4. System Implementation
4.1. Electronic Circuit Design
MHSS is divided into three levels as shown in Figure 2. Each level has different sensor nodes which identifies of stimulants. Each electronic component serves its role
International Journal of Smart Homebased on the arrangement of the respective location. Each component is placed according to system level.
International Journal of Smart Homebased on the arrangement of the respective location. Each component is placed according to system level.
Figure 2. Overall Block Diagram of the Multi Level Security System
4.1.1. System sensor nodes: As shown in Figure 3, 6v power source is supplied to power up the system. The output of each level of MHSS is passed to a PIC that will trigger the following tasks such as turn on the light bulbs and switch on the camera and sending emails. The output signal of each sensor is directed to PIC, and then the “high” or “low” signal will be delivered to the Intel Processor and eventually interpreted in a developed graphical user interface (GUI). A responsive signal will return to the output components such as light bulbs, buzzer and webcam to perform the appropriate programmed functions.
4.1.1. System sensor nodes: As shown in Figure 3, 6v power source is supplied to power up the system. The output of each level of MHSS is passed to a PIC that will trigger the following tasks such as turn on the light bulbs and switch on the camera and sending emails. The output signal of each sensor is directed to PIC, and then the “high” or “low” signal will be delivered to the Intel Processor and eventually interpreted in a developed graphical user interface (GUI). A responsive signal will return to the output components such as light bulbs, buzzer and webcam to perform the appropriate programmed functions.
Figure 3. Block Diagram of the Electronic Components Arrangement
4.1.2. Gate Sensor Nodes:
The circuit is positioned as the first level of MHSS which acts as the indicator. Light Dependent Resistance (LDR) is put at a location where it can detect thieves. Laser diode is used as the light source and the laser beam is adjusted with a reflector to make the beam fall on the LDR. An input source of 5 V is supplied to the laser sensor and LDR. They are arranged in a manner that when the laser beam is blocked by a thief, an output approximately from 3.5 to 4 V is supplied to the LM324, then it will be compared with the reference voltage of 2.5V. Generally, 5V will be supplied by LM324 to the microcontroller as a high signal. The laser sensors can be placed on the wall of the house yard. The output of the sensor, 5V will be directed to the PIC and the responding signal will turn on the light bulbs that placed at the sides of the entrance.
4.1.3. Presence Detecting Node:
A passive infrared sensor (PIR) is placed at side of the house yard and the central position of the wall. It acts as the second level of MHSS. The sensor output voltage is 0.3v when there is no motion detected. When the sensor senses the motion of a thief, its output range of 3.3 to 5v and it will be sent to the signal control unit. Then, it will be processed in the CPU and eventually it will make the webcam start recording.
4.1.3. Break-in Sensing Node:
The principle of this stage is similar to the first stage. The magnetic switch is supplied with 0 signal and the output will be compared with a reference voltage of 2.5V. When the magnetic switch is opened, an output range of 3.5 to 4v is supplied to LM324 for comparison. Then LM324 will send an output, 5V to the microcontroller. The output is treated as a high signal, the microcontroller eventually send an output of 5V to the LEDs and the buzzer as the responding action to the input signal.
4.2 Microcontroller and UART
The microcontroller used in MHSS is PIC184520 from MicroChip Inc. as shown in Figure 4. This microcontroller is interfaced to a PC via the Universal Asynchronous Receiver/Transmitter (UART). UART takes bytes of data and transmits the individual bits in a sequential fashion. Since the microcontroller makes use of Transistor-transistor Logic (TTL) level of UART while the PC serial port uses RS-232. Since both standards uses similar software protocol, both of them are able to communicate via UART.
Figure 4. PIC184520 from MicroChip
UART enables the communication between the sensor nodes and the GUI to be established. UART is configured so that the functions developed on the GUI can be corresponded to the stimulated signal triggered from sensor nodes. The analogue signal is sent to UART. Then the “high” or “low” signal is delivered to the CPU and the GUI will translate it into an ASCII code as programmed. Then the functionality is based on the ASCII code will be returned by the GUI.
4.2.1 PIC Programming:
UART enables the communication between the sensor nodes and the GUI to be established. UART is configured so that the functions developed on the GUI can be corresponded to the stimulated signal triggered from sensor nodes. The analogue signal is sent to UART. Then the “high” or “low” signal is delivered to the CPU and the GUI will translate it into an ASCII code as programmed. Then the functionality is based on the ASCII code will be returned by the GUI.
4.2.1 PIC Programming:
Figure 5. Overall Process Flow of Security Monitoring
The process is initiated by a power source switch as shown in Figure 5. The triggering of each sensor node results in different sequential actions that are aimed to chase the thieves away. The triggered signal will be sent to a microcontroller to be interpreted. Then a responding signal is directed to output components like light bulbs and buzzer. In the first level of MHSS, the laser sensing sensor is in the standby mode where the sensor is actually waiting for the triggering of external stimulant which refers to the thief’s breaking-in e.g. the gate is opened or the wall is climbed over without switching off the main power source of the system. Once the first level is triggered, the light bulbs will be turned on by the responding signal which directed from the microcontroller unit after receiving the triggered signal. This level is basically to alert the house owners that thief has entered the covered area without any authorized mean.
The next flow of the process is followed by the second level of the MHSS where the unauthorized presence of the thief will trigger the second level system which consists of presence detecting sensor node. In the triggering stage of this level, the second set of light bulbs and the camera are turned on. Then, the third level of MHSS makes the light bulbs of the first and the second level to be turned on since the camera needs a higher brightness level to capture the break-in evidence before it is automatically delivered to the house’s owner and the law enforcement body. The buzzer will also make noise in this stage.
The triggered signal is given approximately two minutes before the whole system is reset. It simply means that the light bulbs will turn off automatically even without any manual action. Then the whole system is restarted. The whole logic is mainly controlled by the main control unit of MHSS which consists of an 18F4520 microchip. If one level has not been stimulated, then the prompting will loop from the specific stage until the specified period has past. Figure 5 summarizes the process flow of the security monitoring of MHSS.
The next flow of the process is followed by the second level of the MHSS where the unauthorized presence of the thief will trigger the second level system which consists of presence detecting sensor node. In the triggering stage of this level, the second set of light bulbs and the camera are turned on. Then, the third level of MHSS makes the light bulbs of the first and the second level to be turned on since the camera needs a higher brightness level to capture the break-in evidence before it is automatically delivered to the house’s owner and the law enforcement body. The buzzer will also make noise in this stage.
The triggered signal is given approximately two minutes before the whole system is reset. It simply means that the light bulbs will turn off automatically even without any manual action. Then the whole system is restarted. The whole logic is mainly controlled by the main control unit of MHSS which consists of an 18F4520 microchip. If one level has not been stimulated, then the prompting will loop from the specific stage until the specified period has past. Figure 5 summarizes the process flow of the security monitoring of MHSS.
4.3 Security System Control GUI
The GUI is developed by using Visual Basic 2010 Express Edition. It is used to display and perform the function that is triggered when the signals are received from the hardware. The signal is sent to the GUI through the signal reflected by the UART which enables the communication between the hardware and the software as discussed in the previous section. This calls the video recording function and image capturing function. It also sends instant messages to the house owners and the police station. As shown in Figure 6, the description of the features is divided into two parts which are section A and section B. The GUI enables the communication between the UART and the computer as well as reading data received from the serial ports.
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