Investigation of power management for a sensor and communication circuit

Abstract

This report is concerned with the designing and building of a circuit with temperature and motion sensing functions, with capability to wirelessly transmit data collected. The power management of the device is also studied to explore its powering using solar energy. With careful examination and rationalisation of the components to be used, a basic circuit comprising of a Sensor Node circuit and a Master Control was designed and built. While Arduino Uno was chosen as the microcontroller to be used, and the Grove temperature sensor and motion sensor were interfaced with a Grove Base Shield, XBee modules were used to enable ZigBee wireless transmission of data from the Sensor node circuit to the master control after configuration. Wireless data transmission of the data collected from the sensor node to the computer via the master control was demonstrated. Further improvement to the Sensor node circuit was also explored. This include replacement of the Grove base shield with a breadboard, and the temperature sensor to a smaller sized one, in an attempt to reduce the bulkiness of the Sensor Node circuit. On the contrary, motion sensor was replaced with a larger sensor for greater motion detection sensitivity. In order to make the device a low-powered one suitable for powering with self-sustaining method, power consumption of the sensor node was also reduced by introducing “sleep mode” to the programme via coding Finally, the Sensor Node circuit was linked to a solar panel via a Li-Po rider board to test for powering of the former by solar energy. Our results showed that solar energy conversion efficiency was not sufficient to power the sensor node in real time (to harvest energy and power at the same time). As such, a chargeable Li-battery was introduced for storage of the energy harvested to power up the Sensor Node circuit and this was shown to be successful. This storage ensured the availability of electrical energy to the device when sunlight was not available.