Key Technologies And System Designs For Fire Alarms Based On Power Line Carrier Communications

With the enhancements of enterprises' security awareness,enterprises have their own security risks to improve.The current data show that the direct economic loss caused by a fire accident is about five times of that of an earthquake.Electrical fire accounted for about 30.1%of the total number of fires in 2015,where old equipment is an important factor leading to electrical fires.At present,there is a baking process in the production process of the inauguration company.The equipment used in the process has high temperature under the working condition.The equipment manufacture has been introduced for a long time abroad.It is difficult to reform or renew the equipment alone.Considering that the equipment has been issued with occasional over-temperature events,the security department has issued a fire alarm on the device.Upgrading the production technology,the company has decided add a fire warning system,which is designed by the company itself.In order to control the cost and ensure the reliability,this thesis uses a power line carrier technology to design the fire alarm system.Through the power line transmission signal,the cost can be reduced and the stability can be guaranteed.The Power Line Carrier(PLC)communication uses the transmission line as the transmission medium of carrier signals.The power line carrier communication takes the original power line in the power line as a transmission carrier.The modulated signals are transmited to a specified device.Then a dedicated power line modem is used to separate the high-frequency signal from the power line.in such a case,the final signal is passed to the terminal device.The cause of using the power line carrier communication technology is that there is no need to re-build the communication lines.The data can be transfered as long as there is the power line.Moreover,the power line structure is strong.Therefor,it is highly reliable as a communication medium.This thesis studies the key technologies such as power carrier communications,communication channels,and signal modulations.At the same time,the fire alarm system design is also investigated in detail.When the power line is used as the communication carrier,there exist the large complexity and interference noise.Therefore,it is needed to consider the channel debugging technology.Through analyzing and comparing the current technologies,the direct sequence spread spectrum is selectd as the optimal communication scheme in this thesis.In the early warning system design,the temperature sensor monitoring module is used with the carrier communication modules' circuit power and serial communication modules.The fire monitoring module and the carrier communication module in the whole system are the focus of the system design.The corresponding software design is adopted to realize the whole early warning function.