At work we have a pile of devices that we test software on. It’s mostly a giant mass of Android or Android-like devices. Suffice to say they all charge from a USB plug.
One of the problems is keeping track of all these devices and charging them.
I think I might have a solution to at least part of this: I can build a mass charger.
Basically all it minimally needs to be is a 5V industrial power supply, some USB sockets and some resistors to tell the device that’s being charged that this is a high power charger. The trick is that the standard varies between iOS devices and the general Android device. For Android the spec (I think stupidly) is to short out the data lines. For iOS it’s applying varying voltages to the data lines. I think the Android solution, while simple, is stupid because you only have exactly one way to short the lines. Voltages can vary endlessly to tell the device how much current can be supplied.
But this whole thing got me thinking. Wouldn’t this be a cool design project if you can make this a bit smarter?
If you throw on a sense resistor on the high side of the charger for each port you could tell how much power is being drawn from each port. That coupled with an amplifier you can wire up to an analog-to-digital converter (ADC) of a micro controller to monitor these devices and tell you when they have been charged. (Their current would drop) You could also maybe even have it email you when the device you were waiting to test is charged.
That’s the V1 plan.
V2 could be a lot harrier. What if you could actually talk USB to the devices to see which one is plugged in? Or perhaps you could just affix RFID sensors to the devices to check them in and out… our Amazon badges have an RFID chip in them as well so we could maybe make a device library where you can know who has what device. Hell, you might even get it to lock if you didn’t badge in. If you’re looking for a particular device you could just check the dashboard to see who’s checked it out.
The possibilities are limitless! :-D
For some reason I really geek on stuff like this… it’s just so cool.