The Raspberry Pi computer and its power requirements
I thought i would bring you some notes on the Raspberry Pi and the power required.
I currently have bought a power supply from RS components that works really well,
it outputs 1200mA at 5 volts.
I also bought a power supply from e-Bay for the Raspberry Pi, it outputs 1000mA at 5 volts.
this also works well and runs the Pi without any problems.
OK I thought lets try from a PC USB port so connected my Pi to the USB port on my laptop
using a Nokia USB to micro usb cable. The Pi starts up and displays through the RCA port
that I use to connect to my TV, but the PI USB port will not work so the keyboard doesnt
do anything, this is probably due to the fact that most USB ports are limited to outputting
500mA per port.
So my next attempt was to use a dual USB to single USB cable that came with a USB hard disk
drive housing. This fits the PC fine, but the USB at the PI end is a Male full size one
so it doesnt fit the PI. Right I am now going to buy a Samsung Galaxy S11 USB female to
micro USB male that will fit the PI.
The results are as the picture below
I have laid out a further two cables to the right of the laptop unconnected so you can see
what they look like.
As you probably cant see from the picture, in actual case the Pi is running fine, the twin
to one cable allows about 1000mA to the Pi and it works fine with the USB ports running
connected to a USB disk drive.
If you look at the Pi Specifications it says power required 700mA so all the 3 above solutions
provided adequate power to make the Pi run.
I had one failure - I bought a very cheap powered USB port (about £3.50) from e-Bay, and even
with the double cable, the Pi would only just start up, so this one doesnt produce enough power via 2 usb ports
to power the Pi.
So my recommendation is to buy a 5v power supply with at least 1000mA to run
the Pi, as running from the USB ports on a laptop will limit movement with the laptop, unless
you are running the Pi with a wireless interface.
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