On 22/02/2021 11:14, Dave Plowman (News) wrote:
In article ,
Adrian Caspersz wrote:
On 22/02/2021 09:14, Brian Gaff (Sofa) wrote:
The whole point though is for that to also be a charger, though I have to
say I'm not greatly impressed with their efficiency.
To support the ATX soft start button and wake-on-LAN features, PCs have
long offered a permanent 5V standby supply.
Yes.
So this USB powering thing is using something that was already there as
an independent subsystem. This would be as efficient as a typical
plug-in wall adapter (I'd hope).
But if you'd something like an external HD plugged into USB, does it make
sense for it to be powered 24/7?
Why not?
q
Since all modern 2.5" HDDs are more or less common in their
implementation we can use this specification as a reference, but keep in
mind that other drives could have deviation up to 20% in comparison to
this one (like in question's table).
For archival purposes here is an excerpt from the specification.
Typical power measurements are based on an average of drives tested,
under nominal conditions, at 25°C ambient temperature. These power
measurements are done with DIPM enabled.
Spinup current is measured from the time of power-on to the time
that the drive spindle reaches operating speed.
Read/Write current is measured with the heads on track, based on
three 64 sector read or write operations every 100 ms.
The drive supports two idle modes: Active Idle mode and Low Power Idle
mode.
Power Dissipation 5TB, 4TB & 3TB models
+5V input average (25° C)
Spinup (max) 1.2A (6W)
Write average 2.10W
Read average 1.90W
Idle, low power mode 0.85W
Standby/sleep 0.18W
Standby power is measured at steady state (after 200ms from transition)
/q
from:
https://superuser.com/questions/1171...ve-connected-t