Wireless sensor networks are becoming more and more common in the ubiquitous computing era. The applications of sensor networks are diverse and they are employed in areas such as smart homes, military, ITS, Are monitoring, factory automation, and so on. However, sensor networks are generally battery powered and thus, low power consumption is required for prolonged use. In this paper, we propose a distributed low power scheduling algorithm for sensor nodes to determine its active time slots in a TDMA mechanism working on top of a slotted CSMA network. The performance evaluation shows that an extremely small duty cycle is achieved by the proposed algorithm with a tradeoff in data delay in a sensor network application.