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 algorithm.
(haven't checked the specs though..) My two cents..;). Rafael Ortiz On Tue, May 5, 2009 at 3:24 PM, Reinder de Haan <r...@mveas.com> wrote: > 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 go a long way. > > --scott > > > > measured on a B1 XO1 laptop (where the leds and the series resistor are > wired in parallel it seam) : > > almost dark: 0mv > ~3meter away from a 8w PL; bare led: ~2mv > ~50 cm below ~25W halogen desk lamp; bare led: ~40mv > bright white led directly on bare led ~200mv > bright white led directly on light guide of the bat.led (lcd side) ~50mv > ~50 cm below ~25w halogen desk lamp (~75* angle to the axis of the light > guide) ~5mv > > i measure this between GND of the laptop the led side of the series > resistor. > all leds seam to be about the same.. i did not compare the different > light guides. > the main battery and DC power where removed, the RTC baterry was still > in place. > > > the meter i measured this with was fixed in the 2000mv range > and was abou 10Mohm when i connected it to another meter in resistance > mode; the (volt) meter read 250mv at that time. > > adding a 10Mohm resistor across the meter halved the > ~50 cm below ~25W halogen desk lamp; bare led: ~40mv reading to > ~20mv > > strangely enough when i add that resistor in series the meter said ~60mv > so voltage on the leds must have been ~120mv? i will have to investigate > this at a later time... > > if you want more measurement doen feel free to ask.. i also have a XO1 > (production model ?C1?) that i could measure. > > i dont have a lux meter :-( > > Greetings, > Reinder > > > > > > > > > _______________________________________________ > Devel mailing list > Devel@lists.laptop.org > http://lists.laptop.org/listinfo/devel >
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