How Wireless Charging Works And Why It’s Terrible

April 22, 2024 by Maya Posch 76 Comments

Wireless charging is pretty convenient, as long as the transmitter and receiver speak the same protocol. Just put the device you want to charge on the wireless charger without worrying about plugging in a cable. Yet as it turns out, the disadvantages of wireless charging may be more severe than you think, at least according to tests by iFixIt’s [Shahram Mokhtari] and colleagues. In the article the basics of wireless charging are covered, as well as why wireless charging wastes a lot more power even when not charging, and why it may damage your device’s battery faster than wired charging.

The inefficiency comes mostly from the extra steps needed to create the alternating current (AC) with wireless coupling between the coils, and the conversion back to DC. Yet it is compounded by the issue of misaligned coils, which further introduce inefficiencies. Though various protocols seek to fix this (Qi2 and Apple’s MagSafe) using alignment magnets, these manage to lose 59% of the power drawn from the mains due to these inefficiencies. Wireless chargers also are forced to stay active, polling for a new device to charge, which keeps a MagSafe charger sucking up 0.2 W in standby.

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Pi Zero Runs DOOM Via Wireless Power

July 15, 2023 by Donald Papp 8 Comments

What’s better than a Raspberry Pi Zero running DOOM on a 3.5″ touchscreen? Running it over wireless power, of course!

[atomic14] has been interested in wireless power for a while, and while most of the hardware he’s tested over the years has been less than impressive, he demonstrates one that’s able to reliably deliver 5 V at about 1 A which is more than enough to boot a Raspberry Pi W2 into X and launch DOOM. But while that’s neat, he explains that wireless power isn’t quite yet an effortless solution.

The hardware can deliver 5 V at about 1 A wirelessly, which is plenty, but coil alignment is critical to efficiency.

For one thing, the hardware he’s using — similar to those used for mobile phone charging — need the receiver to be very close to the transmitter. In addition, they need to be aligned well or efficiency drops off sharply. For mobile phones this isn’t much of a problem, but it’s difficult to position a Raspberry Pi and display just so when one can’t see the coils. Misalignment means brownouts and other unreliable operation.

So while the wireless power is capable of running the Pi directly, [atomic14] attempts to put a small battery and charger circuit into the mix in order to make the whole thing both portable and more reliable. But because nothing is easy, he discovers that his charging board — which should be able to output as low as 4.5 V — isn’t able to be adjusted down any lower than 5.66 V. It turns out that a resistor marked 104 (which should be 100 kΩ) is actually measuring 57 kΩ, and the trim pot doesn’t go lower than 10 kΩ. The solution is a bit of component swapping, but we suppose it’s a reminder that sometimes with cheap parts, one pays in other ways.

You can see [atomic14]’s wireless power Raspberry Pi running the classic shooter in the video below. Wireless power may have its issues, but it’s certainly a lot less messy than running DOOM with a gigantic potato battery.

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A Guard Bot For Your Home Assistant

May 14, 2023 by Danie Conradie 31 Comments

While fixed sensors, relays, and cameras can be helpful in monitoring your home, there are still common scenarios you need to physically go and check something. Unfortunately, this is often the case when you’re away from home. To address this challenge, [PriceLessToolkit] created a guardian bot that can be controlled through Home Assistant.

The robot’s body is made from 3D printed components designed to house the various modules neatly. The ESP32 camera module provides WiFi and video capabilities, while the Arduino Pro Mini serves as the bot’s controller. Other peripherals include a light and radar sensor, an LED ring for status display, and a speaker for issuing warnings to potential intruders. The motor controllers are salvaged from two 9-gram servos. The onboard LiPo battery can be charged wirelessly with an integrated charging coil and controller by driving the bot onto a 3D printed dock.

This build is impressive in its design and execution, especially considering how messy it can get when multiple discrete modules are wired together. The rotating caster wheels made from bearings add an elegant touch.

If you’re interested in building your own guard bot, you can find the software, CAD models, and schematics on GitHub. If you’re looking to add other gadgets to your Home Assistant setup, we’ve seen it connect to boilers, blinds, beds and 433 MHz sensors.

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Wireless Charging For Border Patrol Drones

March 17, 2022 by Al Williams 43 Comments

It makes sense to use drones to patrol borders or perimeters. But there’s a problem. Drones have to carry batteries or fuel and mostly have a short operating time. A new paper from the University of Houston proposes a solution by recharging drones in flight using a novel wireless charging mechanism. What’s the cost? Another paper explores the economics of the approach.

The system relies on electric lines running along a border wall feeding wireless power transfer devices that allow the drone to recharge in flight. This is akin, we think, to an electric train that takes power from the third rail except, in this case, the power rail is wireless. Also, the drone would still have batteries to enable it to go off the rail as needed.

The paper mentions that the source power could be from wind or solar, but that’s not necessarily important and it also requires a storage battery in the system that you could omit if using conventional power. In addition, you’d think batteries and solar panels might be targets for theft in remote areas.

