Smart Security SystemSmart homeA smart home is a home which makes it possible for people to control a series of automated domestic electronic equipment and devices remotely by giving commands through special structure wiring. Smart homes connect all the equipment and devices in the house which can communicate with each other and users. The home automation field is increasing rapidly as electronic technologies development and gather. The home network contains communications, security, convenience, and information systems. Smart home technology does not simply switch on and off the devices and equipment, it can monitor the parameters of the indoor environment and the activities that are happening in the house. (Vincent, David, David, Bruno, Laurent, Christophe, 2006) Lots of the same devices which are used in assistive technology are also used in the smart home to develop an environment to make home automated and build communication between devices. (Rosslin and Tai-hoon, 2010)HistoryThe characteristic that defines if it is a smart home or not is the interactive technologies that it uses. Hobbyists built the first ‘wired homes’ in the 1960s. The term ‘smart house’ was first used officially by the American Association of House Builders in 1984. (Richard, 2006, p.1) Smart home, or home automation, started to become popular around 2000. This time, different technology appeared. So smart home gradually became acceptable and affordable. Home networking, indoor technologies, and other equipment began to appear in the shopping mall. Nowadays, smart home mainly focuses on security and living greener. It can help people make their homes sustainable and reduce the consumption of the houses and alert us to intruders.Smart Security systemSafety is the most important and necessary thing in the house for people. With the improvement of economy and science technology especially IT technology and automatic control technology, the role that a smart security monitoring and the alarming system plays becomes more important than before. Security has already been a non-negligible problem in the smart home system. Traditional security systems can provide the basic safety of the house and the household from intruders. A security system usually contains certain parts. Firstly, there is an intrusion detection sensor set near the entries such as doors and windows to sense an intrusion at the entriesHowever, a smart security system can offer more benefits. Life can become easier and more convenient through smart homes. Wherever households are, the smart home will notify them what happened. And a smart security system can provide help in an emergency. For instance, when a fire occurs, not only would the fire alarm alert the resident, but also fans would be switched on automatically to exhaust the smoke which is helpful for rescue. It is necessary for a smart security system to have characteristics such as low cost, simple installation, fast response, and low power consumption.Development board Raspberry Pi 3 MODEL B+ Figure 1 Raspberry Pi 3 MODEL B+ The Raspberry Pi 3 is a small but full-featured computer on a single board. It has Broadcom BCM2837B0 and Cortex-A53 (ARMv8) which is 64-bit and the frequency is 1.4GHz, 1GB RAM, wireless LAN, Bluetooth, Gigabit Ethernet over USB 2.0, extended 40-pin GPIO header, HDMI, four USB 2.0 ports, CSI camera port, DSI display port, 4-pole stereo output and composite video port, Micro SD port for loading your operating system and storing data, 5V/2.5A DC power input and Power-over-Ethernet. It is very easy to connect to the internet and can be programmed through a variety of programming languages. Raspberry Pi is generally used as a server or an arithmetic unit. The system working on the Raspberry Pi is Raspbian which is specially designed. The cost of a Raspberry Pi 3 MODEL B+ is approximately £34. (Raspberry Pi Foundation) BeagleBone BlackFigure 2 BeagleBone BlackBeagleBone Black is a development board based on an AM335x 1GHz ARM® Cortex-A8 processor which has 512MB DDR3 RAM, 4GB 8-bit eMMC flash storage, integrated power management, 2×32-bit 200-MHz programmable real-time units, NEON floating-point accelerator, ARM, Cortex-M3, USB2 client for power and communications, USB2 host, Programmed with Debian Linux. It is widely used in advanced projects such as industrial robotics, drones, and 3D printers. And it can be applied to the projects with a variety of sensors. But this development board whose price is approximately £50 costs a lot more than the other two boards. (BeagleBoard.org Foundation) Arduino and Arduino IDE    Figure 3 Arduino Uno                     Figure 4Arduino Mega 2560 Arduino is a series of development boards. The basic Arduino board based on the ATmega328P is Arduino Uno which has 14 digital pins, 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header, and a reset button. (Arduino) Besides, plenty of options for special needs are also provided such as the board used in the project named Arduino Mega 2560 based on the ATmega2560. Comparing with the Uno, the differences are those it has 54 digital input/output pins, 16 analog inputs, and 4 UARTS which are suitable to connect lots of sensors. The price of an Arduino Mega 2560 is around £27. (Arduino)Microwave SensorFigure 5 Microwave SensorDefinition Microwave sensors, also known as Radar, RF, or Doppler sensors are a type of active intrusion sensors that can detect the movement of every object including humans through the emission regions.Principle Microwave sensors first send out microwave signals through a transmitting antenna. And the microwave will reflex when it collides with objects in the detecting region. This reflexed microwave