Scientists have used Wi-Fi signals to power a battery-free camera five metres away, an advance that brings the idea of Internet of things closer to reality.
Internet of things is the concept that almost every object could be fitted with a chip that broadcasts data such as its location or whether some other parameter such as temperature or pressure is dangerously high or low. However, for the Internet of things to become a reality engineers have to solve one potential problem: how to power these numerous tiny machines.
The researchers have demonstrated that Wi-Fi signals can be used to broadcast power to remote devices. They call their new approach power over Wi-Fi or PoWi-Fi. Wi-Fi radio broadcasts are a form of energy that an antenna can pick up. Wi-Fi receivers have been designed to harvest the information that these broadcasts carry.
Talla and colleagues pointed out that there is no reason why the energy should not be harvested as well. The team’s approach is to simply connect an antenna to a temperature sensor, place it close to a Wi-Fi router and measure the resulting voltages in the device and for how long it can operate on this remote power source alone.
Wi-Fi broadcasts are not continuous. Routers tend to broadcast on a single channel in bursts. This provides enough power for the sensor but as soon as the broadcast stops, the voltages drop.
Talla and colleagues programmed the router to broadcast noise when it is not broadcasting information and employ adjacent Wi-Fi channels to carry it so that it does not interfere with data rates, ‘MIT Technology Review’ reported.
The researchers used three Atheros AR9580 chipsets, standard electronics for Wi-Fi routers, and programmed these devices to broadcast in a way that can provide continuous power to an energy harvesting sensor.
Then they measured the resulting voltages in their temperature sensor and determined how long it can work at various distances from the modified router. They found that the temperature sensor can operate at distances of up around six metres from the router and by adding a rechargeable battery to the mix, it can be increased to about nine metres.
They also connected a camera to their antenna. To store energy, they attached a low leakage capacitor to the camera. 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,” researchers said.
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.