On 2019-01-24, druck  wrote:
> On 23/01/2019 07:37, Rick Christian wrote:
>> 2.5A is the RECCOMENDED POWER SUPPLY. So easy math 3A. Done.
>
> [Snip]
>
>> 10 x 3 = 30Amps.
>
> While rounding up is immaterial for a single power supply, it gets silly
> if you multiply it, and could end up costing more for bigger PSU and
> heavy duty wiring which isn't needed.

It's also general advice based on typical circumstances.  In
particular it assumes that the Pi is loaded up with a few peripherals
e.g. mouse, keyboard, a USB stick and other random devices and that
power are all coming from the same power budget.  For a home user
with a single device that isn't a bad assumption, but in the case
of tens of them in a rack it is an assumption that breaks down,
put simply they won't all be hooked up to a head and input devices
at the same time.  You're also far less likely to have random
devices hooked up to them all, e.g. how many TV tuners or remote
control sensors do you need?

I'd be perfectly happy with a good 60W PSU, that gives you plenty
of headroom for the Pis without the additional expense, bulk and
power wastage of a pointlessly over-rated supply.

--
Andrew Smallshaw
andrews@sdf.org

--- SoupGate-Win32 v1.05