The Festo SME-3-SQ-LED-24-B is a magnetic reed proximity switch — a normally open, contact-closure sensor that detects the presence of a magnetic field, typically from a piston magnet inside a pneumatic cylinder. Rated IP66, it handles washdown environments and dusty plant floors without letting moisture or particulates into the switch body. Switching time max of 0.5 ms means it catches fast-moving cylinder strokes without missing a signal.
Switching current max of 0.5 A and switching capacity max of 10 W define the load it can directly switch — think PLC inputs or small relays, not motor contactor coils. Supply voltage of 27 V AC/DC covers 24 V nominal control circuits with headroom for line drop. Switching frequency of 800 Hz is well above the cycle rate of any pneumatic cylinder — the reed switch is not the bottleneck.
Housing dimensions of 18 x 10 x 20 mm and an M8 3-pin connector make it a direct fit for Festo T-slot cylinders and other grooved actuators. Normally open output means the circuit closes when the magnet is present — standard for end-of-stroke sensing.