Amazon.com: DIGITEN 4 Digital Blue LED Tachometer RPM Speed Meter + Hall Proximity Switch Magnet Sensor NPN + Sensor Mounting Holder for Lathe Conveyor Belt : Industrial & Scientific
Taiss/30 cm Adjustable M18 Diffuse photoelectric Switch Sensor Optical dc Three Lines NPN NC(Normally Closed) Proximity Switch 6-36VDC E3F-DS30B2: Amazon.com: Industrial & Scientific
Amazon.com: uxcell 1-8mm Inductive Proximity Sensor Switch Detector NPN NO DC 6-36V 300mA 3-Wire LJ18A3-8-Z/BX-G for 3D Printer Probe Bed Leveling,MCU Board : Industrial & Scientific
uxcell 4mm Inductive Proximity Sensor Switch Detector NPN NO DC 5-30V 200mA 3-Wire SN04-N for 3D Printer Probe Bed Leveling,MCU Board: Amazon.com: Industrial & Scientific