Wireless Power Transmission in the SmartHome

WE DEVELOP A wireless power transmission system for the Duke SmartHome. This power-transmitting surface is built into the frame of a 35 x 32 cm wooden cabinet and is able to transmit tens of watts of electrical power to power multiple devices simultaneously. We have successfully powered multiple devices including an alarm clock, a USB light, an LED, a USB toy and an iPhone. We have also managed to power 4 iPhones simultaneously. Existing techniques of wireless power transmission involving a pair of strongly magnetically coupled resonators allow transmission of tens of watts of power over a few meters [4]. By introducing high Q L-C resonators, researchers are able to efficiently transfer power from one resonant transmitter to another resonant receiver. However, efficiency greatly deteriorates upon adding more receivers to the strongly coupled system because of the interactions between multiple coupled resonators. We observe that many consumer electronics for example laptops, desk lamps, alarm clocks etc operate off a surface such as a desk or a cabinet. In our research and implementation of a wireless power transmission system, we transmit near field wireless power with a goal not to maximize the distance of power transmission, but rather, to power devices on a surface. Our objective is to allow the introduction of numerous nonresonant pick up coils to enable multiple devices to be powered on the surface at once with only one resonant transmitter. With the goal of powering multiple devices with a single transmitter, we design a system that drives a primary inductor that is coupled with a high Q L-C secondary resonator. Design parameters such as drive frequency, number of turns of resonant coil, type of wire used etc are determined by computer modeling. MATLAB is used to model the behavior of inductive power transfer and PSpice is used to model the behavior of the transmitter and receiving systems respectively.