CL1B power distribution

[John Watlington]

On Apr 28, 2009, at 8:16 PM, david at lang.hm wrote:

> On Tue, 28 Apr 2009, John Watlington wrote:
>
>> On Apr 28, 2009, at 7:31 PM, david at lang.hm 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 have no intention to use one of the existing LEDs.   They don't run  
off logic level
voltages for power reasons, and adding switches would be more  
expensive than
dedicating an LED.

Hence my question...

> 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