PIC16F877A microcontroller is used to control the whole system. It is designed using flash technology. So the PIC can read/write program for more than 100,000 times. The PIC can store up to 8Kbytes program. A program is downloaded into PIC through PIC programmer. This program will be used to operate the system. The PIC can operate using 4.5V to 6V DC voltage. In the project is operating at 5V (by using 7805).
ZigBee is a standard for wireless data transmission just like Wi-Fi and Bluetooth. The entire device (wireless device) is function to move the desired data to the next carrier in the communications path until the data is delivered to the target end-point. MaxStream is a well-known manufacturer of components for wireless communication. ZigBee is one of the MaxStream products. There are two versions of ZigBee that are available from MaxStream which are XBee and XBee PRO. Both versions are functionally identical and pin compatible. The only difference is the transmit power, which is 1mW maximum for XBee and 63mW maximum for XBee PRO. ZigBee’s mission is to cut the traditional wires between sensors, wired slaves devices, and the microcontrollers and microprocessors they serve.
Battery is work as the supply power to the circuit so that the circuit can work at anywhere and anytime. The battery that is used in this project is 9v battery.
The voltage regulator module is used to protect PIC and other connected sensors or actuators from over voltage. This is because PIC and all other connected sensors, actuators all support 5V DC only. Over voltage will cause any of the module burn. LM7805 is used to regulate voltage in the system and output 5V DC (max current: 1000mA). It supports input voltage from 7V DC to 18V DC.
This regulator is to step down the voltage to 3.3v. XBee cannot accept the voltage larger then the 3.3v. If not, the XBee chip will be damage or burn. As for this project circuit, the PIC and other component such as LED can only accept 5v of voltage. So, the voltage need to be filter with this regulator to step down the voltage second time. First, step down the voltage to 5v using LM7805 regulator, then step down again the voltage to 3.3v using LM1086 regulator for the second time.
The variable resistor is to control the dimmer of the light and the speed of the fan. Variable resistors are often called potentiometers in books and catalogues. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle diameter is 6mm.The resistance and type of track is marked on the body 4K7 LIN means 4.7 k linear track and 1M LOG means 1 M logarithmic track. Some variable resistors are designed to be mounted directly on the circuit board, but most are for mounting through a hole drilled in the case containing the circuit with stranded wire connecting their terminals to the circuit board.
A reverse diode 1N4007 is connected with input of relay to avoid reverse spike or over current flow back from the load. It also protects the circuit from over current load.
This selected bulb is easy to use and easy to put in the prototype.
This fan is selected because it is small and it suitable for the prototype.
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