Literature survey & related work

History Of Smart Homes

Smart homes have been in existence for more than 100 years. Starting with electrical power, residential home infrastructure over the decades has improved to provide interior automated communications, entertainment, Internet, video, climate control and security systems.

The 20th century saw a dramatic revolution in domestic technology, a revolution which culminated at the close of the century with the emergence of the previously unimaginable concept of the ―smart home‖. At the beginning of the 20th century most of the available domestic technology would have been easily recognized and used by people from a hundred years earlier. By the end of the 20th century, however, domestic technology had changed beyond recognition. The first major impetus for change was the introduction of electricity into homes in the first quarter of the century. This provided a new source of clean, convenient power for appliances and spurred the introduction of novel equipment for the home. The second major impetus was the introduction of information technology in the last quarter of the century. This opened up possibilities for exchanging information between people, appliances, systems and networks in and beyond the home, possibilities which are still being explored 

In the following brief historical review the survey will introduce the escalating pace and dramatic nature of developments in domestic technology across the 20th century – changes which prepared the ―seedbed‖ for the emergence of the smart home.

History of Smart Homes from 1915 to 1920:

During the early part of the century the emerging middleclasses were experiencing a shortage of domestic servants (Forty, 1986). In line with this labour shortage, electrically powered machines such as vacuum cleaners, food processors, and sewing machines were introduced into the home for the first time. The advertising angle was that with the help of technology, one person alone (inevitably a woman) could manage all the household chores and still have time for leisure activities (Hardyment, 1988). Advertisements used phrases such as ―spring cleaning with electricity‖, ―no longer tied down by housework‖, and ―automatically gives you time to do those things you want to do‖ (Gann et al., 1999). Mains electricity was not yet widespread, however, and so for most housewives such images remained a high tech fantasy.

History of Smart Homes from 1920 to 1940:

By 1940 the proportion of households in UK with mains electricity had risen to around 65 per cent. Many homes still only had electricity for lighting, however, while others had just one 5 amp socket. People sometimes declined to pay the additional cost to have a socket fitted as they were unable to envisage any use for one. Within the home the emphasis switched from production to consumption, with advertisers attempting to understand and appeal to the psychology of the housewife, ―Mrs Consumer‖ (Frederick, 1929). It is an irony that th introduction of new domestic technology actually resulted in women spending more time on housework than ever before, because standards rose – washing machines led to clothes being washed more often (Cowan, 1983), and vacuum cleaners led to floors being cleaned more frequently (Hardyment, 1988).

History of Smart Homes from 1940 to 1945:

During the Second World War, government propaganda portrayed women as technically competent and stressed the valuable role they could play in taking over traditionally male jobs in manufacturing and industry, freeing men to go into the armed forces. Women grew accustomed to working outside the home and (as illustrated by the well-known film Rosie the Riveter) many became technically proficient and enjoyed these new roles. Through working in these comparatively well paid jobs women also came to value their labour in financial terms. These factors helped to pave the way for the uptake of domestic technology after the war.

History of Smart Homes from 1945 to 1959:

After the Second World War, in order to free jobs for men returning to civilian life, government propaganda switched to persuading women that their place now was back in the home. Advertisements of the time show women in the home, waving husbands and children off for the day, and then turning their attention to the daily domestic fight with ―germs rather than Germans‖, as it has been expressed. Home design started to reflect new ways of living alongside modern technology. For example new styles of kitchen emerged to accommodate the refrigerators, electric cookers, and washing machines that were starting to penetrate the domestic market. The concept of the ―television lounge‖ was introduced, the sale of televisions having increased massively prior to the Coronation.

History of Smart Homes from 1960 to 1970:

The 1950s ideal of the stay-at-home-housewife was overturned during the ―swinging 60s‖. With the contraceptive pill and greater choice about whether and when to have children, more women started to go out to work. Numerous labour-saving devices became common in the home, including kettles, toasters, cookers, coffee and tea makers, food processors, hair dryers, electric razors, washing machines, sewing machines, vacuum cleaners, and irons. Other technology became commonplace in the home, for example central heating and thermostats.

History of Smart Homes from 1980 to 1990:

By the beginning of the 1980s, almost three-quarters of households in England and Wales had color television, and by the end of the 80s half also had video recorders (Bowden and Offer, 1994). Microwave ovens, freezers and tumble dryers also became increasingly common during this period which, in addition, saw the introduction of cordless and mobile phones for domestic use. A host of new home entertainment technologies became available and started to penetrate the domestic market – cable TV, DVD, the playstation, and the multimedia PC. The migration of the PC from workplace to home is particularly significant because it opened up the possibility of teleworking, blurring the distinction between home and work. Furthermore, by allowing access to the Internet, the PC connected the home to a host of new services such as banking, shopping and information, services which are still evolving.

