CL1B power distribution

david at david at
Tue Apr 28 19:31:27 EDT 2009

On Wed, 29 Apr 2009, James Cameron wrote:

> On Tue, Apr 28, 2009 at 10:15:47AM -0400, C. Scott Ananian wrote:
>> I wonder if one could easily support running an LED backwards as an
>> ambient light monitor in Gen 1.5 - it seems that automatically
>> powering off the backlight in bright sunlight would lead to a lot of
>> power savings for most young users.
> I agree that an ambient light detector and automatic adjustment of
> backlight would save power.  It would happen transparently, magically.
> But I don't think the LEDs are often specified in terms of their ambient
> light detection properties.
> Perhaps it would be better to use a photodiode, or light dependent
> resistor.
> Then there's the spectrum of light being received.
> Then there's reflection from the laptop display itself to consider.
> I recall we also once had a discussion on whether the camera could be
> used as an ambient light detector.

you don't want to have to run the camera to detect the light (this will 
eat far more power than you would save)

the LED trick has the advantage of not requiring a change to the case, 
just a single additional drive pin to be able to run it as a detector.

David Lang

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