LITERATURE REVIEW
2.0 INTRODUCTION
Motion sensors are very effective in detecting burglars by their movement which greatly improves security and safety of homes. For burglars, breaching homes could even be more difficult and impossible because of the motion sensors turning the house into several layers of security. (Raub, 2016). Home security systems greatly improved throughout the years. Instead of only an alarm during a breach, a home monitoring and remote-control system has been made with improvements which can send and receive information via SMS to have communication with the home owners against home intrusions (Ahmad, A., Jan, N., Iqbal, S., & Lee, C., 2011). However, the home security systems from the word itself focus only in security by sending alerts of intrusions. Other safety measures at home should also be well considered especially of possible fire outbreaks which is. quite common in the community in the country of Philippines.
A microcontroller-based burglar system that uses SMS message alert has also been made. It uses motion sensors to detect burglars’ movements causing the device to alarm and send an alert message maximizing the security through the notification of unusual and suspicious movements. But the device was made with cable wires which can easily be disabled if wires are to be destroyed. It has no emergency or backup power which can be a great strength for burglars to breach by first eliminating the power source. The device was also limited to monitoring a small coverage due to lack of resources for more motion’s sensors and additionally for its improvement recommends a better quality of motion sensors to be used as not to be easily tampered with (Barcos, C. Q., 2015). There is also a security system that uses wireless connection through the internet to be alerted of home status and to remotely control the electronic appliances even if away from home. It provides many benefits given the good features of home automation and a more convenient and user-friendly type of interface for the whole system. However, of the many advantages of a wireless connection, there are threats that also become present to the system. Burglars can just relax and freely breach the system by tampering with the wireless transmission, so there have been made wireless intrusion detectors (Kumar & Kumar, 2013).
2.1 Research
2.1.1Burglar Alarms
Most burglar alarm systems run from a fixed 12V power supply. This is also the standard operating supply voltage for usual subsystems such as any ultrasonic, PIR, heat, pressure or magnetic sensors etc also the majority of the Strobe flashing lights and sirens available also run from 12V. Bearing this knowledge in mind, my burglar alarm control panel should run from a 12V supply, and when an alarm output has to be activated, a supply of 12V should be supplied. A standard also exists for how input sensors operate [M.J Charadva,, R. V Sejpal et al, 2014]. They normally use a normally closed (N.C.) loop for sensors, so that an alarm condition is signaled by a switch being opened within the sensor and cutting the circuit. This also means that should a burglar cut the wires to a sensor, then the loop will be cut and an alarm signal is generated. Most commercial burglar alarms have the capability to monitor the input sensors separately, so that in the event of a burglary, it is known which sensors were and were not triggered so that the point of entry and extent of break in can be deduced.
2.1.2 Microcontroller
A microcontroller (also MCU or µC) is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timers, and watchdog, serial and analog I/O etc. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a, typically small, read/write memory. Thus, in contrast to the microprocessors used in personal computers and other high performance applications, simplicity is emphasized. Some microcontrollers may operate at clock frequencies as low as 32 KHz, as this is adequate for many typical applications, enabling low power consumption (millwatts 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. Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, remote controls, office machines, appliances, power tools, and toys. 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
2.1.3 Analog to Digital Converter
An analog-to-digital converter (abbreviated ADC, A/D or A to D) is a device which converts continuous signals to discrete digital numbers. The reverse operation is performed by a digital-to-analog converter (DAC). Typically, an ADC is an electronic device that converts an input analog voltage (or current) to a digital number. However, some non-electronic or only partially electronic devices, such as rotary encoders, can also be considered ADCs. The digital output may use different coding schemes, such as binary, Gray code or two's complement binary [S.S.Kapre, S.S.Salunkhe, 2014].
2.2 TRANSDUCERS
This section deals with the various possible sensor designs and how they function and which could be appropriate for particular case.
2.2.1 Infrared motion detector
2.2.1.1 Passive Infrared sensor (PIR sensor
Passive Infrared sensor (PIR sensor) is an electronic device that measures infrared (IR) light radiating from objects in its field of view. PIR sensors are often used in the construction of PIR-based motion detectors (see below). Apparent motion is detected when an infrared source with one temperature, such as a human, passes in front of an infrared source with another temperature, such as a wall.
