Melexis US1881 Latching Hall-Effect sensor
Ron Czapala
Posts: 2,418
I came across a neat Hall-Effect sensor that latches in a high or low state depending on whether the north or south pole of magnet triggers it. It maintains the high/low state after the magnet is removed unless the power is cut.
Less than $1 at SparkFun - US1881 datasheet
It reminds me of a switch I made back in the early seventies - I glued a small earphone magnet (broken in half) to a magnetic reed switch. If a stronger magnet was placed on one end the reeds would connect and be held by the glued-on magnets. Placing a stronger magnet on the other end would cause the reeds to disconnect. I placed it in one corner of my windshield as part of a homemade burglar alarm.
Less than $1 at SparkFun - US1881 datasheet
It reminds me of a switch I made back in the early seventies - I glued a small earphone magnet (broken in half) to a magnetic reed switch. If a stronger magnet was placed on one end the reeds would connect and be held by the glued-on magnets. Placing a stronger magnet on the other end would cause the reeds to disconnect. I placed it in one corner of my windshield as part of a homemade burglar alarm.