Issue with limit switches when powering on table

[Pdtwrs]

Hi Everyone,

I have a Thermal Dynamics Cut Master 82 table, running Mach 3 software.

We have the table running properly except for the limit switches. The Emergency Stop and the table switches are all serially wired together with normally closed as the operating mode. Any break from any switch will stop the table. Mach 3 is setup with the x, y, z and Emergency Stop settings all the same because there is only one input to the Bob Board from the table. The low indicated is activated in the Config - Ports, Input tab. The limit switches work properly if power to the table is turned off. When the power to the table is turned on, it switches to normally open instead of normally closed as the operating mode. Why would powering on the table change the limit switch operating mode for normally closed to normally open?

Thanks in advance for your help,

Phillip

[weldguy]

Hmmm, curious myself.

Is your computer using a parallel port connection?

When you say the limit switches work properly when table power is turned off are you determining this by seeing an on screen indicator in Mach3 responding to switch input?

[djreiswig]

Is there a relay in the loop that is switching when it is powered up?

[adbuch]

Perhaps you have them wired wrong, or you have the wrong type of switch. If they have both NO and NC terminals, make sure you are connecting to the correct ones for your application. It is also a possibility that you have a choice in your software as to NO or NC and you have the wrong box checked.
David

[acourtjester]

His problem was a ground loop, now working fine.

[adbuch]

His problem was a ground loop, now working fine.