Examples Of Smart Homes

The Adaptive House (University of Colorado)

The aim of the Adaptive House experiment is to explore the concept of a home which programs itself, freeing the inhabitants from the need to carry out this task. The researchers point out that the software for an automated home must be programmed for a particular family and home, and updated in line with changes in their lifestyle. Given that many people find it difficult enough to program their video recorders, programming a smart home will be beyond their interest and capability, and hiring a professional to do the job would be costly and inconvenient. The prototype system is installed in the home of one of the researchers and controls room temperature, water heat, ventilation and lighting. The home is equipped with sensors which monitor temperature, light levels, sound the opening of windows and so on, as well as control devices for heating, lighting, fans, etc. The system monitors actions taken by the residents, such as turning on a certain configuration of lights, or turning up the thermostat, and looks for patterns in the environment which reliably predict these actions. A neural network learns these patterns and the system then performs the learned actions learned actions automatically

ComHOME (The Interactive Institute, Sweden)

The ComHOME project is described by the researchers as ―a full-scale model constructed of a number of scenario-like room set-ups‖ (Junestrand and Tollmar, 1999). The apartment is equipped with technologies such as sensors, voice control and voice-mediated communication. In this context researchers are investigating different spheres of home-based activity, for example communication, distance work and social activities, and exploring the impact which technology may have on them

House_n (Massachusetts Institute of Technology)

House_n is a collaborative, multi-disciplinary project led by the Department of Architecture. The overall aims include creating environments which suit people of all ages; creating customizable environments; developing algorithms to interpret sensor data to detect what people are doing; exploring the impact of technology on traditional learning environments; inventing interfaces and components that conserve resources; and exploring the impact of home delivery of products and services. There are plans for a ―living lab‖ house but in the meantime a large workshop room is being equipped as a prototype.

In the workshop it will be possible to display digital information on almost any surface, with other surfaces allowing easy user input via touch or special devices. A partition allows division of the floor space for living and sleeping, and provides a ―medical nook‖ for the receipt and analysis of medical information. It is planned to explore a variety of home activities within this context, using an ―active counter‖ that can be used for kitchen tasks, work tasks, and eating; an ―active table‖ with digital surface that can be moved around within the environment; ―video walls‖; and floors that can have video projected onto them. Researchers in the Media Lab at MIT are meanwhile exploring a vision of the kitchen of the future as a digitally connected, self-aware environment with memory of its actions. Concepts and prototypes include a variety of intelligent appliances as well as an intelligent work surface

The Aware Home (Georgia Institute of Technology)

Most of the research by the Aware Home Research Initiative takes place in the Broadband Institute’s Residential Lab – a suburban house equipped with high-speed internal and external connections, cameras and microphones, a house-wide wireless net allowing communication between cordless devices, and a radio-locating system for tracking tagged objects. At the time of writing the house had not been lived in. The Aware Home project is arguably the well-advanced of the smart home research projects, involving researchers from the Broadband Institute, the Everyday Computing Lab, and the Future Computing Environments Group. The over-arching theme which has been adopted is to use the technology to help maintain older people in their own homes for as long as possible. There are two focuses to the research: first, issues and possibilities concerned with making the house aware of the whereabouts and activities of its occupants at all times; and secondly, the implications of maintaining continuous connectivity to the electronic world, particularly as a means to ―reunite the nuclear family of the 21st century‖. There are a wide variety of concepts and projects associated with the Aware Home and in different stages of development. Examples include: software which automatically constructs family albums from video pictures collected in the house; an intercom system which uses voice recognition to allow people to speak to one another by saying their name; software that telephones a person when their photograph is spoken to (after first checking they are awake); electronic tagging of easily mislaid items such as keys and remote controls; reminders from the house about appointments, medication, etc., through subtle images and sounds; a ―smart floor‖ system which identifies and tracks people by their footsteps; digital portraits incorporating iconic data representing the physical and social well- being of the Aware Home occupant; and a smart environment (the kitchen in particular is mentioned) that records contextual information alongside a record of everyday activities to help people resume interrupted activities 

Home Automation: Detection, Security, Control, Monitoring and tracking

There is variety of applications of smart homes that is used to ease the control of phenomena(s) such a light and temperature, also can detect any abnormal event such as a fire or water leakage. Other applications are used for securing the house such as thief intrusion or any abnormal motion inside the house.

Fire Detection

A heat detector is a fire alarm device designed to respond when the convicted thermal energy of a fire increases the temperature of a heat sensitive element. The thermal mass and conductivity of the element regulate the rate flow of heat into the element. All heat detectors have this thermal lag.

Heat detectors have two main classifications of operation, "rate-of-rise" and "fixed temperature."

