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Groups > comp.sys.raspberry-pi > #25511 > unrolled thread

Pi power

Started byTim Streater <timstreater@greenbee.net>
First post2021-01-05 22:54 +0000
Last post2021-01-09 12:03 +0200
Articles 5 on this page of 45 — 21 participants

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  Pi power Tim Streater <timstreater@greenbee.net> - 2021-01-05 22:54 +0000
    Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-05 23:16 +0000
      Re: Pi power "Mayayana" <mayayana@invalid.nospam> - 2021-01-05 19:59 -0500
        Re: Pi power A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-06 07:31 +0000
          Re: Pi power "Mayayana" <mayayana@invalid.nospam> - 2021-01-06 08:18 -0500
          Re: Pi power jornws200602@xs4all.nl (Oscar) - 2021-01-06 14:02 +0000
      Re: Pi power mjb@signal11.invalid (Mike) - 2021-01-06 09:44 +0000
        Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 10:31 +0000
          Re: Pi power Tim Streater <timstreater@greenbee.net> - 2021-01-06 10:44 +0000
            Re: Pi power Joe <joe@jretrading.com> - 2021-01-06 11:03 +0000
        Re: Pi power Tim Streater <timstreater@greenbee.net> - 2021-01-06 10:32 +0000
          Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 10:57 +0000
            Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 11:44 +0000
              Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 12:10 +0000
                Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 13:25 +0000
                  Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 14:41 +0000
                    Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 15:17 +0000
                      Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 16:05 +0000
                        Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 16:14 +0000
          Re: Pi power A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-06 12:02 +0000
        Re: Pi power Andy Burns <usenet@andyburns.uk> - 2021-01-06 10:55 +0000
          Re: Pi power Chris Green <cl@isbd.net> - 2021-01-06 11:19 +0000
            Re: Pi power Axel Berger <Spam@Berger-Odenthal.De> - 2021-01-06 13:13 +0100
              Re: Pi power Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-06 12:47 +0000
                Re: Pi power Joe <joe@jretrading.com> - 2021-01-06 20:20 +0000
                  Re: Pi power druck <news@druck.org.uk> - 2021-01-06 20:43 +0000
                Re: Pi power Eli the Bearded <*@eli.users.panix.com> - 2021-01-06 23:08 +0000
                  Re: Pi power Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-07 07:40 +0000
                    Re: Pi power Axel Berger <Spam@Berger-Odenthal.De> - 2021-01-07 09:08 +0100
                      Re: Pi power John Aldridge <jpsa@cantab.net> - 2021-01-07 09:20 +0000
                    Re: Pi power The Natural Philosopher <tnp@invalid.invalid> - 2021-01-07 08:16 +0000
                    Re: Pi power druck <news@druck.org.uk> - 2021-01-07 09:53 +0000
                      Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-07 12:40 +0000
                    Re: Pi power Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2021-01-07 19:29 +0000
                    Re: Pi power David Higton <dave@davehigton.me.uk> - 2021-01-07 21:05 +0000
            Re: Pi power Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-06 12:39 +0000
              Re: Pi power Chris Green <cl@isbd.net> - 2021-01-06 17:04 +0000
                Re: Pi power Theo <theom+news@chiark.greenend.org.uk> - 2021-01-06 18:02 +0000
            Re: Pi power Theo <theom+news@chiark.greenend.org.uk> - 2021-01-06 16:41 +0000
              Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 17:04 +0000
                Re: Pi power druck <news@druck.org.uk> - 2021-01-06 18:50 +0000
                  Re: Pi power Martin Gregorie <martin@mydomain.invalid> - 2021-01-06 20:39 +0000
              Re: Pi power TimS <timstreater@greenbee.net> - 2021-01-06 18:58 +0000
    Re: Pi power Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2021-01-08 22:33 -0500
      Re: Pi power Anssi Saari <as@sci.fi> - 2021-01-09 12:03 +0200

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#25563

Fromdruck <news@druck.org.uk>
Date2021-01-06 18:50 +0000
Message-ID<rt50ot$fa1$1@dont-email.me>
In reply to#25552
On 06/01/2021 17:04, Martin Gregorie wrote:
> On Wed, 06 Jan 2021 16:41:25 +0000, Theo wrote:
> 
> 
>> Maybe there are use cases where people want to
>> power their Pis from HDMI, I don't know.
>>
> Doing that would make the installation tidier if I wanted to glue the Pi
> enclosure to the back of the screen - provided that the screen
> can provide the wattage needed. Is that likely, bearing in mind that, if
> I did that, I'd also want it to power a keyboard and mouse via the USB
> sockets on the Pi.

HDMI will never power a Pi, way too thirsty.

