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Strange homing problem
« on: January 02, 2015, 08:19:19 AM »
Hi, I'm having trouble setting up homing switches.
I have NC switches on X, Y and Z connected in series to pin 11
I have a NC switch on B (axis is slaved to X) connected to pin 10, "Home Slave with Master axis" is unchecked
There are no other inputs connected or configured.

On the diagnostic page, with axis away from home switches, LEDs for Pin 10 and 11 are unlit and none of the Home LED's are lit. When I press the switch on x, y or Z the LED for pin 11 lights, along with M1, M2, M3 home LEDs. When I press the switch for B, LED for 10 and M5 home LED lights.

All going to plan so far....

When I press the REF ALL HOME button, each axis motor jogs a few steps and stops. one of the LED's for the input pins or homing indicators illuminate  The LEDS on the Zero X , Y and Z buttons change from Red to green and the machine co-ord set to zero as expected, but they are no where near the switches. Pressing again just repeats the motion.
The same happens when I try the individual axis on the diagnostic page.

Does anyone have an idea why I cant Ref Home?

Thanks in advance


Offline Hood

  •  25,835 25,835
  • Carnoustie, Scotland
Re: Strange homing problem
« Reply #1 on: January 02, 2015, 09:28:47 AM »
You have electrical noise on the home switch wires. You ideally want properly shielded and grounded cables for low voltage signal wires.
Setting a debounce Interval of 2000 may help but it is just masking the noise issue and personally I think it better to fix that. You will find the Debounce Interval on General Config page.
Re: Strange homing problem
« Reply #2 on: January 04, 2015, 03:42:55 AM »
Hi Hood,
I replaced all my Cat5 cable that I was using with shielded cable, but still got the same results. Changing the debounce to 2000 worked. Is there any reason I cant leave it like that?

Offline Hood

  •  25,835 25,835
  • Carnoustie, Scotland
Re: Strange homing problem
« Reply #3 on: January 04, 2015, 04:40:19 AM »
Did you ground the shield properly?
Normal practice is to take the shield, at one end only, and connect to a single point and that point connected to Earth.
If you did ground that way and you still have problems then it may be an issue with your breakout board itself.
Leaving the debounce interval at 2000 will be ok if it is the only way you can solve your issue although personally I like to try and get rid of the problem rather than mask it.

Re: Strange homing problem
« Reply #4 on: May 01, 2015, 06:29:37 AM »
So I'm still having some noise issues.
My steppers are 3A and running in unshielded cable in a cable chain along with the 3phase VFD cable (shielded and tied to ground at start of cable). My data cables for home switches and Z zero plate are also running in the same chain but moved as far as practical from the others. Every now and then I see the status lights of the inputs in Mach flash and disconnecting the cables at the BOB stop this. This has proved to me that these wires in the cable are acting like big antenna and still picking up the noise from the steppers.
How can I stop this?
I'm thinking that I may have to route these cables differently, but this is going to mean more cable chain.
How far away from your stepper cables do you have your data cables? Should I ground the switch end of the cable shield as well?