He built this set of no-contact limit switches using a hall effect sensor. The small black package sticking out past the end of the protoboard is the sensor. It is used to detect a magnetic field.

[John Crombie] had a crack at building one using linear Hall effect sensors and magnets as the detection mechanism to good — well — effect. Using the SS49E linear Hall effect sensor in pairs ...

The market for hall-effect current sensors market is anticipated to reach USD 1128.0 million in 2022 and increase to USD 2765.0 million between 2022 and 2032 at a CAGR of 9.4%. Consumer electronics, ...

This use of a magnet turns our keyboard inputs from fixed to dynamic. Once a computer knows how far you’ve pushed the key ...