All objects emit what is known as black body radiation. It is usually infrared radiation that is invisible to the human eye but can be detected by electronic devices designed for such a purpose [R.Dellosa, 2014]. The term passive in this instance means that the PIR device does not emit an infrared beam but merely passively accepts incoming infrared radiation. In passive infrared motion detectors, a sensor containing an infrared-sensitive phototransistor is placed in the area to be protected. Circuitry within the sensor detects the infrared radiation emitted by the intruder's body and triggers the alarm. The problem with using this type of detector is that it can be falsely triggered by warm air movement or other disturbances that can alter the infrared radiation levels in an area. In order to prevent this problem, newer systems use two infrared sensors which monitor different zones within a protected area. Logic within system triggers the alarm only when the two zones are activated in sequence, as would occur if a person walked through the protected area.
Pyroelectric Sensors
The pyroelectric sensor is made of a crystalline material that generates a surface electric charge when exposed to heat in the form of infrared radiation. When the amount of radiation striking the crystal changes, the amount of charge also changes and can then be measured with a sensitive FET device built into the sensor. The sensor elements are sensitive to radiation over a wide range so a filter window is added to the TO5 package to limit detectable radiation to the 8 to 14mm range which is most sensitive to human body radiation.
Typically, the FET source terminal pin 2 connects through a pull-down resistor of about 100 K to ground and feeds into a two-stage amplifier having signal conditioning circuits. The amplifier is typically bandwidth limited to below 10Hz to reject high frequency noise and is followed by a window comparator that responds to both the positive and negative transitions of the sensor output signal. A well filtered power source of from 3 to 15 volts should be connected to the FET drain terminal pin 1.
Figure 1.1
The PIR325 sensor has two sensing elements connected in a voltage bucking configuration. This arrangement cancels signals caused by vibration, temperature changes and sunlight. A body passing in front of the sensor will activate first one and then the other element whereas other sources will affect both elements simultaneously and be cancelled. The radiation source must pass across the sensor in a horizontal direction when sensor pins 1 and 2 are on a horizontal plane so that the elements are sequentially exposed to the IR source. A focusing device is usually used in front of the sensor.
Figure 2.2
Fresnel lens
A Fresnel lens (pronounced Frennel) is a Plano Convex lens that has been collapsed on itself to form a flat lens that retains its optical characteristics but is much smaller in thickness and therefore has less absorption losses.
Figure 2.3
Our FL65 Fresnel lens is made of an infrared transmitting material that has an IR transmission range of 8 to 14um which is most sensitive to human body radiation. It is designed to have its grooves facing the IR sensing element so that a smooth surface is presented to the subject side of the lens which is usually the outside of an enclosure that houses the sensor. The lens element is round with a diameter of 1 inch and has a flange that is 1.5 inches square. This flange is used for mounting the lens in a suitable frame or enclosure. Mounting can best and most easily be done with strips of Scotch tape. Silicone rubber can also be used if it overlaps the edges to form a captive mount. There is no known adhesive that will bond to the lens material [P.Kharat, and J. Khara, 2014].
The FL65 has a focal length of 0.65 inches from the lens to the sensing element. It has been determined by experiment to have a field of view of approximately 10 degrees when used with a PIR325 Pyroelectric sensor.
Figure 2.4
This relatively inexpensive and easy to use Pyroelectric Sensor and Fresnel Lens can be used in a variety of science projects, robots and other useful devices.
2.2.1.2 Active Infrared Motion Detector
Figure 2.5
Figure 2 shows the operation of an active infrared motion detector. In the active system each sensor consists of two housings. One housing contains an infrared-emitting diode and an infrared-sensitive phototransistor. The other housing contains an infrared reflector. When positioned in front of an entrance to a protected area, the two housings establish an invisible beam. A person entering the area interrupts the beam causing an alarm to be triggered. An active motion detector is much more reliable than a passive one, but it requires careful alignment when it is installed. The detector can be falsely triggered if one of the housings moves slightly and causes a discontinuous beam.
2.2.1.3 Magnetic reed switches
Though a house is well protected by installing break proof doors and windows it is necessary to monitor the conditions of the door. This can be done by installing small magnetic switches inside the frame. This activates the alarm when it is disturbed.
