[ozydel]

Hi all, Next are my limit switches, I am thinking about proximity switches. I understand shielded / non shielded switch, but does limit switch wiring have to be shielded? If so how do I wire to switch? would I just cut the wire and rejoin with shielded, does anyone have any advice? thanks.

[embraced]

You definitely want to shield it if you are playing with 5V logic. You do NOT want to connect the shield to ground at both ends as this will create a ground loop. Usually shields are connected to the ground wire where the termination is.

[Al_The_Man]

You do NOT want to connect the shield to ground at both ends as this will create a ground loop. .

That was the thinking in the past, but with the importance of equi-potential bonding to prevent ground loops it is recommended to ground both ends of the shield, see Ch6.
http://www.automation.siemens.com/do.../emv_r.pdf?p=1
Al.

[ozydel]

Cheers Al, so if I wire direct to g540 I do not need to have shielded cable for limit, home switches. Or is it just best to get shielded cable?
Thanks to all.

[Al_The_Man]

Depends somewhat what voltage are you using, generally any thing above 5v, twisted conductor should be OK.
Al.

[meckardt55]

If the switch has a steel housing you should make a ohm check with a meter from the shield to the steel housing. If it is "0" ohms and you are attaching it to a steel mounting and it is over 5 volts I would not ground the shield. If the shield is not grounded to the housing I would ground the shield.

Mike CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[DonKes]

I added a small capacitor to each line and my false signals went away. I can't tell you your cap size, but you can calculate your value by making the time constant about 10 % of your step timing (10 time constants per step.)

Don.

[embraced]

Usually a 10uF capacitor connected from the switch input to ground will also make the problems less apparent. You can increase the capacitor size, but you may experience a slower response to the switch triggering.

[DonKes]

I just checked my capacitors. They are .1 microfarad. I did not want to limit my step frequency.

Don