The Omron D40R-LPB-21-M12 is a reed-style magnetic switch from the D40R series, classified under Specialized Switches and the Reed, Hall-Effect, & Magnetic Switches subcategory. It is a position-sensing component used to detect the presence or absence of a magnetic field — typically from a target magnet mounted on a moving machine part — and switch a signal back to a PLC or safety controller.
What It Does in a Panel
In a typical installation, the D40R-LPB-21-M12 mounts near a moving assembly — a door, a guard, a linear slide — and a magnet on the moving part passes close enough to close the reed contact. The switch then sends a dry-contact signal back to the input card. Because it is a reed switch, it is hermetically sealed and immune to dust and moisture ingress, making it a fit for washdown or outdoor cabinets where a standard limit switch might corrode.