Wireless Sensor with Energy Harvester

Abstract

In this paper a portative device for the ambient temperature and air humidity controlling is described. The source of power for the developed device is a general-purpose battery and an original energy harvester. The ambient parameters values are transmitted to a personal computer through radio-frequency identification (RFID) connection. Described device is also applicable as a wireless link which receives digitized bioelectrical signals from wearable Holter electrocardiographic monitors, electroencephalographs and pulse-oxymeters.

Existing System

Harvesting energy from magnetic fields to power condition monitoring sensors.

Proposed System

The conventional approach to a design of mobile monitoring systems is to use a radio link for data transfer from mobile sensor-enabled unit to user’s terminal. The same link allows setting the monitoring parameters and mobile unit options. Typically, it requires a mobile unit to keep its radio receiver active for long time waiting for the request from user’s terminal to guarantee short response time. In this standby mode, mobile unit powers up its receiver every few seconds or even more. State-of-the-art digital radio transceivers consume from few mA to few tens of mA at few volts in receiving mode that dramatically limits the battery lifetime. Typical standby time for mobile radio-enabled devices rarely exceeds few months. Sometimes the battery life can be as long as few years but only when data is sent rarely (every few minutes) and there is no need to guarantee the real-time data update on user’s terminal (like in car tire pressure monitoring systems). Thus, the most native way to extend the battery life is to lower power consumption of radio interface of the mobile controlling device. Further improvement of the battery lifetime (from few years to literally infinite) is possible only by means of energy harvesting technologies, because any battery has intrinsically limited self-lifetime due to self-discharge and aging. The most promising energy source for such energy harvesting system is electromagnetic field, generated by alternating current (AC) in mains power line.

Architecture

Block diagram of the mobile monitoring unit