Mach 3 and limit switches being seperate of wired into one input.

[woodwurker]

Hi all,

First of all, I want to thank you in advance for any answers that I may receive from this question. I assume the answer to this question is a matter personal preference rather than the answer being "There is ONLY one way to do it." I am putting the finishing touches on my machine and just want to get this ? answered before I proceed.

I am using the G540 as my controller board with which there are 5 total inputs on this board. I have, like most everyone else, have limit switches on all of the axis's. I have two on the X axis, 2 on the y axis and 1 on the Z axis. At present all five of the switches are tide together and run into one input on the Gecko G540. I suppose I am being a little hard headed to say that it would only seem better to have each axis running into its own independent input. At this point, the light indications for M1,M2 and M3 respectively will have have each axis separated. Is this the "right way to do if you have the open inputs or does it really matter? I just want to do it the best way from the beginning of putting this machine together rather that having to change it back to the other way down the road.

I am open to all opinions.....thanks in advance.

Mike

[woodwurker]

The Subject should have been.....Mach 3 and limit switches being seperate or wired into one input.....I hoping to get some input here.

Thanks again.

Mike

[Hood]

Thee only difference, I can think of,  is you will not get a visual indication on screen which axis has hit its limit. Will this matter? to me it wouldnt as a visual inspection of the machine will tell you in two seconds which axis it is.
Only thing I can think of that would make it a benefit of having three separate inputs for the three axis would be if your wiring or a switch fails. With 3 separates it would make finding the offending wiring/switch slightly easier, but not much.
So to me if using the parallel port with limited Inputs then wire into a single input, unless you have plenty spare Inputs and dont think you will ever use them in the future.

Hood

[woodwurker]

Hood,

I appreciate your reply. I was thinking along those same lines but wanted to hear the pros and cons form someone who has been there. I dont foresee any reason not to use one input for eash axis as I dont foresee anyhting coming down the pipe that would need an extra input...do you?

Thank you for your reply...hope your weather is good and the wind is at your back.

Mike

[Hood]

Just depends, you may wish to have external buttons for things such as Start or Feedhold etc which will use up inputs.

Hood

[TOTALLYRC]

I have done it both ways.
On my DSPMC powered machine with lots and lots of I/O I have everything wired separately.
On my pport machine I will wire them all into one so I have the I/o for something else, like a probe.

Mike

[GeorgeRace]

I may be off base here, but wonder if there is quite a difference between wiring the three limit switches in series, to one port, versus individual limit switch lines to three ports.

It would seem to me that if the three limit switches were in series, when you home the mill, the first switch to hit its limit would stop all axis movement toward home.  This would result, for example, I think, if the Z axis limit opens first, the gantry stops with the X and Y no where near the home position.

If you wire the three switches to their own port, then the three axis will always go to the same home position, the place where the three switches go open as determined by the position of the limit switch stop block.

Just another thought about how to do it,

George

[Hood]

Homing is normally done one axis at a time. If you wish to combine homing on two or more axis then you will need separate inputs.
Hood

[TOTALLYRC]

I believe if you check ignore limits during homing adn hook them all to one input it will work.
The machine will home the Z and back off the switch, then it will home the y and back off the switch, lastly it will home the x and back off the switch. IIRC.

Mike

[GeorgeRace]

Mike, thanks I never realized that you could do that.

Neat idea and it would save a couple of inputs for other uses as well.

George