Fixed temperature heat detectors

This is the most common type of heat detector. Fixed temperature detectors operate when the heat sensitive eutectic alloy reaches the eutectic point changing state from a solid to a liquid. Thermal lag delays the accumulation of heat at the sensitive element so that a fixed-temperature device will reach its operating temperature sometime after the surrounding air temperature exceeds that temperature. The most common fixed temperature point for electrically connected heat detectors is 136.4°F (58°C). Technological developments have enabled the perfection of detectors that activate at a temperature of 117°F (47°C), increasing the available reaction time and margin of safety. This type of technology has been available for decades without the use of batteries or electricity as shown in the picture 

Rate-of-rise heat detectors

Rate-of-Rise (ROR) heat detectors operate on a rapid rise in element temperature of 12° to 15°F (6.7° to 8.3°C) increase per minute, irrespective of the starting temperature. This type of heat detector can operate at a lower temperature fire condition than would be possible if the threshold were fixed. Rate of rise detectors may not respond to low energy release rates of slowly developing fires. To detect slowly developing fires combination detectors add a fixed temperature element that will ultimately respond when the fixed temperature element reaches the design threshold

Smoke Detection

A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector itself.

Most smoke detectors work either by optical detection (photoelectric) or by physical process (ionization)

Optical

An optical detector is a light sensor. When used as a smoke detector, it includes a light source (incandescent bulb or infrared LED), a lens to collimate the light into a beam, and a photodiode or other photoelectric sensor at an angle to the beam as a light detector. In the absence of smoke, the light passes in front of the detector in a straight line. When smoke enters the optical chamber across the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus triggering the alarm

"Photoelectric smoke detection is generally more responsive to fires that begin with a long period of smoldering (called smoldering fires)."

"Photoelectric alarms react slower to rapidly growing fires than ionization alarms, but laboratory and field tests have shown that photoelectric smoke alarms provide adequate warning for all types of fires and have been shown to be far less likely to be deactivated by occupants." 

Ionization

An ionization type smoke detector is generally cheaper to manufacture than an optical smoke detector; however, it is sometimes rejected because it is more prone to false (nuisance) alarms than photoelectric smoke detectors. It can detect particles of smoke that are too small to be visible. It includes about 37 kBq or 1 μCi of radioactive element americium-241 (241Am), corresponding to about 0.3 μg of the isotope.The radiation passes through an ionization chamber, an air-filled space between two electrodes, and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm

Performance differences

Photoelectric smoke detectors respond quickly to smoldering fires, which are made up of combustion particles between 0.3 and 10.0 microns. Ionization smoke detectors, however, are superior when detecting flaming fires, which can be characterized by combustion particles between 0.01 and 0.3 microns. Also, ionization detectors are weaker in high air-flow environments, and because of this, the photoelectric smoke detector is more reliable for detecting smoke in both the smoldering and flaming stages of a fire.

Touch Switch

A touch switch is a type of switch that only has to be touched by an object to operate. It is used in many lamps and wall switches that have a metal exterior as well as on public computer terminals. A touchscreen includes an array of touch switches on a display. A touch switch is the simplest kind of tactile sensor.

There are two types of switches called touch switches:

Capacitance touch switch

A capacitance switch needs only one electrode to function. The electrode can be placed behind a non-conductive panel such as wood, glass, or plastic. The switch works using body capacitance, a property of the human body that gives it great electrical characteristics. The lamp keeps charging and discharging its metal exterior to detect changes in capacitance. When a person touches it, it increases the capacitance and triggers the switch.

Resistance touch switch

A resistance switch needs two electrodes to be physically in contact with something electrically conductive (for example a finger) to operate. They work by lowering the resistance between two pieces of metal. It is thus much simpler in construction compared to the capacitance switch. Placing one or two fingers across the plates achieves a turn on or closed state. Removing the finger(s) from the metal pieces turns the device off.

Water Leakage Detection

A Water detector is a small electronic device that is designed to detect the presence of water and alert humans in time to allow the prevention of water damage. A common design is a small device that lays flat on a floor and relies on the electrical conductivity of water to decrease the resistance across two contacts. A battery then sounds an audible alarm in the presence of enough water to bridge the contacts. These are useful in a normally occupied area near any appliance that has the potential to leak water, such as a washing machine, refrigerator with icemaker, dehumidifier, air conditioner, or water heater.

A water leak in a pipeline system that serves an entire building for example, besides representing a financial loss, can lead to low water pressure, which can be frustrating, and damage to equipment, such as washing machines or boilers  

Radar Detection

Especially efficient in outside environments, radar detection accurately finds the leak point and provides information about the size of the leak. It uses radar waves that can travel through most materials. Parts of the wave that hit a material return back and are received by a device that, by calculating their return time and strength, can determine the material that the wave hit.

