INTRODUCTION
Security systems are necessary during any emergencies that occur at homes. Hence in this project, a security system with features like smoke detection, power cut detection are provided.
Using GSM the people of the house are intimated about the security by sending an SMS to their mobiles. At their workplaces, required actions can be taken, which saves time during emergencies.
DESCRIPTION
The Smoke detector detects any gas leakage and a sends signal to the controller. Any power failure is detected by the power cut detection module. In both the cases, a buzzer is turned on and the respective message is displayed on the ALCD. The security keys are pressed in case of the emergency such as theft, this will send message using GSM to the people at different places. The owner can send SMS from his work place to turn on home appliances like geyser, microwave etc.
8051 architecture based P89V51RD2 microcontroller from NxP is used to implement this project. Microcontroller acts as the heart of the project, which controls the whole system. It contains 1k RAM, 64k Flash, 3 Timers, 2 external interrupts, 1 UART, 32 GPIO’s, ISP programming support etc. KEIL IDE is used to program the microcontroller and the coding will be done using Embedded C.
BLOCK DIAGRAM
HARDWARE DESCRIPTION
MICROCONTROLLER
A microcontroller is a self-contained system with peripherals, memory and a processor that can be used as an embedded system. Most programmable microcontrollers that are used today are embedded in other consumer products or machinery including phones, peripherals, automobiles and household appliances for computer systems. Due to that, another name for a microcontroller is "embedded controller." Some embedded systems are more sophisticated, while others have minimal requirements for memory and programming length and a low software complexity. Input and output devices include solenoids, LCD displays, relays, switches and sensors for data like humidity, temperature or light level, amongst others. In microcontrollers several type are there.8-bit, 16-bit, 32-bit, 64-bit.
It is a small computer on a single integrated circuit. In modern terminology, it is a System on a chip or SOC. A microcontroller contains one or more CPUs along with memory and programmable input/output peripherals. Program memory in the form of Ferroelectric RAM, NOR flash or OTP ROM is also often included on chip, as well as a small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications consisting of various discrete chips.
Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes. Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems.
It can be considered a self-contained system with a processor, memory and peripherals and can be used as an embedded system. The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems.
While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays,solenoids, LED's, small or custom liquid-crystal displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind.
Typically micro-controller programs must fit in the available on-chip memory, since it would be costly to provide a system with external, expandable memory. Compilers and assemblers are used to convert both high-level and assembly language codes into a compact machine code for storage in the micro-controller's memory. Depending on the device, the program memory may be permanent, read-only memory that can only be programmed at the factory, or it may be field-alterable flash or erasable read-only memory.
RESET CIRCUIT
The first circuit pulls the RESET pin low to enable the chip. The second circuit is the same, but with a reset button. If you press that, the chip will get reset. When the 5V power is switched on, the capacitor shorts to 5V, and then gradually the RC circuit discharges to bring the reset pin to 0.
A power-on reset (POR) is a circuit that provides a predictable, regulated voltage to a microprocessor or microcontroller with the initial application of power. ... A POR system can be a peripheral, but in sophisticated processors or controllers the POR is integrated on the main chip.
LCD DISPLAY
A liquid-crystal display (LCD) is a flat panel display, electronic visual Crystals display, or video display that uses the light modulating properties of liquid. Liquid crystals do not emit light directly. LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content which can be displayed or hidden, such as preset words, digits, and 7-segment displays as in a digital clock.
ISOLATION CIRCUIT
Isolation circuits designed to withstand the rigors of industrial environments are the focus of this white paper. Industrial electronic equipment commonly uses galvanic isolators to protect systems and users from potentially hazardous s voltages. It is well known that industrial equipment must operate reliably in the harshest environments, where strong electromagnetic fields, surges, fast transients, and high noise floors are the norm. This environment presents challenges for designing reliable isolation circuits that deliver error-free operation over long equipment lifetimes. Over the last four decades, optocouplers have
been the “default” signal isolation device, but recent breakthroughs in silicon isolation technology have spawned smaller, faster, and more reliable and cost-effective solutions that have already begun supplanting optocouplers in many end applications. This white paper discusses industrial isolation issues and ways RF isolation technology can be applied to increase system robustness and performance.
The optocoupler is a hybrid assembly having a light-emitting diode (LED) that emits light when forward biased, with brightness being proportional to LED forward current. Emitted light passes through an optically transparent insulating film (or dielectric), striking a photo detector and causing a current flow that biases the output transistor on. When LED forward current no longer flows, light emission ceases, and the output transistor turns off.
Relay
A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations.
A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays".
Magnetic latching relays require one pulse of coil power to move their contacts in one direction, and another, redirected pulse to move them back. Repeated pulses from the same input have no effect. Magnetic latching relays are useful in applications where interrupted power should not be able to transition the contacts.
Magnetic latching relays can have either single or dual coils. On a single coil device, the relay will operate in one direction when power is applied with one polarity, and will reset when the polarity is reversed. On a dual coil device, when polarized voltage is applied to the reset coil the contacts will transition. AC controlled magnetic latch relays have single coils that employ steering diodes to differentiate between operate and reset commands.
Buzzer
Electronic symbol for a buzzer
A buzzer or beeper is an audio signaling device,[1] which may be mechanical, electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarm devices, timers, and confirmation of user input such as a mouse click or keystroke.
Type of buzzers
Electromechanical
Early devices were based on an electromechanical system identical to an electric bell without the metal gong. Similarly, a relay may be connected to interrupt its own actuating current, causing the contacts to buzz. Often these units were anchored to a wall or ceiling to use it as a sounding board. The word "buzzer" comes from the rasping noise that electromechanical buzzers made.
Mechanical
A joy buzzer is an example of a purely mechanical buzzer. They require drivers.
Piezoelectric
A piezoelectric element may be driven by an oscillating electronic circuit or other audio signal source, driven with a piezoelectric audio amplifier. Sounds commonly used to indicate that a button has been pressed are a click, a ring or a beep. A piezoelectric buzzer/beeper also depends on acoustic cavity resonance or Helmholtz_resonance to produce an audible beep
COMPONENTS USED
• Microcontroller - P89C51RD2– Phillips.
• GSM Module
• Buzzer
• Alphanumeric Display
• Security Keys
• Smoke Detector
• Relays
SOFTWARES USED
• Embedded C
• Keil Compiler
• Orcad Capture
• Flash Magic
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