Power consumption of "screen off" option

[bonacker]

I did the ~ds command in the basic Kindle Touch, 5.6.x.x, to "never show screensaver." Now I have two options. I can leave the most recent page I read displaying (or any page) indefinitely or or I can hold the power button down for ~7 seconds and select "screen off" to get a blank screen. To get the last page back, I push the power button momentarily.

I had thought that no power is consumed merely by the displaying of a page, only a page turn and the drawing of a new page uses power. However it seems that more power is consumed by leaving a page displaying than by clearing the screen to a blank page.

Are there any different behind the scenes operations that the Kindle performs when a page is displaying vs. the blank screen (screen off)? WiFi is always off in both cases. I'm not 100% sure about the different rates of power consumption, but the longer I've been using the "never show screensaver," the more it seems that the "screen off" state uses considerably less power. TIA for any answers.

[susan_cassidy]

Since you are using a nonstandard option, we can't know how it might work internally. It may be checking on something periodically or something else that doesn't happen in standard sleep mode.

[shalym]

Originally Posted by bonacker

I did the ~ds command in the basic Kindle Touch, 5.6.x.x, to "never show screensaver." Now I have two options. I can leave the most recent page I read displaying (or any page) indefinitely or or I can hold the power button down for ~7 seconds and select "screen off" to get a blank screen. To get the last page back, I push the power button momentarily.

I had thought that no power is consumed merely by the displaying of a page, only a page turn and the drawing of a new page uses power. However it seems that more power is consumed by leaving a page displaying than by clearing the screen to a blank page.

Are there any different behind the scenes operations that the Kindle performs when a page is displaying vs. the blank screen (screen off)? WiFi is always off in both cases. I'm not 100% sure about the different rates of power consumption, but the longer I've been using the "never show screensaver," the more it seems that the "screen off" state uses considerably less power. TIA for any answers.

Doesn't the Kindle Touch use infrared rather than capacitive for touch? If so, then it could be that the infrared technology uses a tiny bit more power than capacitive, since (I think) the infrared beams are always on, waiting for something to break the beam and register a touch.

Of course...there is a very large chance that I have no idea what I'm talking about, too

Shari

[HarryT]

Originally Posted by shalym

Doesn't the Kindle Touch use infrared rather than capacitive for touch? If so, then it could be that the infrared technology uses a tiny bit more power than capacitive, since (I think) the infrared beams are always on, waiting for something to break the beam and register a touch.

The IR touchscreen isn't enabled when the device is asleep, whether with a blank screen or not.

[bonacker]

Originally Posted by HarryT

The IR touchscreen isn't enabled when the device is asleep, whether with a blank screen or not.

If the IR touchscreen isn't enabled when in "screen off" or blank screen, then that would seem to answer my question which was what consumes power when the last page viewed remains as the display for hours (since the screensaver never comes on) that doesn't consume power when the "screen off" is selected.

I had thought that a page displayed but never turned used no power. Why was it, I wondered, that there seemed to be more power being used to display a page that never changed than displaying a blank screen.

The answer would seem to be that a blank screen is not IR touchscreen enabled while a screen with text is IR touchscreen enabled as Shalym hypothesized above.

[HarryT]

Originally Posted by bonacker

The answer would seem to be that a blank screen is not IR touchscreen enabled while a screen with text is IR touchscreen enabled as Shalym hypothesized above.

This seems unlikely to me. When the device is asleep, the touch screen is not enabled. What the screen is displaying doesn't change that; you're correct is saying that maintaining an image on an eInk screen uses no power. What does use power, of course, is the CPU, RAM, etc.

[twowheels]

Originally Posted by bonacker

I had thought that a page displayed but never turned used no power. Why was it, I wondered, that there seemed to be more power being used to display a page that never changed than displaying a blank screen.

The SCREEN requires no power in that state, but the rest of the device still needs to be in an "awake" state and ready to accept input, meaning that the processor and touchscreen have to be powered. It's also very likely that the firmware writes out the current state of RAM to the internal storage when the screen is turned off so that it no longer has to keep the RAM powered to refresh it (RAM loses its contents if not periodically refreshed).

[shalym]

Originally Posted by HarryT

This seems unlikely to me. When the device is asleep, the touch screen is not enabled. What the screen is displaying doesn't change that; you're correct is saying that maintaining an image on an eInk screen uses no power. What does use power, of course, is the CPU, RAM, etc.

That's the point...bonacker has disabled the auto-sleep on the Kindle, so that it is always either awake, or in the blank screen "off" state.

Shari

[HarryT]

Originally Posted by shalym

That's the point...bonacker has disabled the auto-sleep on the Kindle, so that it is always either awake, or in the blank screen "off" state.

Shari

Thank you - I had indeed overlooked that. In that case the touchscreen will of course be enabled, the RAM powered, etc, and the device will certainly use more power than it does sleeping.

This really doesn't seem like a terribly good idea to me.

[bonacker]

Thanks. I am clear now on why there is power being consumed when it is left with a page displaying without ever going to sleep.

But what about the state it is in when I hold the power button in for 7 seconds and tap "screen off." The blank screen is no longer touch sensitive. One needs to push the power button to resume use of the device. Is it then in the same state as it would be when the screensaver displays with respect to power consumption?

Knowing what I know now, I will not do the ~ds command again after the next reboot when it is supposed to revert to the normal use of the screensaver.

[HarryT]

Originally Posted by bonacker

But what about the state it is in when I hold the power button in for 7 seconds and tap "screen off." The blank screen is no longer touch sensitive. One needs to push the power button to resume use of the device. Is it then in the same state as it would be when the screensaver displays with respect to power consumption?

Yes, exactly the same.