What is a Hall sensor in a phone?

In smartphones and tablets, several sensors can be used at once, which help the device read additional information. Some time ago we talked about an accelerometer. Today we’ll talk about another sensor, namely, the Hall sensor.

What it is?

The Hall sensor used in modern mobile devices is a measuring element that is capable of detecting the presence, intensity and change in the intensity of a magnetic field. The sensor is named after the American physicist Edwin Hall, after whom the “Hall effect”, discovered in 1879, is called – the phenomenon of the appearance of a transverse potential difference when a DC conductor is placed in a magnetic field.

The bottom line is: if a plate is placed in a magnetic field under voltage, the electrons in the plate begin to deviate perpendicular to the direction of the magnetic flux. The electron density on different sides of the plate will vary, which in turn leads to the potential difference that the Hall sensor picks up.

Here’s what the sensor looks like:

Why do I need a Hall sensor in a tablet or smartphone?

The sensor itself has quite wide capabilities, although it is usually used for its intended purpose, measuring the magnetic field strength. In particular, the sensor is used in rocket engines, in the internal combustion engine ignition system, for measuring liquid levels, etc..

There is a sensor in modern mobile devices, but its capabilities are not fully implemented. The sensor is actually used only in two main tasks:

  • The first is the digital compass that has become familiar to smartphone owners, which is also used to improve positioning.
  • The second task, which is much more urgent, is the interaction with popular covers for smartphones and tablets..

Magnetic Cases

You have probably seen the so-called magnetic cases for both smartphones and tablets. They allow you to lock and unlock the device when opening / closing the cover.

How is this possible? The Hall sensor installed in the device responds to a magnet, which is located in the case itself. When the magnet is located close to the device, the sensor detects the amplification of radiation, resulting in blocking the display. Such cases often have the Smart prefix – “smart”.

When the user opens the flip cover (book cover), the sensor detects a decrease in radiation intensity and unlocks the screen.

But what if the cover has a special window in which information is displayed, even if the cover is closed? In this case, the Hall sensor is also used – it gives a command to switch between different display modes, that is, it displays only certain information in the window, for example, time, date, notifications. An example of such a case is from Samsung:

And by the way, if you use a screen created using AMOLED technology, due to the nature of the technology, the displayed information in the window has almost no effect on battery power consumption.

Does my smartphone have a Hall sensor?

There is a probability of 99%. Most manufacturers indicate it in the specifications for the smartphone, but not always. In this case, pay attention to the accessories: if there are smart magnetic cases, then the Hall sensor in the smartphone is definitely there.