Limit and home switches

[Manuks]

Hi everybody, Im new to CNC and electronics in general. In fact, I got interested in electronics through CNC.

Looking at PMINMO.com "system electronics overview" graph I noticed that there is a + and - switch and also a Home switch. Plus they are connected in parallel.

system electronics overview:
http://www.pminmo.com/wiki/index.php...ystem_Overview

My questions are:
Isn´t - switch and home switch the same?

How does "the system" (pc software?) knows which of the three switches has triggered if they are connected in parallel?

Well, thanks in advance.
I feel this is the first question of many so please be patient with me.

[Geof]

On most pages on CNCzone, including this one, you will see near the top right corner a Search box and below it two circles; one labelled Web, the other cnczone. Type 'Limit and home switch' into the search box, make sure the cnczone choice is active and you will get over 300 hits where limit and home switches have been discussed on cnczone.

[Manuks]

thanks Geof, I did that. First quiestion is answered for me now, but I didn´t find anything for the second one.
Does anyone knows how the software realizes which of the three switches is triggered in case the system has them all (-, + and home switches)

[CJL5585]

Originally Posted by Manuks thanks Geof, I did that. First quiestion is answered for me now, but I didn´t find anything for the second one. Does anyone knows how the software realizes which of the three switches is triggered in case the system has them all (-, + and home switches)

Most software has inputs where one enters the dimensions of the table or cutting area. There are also areas where one indicates whether the machine has limit switches, and on which axis. Included is the ability to use both limit switches and home switches, or a single switch for both. All the parameters are therefore set up in software. Since the machine always has some indication of where it is from home position, it can calculate that it is near a home or limit switch. If the system has lost it's reference, then when it makes a limit switch the machine should stop all movement.

The bottom line is that it is a function of software inputs which the operator programs according to how he wants his machine set up, and the actions the machine takes when a switch is encountered.

Hope this helps.

[Manuks]

now I get it, thanks

[Mitsui Seiki]

These limit switches are connected like that because you first hit the home switch .If you go further you hit the one called Limit switch 1(LS1).Further than that you hit the Limit switch 2(LS2)LS1 is what you can call a "soft hit switch". LS 2 is a "hard hit Switch"
They are all affected at the same time.Home-LS1-LS2, in that order.