will be received by the receiving antenna, and time it takes for the microwave to return to the sensor is measured. This is used to detect the current distance from the objects within the detection range. When a person steps in the detecting region, this will interrupt the microwave and therefore will alter the time of returning received by the microwave sensor. This will be regarded as a change in distance from a current object, and the microwave sensor will send out the alert signal.Temperature and humidity sensorDefinitionTemperature and humidity sensors are the sensors that can transfer the data of both air temperature and humidity into the digital signal as the output. Temperature and humidity sensor is one of the most important sensors that has been widely used in industry, medical industry and domestic area, agriculture, and electronic industry.DHT11Figure 6 DHT11DHT11 digital temperature and humidity sensor is a temperature and humidity composite sensor with the calibrated digital signal output. It uses appropriative digital module gathering technology and advanced temperature and humidity sensing technology. Inside this sensor, there is a resistive humidity sensing element and a sensor for Negative Temperature Coefficient (NTC) temperature measuring devices which connect to a high-performance 8-bit microcontroller. The resistive humidity sensing element has two electrodes with moisture holding substrate between them. (Dan-ao, Fei, 2013) The conductivity of the substrate and the resistance between electrodes will change when the humidity changes. And this change is measured by the integrated circuit which can transfer the data into the form that can be read by the microcontroller. To measure the temperature, it uses an NTC temperature measuring sensor which is actually a variable sensor whose resistance is changed with the variation of the temperature. This sensor is made from the sinter of semiconductive materials such as polymers in order to provide obvious changes in the resistance when there is only a little variation of the temperature. The measuring range of both humidity and temperature are 20-90%RH and 0-50°C, and the precision of measuring humidity and temperature are respectively ±5%RH and ±2°C. This sensor is really cheap which only costs £1-3 each.SHT71Figure 7 SHT71SHT71 digital temperature and humidity sensor is a single chip digital sensor which consists of multiple sensor modules and outputs calibrated humidity and temperature. The whole sensor contains a calibrated temperature sensor and a humidity sensor which connect to a 14-bit analog to digital converter, and an Inter-Integrated Circuit (I²C) bus interface. Besides, it uses CMOSens technology which can protect the sensor from the environment, meanwhile, maintain the original characteristics of the capacitive humidity sensor. Even the sensor is immersed in the liquid, there will be no damage to it. Setting all the components on a several cubic millimeters chip can produce lots of benefits. Because of the integration of sensors and the amplifier, not only would the signal intensity and the anti-interference ability be improved, but also the stability would be guaranteed. (Chen, Min, 2003)The operating range of humidity and temperature are 0-100%RH and -40-254.9°C, and the accuracy of measuring humidity and temperature are respectively ±3%RH and ±0.4°C. The price of SHT71 is approximately £30 which is really expensive. Gas and Smoke SensorsDefinitionA gas detector is a device that monitors the concentration of gas in the air in order to prevent the blast of the gas leakage and the poisoning of gas incomplete combustion. A smoke sensor is a detector that monitors the concentration of smoke in the ambient environment in order to alert the resident in time when a fire accident occurs.MQ-2Figure 8 MQ-2MQ-2 is one of the series of semiconductor smoke sensors that mainly focuses on fire smoke for houses, apartments, shops, and commercial buildings. The gas-sensing material it uses is stannic oxide (SnO2) with low conductivity in clean air. When smoke or combustible gas exists in the ambient environment, the conductivity of the sensor will increase with the increase of smoke or combustible gas concentration. It has high sensitivity to smoke, Liquefied Petroleum Gas, Methane, and Butane. The detecting concentration range is from 300ppm to 10000ppm for combustible gas. The circuit voltage and the heating voltage are both 5V±0.1. The load resistance is adjustable. And the heater resistance is 33?. The sensing resistance is from 3K? to 30K?.  The using temperature is from -20°C to 50°C. The price of the MQ-2 is £1-£3.MQ-4Figure 9 MQ-4MQ-4 is one of the series of semiconductor gas sensors that mainly detects the natural gas in the ambient environment. The sensitive material of MQ-4 gas sensor is the stannic oxide (SnO2) whose conductivity is low in clean air. MQ-4 is sensitive to Natural Gas and Methane and is not really sensitive to alcohol and smoke. When there is Natural Gas or Methane in the ambient environment, the conductivity of the sensor will increase with the increase of Natural Gas or Methane concentration. The detecting concentration range is from 200ppm to 10000ppm for Natural Gas and Methane. The sensor resistance varies from 10k – 60k ohms. Both circuit voltage and heating voltage are 5V±0.1. The load resistance is 20k?, and the heater resistance is 33?