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Author Topic: same switch for all 3 x axis requirements  (Read 4982 times)

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same switch for all 3 x axis requirements
« on: October 14, 2010, 09:10:35 PM »
Can I set 1 switch for X++ and X-- and X Home?  I've tried to wire it this way with all three switches using one cable on Port 1/Pin 10 but can't get Mach 3 to Ref Home. The Limit function of the switches works but not the home.
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Re: same switch for all 3 x axis requirements
« Reply #1 on: October 15, 2010, 01:58:54 AM »
You can use one switch if you want.  You just need to locate it so a trigger device at each end of the travel
will trip the switch at the right time.  You can use two or three switches each wired to an input if you want
 but that is wasteful of the inputs to Mach.

I set my system up so that one switch does X++, X- -, and X home.  Set   X++ to the same pin and port that you specify for
X - - and X home.  Then make sure that the system is setup so that the condition is the same for all three functions. 
That is all three must be looking for a high OR a low.

I would suggest that you set your system up so the contacts are normally "closed" and then open to say that
the limit is reached or that the axis is homed.

 You can use one switch to do both the limit function and the home function. 
When you tell Mach to Ref Home the system is looking for the switch to change state.   When it sees the state change
it will then reverse direction until the state change goes away.  You are then homed.   All other times the system
is looking at that switch as a limit switch and will act accordingly, stopping movement and requiring a reset.

RWW

Offline Hood

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Re: same switch for all 3 x axis requirements
« Reply #2 on: October 15, 2010, 03:03:36 AM »
Further to what has been said you can use two Normally Closed switches per axis and have them wired in series, you can then wire the other  axis switches in series with them and that way you will only require one input to Mach for all axis.

Hood
Re: same switch for all 3 x axis requirements
« Reply #3 on: October 15, 2010, 09:05:58 AM »
Thanks for the responses guys. Reading my OP, I realized I didn't quite word my setup correctly.  I have 2 switches for each axis.  One at ++ extreme and one at -- extreme.  Each axis is wired to a single pin.  X on 10, Y on 11, and Z on 12.  I just can't get the Home to work yet with this setup.  I did find a couple of articles about debounce and will play with that to see if it works and will report my findings.  Right now,  when I home, it only works if I disable ++/-- and have the switch active as Home.  If the ++/-- is enabled, the axis gets to home and then ( I'm guessing) the switch acts like a limit and triggers an Estop.

Thanks again!

Slainte Mhath Hood
« Last Edit: October 15, 2010, 09:08:22 AM by spaceman »
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Offline Hood

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Re: same switch for all 3 x axis requirements
« Reply #4 on: October 15, 2010, 09:08:48 AM »
Do the machine coords zero?
Hood

Offline BR549

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Re: same switch for all 3 x axis requirements
« Reply #5 on: October 15, 2010, 09:35:25 AM »
DO you  have the 2 switches wired in series ?  

Just a thought, (;-) TP
« Last Edit: October 15, 2010, 09:37:01 AM by BR549 »
Re: same switch for all 3 x axis requirements
« Reply #6 on: October 15, 2010, 10:33:46 AM »
The home function didn't work at all so the coords don't zero.  Mach 3 interprets the switch, even in the home function as a limit.

UPDATE: it now works in Ref Home because I set the debounce. I'm going to add capacitors to see if that quiets everything.


DBR549: the switches are in parallel
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Offline Hood

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Re: same switch for all 3 x axis requirements
« Reply #7 on: October 15, 2010, 10:38:35 AM »
If it was a bouncing switch, which it seems as debounce is working,  then it should have zeroed the machine coords. Reason is Mach would have thought homing was complete and reactivated the inputs as limits, so it would trigger the E-Stop.
Hood
Re: same switch for all 3 x axis requirements
« Reply #8 on: October 15, 2010, 10:47:39 AM »
You stated that the axis switches are in parallel.  I strongly recommend that
you change that configuration to a series configuration using the normally
closed contacts on the switches.  I think that will fix your problem. 

RWW
Re: same switch for all 3 x axis requirements
« Reply #9 on: October 15, 2010, 06:02:08 PM »
You stated that the axis switches are in parallel.  I strongly recommend that
you change that configuration to a series configuration using the normally
closed contacts on the switches.  I think that will fix your problem. 

RWW


Are you concerned about the axis crashing if a switch fails or is there another reasone behind it?
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