Figure 2.6
2.2.1.4 Breaking glass detector
Modern glass break detectors consist of small microphone connected to a sound processor. The microphone is tuned to the frequency of breaking glass, and the processor looks for a characteristic sound pattern. Additionally, the shock sensor detects the tiny shock wave that passes all through the building when a window suffers an impact. Only when there is sound of breaking glass, and a shock wave, will the alarm sound. Thus, they are tremendously immune to environmental noise which might cause a false alarm. Glass break detectors must be located within a range of the glasses to protected, usually ten feet or so. Additionally, heavy window treatments can significantly reduce the effective range. Up to now the windows and doors are covered
2.2.1.5 Ultrasonic Motion Detectors
Ultrasonic transducers can be used to detect motion in an area where there are not supposed to be any moving objects. This type of motion detector is most commonly used in burglar alarm systems since they are very effective in this application [J. Bangali , and A. Shaligram, (2013)]. Figure 2.7 shows the operation of an ultrasonic motion detector. There are two transducers: one emits an ultrasonic wave and the other picks up reflections from the different objects in the area. The reflected waves arrive at the receiver in constant phase if none of the objects in the area are moving. If something moves, the received signal is shifted in phase. A phase comparator detects the shifted phase and sends a triggering pulse to the alarm.
Ultrasonic motion detectors have certain advantages and disadvantages when compared with other types of motion detectors. The main advantages are that they are very sensitive and extremely fast acting. However, the largest problem with this type of motion detector is that it sometimes responds to normal environmental vibration that can be caused by a passing car or a plane overhead. Some types of motion detectors use infrared sensors to avoid this problem, but even these detectors have some problems
Figure 2.7
2.2.1.5.1 LV-MaxSonar-EZ1High Performance Sonar Range Finder
With 2.5V - 5.5V power the LV-MaxSonar-EZ1 provides very short to long range detection and ranging, in an incredibly small package. The LV-MaxSonarEZ1detects objects from 0-inches to 254-inches (6.45-meters) and provides sonar range information from 6-inches out to 254-incheswith 1-inch resolution. Objects from 0-inches to 6-inches range as 6-inches. The interface output formats included are pulse width output, analog voltage output, and serial digital output.
Features
Continuously variable gain for beam control and side lobe suppression
Object detection includes zero range objects
2.5V to 5.5V supply with2mA typical current draw
Readings can occur up to every 50mS, (20-Hz rate)
Free run operation can continually measure and output range information
Triggered operation provides the range reading as desired
Designed for protected indoor environments
Sensor operates at 42 KHz
Benefits
Very low cost sonar ranger
Reliable and stable range data
Sensor dead zone virtually gone
lowest power ranger
Quality beam characteristics
Mounting holes provided on the circuit board
Very low power ranger, excellent for multiple sensor or battery based systems
Can be triggered externally or internally
Sensor reports the range reading directly, frees up user processor
Beam Characteristics
People detection requires high sensitivity, yet a narrow beam angle requires low sensitivity. The LV-MaxSonarÒ-EZ1Ô balances the detection of people with a narrow beam width. Sample results for measured beam patterns are shown below on a 12-inch grid. The detection
Pattern is shown for;
0.25-inch diameter dowel, note the narrow beam for close small objects,
1-inch diameter dowel; note the long narrow detection pattern,
3.25-inch diameter rod, note the long controlled detection pattern,
11-inch wide board moved left to right with the board parallel to the front sensor face and the sensor stationary. This shows the sensor’s range capability.
Note: The displayed beam width of (D) is a function of the secular nature of sonar and the shape of the board (i.e. flat mirror like) and should never be confused with actual sensor beam width.
2.2.2 VARIOUS APPROACH.
In order to design this project, the main decision I need to make is what approach I will take for the main alarm processing. In this chapter discussion of these designs dealt with and the reason why one design was chosen.
2.2.2.1 Discrete Component Based Design
This is one of the earliest forms of design which involve discrete components to build the digital systems.
Disadvantages:
Huge power consumption
Large size of a complete system
Difficult to debug the complete system
These systems includes the use of digital gates such as NAND, AND , NOR gates etc .such as 74yy series. To build the system as stated the following components would be used
AND, OR gates
Delay circuits that can be implemented using flip-flop,555 timer ICS.
Motion detector such as infrared motion detector would involve infrared sensitive transistor that are biased to conduct by infrared emitted energy
Generally, if these projects where to be implemented using this way it would be quite bulky expensive and very hard to trouble shoot it in case of failure.
2.2.2.2 COMPUTER BASED DESIGN
Computers are very powerful device that can implement the control unit with minimum components. The only important part is the interface between the sensors, switches, alarm and buzzer to the computer. This can be done through the 1pt printer port (parallel port) which has eight pins and five input pins. To get more pin one can add another input card or include a microcontroller to communicate with the computer serially. By writing software to manipulate the voltage at these pins one is able to scan the conditions of the sensor and perform the appropriate action .However to interface the circuit to computer one as to be careful as the parallel port only accept up to a maximum of 5volts.while things like relay switches ear usually accompanied by the transient which are be harmful to the printer port. These demands use of optiosolator to electrically separate the computer from the external circuits [G.M.Joseph, E.L.Nwankwo, 2015].