Gas Filling

This method is especially effective for inside problems, where access to the pipes is easy. The procedure is simple: a certain gas, usually industrial hydrogen, is introduced into a pipe, and then the track of the pipe is carefully inspected with a device sensitive to that particular gas. Because the gas is pumped at high pressure, if a leak exists, the detector will quickly identify it by detecting the leaking gas. This method can also be applied to outside pipes, but may require digging to get to the pipe, and the detection accuracy depends on the depth the pipe is installed; the deeper the pipe, the less accurate the results will be.

Geophones

Geophones are similar to stethoscopes used by doctors, and their working principle is the same. These devices catch and amplify sound, and a leak can easily be identified by listening to the ground. Every leak, big or small, makes a sound, and finding the sound means finding the leak. The irony is that larger leaks may be quite hard to detect using this method because, through a large leak, water can pour out quite easily without much noise. A small leak in a high pressure pipe usually makes a lot of noise, which, in some cases, can even be heard with the free ear.

Light Control

A lighting control system consists of a device that controls electric lighting and devices, alone or as part of a daylight harvesting system, for a public, commercial, or residential building or property, or the theater. Lighting control systems are used for working, aesthetic, and security illumination for interior, exterior, and landscape lighting, and theater stage lighting productions. They are often part of sustainable architecture and lighting design for integrated green building energy conservation programs.

Lighting control systems, with an embedded processor or industrial computer device, usually include one or more portable or mounted keypad or touchscreen console interfaces, and can include mobile phone operation. These control interfaces allow users the ability to remotely toggle (on-off) power to individual or groups of lights (and ceiling fans and other devices), operate dimmers, and pre-program space lighting levels.

Most commonly used technology for light control is photoresistor.

Photoresistor

A photoresistor or light dependent resistor (LDR) is a resistor whose resistance decreases with increasing incident light intensity. It can also be referred to as a photoconductor. A photoresistor is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its whole partner) conducts electricity, thereby lowering resistance.

A photoelectric device can be either intrinsic or extrinsic.

An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire bandgap.

Extrinsic devices have impurities, also called dopants, and added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction

Magnetic Detection

Magnetic detectors or sensors constitute a part of a system that triggers alarms upon unauthorized entry. They utilize magnetic fields to indicate normal status with a processing unit on one end of the system receives a continuous signal under normal conditions. However, when unauthorized entry disrupts the magnetic field the sensor then opens a switch that discontinues the signal to the processor. When the processor stops receiving the signal, it triggers the alarm.

Using a Magnetic Sensor for Windows, Many experts recommend magnetic sensors for windows. Owners of many large homes and apartment buildings use these devices in conjunction with locking mechanisms. A magnetic seal is able to withstand approximately one ton of applied force, easily impeding unauthorized access.

In cases of emergency, a button on the inside releases the magnetic seal, allowing exit through the door and resealing the door when it closes. Another kind of magnetic detector, the balanced magnetic switch, utilizes magnets on the moving part of the access point and its frame. Some experts warn that a danger with regular magnetic detectors entails causing explosions near flammable materials. Balanced magnetic switches are contained within a casing that negates this type of hazard.

Installing a Magnetic Detector Door Alarm

Consumers may choose either a wired or wireless option; however, both choices bring inherent advantages and disadvantages. Some prefer the wireless option as it is easier to install, requiring simple placement on a window or door and does not affect interior aesthetics.

They are operated by remote radio signals, allowing for quick deactivation. However, wireless systems requiring periodic changes of batteries and the signal may be susceptible to capture and copying. The wired solution does not present any risk for capturing a radio signal and relies on a single power source, not requiring batteries.

Many people also find the wired system easier to comprehend as the technology is not as sophisticated as the wireless option and it is also less expensive. However, each point of entry requires wiring and homeowners should take care that the wires are not placed within reach of would-be-burglars who may be able to disarm them from outside.

Running wiring through a home also requires aesthetic compromises. If the householder chooses a wired solution, experts recommend several different zones with different control panels. Each zone is independent of the other and this independence allows residents to find unauthorized point of entry more quickly. This solution is also alleviates the need to have the same wires run through every room, and allows flexibility to arm part of the house and not another. Residents can also specify different zones for different purposes, e.g., delays for entry or exit.

Nuisance Alarms

Alarms may sound due to high winds rattling doors and windows. Also, poorly fit doors and windows may trigger alarms with only slight movement by these access points.

Micro-Controller and Embedded Design:

A microcontroller (sometimes abbreviated μC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Neither program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications.

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.

Some microcontrollers may use four-bit words and operate at clock rate frequencies as low as 4 kHz, for low power consumption (mill watts or microwatts). They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be just nanowatts, making many of them well suited for long lasting battery applications. Other microcontrollers may serve performance- critical roles, where they may need to act more like a digital signal processor (DSP), with higher clock speeds and power consumption

Embedded Design

A microcontroller 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. These are called embedded 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, LEDs, small or custom LCD 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.

