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Proximity sensor always on?

asked 2013-12-30 00:53:07 +0300

pelsepupi gravatar image

updated 2014-01-10 20:06:36 +0300

lk gravatar image

Is proximity sensor supposed to be always on? I can see the dimm red light coming from the LED even when my Jolla is in standby.

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AFAIK, it should always be on while the device is locked, but while it's on, that might be a bug. Unless the red light is also for the brightness sensor.

Bulder ( 2013-12-30 01:13:35 +0300 )edit

why would it be on when it's locked? what exactly is this led for or this sensor for anyway?

AL13N ( 2013-12-30 02:04:28 +0300 )edit

On my Lumia 720 the LED is visible only when I press the power/unlock button or when I start camera while the phone is locked.

Edit: the LED on Lumia is visible also while making a call. So on Lumia it's only a proximity sensor IMO. Not sure about Jolla though.

pelsepupi ( 2013-12-30 02:45:42 +0300 )edit

On N9 proximity sensor is always on, because it controls the 'always visible' clock on the lock screen. I don't think Jolla currently has any use for proximity sensor when the phone is locked, but I'm guessing there will in the future.

Milo ( 2013-12-30 04:10:50 +0300 )edit

Bulder, I'd go even as far as converting that to an answer.

Milo ( 2013-12-30 14:38:35 +0300 )edit

3 Answers

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answered 2013-12-30 10:39:10 +0300

Bulder gravatar image

The proximity sensor is always on, because it controls the "Double-tap to unlock" thing so it doesn't activate while it's in your picket.

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@tvicol The proximity sensor controls the double-tap-to-unlock thing while the phone is locked. It takes less battery to disable it when the sensor sees the screen is covered iirc.

Bulder ( 2014-03-20 18:37:05 +0300 )edit

Btw, I understand that you need the sensor when you make a call and to prevent accidental unlocking, but I see no other use for it. Why isn't it like on Lumia, so that it's active only when it's needed?

pelsepupi ( 2014-03-23 02:54:16 +0300 )edit

It probably works just like Lumia's but Jolla shows the light clearer. I doubt that it uses that much more battery

Bulder ( 2014-03-23 12:42:46 +0300 )edit

answered 2014-06-11 16:43:37 +0300

spiiroin gravatar image

The proximity sensor is always enabled on purpose.

Having always up-to-date proximity sensor data available makes things easier in general and does not require making changes to legacy logic that assumes so.

The increased power consumption is negligible when the device is actively used. And when the display is blanked, using proximity sensor allows us to turn off double tap detection that could potentially consume much more power than what the proximity sensor does.

@tvicol: Yes, the sensor is put to a less power consuming state when the device is suspended.

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answered 2014-03-20 10:36:55 +0300

tvicol gravatar image

updated 2014-03-20 10:37:21 +0300

If this is the case, than I expect phone to be completely locked while proximity sensor is covered. Right ? Well this is not the case. Even the proximity sensor is covered, you can unlock the phone by pressing power button. Now I understand why I got my phone unlocked while wearing in the pocket.

On other hand, while phone is locked, proximity IR led should change his frequency to a lower rate in order to save battery. Duty cycle may be adjusted as well. Take this as an electronics engineer humble opinion. ;)

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Asked: 2013-12-30 00:53:07 +0300

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Last updated: Jun 11 '14