Power Consumption of Raspberry Pi Model A

As part of my Chompr Pi experiment, I wanted to characterize the power consumption of the Raspberry Pi Model A. To do this, I built a little board that inserts a one ohm resistor in the return path of the power supply. I was then able measure the voltage drop over the resistor and using Ohm's law (V=I*R), calculate the current draw. You really need an oscilloscope to do this because the current draw is not constant. It varies as the processor load changes and peripherals are accessed.

Test board and scope probe attached to the Pi

Power consumption while booting (and then idle)

Power consumption while running 'apt-get update' over WiFi

Here is the approximate current consumption of the Raspberry Pi Model A in different scenarios

Idle, no WiFi            : 120 mA
Idle, with WiFi          : 250 mA
Boot                     : 200-250 mA
Boot, with WiFi          : 300-350 mA 
apt-get update over WiFi : 250 mA with occasional peaks as high as 400 mA
Shutdown with WiFi       : 300 mA with occasional peaks as high as 400 mA