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### Author Topic: How many limit switches  (Read 4733 times)

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#### CHCChrisA

• 15
##### How many limit switches
« on: January 08, 2012, 04:38:27 AM »
HI
I am just a little confused as to how many limit switches?
Do you put 4 on the X axis? either side and at each end?
plus 2 on the Y
And 1 one the Z?
And do you add home switches on top of that?
Or do you just have 3 limit switches and they act as home switches aswell?

Thanks
Chris

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: How many limit switches
« Reply #1 on: January 08, 2012, 05:11:30 AM »
You can do as you wish assuming you have enough inputs. If using the parallel port then inputs are scarce so often what people will do is link all switches from all axis in series and just use one input. You can use the same switches as home switches also.
If you can have a switch in the middle of the travel and have it triggered from each end then you would only need 1 per axis.
They should be Normally closed switches as that is the safest. If a wire breaks then it will be seen as a limit switch triggered where if you used Normally open the first you would know of a wire breaking is when your axis moved onto the switch and kept going because its signal is not seen by Mach.
Hood

#### CHCChrisA

• 15
##### Re: How many limit switches
« Reply #2 on: January 08, 2012, 05:22:00 AM »
Thanks Hood
I dont know how you would use a single switch in the centre but anyway, so you could wire up 8 switches, 4 for x, 2 for y and 2? for Z (<---Linked) and then how would you the use those same switches for home?
Thanks

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: How many limit switches
« Reply #3 on: January 08, 2012, 05:32:36 AM »
Not sure why you are saying 4 on X as normally the most an axis would requre is 3 and that is if you were wishing to have a seperate home switch.
The quick sketch I did  below may help to explain how a single switch can be used for an axis.
Hood

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: How many limit switches
« Reply #4 on: January 08, 2012, 05:34:32 AM »
Oh an if wanting to use the same switches as home switches just set them up in mach with the same pin and port numbers as the switches. When you home Mach will treat the signal as a home signal, once homed they will again be seen as limits.
Hood

#### CHCChrisA

• 15
##### Re: How many limit switches
« Reply #5 on: January 08, 2012, 06:01:32 AM »
I dont really follow your sketch, i have drawn a little sketch of my own, the only ones i havent added is the ones for the Z axis, i thought you put 4 on the X so that the axis will self align when it gets to the end. also if they are wired in series how does mach 3 know which switch went of as in which end set it off
Thanks

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: How many limit switches
« Reply #6 on: January 08, 2012, 06:40:23 AM »
Ah ok it is a Gantry style router you have. You could get away with 3 switches on the X axis if you wished. I have not done anything with gantry routers aand slaved axis but I think you would need a separate home switch on one side for squaring, the other switches could be sharing the same inputs as the rest.
Because it is a gantry style the Y could have 2 or you could indeed just use one if your switch was on the moving part of the Y and the triggers at either end on the stationary part of the Y.
Hood

#### CHCChrisA

• 15
##### Re: How many limit switches
« Reply #7 on: February 01, 2012, 02:17:59 AM »
HI
Been away and sick and still havnt done my limit switches, should i setup limit and home switches on different inputs on the BOB? or just wire them all together in parrallel and in the mach software and set them the same input number for both limit and home
Thanks

#### stirling

• 2,188
• UK
##### Re: How many limit switches
« Reply #8 on: February 01, 2012, 05:31:06 AM »
Many options but minimum, if you want limits AND homing AND gantry aligning is 4 switches and 2 input pins.

Limits and homing: A switch mounted on one end of your gantry (your Y) that hits a wedge at each each end of X travel - that's your X switch. A switch on your Z assembly (not the bit that goes up and down) that hits a wedge on each end of your gantry - that's your Y switch. A switch on the moving part of Z that hits a wedge on each end of the stationary part of the Z assembly - that's your Z switch. Wire all these in series to 1 input pin and set that pin in ports n pins for limits and homing for X,Y and Z.

To add gantry aligning to the above: Several options: 1 option: A switch mounted on the other end of your gantry (your Y) that hits a wedge at one end of X - the end you want to call home. Wire this to a second input pin. Set it as home of your slaved axis in ports n pins.