Definition The current ultramodern technologies are focusing on automation and miniaturization.
The decreasing computing device size, increased connectivity and enhanced interaction
with the physical world have characterized computing's history. Recently, the
popularity of small computing devices, such as hand held computers and cell phones;
rapidly flourishing internet group and the diminishing size and cost of sensors
and especially transistors have accelerated these strengths. The emergence of
small computing elements, with sporadic connectivity and increased interaction
with the environment, provides enriched opportunities to reshape interactions
between people and computers and spur ubiquitous computing researches.
Smart
dust is tiny electronic devices designed to capture mountains of information about
their surroundings while literally floating on air. Nowadays, sensors, computers
and communicators are shrinking down to ridiculously small sizes. If all of these
are packed into a single tiny device, it can open up new dimensions in the field
of communications. The idea behind 'smart dust' is to pack sophisticated sensors,
tiny computers and wireless communicators in to a cubic-millimeter mote to form
the basis of integrated, massively distributed sensor networks. They will be light
enough to remain suspended in air for hours. As the motes drift on wind, they
can monitor the environment for light, sound, temperature, chemical composition
and a wide range of other information, and beam that data back to the base station,
miles away.
MAJOR
COMPONENTS AND REQUIREMENTS Smart Dust requires both evolutionary and
revolutionary advances in miniaturization, integration, and energy management.
Designers can use microelectromechanical systems to build small sensors, optical
communication components, and power supplies, whereas microelectronics provides
increasing functionality in smaller areas, with lower energy consumption. The
power system consists of a thick-film battery, a solar cell with a charge-integrating
capacitor for periods of darkness, or both. Depending on its objective, the design
integrates various sensors, including light, temperature, vibration, magnetic
field, acoustic, and wind shear, onto the mote. An integrated circuit provides
sensor-signal processing, communication, control, data storage, and energy management.
A photodiode allows optical data reception. There are presently two transmission
schemes: passive transmission using a corner-cube retro reflector, and active
transmission using a laser diode and steerable mirrors.
The
mote's minuscule size makes energy management a key component. The integrated
circuit will contain sensor signal conditioning circuits, a temperature sensor,
and A/D converter, microprocessor, SRAM, communications circuits, and power control
circuits. The IC, together with the sensors, will operate from a power source
integrated with the platform.The MEMS industry has major markets in automotive
pressure sensors and accelerometers, medical sensors, and process control sensors.
Recent advances in technology have put many of these sensor processes on exponentially
decreasing size, power, and cost curves. In addition, variations of MEMS sensor
technology are used to build micro motors.
WORKING
OF SMART DUST The smart dust mote is run by a microcontroller that not
only determines the task performed by the mote, but consists of the power to the
various components of the system to conserve energy. Periodically the micro controller
gets a reading from one of the sensors, which measure one of a number of physical
or chemical stimuli such as temperature, ambient light, vibration, acceleration,
or air pressure, process the data, and store it in memory. It also turns on optical
receiver to see if anyone is trying to communicate with it. This communication
may include new programs or messages from other motes. In response to a message
or upon its own initiative, the microcontroller will use the corner cube retro
reflector or laser to transmit sensor data or a message to a base station or another
mote.
The
primary constraint in the design of the Smart Dust motes is volume, which in turn
puts a severe constraint on energy since we do not have much room for batteries
or large solar cells. Thus, the motes must operate efficiently and conserve energy
whenever possible. Most of the time, the majority of the mote is powered off with
only a clock and a few timers running. When a timer expires, it powers up a part
of the mote to carry out a job, then powers off. A few of the timers control the
sensors that measure one of a number of physical or chemical stimuli such as temperature,
ambient light, vibration, acceleration, or air pressure. When one of these timers
expires, it powers up the corresponding sensor, takes a sample, and converts it
to a digital word. If the data is interesting, it may either be stored directly
in the SRAM or the microcontroller is powered up to perform more complex operations
with it. When this task is complete, everything is again powered down and the
timer begins counting again.