America
Indian-origin researcher uses Wi-Fi to power camera
Washington, June 7
In a first such
demonstration, an Indian-origin researcher has developed a system that
uses Wi-Fi internet signals to beam power to remote devices such as a
surveillance camera.
Developed by doctoral student Vamsi Talla
and colleagues at University of Washington in Seattle, the system is
known as power-over-Wi-fF.
The idea is simple in concept. Wi-Fi radio broadcasts are a form of energy that a simple antenna can pick up.
Until now, Wi-Fi receivers have all been designed to harvest the information that these broadcasts carry.
Talla
simply connected an antenna to a temperature sensor, placed it close to
a Wi-Fi router and measured the resulting voltages in the device and
for how long it can operate on the remote power source alone.
Even more ambitiously, the team also connected a camera to their antenna.
This
was a low-power sensor capable of producing 174 x 144 pixel black and
white images, which requires 10.4 milliJoules of energy per picture.
To
store energy, they attached a low leakage capacitor to the camera which
activates when the capacitor is charged and continues operating until
the voltage drops to 2.4 Volts.
The images were stored in a 64 KB random access memory (RAM). In the subsequent tests, the camera performed remarkably well.
"The
battery-free camera can operate up to [about five metres] from the
router, with an image capture every 35 minutes," Talla told MIT
Technology Review.
By adding a rechargeable battery, he increased the distance to seven metres.
The
router could even power the camera through a brick wall, demonstrating
that it would be possible to attach the device outside while keeping the
power supply inside.
"The technology would be hugely useful for
surveillance, perhaps connected to a movement sensor to trigger the
camera when something moves in its field of view," Talla noted.
The team also connected their antenna to a Jawbone fitness tracker and used it to recharge the battery that powered it.
"Using
this, we charge a Jawbone device in the vicinity of the
power-over-Wi-Fi router from a no-charge state to 41 percent charged
state in 2.5 hours," the team pointed out.
According to the MIT
report, power-over-Wi-Fi could be the enabling technology that finally
brings the "Internet of Things" to life.