CL1B power distribution

david at david at
Tue Apr 28 20:16:38 EDT 2009

On Tue, 28 Apr 2009, John Watlington wrote:

> On Apr 28, 2009, at 7:31 PM, david at wrote:
>> 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.
> And where would you place said detector LED, without modifying the case ?
> (I have the pin...)

use one of the existing LED's.

I would guess probably the power LED as it has the largest opening (and so 
would probably be the best choice for detecting light)

David Lang

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