How do these smart phones change screen position

[[email protected]]

How do these smart phones change screen position?

What I mean, is that when the longest part of the phone is vertical then
the phone is tipped to the horizontal position, the screen image
rotates, so the bottom of the page is always downward. How the heck is
tht done? My only guess is that its mercury switches.....

 

[[email protected]]

On Friday, January 18, 2013 3:10:52 PM UTC-5, [email protected] wrote:

Are you serious- mercury switches??? It almost has to be a magnet attached to pendulum hovering over a Hall effect sensor.

 

[[email protected]]

How do these smart phones change screen position?

What I mean, is that when the longest part of the phone is vertical then
the phone is tipped to the horizontal position, the screen image
rotates, so the bottom of the page is always downward. How the heck is
tht done? My only guess is that its mercury switches.....

Accelerometer.

 

[[email protected]]

Probably a silicon MEMS accelerometer. They're pretty cheap these days.



Cheaper, even, than a pendulum with a magnet and a hall-effect sensor,

and probably far more reliable, too.



--

My liberal friends think I'm a conservative kook.

My conservative friends think I'm a liberal kook.

Why am I not happy that they have found common ground?



Tim Wescott, Communications, Control, Circuits & Software

http://www.wescottdesign.com

Don't write off Hall-effect technology just yet. This chip is used for the compass function:
http://www.asahi-kasei.co.jp/akm/en/product/ak8975b/ak8975b.html

 

[[email protected]]

It was the macro-mechanical assembly that I was questioning, not the
sensor.

'sides, I think most of those phones are assumed to have accelerometers.

think they all have, it's used for many games so it is a must have
feature

Where as an antenna is something you add at the last moment if there's
room left

I just saw someone who had tested the big name smartphones in a
standard setup
with an artificial hand and head, the newer the phone the worse the
sensitivity


-Lasse

 

[Adrian Jansen]

It was the macro-mechanical assembly that I was questioning, not the
sensor.

'sides, I think most of those phones are assumed to have accelerometers.

Most phones now have at least 3 axis accelerometers, plus 3 axis
compass. You can get all that plus 3 axis gyros in one chip like the
Invensense MPU9150.

 

[Jamie]

How do these smart phones change screen position?

What I mean, is that when the longest part of the phone is vertical then
the phone is tipped to the horizontal position, the screen image
rotates, so the bottom of the page is always downward. How the heck is
tht done? My only guess is that its mercury switches.....

http://en.wikipedia.org/wiki/Magnetometer

Jamie

 

[[email protected]]

That might have been mine from July 2010:
<http://802.11junk.com/jeffl/cellular/cell-test.htm>
All the phones I tested had problems when the antenna was covered, but
the iPhone 4 was by far the worst.

You might also be referring to SAR testing, which is done with an
artificial head (SAM phantom), but not an artificial hand.  SAR
(specific absorption rate) measures how my RF is being generated by
the phone and frying your brain.  How it's done:
<

>
There is no similar test for sensitivity.  The FCC limit of 1.6
watts/kg is most easily met if the antenna is internal to the phone,
located near the bottom of the phone, and with maximum radiation away
from the body.  Tx power is also limited to about 100mw.  That will
usually pass the SAR tests, but also has side effects in field
strength sensitivity and hand coverage problems.  There is little Rx
sensitivity change between old and newer phones, but there's certainly
a field strength sensitivity difference with the newer phones due to
internal antennas.  There are also additional issues with interference
from the smartphone computah section, which belches quite a bit of
internal EMI/RFI.

It was a danish guy, I'm not sure if it a test standard they are
developing, but it is done with a hand holding the phone next to
a head, you known the way phone is normally used


-Lasse

 

[Jasen Betts]

No it is not done with a magnetometer,
but with those chip acceleration sensors,
those have vibrating mass in it.

some may, others work by thermal convection.

 

[Jamie]

No it is not done with a magnetometer,
but with those chip acceleration sensors,
those have vibrating mass in it.

If you say so. I can tell you that I have 3 devices
that use fluxgates for compass and device position orientation.

2 of them have acceleration sensors but those are only for the
HD park and screen wake up.

Jamie

 

[Spehro Pefhany]

If you say so. I can tell you that I have 3 devices
that use fluxgates for compass and device position orientation.

2 of them have acceleration sensors but those are only for the
HD park and screen wake up.

Jamie

The iPhone and iPad have a 3-axis MEMS accelerometer, a 3-axis MEMS
angular rate sensor AND a 3-axis Hall-effect compass. All the iPhones
and some iPads also have GPS. Some Android devices have a barometer
that is good enough to function as an altimeter.

