Reality Of Wireless Power

How does a wireless network-enabled stapler communicate with a display-sporting desk if it doesn't have a power source? Will all this stuff need batteries? Does a smart can of garbanzos need a power cord? Wireless power sources eliminate those concerns.

Since Tesla's pioneering work with coils, engineers have marveled at the possibility of wireless power transfer. And while a full-blown wireless power grid is a topic of discussion these days, it is still a very long way off as a reality. However, there are methods for wireless power transfer that are a reality. In fact, some are long past the standards phase and have found their way into industrial products such as warehouse inventory systems.

One approach uses inductive coupling,the ability of a magnetic field to induce a current and vice versa,to power devices wirelessly. This is the operating principle behind common power transformers. In these power systems, some type of base (sometimes just a mat) wired to a power source contains a wire coil that generates a varying magnetic field. When a device that needs power is placed on the base, the magnetic field induces a current in another coil built into the portable device, and that current powers the unit.

Another approach uses radio-frequency (RF) energy. A short-range, low-power transmitter beams RF energy into devices in the local vicinity,sometimes just a few inches. An antenna and receiver in the device being powered picks up the RF signal, converts it into direct current and then runs off that current.

One neat twist on this technology is inventory tags about the size of buttons or snaps. The RF power source is usually located in a wand that scans the buttons and read their unique IDs. The wand produces RF that an integrated circuit in the button uses for power. A button being scanned modifies and rebroadcasts the RF signal based on its unique ID code. A receiver (also housed in the wand) picks up this interfering signal and can easily deduce the ID code of the nearby button. In this scenario, RF is used for both power and data transfer.

What are your power principles? Let me know via e-mail at [email protected].