Researchers charge a fitness tracker using Wi-Fi

Wireless charging has been around for a while now, but current implementations are rather limited by their range. Longer distance charging is being talked up as a future technology and researchers from the University of Washington have managed to harvest power from regular Wi-Fi signals. The technology, known as PoWi-Fi, can be used to charge low-power gadgets and IoT devices.

This certainly isn’t the first time that we have heard about technology that aims to transmit power over Wi-Fi networks or that intends to harvest background waveforms for power. But this latest research seems promising, as it could be easy to deploy alongside existing home networks.

How did they do it?

Essentially, PoWi-Fi turns a high frequency Wi-Fi waveform into usable DC power. However, charging was is possible for short bursts while the Wi-Fi transmitter is actually sending data.

To side-step this issue, the researchers modified a Wi-Fi hotspot so that it would transmit random noise instead of turning the signal off while idle. Fortunately, adding in the noise signal did little to slow data transfer rates across the Wi-Fi network.

To explain a little further, the PoWi-Fi harvester circuit makes use of a typical full-wave rectification and a “reservoir” capacitor setup found in AC-powered electronics. The circuit is taking the AC Wi-Fi signal and converting it to a DC power supply that can be used by low-power electronics and gadgets. However, if the Wi-Fi transmitter doesn’t send a signal, the capacitor begins to discharge, which would turn any connected electronic components off. Adding random noise simply keeps the capacitor charging, even when no usable data is being sent over Wi-Fi.

Considerable work has also gone into designing a “matching network” which ensures compatibility across various Wi-Fi channels. Another interesting technical point is that the Wi-Fi signal itself does not generate a high enough voltage for most batteries or low-power micro-controllers. Instead, the design uses a DC to DC converter to step the voltage up from a few hundred millivolts to 2.4V. When using a rechargeable battery, the researchers could also optimize the design further by using the battery to boost the voltage.

To ensure that the technology would work in a range of different environments, the researchers ran a number of trials in various home environments and found that the technology could continue to charge devices even in areas with busy Wi-Fi traffic.

Enough of the technical stuff, you can read all the fine details in the published document. What this means is that PoWi-Fi can deliver smalls amounts of power wirelessly to a selection of different devices and sensors. While unlikely to be able to charge your smartphone in any realistic length of time, this technology certainly has potential benefits for powering low-power internet of things sensors and charging basic gadgets, such as wearables or cameras.

The research team demonstrated its technology powering a low-power surveillance camera and temperature sensor from up to 6 meters (20 feet) away and a camera with rechargeable battery from up to 7 meters (23 feet). PoWi-Fi was also used to charge up a Jawbone UP24 fitness tracker to 41 percent in two-and-a-half hours, which isn’t bad but isn’t practical for anything other than overnight charging.

PoWi-Fi is still in the early stages of development, so there’s plenty more testing and improvements to be done. But this is a promising start that could help make future home IoT devices cheaper and easier to power.

Xiaomi’s cheapest phone is now just $80

Xiaomi has climbed to the top of the smartphone industry with savvy marketing and cutthroat pricing. But just how cheap can Xiaomi go? For now, the answer is about $80. The Redmi 2A is now just 499 yuan ($80) in China, and you will be hard pressed to a lower price for a similar device.

Xiaomi launched the Redmi 2A on March 31, during its fifth anniversary event that also brought the release of new 4K TVs, a connected scale, and the pink edition of the Mi Note.

The Redmi 2A features a 4.7-inch 720p display, a Leadcore L1860C processor, 1GB of RAM, 8GB of storage, a 2,200-mAh battery, TD-LTE dual-SIM, and Android 5.0 Lollipop. This is a barebones device, but the specs are actually decent for the low price of the Redmi 2A.

Initially, the phone was supposed to cost 599 yuan, the equivalent of $100, but now Xiaomi is offering it for just 499 yuan ($80); the device is on open sale today in China, and the company boasts it managed to sell 200,000 units in just seven hours.

The Redmi 2A is, for now, a China-only device, as it only supports TD-LTE connectivity. But it’s likely that Xiaomi will sell a 2A variant or a similar phone in India and in the other markets where it’s currently active (including Malaysia, Indonesia, the Philippines) as well as in Brazil, where the company will open shop later this year.

Xiaomi is able to deliver a “good enough” smartphone experience at $80 to $100, which has profound implications for the industry. Millions of people in the developing world are vying to get their first smartphone and Xiaomi will be a prime option for them. When Xiaomi is offering a fairly decent HD phone for $80, more expensive devices from Samsung, HTC, or even Lenovo/Motorola don’t stand a chance. For now, Xiaomi seems happy to gobble up market share at the low-end, even if it’s functioning almost at cost. In the process, the company is pressuring competitors to bring down their prices, in a typical example of market commoditization.