Implementation of sensor network is rather costly. For a wireless sensor node ensuring that there is always adequate energy available to power the system is an important aspect in the development of WSN. If battery of a node discharges then node will shut its operation. Changing the battery regularly can be costly and inconvenient. And issue with the wired sensor network is the cost of installation of network is high. In such conditions the high cost of sensor networks can be reduced and power

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... onstraints of WSN can be overcome by new technological advances, like the Powerover-Ethernet (PoE).Most of modern houses and offices are equipped with Ethernet cabling, wired sensor network can be built using already laid Ethernet. Another issue in the sensor network is power management, under power constraint situation a tight scheduling algorithm is necessary to use the sensor network efficiently. This work aims at designing of the Sensor network using PoE technology and its centralized power management. This system is proposed for wired sensor network in which the power management is done through Ethernet cable i.e. using PoE technology. This system monitors different events and if event occurs, information is send to controller. Controller will power up corresponding response device. Thus the system is designed as power on demand system. For power management, controller will check for the priority of the event, available power and accordingly power is provided to corresponding response device. Keywords-Power over Ethernet (PoE), Sensor network, Power management, Wireless sensor network (WSN), Power on demand I. INTRODUCTION Sensor network research has attracted considerable attention but the general aspects for designing sensor network includes, wide application areas (e.g. structural and health monitoring), the demand for low cost, low-power sensor networks, the ability to record in real time relevant information for the identification of abnormal states, etc. However, the cost of implementation of sensor systems is considerably high, due to the power consumption, wiring, and operation and maintenance aspects. For example, the sensor system of the Tsing Ma Bridge in Hong Kong costs over 8 million [1]. Over 25% of total cost was attributed to installation, like cable arrangements. In addition, over 75% installation time was spent on cable installation [2]. Lot of additional wiring may be required to be installed to allow sensors to work -unless the sensors used are wireless. Using wireless makes sensor devices much more expensive.Power management system is proposed which focuses on centralized power and information management of the sensor network in which nodes are PoE enabled devices. PoE technology can cut off the man's effort and wiring cost because PoE using LAN cable can deliver power location where power source does not exists, such as the roof, lobby and entrance. So sensor network can be build using PoE technology. Power over Ethernet (PoE) is a technology for hard wired Ethernet LAN's (Local Area Networks) that allows power to flow along cable that would normally be reserved for data signals only. The system works by injecting dc voltage onto the Ethernet cable from a central point which can be a suitable existing network switch or an additional injector. If the end device does not have the inbuilt capability, a splitter is used near the point-of-load to split the power from the data and convert the voltage to what's required by the end