I’ve done something very similar to this. I’ve added the wireless charging coil on the inside of the Samsung Tab A10 and soldered the coil wires directly to the usb port on the inside. So from the outside the device looks unchanged. On the wall i mounted the wireless charger with 3 coils, bought from AliExpress.
At first I wanted to mount the tablet using strong natural magnets on the inside of the carging device and metal plates on the tablet, but this didnt work too well, so now new idea is to create a 3d printed cradle that will latch onto charging device in either horizontal or vertical orientation. I can maybe post some pictures soon.
I have around 12 tablets around the house, many Lenovo Tab3/4 7" and 10", a few Huawei, and a Samsung (still under tests).
I remove their batteries, but I still keep the small battery pcb for the thermistor and id pins, add an Arduino ProMini to power them on after a power loss, add some wires for power. Most of them don’t have the back anymore, I want them to be as slim as possible, under 9mm.
The frames are lasercut from 3x3mm transparent acrylic and a laserable stainless steel looking plastic (Innoplastics LaserPlus)
I disassembled a USB-c wireless charging receiver and only used the small USB connector.
I placed a normal in-wall USB charger and mounted the tablet with velcro.
I did something very similar, but I’ve removed both coils and connected pads on charger and receiver by wire, which is hidden in the wall.
That said has got more stability (wireless is quite often interupted) and as well more stable power.
Now I’m thinking more about using that flat connector as extender for normal cable which will be powered by standard usb charger as I dont really trust in terms of reliability of those wireles boards …
The tablet is flush in the wall. I then put a picture frame through the table saw to make it the right thickness. I used a recessed wall plug behind the tablet.
I tried a solution with an Amazon Fire Tablet 10 and FKB integration. I used a wireless charger with a sonoff switch to automatically charge the tablet or disconnect it. The magnet is strong enough to hold the tablet in place and I experienced no issues.
Although this solution is not very energy friendly as much energy is lost in heat. I found that the tablet consumes quite a lot of power even though FKB switched off the screen and the tablet was in “standby”. I had cycles of 8 hours powered by battery which I found way too few, without switching on the screen. Maybe someone is interested in my wood work, see pitcures below
Hi. Can you please explain how did you find which cable is + and - from the wireless usb? I also try to do the same but I am not sure for the polarity.
Best / safest way is to measure it… Remember, these things work on smoke. Once the smoke escapes because you did something silly, they don’t work any more
I remove the actual batteries, keep the control board from the batteries (it has a thermistor and sometimes other smart chips depending on the model), and power via the actual battery tabs on the original battery control module via some 12V to 4V adjustable DC-DC buck converter (LM2596).
I remember that once modding a Huawei (worst in the world, cannot be rooted, locket BL, sh*tty firmware) that I bent the battery which was glued to the case with the strongest glue in the world and it started swelling, took it out that moment, and toss it as far as I could control board included, back case included. Then the tablet would boot if powered but kept shutting down instantly with “Battery error”. The battery connector has 3/4 terminals Vcc, Gnd and a thermistor pin, just put a resistor there to emulate the normal temperature for the missing battery and it kept working ever since.
Another funny story with a Samsung this time, using all original board, set the reg voltage to 4.08-4.1V so tablet boots up and shows something like 97% Bat, then after an hour or so it goes to 50% ?!? Check voltages, all good, 4.1V, WTF? It has some sort of a sh*tty software counter which shows the battery as running down even though it’s wall powered, that counter is baked into the hw somehow (changing roms doesn’t solve it). What I did was use Tasker (thanks God Samsung is rootable) to run “dumpsys battery set ac 1” at boot and then the she’s always happy running forever.
LE. I use a small arduino ProMini 5V in each of them to give them a power on signal on the power button pins at powerup (simple sketch like: wait 5s, apply a 500ms low pulse to boot it up, wait forever), much more reliable than software automatic boot tricks and cheap too ($1 per ProMini)
I read, that wireless charging is not safe for 24/7 charing, it should get very hot.
It was my first option for wall mount tablet and charing, but maybe I should use USB-C Flexcable instead, but my idea is, to take the tablet from the mount any time.
The heat generated by any electronic device (phone, tablet, wireless charger, USB power bank, AD adapter, etc.) is due to the fact that energy transfer/conversion is never a 100% efficient process. When you have inefficient energy transfer, most of the lost energy becomes heat. Last I heard, it’s generally about 80% efficient, and 20% lost energy (but I haven’t looked that up in a long time).
If a tablet is constantly trying to draw max power from a wireless charger, it’ll generate a lot of heat. And if it keeps doing that, the heat will build up. That’s usually bad for a device’s battery (and electronics). So in these cases, 24/7 wireless charging would probably be unsafe.
Some newer wireless devices and chargers have temperature sensors and maintenance modes to manage the heat. So they’ll turn on for awhile, then turn off when there’s too much heat (I’m oversimplifying). However, if you use a 3rd-party wireless coil that plugs into a USB port, the tablet won’t know any of that. As far as it’s concerned, it’s just a USB cable. So it might be fine, but it really depends on how the tablet consumes power. And even if it’s good, it has no idea that there’s a wireless charger generating heat next to its battery.
So yeah, it depends.
Personally, I don’t recommend this. If you’ve got an old tablet or phone laying around, just repurpose that as a permanent fixture. That way, your OH information screen is always where you expect find it, and not sitting on a table somewhere with a dead battery.
Speaking of batteries, if you use an old device you should regularly check to ensure that they aren’t bulging at the seams. When that happens, those batteries are a fire risk and should not be charged.
