Before the Hall effect sensor came to us phoneshas come a long way. It all started in the laboratory of the American physicist Edwin Hall in 1879. The researcher then discovered something that initially seemed just a curiosity – a current flowing through a conductor in a magnetic field creates a voltage across the conductor. Who would have thought that this phenomenon would one day revolutionize the world of electronics?
From theory to practice
For many years, Hall's discovery had been waiting for its chance. Only the development of semiconductors opened up new opportunities for him. Engineers quickly saw the potential in miniature sensors that accurately detect magnetic fields.
Hall effect sensor in smartphones primarily plays the role of screen guardian. When we close the case with a built-in magnet, the sensor immediately detects it and lets the phone know that it's time to turn off the screen. The same thing happens the other way around – opening the case is a signal to wake up the display.
The Hall effect sensor has more applications. In cars they are primarily used to measure the rotational speed of various elements, and this data can then be used by various systems in the car, including ABS or ESP. IN printer checks whether there is no paper out. And w laptop? There it makes sure that the screen turns off when we close the lid.
It's also worth knowing that Hall sensor is not the same as proximity sensor, which is used to turn off the screen during a phone call. This one works on a different principle – it uses infrared rays to detect nearby objects (e.g. our ear or face).
Three types of sensors
Equipment manufacturers can choose from three types of sensors: unipolar (react only to one pole of the magnet), bipolar (turns on at one pole, turns off at the other) and omnipolar (sensitive to each pole). Depending on needs, manufacturers select the appropriate type for a specific application.
How to check if it works? Take a magnet and place it on phone – the screen should go dark. There are also special applications for testing sensors, but an ordinary magnet is enough for home diagnostics.