Limitations for computer-based design:
High cost of computer
The computer has to be continuously, this means the need for dedicated computer which is uneconomical
Due to constant power losses there is need to include power backups which and the cost.
2.2.2.3 MICROCONTROLER BASED DESIGN
Circumstances that we find ourselves in today are in the field of microcontrollers which had their beginnings in the development of technology of integrated circuits. This development has made it possible to store hundreds of thousands of transistors in to one chip. That was a perquisite for production of microprocessors, and the first computers were made by adding external peripheral such as memory, input –output lines timers and other further increasing of the volume of the package resulted in creation of integrated circuits. these integrated circuits contained both processor and peripherals. That is how the first chip containing a microcomputer, or what would later be known as microcontroller came about. Microcontroller differs from microprocessor in many ways. First and fore most important is its functionality. In order for a microprocessor to be used other components such as memory, or components for receiving and sending data must be added to it .in short that means that microprocessor is very heat of computer in other hand microcontroller is designed to be all of that in one. No other external component is needed for its application because all necessary peripherals are already built into it, thus we save the time and space needed to construct devices [R.K.Mendoza, 2016].
In this project microcontroller will form the heart of the system. This would perform the function of polling sensors interpreting input and perform the necessary action. This is so because using instead of using intelligent sensor s that would be reporting to central unit the project will utilize dump sensors. Most microcontrollers come with several ports than several bit wide for example in this case the Atmega168 from Atmel Company has two 8bit ports and one 7bit port. These ports can be connected to the various sensors whose high condition are 5.5volts and low are 1.8volts.
Advantages of microcontroller-based design
Can be produced in small packages that users can be able to configure on their own
Low Power Consumption thus cheap to maintain can be run by batteries -Active Mode: 250 μA at 1 MHz, 1.8V15 μA at 32 kHz, 1.8V (including Oscillator) – Power-down Mode: 0.1μA at 1.8V
They stand alone equipment that require little maintenance.
They are easy to debug in case of fault as they consist of very few co-peripheral components.
They are easy to upgrade due to compatibility of AVR microcontrollers of differed series for example the code written for ATmega48 can be run in ATmega88 with minor modification.
The ATmega48/88/168 has Advanced RISC Architecture (reduced instruction set computer).
131 Powerful Instructions – Most Single Clock Cycle Execution
32 x 8 General Purpose Working Registers
Fully Static Operation
Up to 20 MIPS Throughput at 20 MHz
On-chip 2-cycle Multiplier
Thus, they are easy to learn and develop software having in mind the need to shorten development time and reduce time to market. This is very important aspect in modern world.
High Endurance Non-volatile Memory segments
4/8/16K Bytes of In-System Self-programmable Flash program memory
256/512/512 Bytes EEPROM
512/1K/1K Bytes Internal SRAM
Write/Erase cycles: 10,000 Flash/100,000 EEPROM
Data retention: 20 years at 85°C/100 years at 25°C
Optional Boot Code Section with Independent Lock Bits In-System Programming by On-chip Boot Program True Read-While-Write Operation
Programming Lock for Software Security
Thus, reduce cost of field up grades since the cost of upgrading a system code can be dramatically reduced. with very little effort and planning, flash based system can be designed to have code upgrades in the field for AT mega FLASH device the entire code can be rewritten with new code new code segments and parameter tables can be easily added in program memory areas left blank for upgrade purpose, only portion of code (such as key algorithm) require update. • Calibration and customization of your system
Calibration need not be done only in factory during installation of the system can be calibrated to actual operating environment. In fact, recalibration can be easily done during periodic servicing and maintenance.
Customization need not to be done in factory only. In many situations customizing a product at installation time is very useful. .a good example is a home or car security systems where ID code, access code and other such information can be burned in after the actual configuration is determined [A.VBhatkule, 2016].
Add unique Id code to your system during manufacturing.
Many products require a unique ID number or a serial number. An example application would be remote keyless entry device. Each transmitter has a unique “binary key” that makes it very easy to program in the access code at the very end of the manufacturing process and prior to final test. Serial number, revision code, date code, manufacture ID and a variety of other useful information can also be added to any product for traceability