Wireless Charging in a Nutshell


Wireless charging seems so great, I plug this thingy in and then set this other thingy on it and then there’s power! But how the heck does electricity get from the wall into my phone? You’re probably reading this article via a device that has a battery–laptops, mobile phones, toothbrushes, though. All these things need charging and for the moment we’re still using cords and plugs for this. Inductive charging isn’t new, it’s been used since the early 1990s in electric toothbrushes, and for surgically implanted devices like artificial hearts. You’ve even heard of this in pop culture! In the late 1800s, Tesla was allegedly able to power light bulbs with no wires, and claimed to be able to transmit power from one location to another with no wires. To make it work relies on simple physics.

If you ever wrapped a coil of wire around a nail and attached a battery, then you know the electricity in the battery runs through the wire creating an electromagnetic field, or flux. Do it at home, it’s fun and you can use it to pick up paperclips or whatever. With that same principle, a coil of wire, magnet, battery, you can make it go the other way too. Spin a magnet in the coil and you’ll generate electricity by taking that magnetic flux and moving it through that coil to create electricity. The battery creates a stable electromagnet because it’s direct current, it’s going one way. The power from your walls is alternating current, changes direction 60 times a second — or cycles at 60 hertz — so the electrons are moving back and forth — remember that because that’s the key to the charging.

Wireless inductive charging gets its name from that magnetic field interaction, called induction. Inside of the charging pad, and the inductive charging device are tiny coils of wire. The pad, being plugged into the wall, is fully powered — and the power is cycling. When the other coils come within a short distance their flux will interact with the flux in the device, move the electrons around and charge the battery. Chances are, the number of cycles per second isn’t going to be 60 hertz, but like, 5 or 10, so it doesn’t mess up other things in your house. Your WiFi network cycles at 2.4 gigahertz or 2.4 billion cycles per second, so it’s DEFINITELY not going to mess THAT up, but with all the radio waves flying around, you can’t be too careful. If it’s that easy, you’d think it would be everywhere, but the problem is efficiency. You waste a lot of power filling up two coils and letting them talk to each other. It’s SO much better to just plug right in. The future of wireless charging is unclear. It seems like a great idea, but it’s still going to be a short-distance system for a while.

Head to Head: Eyes against Camera Explained

Eyes vs Camera

Don’t you hate it when you see something beautiful, and you pull out your camera, and you just can’t make it look the same. What is wrong here? Is it me or the camera?! When you think of a robotic version of a human eye, or even a prosthetic eyeball, you probably picture some kind of camera. It makes sense, they both capture images and video, but aside from general comparisons, they’re really not the same at all! When you’re looking out through your eyeball, it’s doing the same things as a camera, adjusting the lens, focusing and trying to make the image look as good as possible. In fact, generally speaking, both the eye and a camera have a lot in common! Both have adjustable apertures to let in the right amount of light, both have a lens, and both have a way to absorb the light. But from there, comparisons get a little fuzzy.

The reason your photos don’t look the same way your eye sees them is because of the way the two different mechanisms function. The eye is 28 grams of vitreous fluid, muscles, cells and nerves. Cameras can be formatted and customized to do thousands of different types of shoots. When focusing, the lens of the eye uses the ciliary muscle to change its shape, a lens needs to be physically moved. When it’s bright or dim, the pupil uses the sphincter pupillae to adjust the amount of light being let into the eyeball — a camera uses an aperture to adjust the amount of light. According to research conducted in Canada in the late 50s, the f-stop of the human eye might be around f/3.2 to f/3.5… It was cited a lot, but I couldn’t find the study to double check. Regardless, cameras have a far wider range of f-stops and ISO sensitivity to pick up dim light. When a full-frame camera absorbs light, it does so with a 35 millimeter sensor, compared to the eyeball — which has a retina at the back. That wall of cells is CURVED, but is almost the same exact size as the camera — about 32 mm! The difference is, the retina isn’t very clear. We can only see 20/20 at the macula, or fovea. A spot on the retina that is ALL cone cells. Outside of the fovea are a mix of rods and cones, followed by just cones at the edge. This is why you can’t read something you’re not looking directly at, and why peripheral vision is mainly just for movement. Additionally, your eye only sees color where there are lots of cones, so closer to the fovea the more color.

A camera, by contrast, can pick up detail across the whole of the sensor, all in color! However, even though the camera can see a wider field, the amount of information is relatively low. Most high-end cameras process around 24 megapixels, but the human eye can get 52 megapixels on average and HUNDREDS of megapixels if you take into account the whole field of vision! It get’s pretty ridiculous. What you see isn’t just one image, it’s dozens or more! You don’t worry about overexposing, shutter speed, or aperture because your brain does that for you and filters out any errors in color or depth. In the end, the reason your photos don’t look like what you see, is because what you see isn’t really real. It’s what your brain created while sucking in all that visual information and compiling it into a three dimensional, multi-million-pixel world.

Inflight Wifi – Innovation at its Finest

Inflight Wifi

Who among you here have ridden on an airplane? If you do, then have you ever wondered why don’t cell phones work inside it while in flight? The short answer is that when you’re 35,000 feet in the air going 500 miles per hour, you’re just too far from a cell tower. But that got us thinking: how does wifi work in an airplane?

“Why don’t phones work in planes while they’re in the sky?”. Some of you know that they can work, if you’re on a plane with wifi. From the passenger’s perspective, in-flight wifi is as simple as turning on your computer and connecting to the network. But there’s a lot more going on than we see. There are a couple of ways to connect to the Internet in a plane. One is by a ground-based system sort of like a cellular network. Stations set up around the country provide overflying planes with contact points. An antenna on the plane’s underside transmits and receives signals to and from these ground-based towers, bringing wifi into the plane. But of course, this doesn’t work when you’re flying overseas or out of range of the ground network.

The alternative is a satellite-based system that uses an antenna on top of the plane that talks to satellites in orbit sometimes in conjunction with that antenna on the bottom of the plane that talks to ground based towers. In both cases, the wifi signal you request from your seat gets to the plane. But that’s only half the battle since the information has to get to you in your seat. And here’s where things get a little more complicated. Wireless signals bounce around in small spaces like airplanes, and not just off the walls. The seats, luggage, and even the passengers in their seats can disrupt the electromagnetic environment in an airplane and affect the way a wireless signal moves. And if people are up out of their seats moving around, and the drink cart is being pushed down the aisle, well, that just disrupts the environment more. This translates to a spotty internet connection, one that not only varies from seat to seat, it can vary depending on where your laptop is placed on that tray table in front of you.

Manufacturers are working on the problem. In 2012, Boeing filled an airplane’s seat with potatoes — spuds apparently mimic the electromagnetic disturbance of human flesh — to try and understand how wireless signals bounce around to bring stronger and more reliable wifi signals to future flights. And providers are doing their part, too, beefing up ground networks and developing new systems that can transmit more data. Do you guys use in-flight wifi, or do you like having an excuse to go offline when you fly? Let us know in the comments, and for more DNews every day of the week don’t forget to subscribe.