That explanation is excellent, thank you!
I do believe I'll need your help acquiring a 4A power supply, though, since
the current prototype is experiencing power loss on a 3A wall wort. Part of
this (much of it) might just be resistance along its wire. It's got like a
6 foot UBS cable.
Can you recommend a part? I genuinely wouldn't start contemplating
Frankenplug up there if I wasn't reaching the bottom of the idea barrel.
*Andrew R Gross, (he/him)*
412.657.5332 -
<http://www.shrad.org>
On Sat, Nov 19, 2022 at 12:22 AM Jake <jake(a)spaz.org> wrote:
the Pi does not need 3 amps. That would be 15 watts.
Since the Pi has
USB sockets, its theoretical demand could include those sockets, but the Pi
itself probably tops out at less than 1.5 amps:
"...the RPi 4B power dissipation tops out at approximately 6.4 Watts..."
which is 1.28 amps.
https://raspberrypi.stackexchange.com/questions/114239/pi-4-maximum-power-c…
to answer your other question about power supplies, first I can say that
there are definitely 4-amp 5V supplies and I can probably find one, but it
won't be necessary, I think 2 or 3 will be enough for what you're doing.
As for why you can't put regulated power supplies in parallel, think of it
this way: a regulated power supply (like all the ones you looked at) has a
chip which is adjusting the power production in order to achieve the
correct voltage at the output terminals, which is in this case 5.0 volts.
If you connect two power supplies together, their output terminals see the
voltage that they're both connected to, so if one does the job of making 5
volts, the other says "well I guess that's taken care of, so i don't have
to do anything" or worse, they're exactly equal, and they both
simultaneously try to do the job of making 5v, but end up tripping over
each other and bumping into each other, causing chaos. In most situations
it will probably work OK, but only because switching power supplies can
usually do more power than they're rated for so you're getting lucky.
When people do "power injection" with long addressible LED tapes, the
resistance of the LED tape's power wires ends up helping them by creating
electrical distance between the power supplies.
-jake
On Fri, 18 Nov 2022, Andrew R Gross via sudo-discuss wrote:
I need to power a device with an LCD screen
running on a Raspberry Pi.
Both need 5 V. The Pi needs about 3 Amps. The screen needs between 0.5
and
1 A, depending on brightness. So I figure I can
power both off of a
shared
5 V power supply as long as it provides at least
4 A. But I can't find a
5V
4A power supply. So I'm wondering... could I
just wire two 5V 2.5A power
supplies in parallel? Would this work? I feels wrong but I can't think of
why.
[image: image.png]
*Andrew R Gross, (he/him)*
412.657.5332 -
shrad.org <http://www.shrad.org>