Given that one of the projects I have in mind for my Raspberry
Pi is to build an autonomous robot I need to be
able to power it from batteries. Using a switching DC-DC converter
and a micro USB cable I’ve managed to get the Pi running of a set of AA
batteries. The DC-DC converter is important to:
- make sure that the Pi does not get subjected to excessive voltage (see this thread on the RaspberryPI forums), and
- to ensure that the supply voltage stays constant as the batteries run down
The RaspberryPi is designed to be powered from a phone charger and has a
micro-USB power input socket. I used this pinout
diagram of
the micro USB socket to work out which pins I needed for ground and +5v and
then used a multimeter to verify that this was correct.
At first I wasn’t able to to adjust the output voltage of the converter but
finally realised that it needs a load in order to be able to give a meaningful
output voltage. Not wanting to risk trashing the Pi I used a DC motor as the
load until I managed to get the converter’s output voltage to 5v.
Plugging the Pi into the converter’s output resulted in it booting and
appearing to be fully operational. My desk is currently too messy to be very
photogenic so the photo below shows the Pi powered on but on the kitchen table
without keyboard and monitor but with the multimeter that I was using to
monitor the voltage to the Pi during testing.
