Magnetic contact switch (door sensor)

via Adafruit
$8.90
SKU AF-375

We can get 100 units into Australia from Adafruit. If you order today, we can dispatch this stock between Nov 30, 2024 - Dec 03, 2024.

This sensor is essentially a reed switch, encased in an ABS plastic shell. Normally the reed is 'open' (no connection between the two wires). The other half is a magnet. When the magnet is less than 13mm (0.5") away, the reed switch closes. They're often used to detect when a door or drawer is open, which is why they have mounting tabs and screws. You can also pick up some double-sided foam tape from a hardware store to mount these, that works well without needing screws.