This is a simple 6 port USB device charger with a individual current monitor on each port. The charging current is indicated using RGB LEDs. Blue means slow charge (under 250mA), green means 250mA to 750mA, red means over 750mA, and purple means over 1500mA (for tablets). This circuit involves an ATmega328P, INA169, and a OKR-T10-W12.
The problem I faced was that I had too many devices to recharge at once, not having enough chargers and not having enough AC jacks. Also my new Sony wireless headset was being picky about both the cable I use and the charger I use. I decided to troubleshoot this problem by building this tool.
Construction is mainly done on perfboard, using through hole components mostly (where I must or where I need mechanical strength), mixed with surface mounted components whenever possible (0603, 0805, and SOT-23-5). Wiring is done using 30 gauge Kynar coated wire, with thicker wiring where high current is needed. A decently capable wall-wart is needed, anywhere between 4.5V to 12V is acceptable, and it must be able to supply enough current for all the devices to be charged. A DC/DC converter is used to increase efficiency, so a 12V wall-wart supplying 4A can actually charge about 8A total. A piece of acrylic plastic on the bottom prevents the wiring from being damaged when the circuit is sitting on a desk or being handled. The D+ and D- signals have the appropriate resistors to enable high charging rates on Apple devices (which is also compatible with Sony, Samsung, and other brands).
This project is inspired by Adafruit’s USB current gauge.
More pictures, the schematic, and the firmware source code are available on Frank’s website.