Interrupts

Microcontrollers must provide real time (predictable, though not necessarily fast) response to events in the embedded system they are controlling. When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and to begin an interrupt service routine (ISR, or "interrupt handler"). The ISR will perform any processing required based on the source of the interrupt before returning to the original instruction sequence. Possible interrupt sources are device dependent, and often include events such as an internal timer overflow, completing an analog to digital conversion, a logic level change on an input such as from a button being pressed, and data received on a communication link. Where power consumption is important as in battery operated devices, interrupts may also wake a microcontroller from a low power sleep state where the processor is halted until required to do something by a peripheral event.

Programs

Microcontroller programs must fit in the available on-chip program memory, since it would be costly to provide a system with external, expandable, memory. Compilers and assemblers are used to convert high-level language and assembler language codes into a compact machine code for storage in the microcontroller's memory. Depending on the device, the program memory may be permanent, read-only memory that can only be programmed at the factory, or program memory may be field-alterable flash or erasable read-only memory.

Other microcontroller features

Microcontrollers usually contain from several to dozens of general purpose input/output pins (GPIO). GPIO pins are software configurable to either an input or an output state. When GPIO pins are configured to an input state, they are often used to read sensors or external signals. Configured to the output state, GPIO pins can drive external devices such as LEDs or motors.

Many embedded systems need to read sensors that produce analog signals. This is the purpose of the analog-to-digital converter (ADC). Since processors are built to interpret and process digital data, i.e. 1s and 0s, they are not able to do anything with the analog signals that may be sent to it by a device. So the analog to digital converter is used to convert the incoming data into a form that the processor can recognize. A less common feature on some microcontrollers is a digital-to-analog converter (DAC) that allows the processor to output analog signals or voltage levels.

In addition to the converters, many embedded microprocessors include a variety of timers as well. One of the most common types of timers is the Programmable Interval Timer (PIT). A PIT may either count down from some value to zero, or up to the capacity of the county register, overflowing to zero. Once it reaches zero, it sends an interrupt to the processor indicating that it has finished counting. This is useful for devices such as thermostats, which periodically test the temperature around them to see if they need to turn the air conditioner on, the heater on, etc.

Time Processing Unit (TPU) is a sophisticated timer. In addition to counting down, the TPU can detect input events, generate output events, and perform other useful operations.

Pulse Width Modulation (PWM) block makes it possible for the CPU to control power converters, resistive loads, motors, etc., without using lots of CPU resources in tight timer loops.

Universal Asynchronous Receiver/Transmitter (UART) block makes it possible to receive and transmit data over a serial line with very little load on the CPU. Dedicated on-chip hardware also often includes capabilities to communicate with other devices (chips) in digital formats such as I2C and Serial Peripheral Interface (SPI).

Computer – Microcontroller Communication

The need to provide data transfer between a computer and a remote terminal has led to the development of serial communication. Serial data transmission implies transfer data transfer bit by bit on the single (serial) communication line.

In case of serial transmission data is sent in a serial form i.e. bit by bit on a single line. Also, the cost of communication hardware is considerable reduced since only a single wire or channel is require for the serial bit transmission. Serial data transmission is slow as compared to parallel transmission [22].

However, parallel data transmission is less common but faster than serial transmission. Most data are organized into 8 bit bytes. In some computers, data are further organized into multiple bits called half words, full words. Accordingly data is transferred sometimes a byte or word at a time on multiple wires with each wire carrying individual data bits. Thus transmitting all bits of a given data byte or word at the same time is known as parallel data transmission.

Parallel transmission is used primarily for transferring data between devices at the same site. For e.g.: communication between a computer and printer is most often parallel, so that entire byte can be transferred in one operation.

Transfer

Serial communication transfers one data bit at a time, while parallel communication transfers many data bits at a time. Serial communication transmits data bits sequentially, while parallel communication transmits data bits simultaneously allowing larger amounts of data to be transferred.

Serial communication requires less wires and cables and is ideal for transferring data over long distances. Parallel data transmission uses more wires but transfers data rapidly means parallel communication is much faster than serial communication

HVAC

HVAC (Heating, Ventilation, and Air Conditioning) refers to technology of indoor or automotive environmental comfort. HVAC system design is a major sub discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. Refrigeration is sometimes added to the field's abbreviation as HVAC&R or HVACR, or ventilating is dropped as in HACR (such as the designation of HACR-rated circuit breakers).

HVAC is important in the design of medium to large industrial and office buildings such as skyscrapers and in marine environments such as aquariums, where safe and healthy building conditions are regulated with temperature and humidity, as well as "fresh air" from outdoors.

