tion from sparking on. Such concepts
require a development platform that
hosts both sensors and communications hardware.
One such platform is SquidBee and
its successor, Waspmote. Both originated at the Spain-based company
Libelium, which also produces three
types of Waspmote sensor boards. One
determines the presence of gases, such
as carbon dioxide and methane; the
second senses environmental changes,
such as vibration, pressure, and moisture; and the third is a prototype board
that will host any other sensor types a
developer might have. For applications
that don’t require immediate communication or in situations where immediate communication is impossible,
the Waspmote board contains two gig-abytes of internal memory for later
making sensors talk
Both Patel and Libelium’s devices re-
quire a way to communicate their find-
ings to the outside world. Waspmote
uses a variety of methods, including
USB, GPS, 802.15.4, and a range of
radio frequencies. Patel is agnostic
about the communication methods his
still-in-development devices will use.
“We’re innovating on the hardware, ag-
gregation, and signal processing,” he
says, “but not on the network.”
One specification that both plan
to use is ZigBee, an extension of the
802.15.4 standard promoted by the
nonprofit, industry-based ZigBee Al-
liance. According to ZigBee Alliance
Chairman Bob Heile, ZigBee was de-
signed specifically “to create open,
global standards for wireless sensor
networks.” As such, it prioritizes power
consumption and transmission integ-
rity so that the devices—which might
be used in difficult-to-access areas—
can operate trouble-free for a long pe-
riod of time. “We’re achieving devices
that go for five to 10 years on an alka-
line battery or 10 to 20 years on lithi-
um-ion,” says Heile.
The ZigBee Alliance also prioritized
scalability well beyond the residential
needs. Heile says the ARIA Resort &
Casino in the new CityCenter development in Las Vegas has more than
90,000 ZigBee-compliant devices to
control both common-area and guest-room environments. On the other
hosts an annual dorm
with prizes for
the dorm that
achieves the greatest
hand, ZigBee largely ignores issues of
bandwidth and quality of service, as
would be needed for a telephony or
The ZigBee specifications cover all
seven layers of the Open Systems Interconnection model, in three parts. The
bottom two—the physical and data-link layers—are the 802.15.4 standard,
with no changes. Layers three to six
comprise the “ZigBee stack,” including algorithms for organization among
nodes, error routing, and AES-128 security. (As a wireless technology, the security portion is especially important to
prevent outside tampering that could
cause unpredictable device behavior.)
When layers one through six are implemented according to the ZigBee specification, it qualifies for ZigBee platform
compliance certification. ZigBee-cer-tified products also implement layer
seven, which is a ZigBee public profile
such as smart energy, home automation, or health care.
acting on Data
Once the data is collected, it needs to be
presented in ways that are understand-
able to humans and to other devices.
“We don’t want to overwhelm the con-
sumer with a bunch of data,” says Patel.
“We could provide them with a ‘Top Ten
Energy Consumers in Your Home’ list
to give them something to work on. Or
if we see that the compressor in their re-
frigerator is degrading in performance
over time, we could give them targeted
advice on blowing out the coils.”
One example of how such data is be-
ing used is found in Oberlin College’s
campus resource monitoring system.
The environmental studies program
monitors electricity use in each of the
college’s dorms, in some cases with
multiple sensor points per dorm. Ad-
ministrators make adjustments to dis-
count nondiscretionary expenditures,
such as a kitchen in those dorms with
cafeterias, then take a baseline reading
to determine typical usage. Data from
dorms’ current energy use is displayed
in three ways: on the Web at oberlin.
edu/dormenergy; as building dash-
board video displays throughout cam-
pus; and as color-changing orbs placed
in several campus locations, including
the dorms themselves.
Patel, S.n., robertson, T., Kientz, J.A.,
reynolds, M.S., Abowd, G.D.
At the flick of a switch: detecting and
classifying unique electrical events on
the residential power line. Proceedings
of Ubicomp 2007, Innsbruck, Austria,
September 16–19, 2007.
Patel, S.n., reynolds, M.S., Abowd, G.D.
Detecting human movement by differential
air pressure sensing in hVAC system
ductwork: an exploration in infrastructure
mediated sensing. Proceedings of Pervasive
2008, Sydney, Australia, May 19–22, 2008.
Petersen, J.E., Shunturov, v., Janda, K.,
Platt, G., Weinberger, K.
Dormitory residents reduce electricity
consumption when exposed to real-time visual feedback and incentives.
International Journal of Sustainability in
Higher Education 8, 1, 2007.
Feedback on household electricity
consumption: a tool for saving energy?
Energy Efficiency 1, 1, Feb. 2008.
Wireless Sensor networks research Group
Tom Geller is an oberlin, ohio-based science, technology,
and business writer.