I’m looking for some advice from the EEs out there. My company has dozens of iPhones/iPads/Android tablets, etc. and I’ve been asked to build an inventory solution for these that will involve cataloging and check in/out. More to come on this later. The problem I want to discuss now is how to have all these devices in the storage device charging at the same time and in as little space as possible. In other words, I don’t want to have a separate power supply for each device.
My best idea so far is to use a PC power supply (ex. +5V 25A) and wire up some USB ports to the +5V output. Assuming all the devices are iPads that can pull 2.1A each then I could charge 11 or so off one power supply. So, my question is - is it enough to just supply +5V or does the charger need to have more intelligence than this solution would provide?
The reason I’m looking at this problem first is that our CEO approached me with a very similar problem today. He travels with several of these devices and wants a single solution for charging them all on the road instead of carrying a bag full of chargers around. If this will work then I’ll build something very special for him.
There is doco on how to get an iDevice to charge out “there”; it’s not as simple as wiring up the appropriate power supply, but from memory it’s not that hard either (the device senses current on a data line or something equally weird).
I have tried to charge an iphone by modding a 12v Car Cigarette Lighter adapter to an USB A receptacle. I did not have much luck, the phone would charge for a short duration and display a “This accessory is not made …” error.
I have read the article that Brett has pointed out, but need to try it sometime.
Thanks for the info, guys! One other question - in the MintyBoost they are using an LT1302 to step up the 3V3 to 5V. If I’m using +5V directly from a quality power supply, do you recommend adding something between the power supply and the iPad to regulate or would I be safe just running the +5V directly to the USB?
That looks nice but I don’t think it’s going to work for what I need. I’ll need to be able to charge at least 4 devices simultaneously. That device can only supply a max of 1A. A single iPad can consume 2.1A.
The minty is not designed to charge a tablet, but is fine (albeit slow) for smartphones and other stuff that draws a maximum of 500mA.
Charging 4 devices at once “on the road” will obviously require something big and beefy. It might weigh more than all those chargers, and draw attention during airport screening…