Jog and run working fine, homing jerks

When I try to home my machine, the axis will start to move towards the home switch, but will (seemingly) randomly stop and then start moving again towards home. About half the time, homing will actually succeed (in this jerky fashion), but the other half of the time, Axis will complain that the home switch is toggled before motion starts (or something like this).
When I actually get all three axes homed, I can run a job, and it works great. Jogging also works great, It seems that the only problem for me is homing.

That sounds like noise getting into the home switch circuit.. Are the wires shielded? Grounded on only 1 end?

sam

Thanks for the reply. That is a good thought, but i (respectfully) doubt that noise on the switch input is causing this problem:
I will give more details. The CNC is a 3 axis mill, TECHNO brand. We are currently using this mill successfully on its original software (DOS based, ancient, does not speak G-Code) homing works fine on old software. The only hardware difference is the computer. Drivers are same in both tests. We are wanting to update the computer to linuxcnc, to improve our production capabilities (mostly by incorporating g-code) Right now we have to program each job in a proprietary language.

I will investigate the noise on the home switch wires (grounded on only one end, unshielded) with a scope to see if noise is hitting it, but wouldn't this cause linuxcnc to think that the home switch was hit and then reverse direction to latch?

Thanks Again
Andy

It could be the original software had some debounce.. In linuxcnc you could try adding debounce between the pin and linuxcnc.

www.linuxcnc.org/docs/2.5/html/man/man9/debounce.9.html

sam

Thanks. I'll give it a try.

That was it!

I added debounce to the pins, and it worked beautifully.

Thanks for the help, sorry I ever doubted you!