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Limit/Home Switch Wiring

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wileel

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#1
So I finally got back from deployment and started opening boxes and playing with toys I got while away. First project of mine was to assemble my CNC control box (I got the aluminum box and parts from Automation Tech). So far so good, although its taking longer than I would like since I'm anal, getting all the wires you will never see to have nice bends and such...

Anywho...I'm about to wire up the board to limit switches and was going to keep the wiring clean I was going to use a common ground but wanted to see if anyone thought that would cause any headaches. Let me explain the idea...

Breakout board has 6 outputs, 3ea 5v and 3ea com.
Box has enough extra cut outs form me to run individual cables to each switch but only one is actually labeled "limit switch" .The idea was to use this one cutout for all of them with 18/4s cable.
Wiring it like this; Breakout board to 4pin plug jack with each 5v port connect to separate pins and all com ports connected to a single pin. section of cable heading to the machine and then splitting back out into individual cables to the switches. Although I' may be over complicating it I don't see any problems with its design but I have no idea if the signal could cause some chaos while connected to a computer. Any thoughts?
 
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Robert LaLonde

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#2
IF you are using Mach 3 you can wire all limit switches into one input. When you home the machine it moves the appropriate axis until the limit is tripped, and then it back off the limit and moves the next axis. If a limit is tripped you do have to manually jog hte machine off the limit switch before homing, but that would be true for any particular axis with indvidual inputs as well. I'm pretty sure you can do it similarly on LinuxCNC as well.
The typical parallel port or parallel port replacement has five inputs. If you could quickly use them all up on just limit switches. Of course other boards like the MESA boards or a Smoothstepper with a good breakout board may will have more inputs and outputs.
 

wileel

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#3
I plan to use Mach3 so if Im reading your reply correctly I should be fine to do what I had planned?
 

Boswell

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#4
It is common to wire the limit switches in Series while it sounds like your description is parallel. For them to work in Series they must be Normally Closed switches that open when tripped. One important advantage to this method is that if a wire breaks or a connection fails, it will look the same as a limit trip to Mach3 and trigger a e-stop.
 
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Robert LaLonde

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#5
NC in series is the way to go.
 
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