Using proximity sensors for homing

Hi all,
I'm using some proximity sensors as home switches and they have been giving me fairly consistent positioning (their accuracy are about within +/- 0.02mm so I think that's pretty good although I've seen some that can hold even tighter tolerance).

Instead of using limit switches I plan on setting up the travel limits in my configuration file. I think these soft limits rely on the home sensors positioning to work properly, is that correct? In this case, would it be more fail safe to have a NC or NO proximity sensors (used as home switch only)? I understand that for limit switch they should always be NO to be safer, but I think my case is a little different and want to know if someone can give me some advice.

As mentioned I use them as home switches only. Actually I have tried setting them up as home/limit shared but it would cause error saying " joint [x] on limit switch error" every time I tried homing. So the only way I've been able to home the machine is by setting up the sensors as Home switch only.

usert_l wrote:

Hi all,
Actually I have tried setting them up as home/limit shared but it would cause error saying " joint [x] on limit switch error" every time I tried homing. So the only way I've been able to home the machine is by setting up the sensors as Home switch only.

You need to use the homing offset to move the axis away from the homing switch far enough that the sensor is no longer triggered at the home position and then you will be sweet!

rodw,
Thanks for the tip. I checked and sure enough the home offset was set at 0 in my ini file. Changed it to a reasonable distance and now it homes without issues.

Actually I just noticed in my ini file that there is a variable called HOME and another called HOME_OFFSET. Is there a difference between the two?

Sorry I'm away for the weekend just google "linuxcnc homing sequence "

usert_l wrote:

Actually I just noticed in my ini file that there is a variable called HOME and another called HOME_OFFSET. Is there a difference between the two?

Does this help:- www.linuxcnc.org/docs/2.7/html/config/in....html#_home_sequence