The primary use of HVAC is to regulate room temperature, humidity, and air flow, ensuring that such elements remain within their acceptable ranges. Effective control of such factors minimizes health-related risks. A very humid atmosphere impairs the body’s ability to regulate body temperature as it prevents the evaporation of sweat. High humidity also decreases physical strength, which usually leads to fatigue. An unhealthy surrounding can also affect people’s thinking abilities. Hypothermia, heat stroke, and hyperpyrexia, among others, are some of the illnesses that may also occur.

Three Functions of HVAC

Heating is significant in maintaining adequate room temperature especially during colder weather conditions. There are two classifications of heating: local and central. The latter is more commonly used because it is more economical. Furnace or boiler, heat pump, and radiator make up the heating system.

Ventilation, on the other hand, is associated with air movement. There are many types of ventilation, but they all function similarly. Ventilation is necessary to allow carbon dioxide to go out and oxygen to get in, making sure that people are inhaling fresh air. Stagnant air causes the spreading of sickness, usually airborne, and allergies. But it is also essential to maintain an efficient ventilation system, especially in the attics. Insufficient ventilation usually promotes the growth of bacteria and fungi such as molds because of high humidity. It will also decrease the effectiveness of rafter and roof sheathing insulation because of water vapor condensation.

The air-conditioning system controls the heat as well as ventilation. They often come in different sizes. Most air conditioners have large air ducts, so it is better to check out the building first to see if they can be installed. Or else, can use the split system or remote coils. It is necessary, though, that air ducts are properly cleaned. Pathogens thrive in dirty air ducts. Return-air grills are also vulnerable to chemical, microbiological, and radiological elements. Thus, HVAC return-air grill height should be that it is not accessible but visible for any observation.

Thermistor

Thermistors are inexpensive, easily-obtainable temperature sensors. They are easy to use and adaptable. Circuits with thermistors can have reasonable output voltages - not the mill volt outputs thermocouples have. Because of these qualities, thermistors are widely used for simple temperature measurements. They're not used for high temperatures, but in the temperature ranges where they work they are widely used. Thermistors are temperature sensitive resistors. All resistors vary with temperature, but thermistors are constructed of semiconductor material with a resistivity that is especially sensitive to temperature. However, unlike most other resistive devices, the resistance of a thermistor decreases with increasing temperature. That's due to the properties of the semiconductor material that the thermistor is made from. For some, that may be counterintuitive, but it is correct. Here is a graph of resistance as a function of temperature for a typical thermistor. Notice how the resistance drops from 100 kW, to a very small value in a range around room temperature. Not only is the resistance change in the opposite direction, but the magnitude of the percentage resistance change is substantial [19].

Advantages of using Thermistor

-They are inexpensive, rugged and reliable.

-They respond quickly.

Disadvantages of using Thermistor

-They can’t be used in measuring high temperatures.

- The measured temperature should be converted from oK into oC .

Thermocouple

A thermocouple is a junction formed from two dissimilar metals. Actually, it is a pair of junctions. One at a reference temperature (like 0 oC) and the other junction at the temperature to be measured. A temperature difference will cause a voltage to be developed that is temperature dependent. Thermocouples are widely used for temperature measurement because they are inexpensive, rugged and reliable, and they can be used over a wide temperature range. In particular, other temperature sensors (like thermistors and LM35 sensors) are useful around room temperature, but the thermocouple can [20].

Advantages of using Thermocouple

-They are inexpensive.

-They are rugged and reliable.

-They can be used over a wide temperature range.

Disadvantages of Using Thermocouple

-It is not easy to be used to measure room temperature.

-It is not practical to be used on moving vehicle like a smart guard. -At some cases it can’t measure high temperatures.

-It produces a volt and then this volt is converted so it is not practical.

LM35

The LM35 is an integrated circuit sensor that can be used to measure temperature with an electrical output proportional to the temperature (in oC). user can measure temperature more accurately than a using a thermistor. The sensor circuitry is sealed and not subject to oxidation, etc. The LM35 generates a higher output voltage than thermocouples and may not require that the output voltage be amplified.

The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package [22].

How does LM35 WORK?

It has an output voltage that is proportional to the Celsius temperature. The scale factor is .01V/oC. The LM35 does not require any external calibration or trimming and maintains an accuracy of +/-0.4 oC at room temperature and +/- 0.8 oC over a range of 0 oC to +100 oC. Another important characteristic of the LM35DZ is that it draws only 60 micro amps from its supply and possesses a low self-heating capability. The sensor self-heating causes less than 0.1 oC temperature rise in still air [23].

Advantages of using LM35

-It is an integrated circuit so it can be easily used and fixed on bread board to be movable and usable at any place.

-It measures the temperature in oC and that is better and more practical. -It produces a linear output.