Similar devices such as an Amazon Firestick have to have an external 
PSU, as they require more power than even the TV's USB port can supply. 
Note that if this does seem to work, you are probably overstressing your 
TVs electronics, which will lead to premature failure.

---druck

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#25569

FromMartin Gregorie <martin@mydomain.invalid>
Date2021-01-06 20:39 +0000
Message-ID<rt5756$quk$2@dont-email.me>
In reply to#25563
On Wed, 06 Jan 2021 18:50:04 +0000, druck wrote:

> On 06/01/2021 17:04, Martin Gregorie wrote:
>> On Wed, 06 Jan 2021 16:41:25 +0000, Theo wrote:
>> 
>> 
>>> Maybe there are use cases where people want to power their Pis from
>>> HDMI, I don't know.
>>>
>> Doing that would make the installation tidier if I wanted to glue the
>> Pi enclosure to the back of the screen - provided that the screen can
>> provide the wattage needed. Is that likely, bearing in mind that, if I
>> did that, I'd also want it to power a keyboard and mouse via the USB
>> sockets on the Pi.
> 
> HDMI will never power a Pi, way too thirsty.
> 
> Similar devices such as an Amazon Firestick have to have an external
> PSU, as they require more power than even the TV's USB port can supply.
> Note that if this does seem to work, you are probably overstressing your
> TVs electronics, which will lead to premature failure.
>
Makes sense in light of the content of earlier posts: if the HDMI cable 
only carries power so it can wake up some HDMI chip in the, possibly 
powered-off, device at the far end which tells the initiator what it is 
talking to and what that can or cannot do, then it follows that doing 
this only needs a few milliamps.
  
I thought that might be the case: thanks for confirming it.


-- 
--  
Martin    | martin at
Gregorie  | gregorie dot org

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#25564

FromTimS <timstreater@greenbee.net>
Date2021-01-06 18:58 +0000
Message-ID<i5mfiuF87baU2@mid.individual.net>
In reply to#25551
On 06 Jan 2021 at 16:41:25 GMT, Theo <theom+news@chiark.greenend.org.uk>
wrote:

> Chris Green <cl@isbd.net> wrote:
>>  Andy Burns <usenet@andyburns.uk> wrote:
>>  > The Pi is the HDMI source, and the monitor is the HDMI sink, per the 
>>  > spec the 5V power should be supplied from the Pi to the monitor, not the 
>>  > reverse ...
>>  > 
>>  I've heard it said that the HDMI spec is a real can of worms.
>>  
>>  This thread is just another thing that increases my dislike of HDMI.
> 
> It's exactly the same with VGA.
> 
> The purpose of this is for the computer to read the EDID ROM from the
> monitor.  It supplies 5V to allow detection of the connected monitor even if
> it's turned off.
> 
> The monitor/KVM should not be emitting power on this rail.

I shutdown the Pi and when it had, turned off its power at the switch on the
socket strip. This caused the green-LED fluttering I mentioned before. I then
disconnected the HDMI cable from my Mac (the cable that goes to the other
input of the KVM unit). The green and red LEDs on the Pi then went out.

So it's my Mini that's doing this, but that is perhaps not surprising given
what I've learnt in this thread.

-- 
Tim

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#25636

FromDennis Lee Bieber <wlfraed@ix.netcom.com>
Date2021-01-08 22:33 -0500
Message-ID<go8ivfl9gdjb0i5spvcm7hgnlmj3op6r6c@4ax.com>
In reply to#25511
On 5 Jan 2021 22:54:36 GMT, Tim Streater <timstreater@greenbee.net>
declaimed the following:


>The Pi carried on being powered. After dismissing the possibility of sentient
>self-powered computers taking over, I discovered that the volts were coming
>via the HDMI port.
>
	https://en.wikipedia.org/wiki/HDMI look at the pin-out... Pin 18 is
intended to provide power for "active cables"
https://www.hdmi.org/spec/hdmi2_1 https://www.hdmi.org/spec21sub/cablepower


-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
	wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

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#25645

FromAnssi Saari <as@sci.fi>
Date2021-01-09 12:03 +0200
Message-ID<sm08s924ebc.fsf@lakka.kapsi.fi>
In reply to#25636
Dennis Lee Bieber <wlfraed@ix.netcom.com> writes:

> 	https://en.wikipedia.org/wiki/HDMI look at the pin-out... Pin 18 is
> intended to provide power for "active cables"
> https://www.hdmi.org/spec/hdmi2_1 https://www.hdmi.org/spec21sub/cablepower

Cable power yes, but it's also very convenient that an HDMI port can
power an HDMI to VGA converter. There are so many old projectors in so
many meeting rooms with VGA cables even today. The minimum current to
provide through pin 18 is only 55 mA though. Not enough to run a Pi.

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