home switches - why three prongs?

[mhickler]

I am pretty hopless with electronics. I bough a 4 axis cnc controller which is working fine, I want to implement home switches. The ones that came with the controller have three contact prongs. Which do I use?

[One of Many]

There will be a common, a NO(normally open) and NC(Normally Closed). Which NO or NC will be depending on what logic the inputs use. If you have a schematic, it will show the configuration as the appropriate symbol. Not all micro-switches come as SPDT(single pole, double throw) having both NO and NC contacts. Some come as SPST(Single pole, single throw) having either NC or NO, but not both.

Typically the common prong will connect to the positive power source and the NO will go to the input for its axis. In some circuits, they may use the ground as an input so the common prong would be connected in that manner.

This is different than in an E-stop circuit. Here you would connect the common prong to the supply or the previous micro-switches NC prong. The concept here is to daisy chain all the E-stops switches in series so that any one that gets opened will trigger the input.

DC