The paper mentions that another alternative is to simply have charging towers along the wall where drones land to recharge. This is easier, we think, but it does put the drone out of full operation status while charging. On the other hand, cheap drones could work in shifts to cover an area, so it seems like that might be a better solution than charging while flying.

What do you think? How would you make a long-duration drone? Fuel cells? In-flight battery swapping from a refueling drone? Laser power? Maybe a magnetic battery swap system where the drone swoops over a charger to drop off and pick up a fresh battery? Let us know what you would try or — even better — what you have done.

We’ve seen a drone pit stop robot already. Refueling drones have been done, too. But it does seem like something better is possible.

Adding Wireless Charging To The Switch Lite

October 13, 2021 by Tom Nardi 3 Comments

The Nintendo Switch is a monstrously popular machine, and it’s had no difficulty raking in the bucks for the Japanese gaming giant, but there’s no denying that it’s technologically a bit behind the curve. Until the long-rumored “Pro” version of the Switch materializes, industrious gamers like [Robotanv] will simply have to make up for Nintendo’s Luddite ways by hacking in their own upgraded hardware.

In this case, [Robotanv] wanted to add Qi wireless charging to his Switch Lite. He figured that if all of his other mobile devices supported the convenient charging standard, why not his portable gaming system? Luckily, the system already supports the increasingly ubiquitous USB-C, so finding an aftermarket Qi receiver that would connect to it was no problem. He just needed to install it into the handheld’s case.

After liberating the Qi receiver from its protective pouch enclosure to get it a bit thinner, [Robotanv] taped it to the inside of the system’s case and ran thin wires to the rear of the USB-C port. As luck would have it, Nintendo was kind enough to put some test pads for the power pins right behind the port, which made for an ideal spot to connect the charger.

At first he only connected the positive and negative lines from the charger, but quickly realized he also had to connect the CC pin to get the juice flowing. After that, it was just a matter of buttoning the system back up. All told, it looks like a pretty simple modification for anyone who’s not bashful about taking a soldering iron to their $199 console.

We’ve seen these Qi receivers retrofitted into devices before, and it remains an excellent way to add the feature not only to commercial products, but to your own projects.

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19 Coils Make Charging Wireless

June 20, 2021 by Al Williams 57 Comments

Wireless charging is conceptually simple. Two coils form an ad hoc transformer with the primary in the charger and the secondary in the charging device. However, if you’ve ever had a wireless charging device, you know that reality can be a bit more challenging since the device must be positioned just so on the charger. Xiaomi has a multi-coil charger that can charge multiple devices and is tolerant of their positioning on the charger. How does it work? [Charger Lab] tears one apart and finds 19 coils and a lot of heat management crammed into the device.

The first part of the post is a terse consumer review of the device, looking at its dimensions and features. But the second part is when the cover comes off. The graphite heat shield looks decidedly like an accidental spill of something, but we’re sure that’s just how it appears. The coils are packed in tight in three layers. We have to wonder about their mutual interactions, and we assume that only some of them are active at any given time. The teardown shows a lot of the components and even pulls datasheets on many components, but doesn’t really go into the theory of operation.

Still, this is an unusual device to see from the inside. It is impressive to see so much power and thermal management in such a tiny package. We wonder that we don’t see more wireless charging in do-it-yourself projects. We do see some, of course. Not to mention grafting a charging receiver to an existing cell phone.

Gaming Headset Gets Simple Wireless Charging

May 17, 2021 by Tom Nardi 9 Comments

Despite the technology itself being widely available and relatively cheap, devices that offer wireless charging as a feature still aren’t as common as many would like. Sure it can’t deliver as much power as something like USB-C, but for low-draw devices that don’t necessarily need to be recharged in a hurry, the convenience is undeniable.

Sick of having to plug it in after each session, [Taylor Burley] decided to take matters into his own hands and add wireless charging capability to his Turtle Beach Recon 200 headset. But ultimately, there’s nothing about this project that couldn’t be adapted to your own particular headset of choice. Or any other device that charges via USB, for that matter.

To keep things simple, [Taylor] used an off-the-shelf wireless charging transmitter and receiver pair. The transmitter is housed in a 3D printed mount that the headset hangs from, and the receiver was simply glued to the top of the headset. The receiver is covered with a thin 3D printed plate, but a couple turns of electrical tape would work just as well if you didn’t want to design a whole new part.

Once everything was in place, he then ran a wire down the side of the headset and tapped into the five volt trace coming from the USB port. So now long as [Taylor] remembers to hang the headset up after he’s done playing, the battery will always be topped off the next time he reaches for it.

Considering how many projects we’ve seen that add wireless charging to consumer devices, it’s honestly kind of surprising that it’s still not a standard feature in 2021. Until manufacturers figure out what they want to do with the technology, it seems like hackers will just have to keep doing it themselves.

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