement of the application along with the embedded software that is executed by the processor for meeting that specific requirement. The embedded software is also called “firm ware”. The desktop/laptop computer is a general purpose computer. You can use it for a variety of applications such as playing games, word processing, accounting, software development and so on. In contrast, the software in the embedded systems is always fixed listed below:
• Embedded systems do a very specific task, they cannot be programmed to do different things. . Embedded systems have very limited resources, particularly the memory. Generally, they do not have secondary storage devices such as the CDROM or the floppy disk. Embedded systems have to work against some deadlines. A specific job has to be completed within a specific time. In some embedded systems, called real-time systems, the deadlines are stringent. Missing a deadline may cause a catastrophe-loss of life or damage to property. Embedded systems are constrained for power. As many embedded systems operate through a battery, the power consumption has to be very low.
• Some embedded systems have to operate in extreme environmental conditions such as very high temperatures and humidity.
Application Areas
Nearly 99 per cent of the processors manufactured end up in embedded systems. The embedded system market is one of the highest growth areas as these systems are used in very market segment- consumer electronics, office automation, industrial automation, biomedical engineering, wireless communication,
data communication, telecommunications, transportation, military and so on.
Central Processing Unit (CPU):
The Central Processing Unit (processor, in short) can be any of the following: microcontroller, microprocessor or Digital Signal Processor (DSP). A micro-controller is a low-cost processor. Its main attraction is that on the chip itself, there will be many other components such as memory, serial communication interface, analog-to digital converter etc. So, for small applications, a micro-controller is the best choice as the number of external components required will be very less. On the other hand, microprocessors are more powerful, but you need to use many external components with them. D5P is used mainly for applications in which signal processing is involved such as audio and video processing.
POWER SUPPLY
The input to the circuit is applied from the regulated power supply. The a.c. input i.e., 230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The output obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c voltage, the output voltage from the rectifier is fed to a filter to remove any a.c components present even after rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.
MICROCONTROLLERS
Microprocessors and microcontrollers are widely used in embedded systems products. Microcontroller is a programmable device. A microcontroller has a CPU in addition to a fixed amount of RAM, ROM, I/O ports and a timer embedded all on a single chip. The fixed amount of on-chip ROM, RAM and number of I/O ports in microcontrollers makes them ideal for many applications in which cost and space are critical.
The Intel 8052 is a Harvard architecture, single chip microcontroller (µC) which was developed by Intel in 1980 for use in embedded systems. It was popular in the 1980s and early 1990s, but today it has largely been superseded by a vast range of enhanced devices with 8052-compatible processor cores that are manufactured by more than 20 independent manufacturers including Atmel, Infineon Technologies and Maxim Integrated Products.
8052 is an 8-bit processor, meaning that the CPU can work on only 8 bits of data at a time. Data larger than 8 bits has to be broken into 8-bit pieces to be processed by the CPU. 8052 is available in different memory types such as UV-EPROM, Flash and NV-RAM.
The microcontroller used in this project is AT89S52. Atmel Corporation introduced this 89S52 microcontroller. This microcontroller belongs to 8052 family. This microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one serial port and four ports (each 8-bits wide) all on a single chip. AT89C51 is Flash type 8051
PROGRAMMING THE FLASH
The AT89S52 is normally shipped with the on-chip Flash memory array in the erased state (that is, contents = FFH) and ready to be programmed. The programming interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The low-voltage programming mode provides a convenient way to program the AT89S52 inside the user’s system, while the high-voltage programming mode is compatible with conventional third party Flash or EPROM programmers. The AT89S52 is shipped with
LED INTERFACING:
LED stands for Light Emitting Diode.
Microcontroller port pins cannot drive these LEDs as these require high currents to switch on. Thus the positive terminal of LED is directly connected to Vcc, power supply and the negative terminal is connected to port pin through a current limiting resistor.
This current limiting resistor is connected to protect the port pins from sudden flow of high currents from the power supply.
Thus in order to glow the LED, first there should be a current flow through the LED. In order to have a current flow, a voltage difference should exist between the LED terminals. To ensure the voltage difference between the terminals and as the positive terminal of LED is connected to power supply Vcc, the negative terminal has to be connected to ground. Thus this ground value is provided by the microcontroller port pin. This can be achieved by writing an instruction “CLR P1.0”. With this, the port pin P1.0 is initialized to zero and thus now a voltage difference is established between the LED terminals and accordingly, current flows and therefore the LED glows. LED and switches can be connected to any one of the four port pins.
ASYNCHRONOUS AND SYNCHRONOUS SERIAL COMMUNICATION
Computers transfer data in two ways: parallel and serial. In parallel data transfers, often 8 or more lines are used to transfer data to a device that is only a few feet away. Although a lot of data can be transferred in a short amount of time by using many wires in parallel, the distance cannot be great. To transfer to a device located many meters away, the serial method is best suitable. In serial communication, the data is sent one bit at a time. The 8051 has serial communication capability built into it, thereby making possible fast data transfer using only a few wires.
The fact that serial communication uses a single data line instead of the 8-bit data line instead of the 8-bit data line of parallel communication not only makes it cheaper but also enables two computers located in two different cities to communicate over the telephone.
Serial data communication uses two methods, asynchronous and synchronous. The synchronous method transfers a block of data at a time, while the asynchronous method transfers a single byte at a time. With synchronous communications, the two devices initially synchronize themselves to each other, and then continually send characters to stay in sync. Even when data is not really being sent, a constant flow of bits allows each device to know where the other is at any given time. That is, each character that is sent is either actual data or an idle character. Synchronous communications allows faster data transfer rates than asynchronous methods, because additional bits to mark the beginning and end of each data byte are not required. The serial ports on IBM-style PCs are asynchronous devices and therefore only support asynchronous serial communications.
Asynchronous means "no synchronization", and thus does not require sending and receiving idle characters. However, the beginning and end of each byte of data must be identified by start and stop bits. The start bit indicates when the data byte is about to begin and the stop bit signals when it ends. The requirement to send these additional two bits causes asynchronous communication to be slightly slower than synchronous however it has the advantage that the processor does not have to deal with the additional idle characters
CONCLUSION
In this project work, we have studied and implemented a complete working model using a Microcontroller. The programming and interfacing of microcontroller has been mastered during the implementation. This work includes the study of GSM modem