Wireless sensor networks, consisting of sensing devices which sense the environment and communicate information among each other, is an emergent field in wireless networking with many potential applications. The efficiency of energy consumption is an important objective for wireless sensor networks. All the sensor nodes have limited battery supplies with limited sensing capabilities and communication ranges. A sensor network has a large numbers of nodes, allowing some nodes to sleep for particular time intervals can result in an increased network lifetime. In this paper, a mathematical model using integer linear programming and a coverage algorithm is developed and implemented to schedule sleep/wake cycles for the sensors, to extend the network lifetime and to determine the sensing coverage. This scheduling model intelligently decides which sensors should be turned on and off for sequential time periods until the model fails to generate a feasible coverage solution.