Mains
If mains power is available, and is compatible with the
desired application, it is nearly always the preferred choice. In most areas of
the world, it is more reliable than other sources; it is practically
inexhaustible and, considering the very low power consumption of wireless sensor
networks, has a trivial operating cost. It has its drawbacks as a supply for
wireless sensor network nodes, however, not the least of which is the inherent
contradiction of connecting a wire to a wireless device. Mains power will
require a significant amount of conversion to make it compatible with the needs
of typical wireless sensor network node circuits — it must be converted from AC
to DC, and in voltage from one or two hundred volts to a few volts. This
conversion can be expensive; it will require specialized hardware, and even a
wall plug-mounted power converter is a significant size and cost expense for a
wireless sensor network node. The effective internal resistance seen by the load
(the network node) will be the internal resistance of these conversion circuits.
In addition, the many different standards used around the world, with their
differences in voltage, frequency, and hardware, can add significant complexity
to a design intended for worldwide use or distribution. Similarly, obtaining
safety regulatory approval can be challenging.
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