Power supply monitoring for wireless sensor platforms

Sammanfattning

Most of the portable electronic devices use a battery as a primary power

source. Nowadays, when the applications are becoming smaller and smaller and

more power efficient, the designer needs to concentrate more on reducing

power consumption, using secondary power sources and introducing power

storage devices. Multiple power source availability and a power storage

device on the board will make the applications much more useful and

efficient in everyday use.

This thesis proposes a power supply unit (PSU) for wireless sensor platforms

which is capable of supplying a sensor node with energy from multiple

sources, as well as status information from the PSU.

Present power storage devices, like electric double-layer capacitors (EDLCs)

and batteries, have become more and more common as their characteristics have

developed. The EDLCs are popular due to their ability to charge and discharge

efficiently and quickly at high currents. In addition, there are no limits

for the number of charge and discharge cycles. The advantage of batteries is

their ability to store a larger amount of energy (with longer charging

period) and their decreasing size. In this design, both battery and EDLCs

are used. Batteries will be used only in critical conditions. Otherwise, the

system will be powered by renewable solar energy which will charge the EDLCs

at the same time.

The device’s architecture contains a context- and power-aware task manager,

which controls the node’s low-power modes and decides when they are

activated. Its main responsibility is to schedule the moments when the

energy consuming task can be dispatched. Depending on task priority and

system configuration, the task can be dispatched, discarded or delayed.