You can get and IOS clinometer app that has a resolution of 0.1
angular degree and some nice 2-axis bubble level apps. The compass is
a bit flakier- influenced by metal such as computer boxes and by the
magnets that Apple put into the iPad covers (dunh).

The accelerometer is great for orientation relative to gravity (roll
and pitch), but, of course, completely useless for yaw.

Display orientation is controlled by the accelerometer.




Best regards,
Spehro Pefhany

 

[Jamie]

I think you are wrong about that.
Provide links, software, diagrams.




I think you are wrong about that.





I have designed my own fluxgate compass,
and I can imagine plenty of situations where that would NOT work,
for horizontal versus vertical orientation.

If there is an acceleration sensor, then it will be used for that.

Oh really? how strange.. Works for us for angle sensing.


Jamie

 

[rickman]

How do these smart phones change screen position?

What I mean, is that when the longest part of the phone is vertical then
the phone is tipped to the horizontal position, the screen image
rotates, so the bottom of the page is always downward. How the heck is
tht done? My only guess is that its mercury switches.....

No, they use weighted pixels so they shift when you turn the screen.

Rick

 

[[email protected]]

Probably a silicon MEMS accelerometer. They're pretty cheap these days.

This seems to be the generally agreed answer to this question. However
I have no clue what these things are. Being silicone, they must be a
chip, but how do they work? Any chip or semiconductor works in any
direction and does not change the circuit when the chip or item it's in,
is rotated. Could you please explain how they work. Thanks

 

[Jasen Betts]

This seems to be the generally agreed answer to this question. However
I have no clue what these things are. Being silicone, they must be a
chip, but how do they work? Any chip or semiconductor works in any
direction and does not change the circuit when the chip or item it's in,
is rotated. Could you please explain how they work. Thanks

I could but i's just be paraphrasing the manufacturer's documentation.
they invent these things, patent them, and then brag about it in the
datasheet.

 

[Spehro Pefhany]

This seems to be the generally agreed answer to this question. However
I have no clue what these things are. Being silicone, they must be a
chip, but how do they work? Any chip or semiconductor works in any
direction and does not change the circuit when the chip or item it's in,
is rotated. Could you please explain how they work. Thanks

Accelerometers generally have a proof mass and a flexure, and they
sense displacement (capacitive is the usual method on a chip). Pretty
simple concept. Getting to three axis on a monolithic structure gets
more interesting:-

http://www.public.asu.edu/~jchae2/Publications_files/3axis accel JMEMS05.pdf





Best regards,
Spehro Pefhany

 

[josephkk]

Probably a silicon MEMS accelerometer. They're pretty cheap these days.

Actually, usually two or three. More than enough to reasonably the
accelerated field we live in.

 

[josephkk]

some may, others work by thermal convection.

Cite?
Otherwise "Baloney"! Bloody insufficient space and overwhelming other
thermal drives make that unbelievable.

?-)

 

[josephkk]

Repeatability, close to metal, big metal objects, magnets.
'Works' in a limited environment, sure out _changes_.
But in the wild it will be very unreliable.
On top of that fluxgate compasses may need calibration.

There is a reason for those accellerometer chips.

I use the MPU6050, quote from the datasheet:
The MPU-60X0 is the world's first integrated 6-axis MotionTracking device that combines a 3-axis
gyroscope, 3-axis accelerometer, and a Digital Motion ProcessorTM (DMP) all in a small 4x4x0.9mm
package.

Note the gyroscope.

That soft also drives a 3 axis magnetic compass HMC5883L

But for the attitude data the MPU6050 (gyroscope) is used.
The compass requires calibration everytime after power up,
you have to turn it around a few times so it finds north,

I have also written a nice GUI where you can wave the thing around to move an airplane on the screen.
All code is on my site, and links were posted in tehis newsgroup at thattime.

Your turn.

+2

?-)

 

[josephkk]

The smart phone does not change its position. The user changes the
smartphone position.


Mercury is banned by RoHS rules.
<http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive>

Behind the glass screen are liquid crystals. The heavier crystal fall
to the bottom of the screen, while the lighter crystals float to the
top. When you tip the display, the heavier crystals remain at the
bottom of the glass tank, while the lighter crystals float to the top.

"How a Smartphone Knows Up from Down"
<http://www.engineerguy.com/elements/videos/video-accelerometer.htm>

Cool.

Jeff, enclosing the links in carets is ok for email where HTML is accepted
but worthless in usenet where HTML is not acceptable. Your choice, just
thought to explain why.

?-)