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I am not that much into magnetism, but I am facing the problem of defining the pole of the closest outer magnet it faces the circuit with. The magnet is completely out of control and might as well disappear and reappear again, facing the circuit with another pole.

I do not really need the intensity of the field, just its polarity.

So far, I did a research on the Internet and found no ways to do that. Is there a way to implement such a scheme, with/without affecting the outer magnet?

UPD: Reed relay is exactly what I need for polarity.

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  • \$\begingroup\$ The situation isn't quite clear, does a magnetometer/hall effect sensor (or a pair to handle the situation of the opposite pole) do what you want? If not, why not? \$\endgroup\$
    – nanofarad
    Commented Oct 28, 2021 at 17:38
  • \$\begingroup\$ @nanofarad I might not be that well aware, but so far I have seen the magnetometer to only define the intensity of magnetic field, but not the pole. Is it not the only piece of information you can get from them? \$\endgroup\$
    – Ver Nick
    Commented Oct 28, 2021 at 17:47
  • \$\begingroup\$ The magnetometer in my phone is sensitive not only as a signed scalar (north/south) but has all three axes of magnetic field direction (X/Y/Z). A simpler chip may offer a signed scalar only, but that is still enough. \$\endgroup\$
    – nanofarad
    Commented Oct 28, 2021 at 17:51
  • \$\begingroup\$ @nanofarad Thank you! \$\endgroup\$
    – Ver Nick
    Commented Oct 28, 2021 at 17:53
  • \$\begingroup\$ Many hall-effect sensors might fall into that category (signed scalar.) \$\endgroup\$
    – rdtsc
    Commented Oct 28, 2021 at 18:06

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Both DC Hall sensors and Reed Relays are magnetic polarity sensitive.

So it depends exactly what you need for proximity , polarity, supply, speed cost, size , soldering method and mechanical life,

https://www.wikiwand.com/en/Hall_effect_sensor

These are used in almost every DC fan and BLDC motor.

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    \$\begingroup\$ Thank you for the information! \$\endgroup\$
    – Ver Nick
    Commented Oct 28, 2021 at 17:54
  • \$\begingroup\$ Be sure to specify your assumptions listed in my question for SPECS before choosing a solution. A Reed Relay is the simplest if you just want the magnet to operate the switch with using the coil. Then you only need to mount it close enough in the right orientation to switch the strong magnet attached to the Reed. ( ~>1mm depending on how strong your external moving magnet is) Often you need a motor with the Hall Sensor mounted inside for each pole like in DC fans when outer fixed magnets are used to sense the rotor. \$\endgroup\$
    – D.A.S.
    Commented Oct 28, 2021 at 18:00
  • \$\begingroup\$ More details may be necessary on your application. \$\endgroup\$
    – D.A.S.
    Commented Oct 28, 2021 at 18:03
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    \$\begingroup\$ A Hall sensor itself is sensitive to the field polarity -- but many of the sensors you can buy "off the shelf" are designed to respond to either pole of a magnet. They're usually called "bidirectional", but other names may be out there. So shop with care. \$\endgroup\$
    – TimWescott
    Commented Oct 28, 2021 at 20:17
  • \$\begingroup\$ @TonyStewartEE75 I think I have already specified in the question that polarity is enough for my project, but I have added another sentence in it, to be sure. \$\endgroup\$
    – Ver Nick
    Commented Oct 29, 2021 at 12:08

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