iSight Power

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Al - 03 May 2007 14:15 GMT

I turn my iSight camera off and log off the software. Even though the
green light is not ON on the camera, it feels warm to the touch. Doesn't
the thing power down? Do I have to pull the USB plug every time I am not
using it?

Al

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Jolly Roger - 03 May 2007 15:27 GMT

> I turn my iSight camera off and log off the software. Even though the
> green light is not ON on the camera, it feels warm to the touch. Doesn't
> the thing power down?

It powers partly down, but not all the way.

> Do I have to pull the USB plug every time I am not
> using it?

That's totally up to you. I leave mine connected 24/7.

It's a Firewire plug (not USB), by the way.

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Al - 03 May 2007 20:59 GMT

> > I turn my iSight camera off and log off the software. Even though the
> > green light is not ON on the camera, it feels warm to the touch. Doesn't
[quoted text clipped - 8 lines]
>
> It's a Firewire plug (not USB), by the way.

I stand corrected.

It's just that I have on/off switches on most everything to save power.
It might only be 10 watts for my house, but times 10 million houses,
that's 100 Mwatts or at least one power plant and all the crap
associated with that.

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Clever Monkey - 03 May 2007 22:06 GMT

>>> I turn my iSight camera off and log off the software. Even though the
>>> green light is not ON on the camera, it feels warm to the touch. Doesn't
[quoted text clipped - 13 lines]
> that's 100 Mwatts or at least one power plant and all the crap
> associated with that.

Any standby power the iSight uses is dwarfed in comparison to the juice
a Mac sucks up when it is running. Assuming that FW devices are put
into a low/no-power standby when the Mac is asleep, this should be good
enough, no?

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David Empson - 04 May 2007 09:13 GMT

> >>> I turn my iSight camera off and log off the software. Even though the
> >>> green light is not ON on the camera, it feels warm to the touch. Doesn't
[quoted text clipped - 8 lines]
> into a low/no-power standby when the Mac is asleep, this should be good
> enough, no?

No.

The developer documentation for some Mac laptops says that the Firewire
port will supply power "if the computer is on or the power adapter is
connected".

I'm pretty sure I've observed this with my PowerBook G4 (DVI) - it was
supplying Firewire power while asleep, until I unplugged the power
adapter. I don't recall what I was using to test this - might have been
someone else's bus powered 2.5" hard drive.

In theory, the computer would also supply Firewire power while shut
down, as long as the power adapter is connected (I haven't tried that).

For desktop models (e.g. PowerMac G4), the developer notes are a little
vague. Early models say they only supply Firewire power while the
computer is on, later ones don't say anything specific about it.

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David Empson
dempson@actrix.gen.nz

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Clever Monkey - 04 May 2007 16:53 GMT

>>>>> I turn my iSight camera off and log off the software. Even though the
>>>>> green light is not ON on the camera, it feels warm to the touch. Doesn't
[quoted text clipped - 18 lines]
> adapter. I don't recall what I was using to test this - might have been
> someone else's bus powered 2.5" hard drive.

You mean it has its own wall-wart? I guess that is a different case.
Since Firewire is hostless, it may be that the device when powered on
tells the thing on the other end of the wire it is still alive, or
something.

> In theory, the computer would also supply Firewire power while shut
> down, as long as the power adapter is connected (I haven't tried that).

Again, I'm not sure what it means to say "power adaptor", but I assume
that the Firewire connection itself does not supply significant current
when the box is in ACPI S3, or "sleep" mode. That is, devices only
connecting via a proper 6-wire cable, and no external power adaptor,
will not draw significant power when the computer is in ACPI S3.

However, since the ACPI spec allows for implementations that track the
state of USB and Firewire devices, it may be necessary to keep them
powered up. Not to mention that getting ACPI, USB and Firewire
implementations to play nice has been a challenge, to say the least.

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Tom Harrington - 04 May 2007 17:49 GMT

> > I'm pretty sure I've observed this with my PowerBook G4 (DVI) - it was
> > supplying Firewire power while asleep, until I unplugged the power
[quoted text clipped - 5 lines]
> tells the thing on the other end of the wire it is still alive, or
> something.

I think he means the power adapter for the PowerBook, since iSights do
not have their own power adapter.

> > In theory, the computer would also supply Firewire power while shut
> > down, as long as the power adapter is connected (I haven't tried that).
[quoted text clipped - 4 lines]
> connecting via a proper 6-wire cable, and no external power adaptor,
> will not draw significant power when the computer is in ACPI S3.

I believe you are mistaken here. For some time now Apple laptops have
supplied power to the Firewire port even while in sleep mode. For
example it's possible to charge and iPod that's plugged into the Mac's
Firewire port even if the Mac is sleeping.

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Clever Monkey - 04 May 2007 18:11 GMT

>>> I'm pretty sure I've observed this with my PowerBook G4 (DVI) - it was
>>> supplying Firewire power while asleep, until I unplugged the power
[quoted text clipped - 22 lines]
> example it's possible to charge and iPod that's plugged into the Mac's
> Firewire port even if the Mac is sleeping.

I see. I did notice this with my iPod mini at first, but then it
stopped charging unless the Mac was on. I never dug into why this was so.

Then the specs I've been reading about ACPI supporting USB, Firewire
state is correct, and Apple has implemented this. Good to know.

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David Empson - 06 May 2007 05:39 GMT

> >>> I'm pretty sure I've observed this with my PowerBook G4 (DVI) - it was
> >>> supplying Firewire power while asleep, until I unplugged the power
[quoted text clipped - 8 lines]
> > I think he means the power adapter for the PowerBook, since iSights do
> > not have their own power adapter.

Yes, that is what I meant.

> >>> In theory, the computer would also supply Firewire power while shut
> >>> down, as long as the power adapter is connected (I haven't tried that).
[quoted text clipped - 15 lines]
> Then the specs I've been reading about ACPI supporting USB, Firewire
> state is correct, and Apple has implemented this. Good to know.

Ah - charging the iPod. That is where I noticed it.

Confirming the details:

My PowerMac G4 (QuickSilver 2002) does not supply Firewire power while
the computer is powered off (but still plugged in), nor while the
computer is asleep.

My PowerBook G4 (DVI) does supply Firewire power while the computer is
powered off or asleep, as long as the laptop's mains adapter is plugged
in.

Unfortunately in the process of testing this, I discovered that my
laptop has developed some serious faults. At the moment it looks like it
might be a problem with the PMU and/or internal backup battery (won't
start up properly, with various weird symptoms that persist over a PMU
reset and attempts to reset PRAM).

I've transferred everything to my PowerMac while trying to identify the
laptop fault more clearly, so I'm tethered to my desk again.

When will the next laptop models be released?

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David Empson
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Mac Forum / Applications / Mac Applications / May 2007

iSight Power