Re: [Fwd: Re: Ambient light sensing via LED response]

2009-05-10 Thread C. Scott Ananian
On Wed, May 6, 2009 at 6:14 PM, Reinder de Haan r...@mveas.com wrote:     Absolutely not.  The A/D is eight bits, with an input range spanning     0 - 3.3V, so the best you     can hope for is about 13 mV per LSB.  I would guess actual accuracy     to be closer to 26 mV. I think the actual

Re: [Fwd: Re: Ambient light sensing via LED response]

2009-05-10 Thread Reinder de Haan
C. Scott Ananian wrote: On Wed, May 6, 2009 at 6:14 PM, Reinder de Haan r...@mveas.com wrote: Absolutely not. The A/D is eight bits, with an input range spanning 0 - 3.3V, so the best you can hope for is about 13 mV per LSB. I would guess actual accuracy to be closer to 26

Re: [Fwd: Re: Ambient light sensing via LED response]

2009-05-10 Thread C. Scott Ananian
On Sun, May 10, 2009 at 5:01 PM, Reinder de Haan r...@mveas.com wrote: C. Scott Ananian wrote: On Wed, May 6, 2009 at 6:14 PM, Reinder de Haan r...@mveas.com wrote:     Absolutely not.  The A/D is eight bits, with an input range spanning     0 - 3.3V, so the best you     can hope for is about

Re: [Fwd: Re: Ambient light sensing via LED response]

2009-05-10 Thread Mark Bauer
Hi guys, How can I help with this, I still teach electrical engineering at the University of Nebraska, and before that I have about 25 years in the field. Mostly embedded microcontrollers and stuff. I do have several XOs to work with. I would have jumped in earlier but the end of the

Re: Ambient light sensing via LED response

2009-05-06 Thread NoiseEHC
But why do you say you would need 1 mV accuracy ? Bright sunlight is far stronger than the light sources he used. I am not an engineer so forgive me if I am saying something stupid, but is not the goal to switch off the backlight if and only if there is no difference between the

[Fwd: Re: Ambient light sensing via LED response]

2009-05-06 Thread Reinder de Haan
Original Message Subject: Re: Ambient light sensing via LED response Date: Thu, 07 May 2009 00:02:49 +0200 From: Reinder de Haan r...@mveas.com To: raf...@laptop.org References: 200904290017.n3t0hl2v006...@new.toad.com c5d4a4e5-b183-4b7d-bafb-3488e15f7...@laptop.org

[Fwd: Re: Ambient light sensing via LED response]

2009-05-06 Thread Reinder E.N. de Haan
Original Message Subject: Re: Ambient light sensing via LED response Date: Thu, 07 May 2009 00:02:49 +0200 From: Reinder de Haan r...@mveas.com To: raf...@laptop.org References: 200904290017.n3t0hl2v006...@new.toad.com c5d4a4e5-b183-4b7d-bafb-3488e15f7...@laptop.org

Re: Ambient light sensing via LED response

2009-05-05 Thread Reinder de Haan
Hallo, C. Scott Ananian wrote: snip A last resort would be hooking up a MOSFET as a simple amplifier -- again, you're not worried about linearity or any such niceties, but you'd still need a good match for your MOSFET's threshold voltage... some real measurements to replace the WAGes would

Re: Ambient light sensing via LED response

2009-05-05 Thread Rafael Enrique Ortiz Guerrero
These measurements are really cool. But the question remains in whether the ADC could have a resolution of 1mv?, i mean in light of these measurements is necessary to have an ADC that can reliable sense these variations and then with that basis have a transfer function and add it to the

Re: Ambient light sensing via LED response

2009-05-05 Thread John Watlington
On May 5, 2009, at 6:44 PM, Rafael Enrique Ortiz Guerrero wrote: These measurements are really cool. But the question remains in whether the ADC could have a resolution of 1mv?, i mean in light of these measurements is necessary to have an ADC that can reliable sense these variations

Re: Ambient light sensing via LED response

2009-05-05 Thread Rafael Enrique Ortiz Guerrero
On Tue, May 5, 2009 at 8:34 PM, John Watlington w...@laptop.org wrote: On May 5, 2009, at 6:44 PM, Rafael Enrique Ortiz Guerrero wrote: These measurements are really cool. But the question remains in whether the ADC could have a resolution of 1mv?, i mean in light of these measurements is

Re: Ambient light sensing via LED response

2009-05-04 Thread Peter Robinson
we had a dedicated light sensor on the last product i worked on (which, in retrospect, given that it had 15 watts (!) of backlight seems like maybe the wrong place to have started trying to save power ;-).  i implemented a proof-of-concept algorithm for automatic control, but found it a

Re: Ambient light sensing via LED response

2009-05-04 Thread C. Scott Ananian
On Sat, May 2, 2009 at 8:38 AM, p...@laptop.org wrote:   By the way, has anyone really thought about this feature ?  I grok   the intent, but you have to make   sure that kids who happen to be in brightly lit rooms (glaring   fluourescents aren't uncommon)   don't loose their backlight, and

Re: Ambient light sensing via LED response

2009-05-04 Thread C. Scott Ananian
On Fri, May 1, 2009 at 11:59 PM, John Watlington w...@laptop.org wrote: Oh, yeah, you should be able to wire the top side of the LED directly to the LED and measure the photovoltaic current directly; that's not patented:                  battery voltage              Q1  | ---from EC--|

Re: Ambient light sensing via LED response

2009-05-04 Thread david
On Tue, 5 May 2009, C. Scott Ananian wrote: On Fri, May 1, 2009 at 11:59 PM, John Watlington w...@laptop.org wrote: Oh, yeah, you should be able to wire the top side of the LED directly to the LED and measure the photovoltaic current directly; that's not patented:                  battery

Re: Ambient light sensing via LED response

2009-05-02 Thread pgf
john wrote: By the way, has anyone really thought about this feature ? I grok the intent, but you have to make sure that kids who happen to be in brightly lit rooms (glaring fluourescents aren't uncommon) don't loose their backlight, and wonder why ? The keyboard lighting

Re: Ambient light sensing via LED response

2009-05-01 Thread C. Scott Ananian
On Tue, Apr 28, 2009 at 8:38 PM, John Watlington w...@laptop.org wrote: I don't have time to take a look at this right now, but we have a A/D input to dedicate to this, if it helps work around the patent. We can talk to MERL if needed. I probably still know a handfull of people around

Re: Ambient light sensing via LED response

2009-05-01 Thread Nate Ridderman
On Fri, May 1, 2009 at 2:28 PM, C. Scott Ananian csc...@laptop.org wrote: Oh, yeah, you should be able to wire the top side of the LED directly to the LED and measure the photovoltaic current directly; that's not patented: battery voltage Q1 | ---from

Re: Ambient light sensing via LED response

2009-05-01 Thread John Watlington
On May 1, 2009, at 2:28 PM, C. Scott Ananian wrote: On Tue, Apr 28, 2009 at 8:38 PM, John Watlington w...@laptop.org wrote: I don't have time to take a look at this right now, but we have a A/D input to dedicate to this, if it helps work around the patent. We can talk to MERL if

Re: Ambient light sensing via LED response

2009-05-01 Thread John Watlington
The back-bias voltage is a sensitive topic. If you could guarantee periodic clearing of the integrator, I could provide up to 10V or so. Otherwise, it should probably be limited to +3.3V. wad On May 1, 2009, at 11:59 PM, John Watlington wrote: On May 1, 2009, at 2:28 PM, C. Scott Ananian