Amazon.com: 2pcs DC 5V NPN NO M12 4mm Sensor LJ12A3-4-Z/BX Inductive Proximity Sensor Switch for 3D Printer CNC Z Probe auto Bed Leveling : Industrial & Scientific
Leyton Lighting PIR Sensor Switch (SENTIM, 2.5m range, adjustable time delay) : Amazon.co.uk: DIY & Tools
Understanding sensors and limit switches
Inductive Sensor with Increased Switching Distance I04H003 | wenglor
Door Sensor Switch, Soft On/Off Switching - in the Häfele Canada Shop
GE Motion-Sensing Switch with Automatic Shut-Off Feature, White 11927 - The Home Depot
Outdoor DC-12V Automatic Infrared PIR Motion Sensor Switch for LED Light | eBay