30-07-2012, 01:19 PM
AN ONLINE MONITORING SYSTEM OF TEMPERATURE POWER AND CURRENT
AN ONLINE MONITORING SYSTEM.pdf (Size: 523.95 KB / Downloads: 63)
INTRODUCTION
GSM (Global System Mobile Communications) is a global digital mobile communication system, whose coverage is the most widely, phone owners is the largest, and reliability is very high.
SMS (Short Message Service) is a kind of short message service, by which the limited data or text message can be transmitted. In fact, the information transmission is achieved by receiving and sending text message in the businesses center between mobile phones and other short message carriers, and the businesses center is an independent operating system of GSM network whose main function is submitting, storing, and transferring short message.
SMS is a special and important service as well as calling for users by GSM system. In this paper, a self-designed industrial GSM module is selected to finish the transmission and the decoding of the monitoring data through AT command and coding of short message PDU.
The method is a breakthrough of current technical regulations, the impact caused by improving conductor temperature on conductors, the mechanical strength and the lifespan of matched fittings, the increase in sag and so on should be studied. In addition, if the conductor temperature and the sag can be real-timely monitored, the dynamic regulation of the transmission capacity, such as day and night, cloudy and sunny, summer and winter under the different environmental conditions can be realized to improve the transmission capacity.
POWER SUPPLY
The system requires a regulated +5v supply for the semiconductors and a +12V unregulated supply for the relay. These can be delivered from the 230V domestic supply. Before applying this to the system we must step down this high voltage to an appropriate value. After that it should be rectified. To achieve +5 V DC we should regulate this. All this run in the power supply circuit.
Power supply is used to give sufficient power to the microcontroller. A step down transformer and a bridge rectifier is used here to convert AC to DC. A regulator IC is also used here to give constant supply.7805 IC is used for power supply and it is connected to the bridge rectifier.
A 12-0-12V step down transformer is connected to provide the necessary low voltage. The transformer also works as an Isolator between the hot and cold end. The hot end refers to the 230v supply, which is hazardous one, and the cold one refers to the low, safe voltage .Now the hot portion appears only at the primary of the transformer. The secondary of the transformer deliver 12v ac pulses along with a ground.
This ac supply goes to a center tap rectifier, which converts the ac into a unidirectional voltage. The ripples in the resulting supply is filtered and smoothed by a 2200micro FD/25V capacitor
This voltage is given to the regulated IC 7805.This IC provides a regulated 5V positive supply at its 3rd pin. This required input for this is more than 7.5V.
Power supply
This circuit can give +5V output at about 150 mA current, but it can be
increased to 1 A when good cooling is added to 7805 regulator chip. The circuit
has over overload and terminal protection.
Circuit diagram of the power supply
The capacitors must have enough high voltage rating to safely handle the
input voltage feed to circuit. The circuit is very easy to build for example into a
piece of Vero board.
Pin out of the 7805 regulator IC
1. Unregulated voltage in.
2. Regulated voltage out.
3. Ground.
O/P
.
RECTIFIER
REGULATOR IC
If we need other voltages than +5V, we can modify the circuit by replacing the 7805 chips with another regulator with different output voltage from regulator 78xx chip family. The last numbers in the chip code tells the output voltage. Remember that the input voltage must be at least 3V greater than regulator output voltage of otherwise the regulator does not work well.
PIC16F877 MICROCONTROLLER
Controller is the heart of the system and it controls the entire unit. The controller we use is PIC16F877 of the MICROCHIP company. Nowadays most commonly used microcontroller is PIC .These microcontroller have five ports, 368 x 8 bytes of Data Memory (RAM), 256 x 8 bytes of EEPROM Data Memory,8K x 14 words of FLASH Program Memory.