I designed this board in order to eliminate all the false positive that my CNC controller board receives from mechanical switches during normal operation, because of electromagnetical interferencies or vibration. Of course, this board si suitable even for 3D printers controller boards because the principle behind is the same.

This board implement a noise filtering system in order to have a clear output signal when hard limits are triggered ignoring noise and all the weak signal that will cause otherwise false positive. This feature is provided by the cores of this board: optocouplers This components allow to have:

• physical isolation between switches and controller board because they wire them together without direct galvanic connection, using light;

• filtering effect because they are current driven element: in this way in fact, the noise requires a huge amount of energy to pass through and that means that in normal operating conditions, optocouplers cut out all the noise and at the samte time, short glitches will not pass at all.

How it works? Firs of all, the board must be connected to a +5V supply. Then, when the couple of pins of the desired axis are wired together (so, contact is closed), the diode inside optocoupler will turn on and the light will activate the base of phototransistor (placed also in the same optocoupler) in order to get it into conduction. In the other hand, output pin of corresponding axis will put GND. In the opposite condition, corresponding output pin will remain stable at +5v thanks to a pullup resistor. Notice that despite the board has 3 channels (X,Y and Z), this does not means that can handle only three switches: you can create, for example, a closed loop with multiple switches wired in series (all NC or NO, preferably NC for better system stability) in the same channel; the board will work anyway as well as planned.

Suitable for every kind of switches for both normally closed and normally opened configurations. Because of commonly used voltage leves, it can be used with most commons CNC and 3D printers controller boards.

If you are looking for stable limit switches that cant't be affected by noise, you can look at those Magnetic Limit Switches !

For more detailed information on operating pricniples and wirings, please check the datasheet attached. If you have some question, feel free to contact me.

Available in two versions:

• Complete soldered kit
• Only PCB

I USUALLY SHIP IN MOST COMMON DESTINATION BUT IF YOUR COUNTRY IS NOT ON MY LIST, PLEASE CONTACT ME FOR FINDING THE BEST SOLUTION.