±5%. The sensing resistance is from 10K? to 60K?. The using temperature is from -10°C to 50°C. The cost of MQ-2 is £1-£3. (Dipanjan, Akash, Sourabh, Sushabhan, 2010) Passive Infrared SensorFigure 10 Passive Infrared SensorDefinitionA passive infrared sensor (PIR sensor) is a device that detects motion of the objects that emits the infrared light which is widely used in the security system.PrincipleThe objects whose temperature is above absolute zero which is -273°C generate heat radiation. And the heat radiation spectrum of the objects whose temperature is below 1725°C gathers in the infrared region which is not visible to the human eye. However, it can be detected by the passive infrared sensor. The term ‘passive’ means the PIR sensor itself does not emit any energy but only accept infrared radiation energy passively. When an intruder steps in the detecting area, because the human has a constant body temperature 37°C which emits a special length infrared which is approximately 10?m, it can be detected by the sensor. The infrared will be enhanced through a Fresnel lens and then focus on the infrared induction module which is usually made of pyroelectric element. Then the temperature of the infrared induction module will vary, and then the signal will be sent out.FanA fan is an apparatus to use rotating blades to create flow within a fluid such as air for cooling or ventilation. A basic fan consists of a rotor which is the rotating assembly of blades and hub, a stator which is used to fix the fan and a control circuit to control the parameters of the fan such as speed. AlarmA security alarm is a system designed to detect intrusion – unauthorized entry – into a building or other area. Security alarms are used in residential, commercial, industrial, and military properties for protection against burglary (theft) or property damage, as well as personal protection against intruders. Security alarms in residential areas show a correlation with decreased theft.[1] Car alarms likewise help protect vehicles and their contents. Prisons also use security systems for the control of inmates.CameraA camera is an optical instrument that can capture images and record videos which can be stored in a physical medium such as a film. The camera is the main instrument in the art of photography and captured images may be reproduced later as a part of the process of photography, digital imaging, and photographic printing.Vemont Full HD 2.0 Inch Action Camera 1080P 12MP Sports CameraAction Camera FMAIS Full HD 1080P WaterproofCrosstour Wifi Action Camera Full HD 1080P Waterproof Global System for Mobile CommunicationDefinitionGlobal System for Mobile Communication (GSM) is a digital mobile communication standard formulated by European Telecommunications Standards Institute (ETSI) currently in service in most regions of the world. GSM uses a variation of Time Division Multiple Access (TDMA) technology. The network structure consists of the Base Station Subsystem, Network and Switch Subsystem which is similar to a fixed network, GPRS Core Network which realizes packet-based Internet connections, and Operations support system for network maintenance.SIM900AThe SIM900A is a GSM/GPRS module that can be used for developing Internet of Things and Embedded Applications. SIM900A’s working frequencies are EGSM 900MHz and DCS 1800MHz. SIM900A supports GPRS multi-slot class 10/ class 8 and the GPRS coding schemes CS-1, CS-2, CS-3, and CS-4. TCP/IP protocol is embedded in the module which is useful in data transmission. It has 68 pins, keyboard and SPI interface, audio input and output, and programmable GPIO. SIM900A can be used in cellular communication, robotics, servers, and automobile.SIM800C    ReferencesVincent, R., David, M., David, D., Bruno, M., Laurent, D., Christophe, L. (2006) ‘The Smart Home Concept: our immediate future’, IEEE, 13(9), pp.23-28.Available at: https://ieeexplore.ieee.org/abstract/document/4152762 (Accessed: 13th November 2018)Rosslin John, R., Tai-hoon, K. (2010) ‘A Review on Security in Smart Home Development’ International Journal of Advanced Science and Technology  pp.13-22 Available at: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.178.1685&rep=rep1&type=pdf (Accessed: 3th November 2018)Richard, H. (2006) Inside the Smart Home Available at: https://books.google.co.uk/books?hl=zh-CN&lr=&id=3J0MBwAAQBAJ&oi=fnd&pg=PA1&dq=smart+home&ots=zngAjFdkkB&sig=X07hvLbGwce2km_fZT-7J_atYxY&redir_esc=y#v=onepage&q=smart%20home&f=false (Download: 30th November 2018)Raspberry Pi Foundation. (n.d.)Raspberry Pi 3 Model B+ – Raspberry Pi. Available at: https://www.raspberrypi.org/products/raspberry-pi-3-model-b-plus/ (Accessed: 11th November 2018)BeagleBoard.org Foundation. BeagleBoard.org – black. Available at: https://beagleboard.org/black (Accessed: 11th November 2018)Arduino. (n.d.) Arduino Uno Rev3. Available at: https://store.arduino.cc/arduino-uno-rev3 (Accessed: 11th November 2018)Arduino. Arduino Mega 2560 Rev3. Available at: https://store.arduino.cc/arduino-mega-2560-rev3 (Accessed: 11th November 2018)HANWEI ELECTRONICS, ‘TECHNICAL DATA MQ-4 GAS SENSOR’https://www.sparkfun.com/datasheets/Sensors/Biometric/MQ-4.pdfDan-ao, H., Fei, W. (2013) ‘Research application of the digital temperature and humidity sensor DHT11’, Electronic Design Engineering, pp.83-85&88, Available at: http://www.cqvip.com/qk/98233a/201313/46341968.html (Accessed: 18th November 2018)Chen, M., Min, L. (2003) ‘Digital Temperature and Humidity Sensor SHT71 Based on I2C Bus and Its Application’, GLOBAL ELECTRONICS CHINA, pp.66-68.Available at: http://www.cqvip.com/qk/90261x/200308/9044634.html (Accessed: 18th November 2018)Dipanjan, B., Akash, K., Sourabh, K., Sushabhan, C. (2010), ‘Design and Development of Wireless Sensor Node’, International Journal on Computer Science and Engineering, 19 (11), pp. 2431-2438. Available at:http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.301.1850&rep=rep1&type=pdf (Accessed: 19th November 2018)