Limit switch (Endstop)

Micro limit switches are small electromechanical devices whose task is to open and close a circuit or to supply and disable a device. Limit switches are commonly used in small home appliances, emergency stop buttons, gas water heaters, gas burners, arduino, electronic products, power tools, the automobile industry, communications equipment, test instruments, medical equipment, military products, and so on. In 3D printers, limit switches play the role of sensors that let the 3D printer detect the physical limits of the printer's movement, i.e. find the ends of the linear guides.

Image 1: The Winfred micro limit switch. Source: Filament2Print.

The SPDT (single pole, double throw) terminal has 3 pins (5 mm long) for one input and two outputs. The switch operates on the momentary 1NO + 1NC principle, which stands for "normally closed contact" and "normally open contact". The movement of the hinge roller actuator applies force to an over-center mechanism which creates a quick change in contact state (ON/OFF) when the trip point is reached.

Image 2: The Winfred micro limit switch. Source: Filament2Print.

This micro limit switch is made of copper and measures 20 mm in length, 7 mm in width and 10 mm in height, with the lever arm of the hinge roller actuator 18.5 mm long and 4 mm wide. The rated current of this switch is 5 A and the voltage is 125-250 V.