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What is the use of hall effect sensor in mobile phones?

Question asked by Kaustubh Katdare in #Coffee Room on Feb 6, 2014
Kaustubh Katdare
Kaustubh Katdare · Feb 6, 2014
Rank A1 - PRO

Was going through Moto G specs and found that it has a hall effect sensor. Just read about and remembered the 'hall effect' I had studied during my engineering course. It looks like the primary purpose of the Hall Effect Sensor in mobile phones is for proximity switching, positioning, speed detection and also various current sensing applications.

I'm not exactly sure if that's what these sensors are primarily used for. Because I was under impression that proximity sensor and accelerometers are the ones that are dedicated for the above functions. If that's true, can someone throw some light on the exact purpose of hall effect sensor in mobile phones?

Posted in: #Coffee Room
Anoop Kumar
Anoop Kumar · Feb 6, 2014
Rank A2 - PRO
Here is all the explanation about Hall effect sensor and application in mobile.
https://www.digikey.com/en/articles/techzone/2011/may/applications-for-hall-effect-ic-switches
Chinna Rao
Chinna Rao · Feb 18, 2014
Rank E2 - BEGINNER
Hello there...AFAIK the Moto G flip cover is the only accessory which uses the Hall Effect sonsor of the Moto G...you can see it turn on the display in the following video

Manu Pillai
Manu Pillai · Mar 23, 2014
Rank E1 - BEGINNER
Well I own a Moto G myself. The sensor (Magnetometer or Hall sensor) located at the top right activates the auto screen sleep/wake. I have tested it with a small magnet.

Generally we find on most smartphone specs that a Magnetometer is present and that is responsible to detect a magnetic field and the android code/driver does the job of activating auto scree sleep/wake. (personally tested a Nexus 7 (2013) )

But since I found written on some websites, that Moto G has hall effect sensor, I checked the sensor list on the Moto G using an app, and I cannot find it listed (but found that a Magnetic sensor/Compass is present)

Since a hall sensor on phones is meant for pure switching (analog circuitry + CMOS output), I wonder if really Moto G has it. If yes, is it to save power instead of using software switched action using Magnetometer?

As far as the design of the Motorola Official Flip cover is concerned, the FLAP has two magnets of different strengths. One is for Screen on/off and the other more powerful one is for locking the FLAP over the screen with magnetic action (which is actually very feeble)

I found that there is a 1cm square golden bronze colored metal strip on the inside of the Flip case (just below the Magnetic sensor/hall sensor). I suspect that it would be a Magnetic shield to prevent activation of screen on/off when the FLAP is folded back by the user (which is highly UNDESIRABLE) (this has happened with some flip covers of Nexus 7)
[Real info about the square metal is welcome]

UPDATE (after some more research): Okay so I was curious whether Moto G has a dedicated Hall Effect based Switch for the display. Actually it does not, it is having a (Asahi Kasei) AK8963 3-axis Electronic Compass IC (which has Hall Elements and a self-magnet too).

The AK8963 Chip has an ADC block that converts analog magnetic field info into bits and then through an Interface Logic & Register block sends it to the processor.

I believe that the "Orientation Sensor" listed in the Moto G is again the output of this AK8963 package.

Range: 2000 microTesla
Resolution: 0.0625 microTesla
Power: 6.8 mA
Ankita Katdare
Ankita Katdare · Mar 27, 2014
Rank A1 - PRO
@Manu Pillai Thanks for the information bro. It is very useful.
From what I read on other sites, on Moto G the Hall Effect sensor that can detect the magnetic field is used. This means that if the mobile cover has a magnet in it, then because of the magnetic field it can get the smartphone into the locked/standby mode automatically.
Manu Pillai
Manu Pillai · Mar 27, 2014
Rank E1 - BEGINNER
Kaustubh Katdare
Was going through Moto G specs and found that it has a hall effect sensor. Just read about and remembered the 'hall effect' I had studied during my engineering course. It looks like the primary purpose of the Hall Effect Sensor in mobile phones is for proximity switching, positioning, speed detection and also various current sensing applications.

I'm not exactly sure if that's what these sensors are primarily used for. Because I was under impression that proximity sensor and accelerometers are the ones that are dedicated for the above functions. If that's true, can someone throw some light on the exact purpose of hall effect sensor in mobile phones?
Orientation Sensor on the Moto G is based on the AK8963 Electronic Compass chip, the same chip that Outputs Magnetic field readings for Compass.

For speed detection an Accelerometer may be used, while for Positioning (Orientation) this Hall-element based sensor has to be used.

Applications include GPS Pedestrian Navigation using Compass, Auto-screen sleep/wake based on the angle of placement on a flat surface or inside a shirt pocket. (This comes default in the Moto X, while can be easily setup in Moto G using the "Gravity Screen" app)

So the uses are Proximity switching (as seen in smart flip covers), Positioning (Pedestrian GPS navigation, shirt pocket), Metal sensing application.
Vishwas_p13
Vishwas_p13 · Mar 29, 2014
Rank D3 - MASTER
Afaik Hall Effect Sensors were used earlier for basic applications of switching on/off the screen in Slider and Clamshell phones. Today its used for advanced applications like magnetic compass, proximity switching and accelorometer applications.
Manu Pillai
Manu Pillai · Mar 30, 2014
Rank E1 - BEGINNER
Vishwas_p13
Afaik Hall Effect Sensors were used earlier for basic applications of switching on/off the screen in Slider and Clamshell phones. Today its used for advanced applications like magnetic compass, proximity switching and accelorometer applications.
Yes, Hall Sensor based Switching was seen in Clam-shell phones like the Popular Moto RAZR V3.

Note that, Accelerometer chip is different package from a Electronic Compass chip.

Some phones used resistive/capacitive methods of detection. Some clam-shell swivel type phones used Bi-polar Magnetic sensing Hall sensors to detect appropriate positioning of the screen.

Interstingly the Motorola Support guys on Twitter don't have much clue about the AK8963 Eelctronic compass present inside Moto G. But they acknowledged about the clam-shell Moto RAZR sensor !!
Sarathkumar Chandrasekaran
Rank A2 - PRO
neat and detailed explanation. thanks to whole CE team
Noothan Kumar
Noothan Kumar · Jan 24, 2020
Rank C1 - EXPERT

A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall effect sensors are used for proximity switching, positioning, speed detection and current sensing applications, In its simplest form, the sensor operates as an analog transducer, directly returning a voltage.

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