Limit switchs

jeffie-3 wrote: O.K. GND is different than -5v or -12v
TB1 pin 1 and TB2 pin 8 run to the same terminal and that terminal runs to the negative side of the 5 volt supply.

They can be connected together but you will loose all isolation from the noisy side of the machine.
It is not advisable to wire them together, you can use a separate power supply for the TB1 part, or use a USB cable to power it from a spare usb on the PC, or you can power it from the 5I25/6I25/7I92

O.K. Thank you. I have both 12 volt supply and 5 volt supply in the machine. I will change that.

PCW wrote:

tommylight wrote: NC switches should give 12V at the Mesa inputs when not tripped.
Check the wiring.

Yep and also, inputs must be 12V relative to field power GND = TB2 pin 8 when on

O.K. I have 11.74 volts from TB8 pin 1, TB8 pin 2, TB8 pin 3, TB8 pin 4 to TB2 pin 8. Checked the voltage at the switchs and it is 0.

Sounds like your switch common is not connected to 12V

I checked the one side of the switch and the other side ground. There is 11.74 volts.

So is there ~12V at the 7I77 field inputs when the NC switches are
not activated (or 12V when NO switches are activated) ?

If not, you have a wiring error.

wiring should be:

+12V field power --> switch common --> switch output --> 7I77 field input