Inductive charging is a technology that has promised a lot, but hasn’t quite delivered on the promise of never needing to plug in your phone again. The technology behind it is surprisingly simple though, and [Vinod.S] takes us through it all with an ATtiny13-based example.
An inductive charger has to be clever in its operation, for if it were to operate continuously it would soon have more in common with an inductive hob and thus become a fire risk, so it has to be sure that a compatible device is resting upon it before it tries to transmit power. It achieves this by periodically sending out a pulse of power intended to wake any devices in contact with it, and the device responds with a serial data stream encoded onto the device’s field by modifying the resonance of the receiver tuned circuit. This is done by a pair of MOSFETs under the control of the ATtiny in [Vinod]’s device, resulting in a functioning inductive power receiver built on a piece of prototyping board and sporting a buck converter capable of supplying 5 volts suitable to charge a phone. You can find the code on GitHub and see it in action below the break.
This tech has made an appearance here before a few times, such as when a Qi charger was integrated into a Chromebook.
Continue reading “Implementing Qi Inductive Charging Yourself”
When you want to jam out to the tunes stored on your mobile devices, Bluetooth speakers are a good option. Battery power means you can take them on the go and the Bluetooth connection means you don’t have to worry about cables or wires dangling around. Unfortunately the batteries never seem to last as long as we want them too. You can always plug the speaker back in to charge up the battery… but when you unhook those cords they always seem to end up falling back behind the furniture.
[Pierre] found himself with this problem, but being a hacker at heart meant that he was able to do something about it. He modified his JAM Classic Bluetooth Wireless Speaker to include an inductive charger. It used to be a lot of work to fabricate your own inductive charging system, or to rip it out of another device. But these days you can purchase kits outright.
The JAM speaker was simply put together with screws, so no cracking of the plastic was necessary. Once the case was removed, [Pierre] used a volt meter to locate the 5V input line. It looks like he just tapped into the USB port’s power and ground connections. The coil’s circuit is soldered in place with just the two wires.
All [Pierre] had left to do was to put the speaker back together, taking care to find space for the coil and the new circuit board. The coil was taped to the round base of the speaker. This meant that [Pierre] could simply tape the charging coil to the underside of a glass table top. Now whenever his Bluetooth speaker gets low on battery, he can simply place it on the corner of the table and it will charge itself. No need to mess with cables.
Lights on the tree? Check. Presents under the tree? Check. Lights in the presents? Why not! If your gifts don’t look festive enough and you have a spare inductive charging system lying around the house—though, you could always build your own from scratch—you can brighten things up by installing a few LEDs in the packaging.
The Instructable takes advantage of those new-fangled LED Christmas lights, one strand of which typically draws under 1A and requires around 5V, putting it in the ballpark for popular induction systems used to charge cell phones such as the Powermat. In this particular example, the strand ran off 3 AA batteries, or 4.5V, which meant stepping down the voltage either with a power regulator or, more conveniently, a simple diode in series.
Some additional modifications to the packaging tidy up the installation, including carving out some of the cardboard to recess the receiver and securing everything with hot glue before wrapping it all in paper. You can see a quick demonstration video below.
Continue reading “More Lights For Your Presents”
This is an advanced inductive charging system into which [David McIntosh] has put a lot of hard work. It uses the same coil-based concepts that we’ve seen in other DIY systems, but the game changer is a communications function that just isn’t found in home brew versions of the hardware. It lets the receiver (device being charged) give feedback to the transmitter by rolling another signal into the EM field being generated.
Do why would you need feedback? Well, if the two coils are not positioned well, the power produced on the receiving end can vary greatly. For instance, you may have the wrong voltage because the coils are not balanced. Or there may not be enough current to properly start charging. The feedback system is designed to let the sending unit change frequency to try to account for physical orientation, or to shut itself off if the charge is just not possible. This is done in expensive commercial devices, and that’s what [David] used as his model.