One basic need of a computer scientist is to measure the power that a USB device drains off the PC. This device is plugged between the PC and a USB device and displays the current on an LCD. For currents under 100mA it is displayd in 0.5mA steps and 1mA steps for currents over 99.5mA. It is built with an AVR programmed in assembler.
It comes with a little adapter.
It is built up with a Texas Instruments INA226 I2C current sensor. I got the chip as a free sample. The brain is an ATmega32. The AVR runs at 1MHz and drives the LCD (see this project). As the INA226 comes in a very small S-PDSO-G10 package with a 0.5mm grid it was essential to use an etched PCB.
The layout made with EAGLE.
The gut of the device. The LCD module is very compact and uses no more space than the LCD itself.
Here the device is hooked up to the ATMEL JTAG ICE and displays a current of 217mA.
One can nicely show the difference in the current of an inactive USB stick (left) and while copying files (right)
Of course it is also possible to hook it up to a phone charger.
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