Motion Detection

A motion detector is a device that contains a physical mechanism or electronic sensor that quantifies motion that can be either integrated with or connected to other devices that alert the user of the presence of a moving object within the field of view. They form a vital component of comprehensive security systems, for both homes and businesses.

Overview

The principal methods by which motion can be electronically identified are optical detection and acoustical detection. Infrared light or laser technology may be used for optical detection. Motion detection devices, such as motion detectors, have sensors that detect movement and send a signal to a sound device that produces an alarm or switch on an image recording device.

An electronic motion detector contains a motion sensor that transforms the detection of motion into an electric signal. This can be achieved by measuring optical or acoustical changes in the field of view. Most motion detectors can detect up to 15–25 meters (50–80 feet).

A motion detector may be connected to a burglar alarm that is used to alert the home owner or security service after it detects motion. Such a detector may also trigger a red light camera or outdoor lighting. An occupancy sensor is a motion detector that is integrated with a timing device. It senses when motion has stopped for a specified time period in order to trigger a light extinguishing signal. These devices prevent illumination of unoccupied spaces like public toilets. They are widely used for security purposes.

Sensors:

There are basically four types of sensors used in motion detectors spectrum:

• 
  
  1-Passive infrared sensors (Passive)
  Looks for body heat. No energy is emitted from the sensor.
  
  
• 
  
  2- Ultrasonic (active)
  Sends out pulses of ultrasonic waves and measures the reflection off a moving
  
  
  object.
• 3- Microwave (active)
  Sensor sends out microwave pulses and measures the reflection off a moving object. Similar to a police radar gun.
  4- Tomographic Detector (active)

Senses disturbances to radio waves as they travel through an area surrounded

by mesh network node.

IP Cameras

Hidden camera and surveillance camera equipment let the householders know what happens when they are absent from the place in question. Surveillance cam can be used to watch over elder parent, home, business, and employees.

Possibilities of Surveillance Cameras:

•A very inexpensive tiny wireless surveillance camera, full color, up to 100 feet line- of-sight, 1/3" color camera with a built-in transmitter.

•A wireless hidden camera/clock system, cleverly concealed inside a working, attractive wall clock—contains a hidden transmitter and a pinhole, hidden camera built inside the unit. This surveillance cam wall clock system is perfect for permanent observation system, although it can be moved easily.

•A wireless color hidden surveillance camera kit easily sends wireless video signals to the receiver and can penetrate through walls and windows. The receiver should be connected to a TV, VCR, or a monitor.

•Wireless hidden cameras disguised as everyday objects such as a plant, lamp, teddy bear, smoke alarm, cell phone, ball cap, book and many more.

•Wired hidden cameras, cheaper than their wireless counterparts, are also simple to use and take less than 10 minutes to completely set up! Some options for wired surveillance cams are a boom box, desk clock, surveillance clothing button or a vcr. These are perfect where total covert operations are a must!

•Pinhole Surveillance Cameras are oh-so convenient and offer 3 to 5 hours of operation power. Pinhole cameras are used when a larger security camera will not fit into the environment. The camera can be placed in a tissue box or any other household or office item. This surveillance cam also comes in a kit.

•A Bullet Camera is a very high-quality, compact, security camera. The camera is easily concealed and is for indoor or outdoor use. It’s weatherproof, but not waterproof.

•A covert surveillance pen camera video cam is versatile, compact, and very portable. It produces a strikingly high-resolution video and offers easy plug and play operation, even for beginners

TYPES OF SURVEILLANCE CAMERAS

With growing security concerns and increasing crime rates, the need to protect homes and offices has increased manifold. Surveillance cams or hidden cameras help in keeping an eye on things when people are not around. These are also used in crowded places like stores to nab shoplifters.

There are many types of surveillance cameras available today. Some of these include wireless hidden cameras, wired hidden cameras, pinhole surveillance camera, bullet camera, pen cameras, night vision cameras, indoor cameras and outdoor cameras.

The wireless surveillance camera is small in size, light in weight and requires only low power to operate. It has a hidden transmitter and receiver. It has a line of sight up to 300 feet (some cameras have a line of sight up to 1000 feet) and the signals it sends and receives can penetrate through walls and windows. These cameras due to their small size can be disguised as everyday objects like toys, lamps, smoke alarms, cell phone, wall clocks, books and more.

Wired surveillance cameras are cheaper than the wireless ones. They can be configured with ease. They can be set up in speakers, clocks, VCRs, smoke detectors or a cassette player. Pinhole cameras are used when a larger surveillance cam can't fit into the available space. They provide 3-5 hours of operation power. They can be placed in tissue boxes or any household item.

A bullet camera is a very sophisticated and compact device suitable for indoor and outdoor use. It is weather proof and consumes extremely low power. It also has CCD area image sensors to guarantee durability and long life.

