MAGNETIC DETECTOR

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Very often, when building various electric generators or motors, it is necessary to determine the pole of the magnet. Almost everyone, from school physics lessons, knows that a magnet has two poles: the north (indicated by blue letter "N") and the south (indicated by red and letter "S").
This simple electronic detector will help you determine the name of the magnet pole. For its non-construction you will not need scarce parts and components.
As a sensor in the detector, a Hall sensor is used, which can be removed from an old cooler from a computer. Fortunately, there is such a "good" now in bulk.
As you know, computer fans incorporate a brushless motor. Which consists of two windings at 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 outputs. Two is the power supply, and two outputs, on which there is power, depending on the magnetic field. That is, the power level can only be on one of the conclusions.

Magnetic detector circuit

For the place of the windings we will connect multi-colored LEDs, through a limiting resistor. We will feed the entire circuit from a 3 Volt “tablet” battery.
We assemble the circuit on a breadboard. We derive the sensor a little at the terminals.

We check. The only disadvantage of this sensor is that the level is always present on one of the terminals, regardless of the presence of a magnetic field. Therefore, I added a power button to switch the circuit with the source. As a result, it works like this: brought it to the magnet, pressed the button - the LED indicating the field lights up, everything - the button can be released.

I put the board in the case from a flat marker. Everything turned out very beautifully. As a result, I became the owner of such a pocket indicator of the magnetic field. The farm fit.