Mechanical Endstop

Common implementations

(Updated 31/MARCH/2021)

The main mechanical endstop we find uses a [lever switch] to detect when an axis has reached a minimum or maximum bound. The basic operation of these endstops is to set the logical state of a pin in the arduino (other controller board) to indicate when the bound was reached.

The pin is kept LOW to indicate that everything is fine and raised to HIGH when the lever is pressed. The lever switch or "limit switch" has a common contact (frequently labeled as C on the switch) that is either in an open state or a close state.

The Common pin on the switch is attached to an IO pin in the controller, that's called the "signal" pin and is commonly labeled as "S". The NC (Normally Closed) is a pin in the switch that is touching the Common whenever the switch is open. The NC (Normally Closed) contact is tied to ""GND" and thus the Common pin is put in the default LOW state.

Since new microcontrollers and boards provide a fair level of protection in their I/O pins (eg pull-up resistors, etc) the basic design of a limit switch with their common and NC pins is still in use, we see it in printers like ANET8 and Prusas's MK series, their derivate clones, and in many simple designs.

Over the years with the availability of clone printers and many budget options the popularity of some type of printer in particular Ender/CR type of printers has push the availability and design of endstops towards the ones used by these popular printers.

Todays designs are characterized by the addition of leds to visualize the state of the endstop and the use of an RC (resistor-capacitator) circuit to reduce/limit signal noise (Electromagnetic Interference [EMI])) generated by the switches.

Today the Makerbot design with a led and the RC circuit is the defacto implementation for mechanical endstops using limit switches.

How to wire a mechanical switch to replace an optical endstop.