Tech Briefs Magazine - June 2021 - ST-16

TECHNOLOGY LEADERS Sensors
RF Wireless Power Unleashes the Ubiquity
of Sensor Networks
W
e are in the age of an AI
(artificial intelligence) ex -
plosion. Everything - from
your refrigerator to your
dog's bowl - will become part of the AI
neuron network. Worldwide revenues for
the AI market, including software, hardware,
and services, are forecast to grow
16.4 percent year over year in 2021 to
$327.5 billion, and by 2024 the market is
expected to break the $500 billion mark.
While these numbers are impressive,
AI will only reach its full potential when
it can be fed with a constant stream of
data from a plentitude of diverse
sources. In order to gather data at a rate
that enables high value AI output, you
need a ubiquitous sensor network in
place. Sensors are the neurons that fire
the AI synapses. These synergies are
imperative to the frequency and quality
of the output.
Over the past few years sensors have
begun to make their mark as the framework
of the IoT. In 2022, motion sensors
are expected to account for 8.35 percent
of the global IoT-enabled sensors market.
Total revenue generated by the
enabled sensors market is estimated to
reach $56 billion in 2022.
Sensor networks need to continue to
expand in order to be able to truly support
the adoption and fulfillment of
high value AI. However, scalable
expansion of sensor networks is being
stifled by the restrictions of placement
due to needing access to power. So how
can we " keep the lights on and the neurons
firing? "
Historically, sensors are powered by
wires and/or batteries. However, both
these options have limitations. Wires
can be expensive to run and often
restrictive - with limits in cable
length and potential for breakage
points. Batteries have limited life; they
need to be replaced on a regular basis
and are thrown away when spent. In
short, they are not dependable for the
time cycles required; they are a repetitive
cost, and they are environmentally
unsustainable.
An Alternative to Traditional Power
A substitute for wires and batteries is
energy harvesting (capturing available
energy). Or wireless charging (generating
energy to wirelessly power a device),
which is the process where energy is
derived from predictable external energy
sources, captured, and stored for
applications including small wireless
autonomous devices like those used in
wireless sensor networks.
There are many methods of wireless
charging, which we'll briefly take a
look at:
* Vibration is the concept of converting
vibration energy to electrical energy.
This method is only ideal for machinery
that vibrates.
* UV/IR energy must have direct line of
sight between the transmitter and the
receiver for it to work properly, any
obstructions result in no power reaching
the receiver.
* Qi is inductive charging and offers
watts of power, but is only for applications
where the transmitter and receiver
are a few millimeters apart; device
alignment is quite restrictive.
* Solar and wind, in most cases, must be
outdoors and therefore can be costly
to build and can also be a bit limited
in its capabilities.
* Radio frequency (RF) does not
require direct line of sight, can deliver
power into waterproof enclosures, is
low power (μW to mW) and is more
versatile than the processes previously
mentioned.
Wireless Sensor Networks
Figure 1. Wireless and battery-less sensor board development kit. The on-board sensors include temperature,
humidity, and light, and there is a terminal for an external sensor. (Courtesy of Powercast)
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ToC
RF wireless power technology is
unique because it uses radio frequency
electromagnetic waves rather than magnetic
fields to charge a device. An RF
transmitter uses electronics to generate
an RF signal. The RF signal is sent to an
antenna, which transmits the RF waves
to a receiver embedded within a device,
which picks them up using an antenna.
They are then converted into usable DC
using an embedded chip. This powers
Sensor Technology, June 2021

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Tech Briefs Magazine - June 2021

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