Magnetic detector

Very often, when building various electrical generators or motors, it is necessary to determine the pole of a magnet. Almost every person knows from school physics lessons that a magnet has two poles: north (indicated in blue by the letter “N”) and south (indicated in red by the letter “S”).
This simple electronic detector will help you identify the name of a magnet's pole. To build it, you don’t need scarce parts and components.
The detector uses a Hall sensor as a sensor, which can be removed from an old computer cooler. Fortunately, everyone has a lot of such “good” now.
As you know, computer fans have a brushless motor. Which consists of two windings on the armature and a switching element - a Hall sensor. This sensor switches the windings depending on the position of the movable magnetic ring located in the impeller.

Fan circuit

This element has four pins. Two are the power supply, and two outputs at which the power is located depending on the magnetic field. That is, the power level can only be on one of the pins.

Magnetic detector circuit

In place of the windings we will connect multi-colored LEDs, through a limiting resistor. We will power the entire circuit from a 3 Volt coin cell battery.
We will assemble the circuit on a breadboard. Let's display the sensor a little on the terminals.


Let's check. The only disadvantage of this sensor is that the level is always present at one of the terminals, regardless of the presence of a magnetic field. Therefore, I added a power button to connect the circuit to the source. In the end it works like this: bring it to the magnet, press the button - it lights up Light-emitting diode indicating the field, all - the button can be released.



I put the board into the housing from a flat marker. Everything turned out very beautiful. As a result, I became the owner of such a pocket magnetic field indicator. Suitable for farming.


A magnetic detector for determining the magnetic pole can find other uses in everyday life or in production, so it is a completely necessary thing.

Watch the video of assembly and testing of the magnetic sensor