Is there a magnetic switch (like a reed switch) but with no moving parts?

I need a switch that can be turned on by a magnetic field but won't move around due to tremendous shock absorption.

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    \$\begingroup\$ Its called hall sensor. \$\endgroup\$ – Marko Buršič Jan 23 '16 at 23:22
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    \$\begingroup\$ You could use a hall-effect sensor to control a FET or a solid-state relay (SSR). \$\endgroup\$ – Brian Drummond Jan 23 '16 at 23:22
  • \$\begingroup\$ Hall sensors are triggered by magnets, but have no moving parts. They are used in engines, but what does "tremendous shock absorption" mean? Please quantify or explain. \$\endgroup\$ – gbulmer Jan 23 '16 at 23:26

Yes. Search for 'hall effect' switches.

enter image description here

Figure 1. Hall-effect sensor.

The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current. It was discovered by Edwin Hall in 1879.

Hall effect on Wikipedia.

Hall sensor

Figure 2. Hall sensor available from Sparkfun for < $1.

Analog sensors are available with built-in electronics to amplify the small signal generated by the hall-effect to a more useful level, typically 0 to 5 V or 0 to 10 V. The output voltage will then be a function of the magnetic field strength - typically determined by the proximity of the magnet.

Digital sensors are available with built-in electronics to amplify the hall-effect signal and turn on a digital output when the level exceeds a specified magnetic field strength. Usually a little hysteresis is employed so the field strength has to fall a bit before the switch turns off. This prevents rapid switching when the field strength is just on the threshold.

The Sparkfun device listed above has an 'open-collector' output to interface to your micro. This will require a pull-up resistor. Ask if you need help with this.

Read OP and @davidcary's comments below on latching types. I was not aware of these and hadn't read the details on the Sparkfun device I linked to. I learn too!

  • \$\begingroup\$ From what I can tell when the magnetic field is applied the current can flow (switch becomes "on"), but when the magnetic field is removed the current keeps flowing (switch stays on) until you apply a magnetic field of opposite polarity. Is this the case? \$\endgroup\$ – Albert Renshaw Jan 23 '16 at 23:53
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    \$\begingroup\$ Yes, the Melexis US1881 Hall effect sensor (pictured) turns "on" only when a North pole points into its marked face, and stays on when the magnet is removed until a South pole points into its marked face, turning it "off". Others, such as the Diodes AH9248Z3, turn "on" when a magnetic field of either polarity is applied, and turns off when the magnetic field is removed. \$\endgroup\$ – davidcary Jan 24 '16 at 0:10
  • \$\begingroup\$ link: Diodes AH9248Z3 \$\endgroup\$ – davidcary Jan 24 '16 at 0:35

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