[Nut-upsuser] Weekend Puzzle: computer posing as an UPS

[Jim Klimov]

I guess I should scratch the idea about fan sockets as the power source:
they are rated typically at 0.2A each, so fan headers should be expected 1A
max (3A in some vendors/models), well under the 5A that the RPi5 wants.

Jim


On Sat, Sep 28, 2024 at 11:52 AM Jim Klimov <jimklimov+nut at gmail.com> wrote:

> Follow-up:
>
> * Powering the Raspberry Pi5 from an USB-C port wired on the motherboard
> was much more promising, it survived over 8 hours building NUT in a loop
> (in a tmpfs). And in the morning I found it turned off (red light on the
> Pi).
>
> * Per
> https://stackoverflow.com/questions/4702216/controlling-a-usb-power-supply-on-off-with-linux
> it seems not possible to programmatically truly power-cycle USB port/hub,
> as 5V pins are "always on"; and per
> https://stackoverflow.com/a/16316401/4715872 - at least not on MoBo ports
> (some hubs may have invested into being fully up to spec and control power
> fully). The referenced uhubctl <https://github.com/mvp/uhubctl> on my PC
> said "No compatible devices detected!" so I guess that's it.
>
> * Whatever I could find with (suggestions welcome) `grep -r . `find
>  /sys/devices/pci0000\:00 -name '*usb*port*'` /sys/bus/usb/devices/` did
> not expose any differences beside timestamps with the RPi5 plugged and off,
> unplugged, and plugged back in again (with auto-boot). I hoped for some
> power draw statistics to at least learn which port it lives on, to try
> managing that somehow.
>
> * Overall, housing the Pi inside a cooled and somewhat dust-protected PC
> case seems a neat idea, but for powering the Pi, it seems I would need to
> use a real wall-power adapter (as noted many times on the net, ideally
> Raspberry's own one as others tend to vary in actual voltage provided under
> load).
>
> * But before that, I'm thinking if I could tap into the ATX power supply
> though (using "HDD" or "FDD" plugs) or fan sockets (could be individually
> manageable? gotta exempt one from OS/HW temperature-based mgmt then).
>
> Did anyone trod these side paths yet, any learnings? :D
>
> Jim
>
>
>
>
>
>
>
> On Fri, Sep 27, 2024 at 4:43 PM Jim Klimov <jimklimov+nut at gmail.com>
> wrote:
>
>> FWIW, a few lessons learned:
>>
>> * Different USB-A sized ports (even if marked USB-3.2) did not prove a
>> stable source, with Pi5 occasionally turning off or rebooting. Sort of
>> behaved well for days, but as soon as I added load like package installs or
>> NUT builds, it did not survive 5 minutes...
>>
>> * Might be the MoBo turning off or cycling the port due to "overload"?..
>>
>> * Tried the `usb_resetter` script (referenced in NUT contribs) and host
>> `dmesg` did show re-detection of keyboard etc., but a turned-off Pi did not
>> boot up. Did not check much further, but did harbor hopes that a funny NUT
>> driver could "shutdown/reboot" the USB port acting as an UPS for Pi...
>>
>> * The Pi power socket is dumb-USB so the host does not "see" any IDs
>> about it.
>>
>> * Currently trying with a USB-C port on the MoBo, and a USB-C to USB-C
>> cable rated for 60W -- and so far it survived a few loops of NUT fightwarn
>> builds. Complains of undervoltage fairly frequently (every 30-60s), but now
>> did not crash yet.
>>
>> Jim
>>
>>
>> On Mon, Sep 16, 2024, 13:57 Greg Troxel via Nut-upsuser <
>> nut-upsuser at alioth-lists.debian.net> wrote:
>>
>>> Kelly Byrd <kbyrd at memcpy.com> writes:
>>>
>>> > With USB-C ports and cables, there are a ton of profiles, I don't know
>>> what
>>> > the new Pi's support, but likely something like 3A @ 5V, 9V, or 12V
>>> over
>>> > USB-C
>>>
>>> Up to the RPI4, I was pretty sure there wasn't PD, just 5V and it drew
>>> what it drew, and you hoped that the supply was big enough.
>>>
>>> It seems the RPI5 will use PD if given a capable supply.  Looks like 5V
>>> 5A, and it won't negotitate higher voltages.   There's an official
>>> supply that does PD
>>>
>>>
>>> https://www.newark.com/raspberry-pi/sc1153/power-supply-usb-c-5-1v-5a-white/dp/82AK3955
>>>
>>> and the output spec is
>>>
>>>   5A at 5.1V, 3A at 9V, 2.25A at 12V, 1.8A at 15V
>>>
>>>   looks like a TUV seal
>>>
>>>
>>>
>>> I find Jim's way of using this interesting, but my approach is totally
>>> different.  First, when I'm using a Pi, it's because I want a low power
>>> computer that I can leave on all the time, or can place in a different
>>> physical location I don't particularly want to do things on a Pi instead
>>> of a desktop.  And then I want it to be reliable.
>>>
>>> That leads me to plug a power supply into a UPS, or to use POE (from a
>>> POE switch which is plugged into a UPS).  For RPI3, I found a POE
>>> ejector that splits the POE ethernet cable into ethernet only and a
>>> micro USB.
>>>
>>>
>>> _______________________________________________
>>> Nut-upsuser mailing list
>>> Nut-upsuser at alioth-lists.debian.net
>>> https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/nut-upsuser
>>>
>>
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