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Comment by romland | Hacker News Reader

I consumed this article with much enthusiasm. It was filled with information and still very easy to read.

My immediate thought though: I wonder how much battery-time you would gain by making the device monochrome (black/green) when you just intend to use it to, say, call or perhaps even read something.

Maybe a mode like this already exists in Android? I don't have a Nexus one, so... :) Heck, if it doesn't exist, then I guess this might be an app for the Android app-store. Send me a cookie if you write one!

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If (and this is totally hypothetical, I really don't know) the pixels respond non-linearly to power input, it might actually use less power to turn on all the subpixels to a low brightness than to make one subpixel really bright. It might take more power to go from 50% to 100% than from 0% to 50%.

I still want to see some real numbers on energy consumption between a 100% white and 100% black (but still powered) AMOLED. As the first two letters stand for active matrix, there's still a control voltage going through each pixel when it's at RGB000, so the difference may not be as great as it's often made out to be.

Active matrix just means every pixel has it's own switching transistor, as opposed to just every row and column. There may be drive voltage at every pixel but not current.

Here's a good presentation from mid-2008 by 4D Systems, a company that makes integrated display modules http://data.4dsystems.com.au/downloads/micro-OLED/Docs/4D_AM... . I don't think they manufacture the panels themselves, but they still probably have a good idea what they're talking about. Slides 15-18 are most pertinent.

Basically, it looks like AMOLED uses 3x the power of an LCD for an all-white screen, and about 1/10 the power of an LCD for an almost all-black screen. The LCD power stays the same, the AMOLED power varies by 20-30x.

I put an ammeter on my Nexus One and measured 160 ma in black screen, and about 450 ma in white screen (with a "flashlight" application).

When on but screen powered down (normal "waiting for a call" mode) I measured 2 ma, average, with occasional blips much higher (to 400 ma, measured with a Fluke 87 in MIN/MAX mode).

When powered "off" the phone takes 60 uA - I attribute this to keeping an internal RTC active, possibly keeping some sort of pseudo-static RAM active - but those are just guesses.

The battery voltage measured 4.1

I did these current measurements by wedging in two thin pieces of copper tape with an insulator in between, placed between the + battery terminal and the phone's + input.

The phone indicated "4 bars" and Edge service (not 3G) when I made these measurements.

Kudos for actually making the effort to take the measurements. Thank you

> It was filled with information and still very easy to read.

I completely agree--I knew nothing about how these type of displays work, and yet I found the article to be very understandable and enriching.

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