A cover pen camera is most suitable for undercover operations. In a pen camera, a small camera is placed inside a pen. The transmission range is 180 feet and it produces good quality color images. It can place it in a shirt pocket, desk, and purse.

Night vision cameras help to carry out surveillance activities in the night. They produce fantastic color images. These cameras have a special lens for day time viewing and Infra-Red LEDs for night operations.

Surveillance cams have now become the most preferred tools for setting up a home or office security system.

TYPES OF WIRELESS CAMERAS

Standard Wireless Cameras- These cameras though small and discreet, still look like surveillance devices. No doubt, anyone in the same room will understand they are "being watched" if they notice one of these high tech looking devices pointing their way. Standard Wireless web cameras, like any digital product grow more expensive as the features and technical specs become more "high end."

Higher end means better picture quality, and housing options. Keep in mind, many of the lower price wireless web cameras have many features such as pan, tilt, zoom, motion detection, email forwarding of images etc...

The price difference has to do with the quality of the components, not necessarily the features.

TYPES OF IP CAMERAS

An IP camera, also called a network camera, is a camera with an IP network connection. It can also be described as a camera and computer combined into one unit. Captured video is transported over an IP network via network switches and is recorded to a PC server with video management software.

Different types of cameras:

•Fixed IP Cameras

•Dome IP Cameras

•Wireless IP Cameras

•Indoor IP Cameras / Outdoor IP Cameras •PTZ IP Cameras (Pan/Tilt/Zoom)

IP CAMERAS VS. CCTV ANALOG CAMERAS

Aside from how they’re connected and accessed, IP cameras surpass their analog predecessors with advanced features such as video motion detection, alarm handling, audio monitoring, and audio alarms.

INDOOR / OUTDOOR

IP cameras are designed for indoor use only or both indoor and outdoor use. A protective housing for the camera or a certain lens (to regulate the amount of light) may be necessary for outdoor use.

DAY / NIGHT

IP cameras can also offer day and night functionality with use of a IR-cut filter or IR- blocking filter that improves light sensitivity to provide clear, high quality black and white images at nighttime. IR illuminators can also be used in conjunction with an IR- sensitive camera to further enhance quality during low-light or nighttime periods. Thermal IP Cameras are also available that use thermal imaging, which allows users to detect people, objects and incidents in complete darkness and difficult conditions such as smoke, haze, dust and light fog.

IP CAMERA FUNCTIONS

Other useful functions that IP cameras offer are:

• EIS (Electronic Image Stabilization): The camera’s processor will automatically stabilize images in areas with high wind or heavy vibrations.

• Privacy Masking: Sensitive areas of a scene can be blocked or masked from an operators view.

• E-Flip: To ensure images will not be viewed upside down from a PTZ camera there is an electronic rotation of the image when a person passes directly underneath.

TYPE	FEATURES
Fixed IP Camera	Viewing angle fixed once mounted Exchangeable lenses Indoor/outdoor installation Traditional camera type with high visibility
Fixed Dome IP Camera	Fixed camera in small dome housing Discreet non-obtrusive design - camera angle indeterminable Tamper resistant Vari-focal lens (field of view adjustment) No external housing required - often designed with vandal resistant or, IP66-rated enclosure for outdoor use Wall/ceiling mount
PTZ IP Camera(Pan, Tilt, Zoom)	Pan, tilt, and zoom thru auto or manual control Primarily used indoors with an operator Visible camera angle DOES NOT have full 360° pan & is not made for continuous “Guard Tours” Optical zoom from 10X to 26X Wall/ceiling mount
Non-mechanical-PTZ IP Camera	Viewing angle of 100° to 180° with use of megapixel

	sensor & wide-angle lens Zoom requires NO mechanical movement Non-mechanical = NO wear & tear Ideal for discreet install. - camera angle not visible Wall mount
PTZ Dome IP Camera	Wide area coverage with great pan/tilt/zoom flexibility 360° Pan 180° Tilt Ideal for discreet install. - Works well with drop ceilings and camera angle not visible Continuous Guard Tour mode (camera is mechanically robust for this app.) Indoor/outdoor install. All commands sent over IP network. RS-485 wires not needed.
Day & Night IP Camera	Day & Night functionality can be offered w/all camera types (Fixed, Fixed Dome, PTZ) Indoor/outdoor install. IR-cut filter or IR-blocking filter is used when camera switches to night mode IR-illuminator can be used in conjunction with camera if 24/7 surveillance is necessary in low-light areas
Megapixel IP Camera	Minimum resolution of 1280×1024 pixels allows greater detail Covers larger part of a scene than non-megapixel camera in a comparable scale Detailed images clearly identify people or images Offered with Fixed, Fixed Dome, & Wireless network cameras Requires higher bandwidth & storage space.