Emcoturn 120 lathe retrofit

You can probably take the 5V supply from the PC PSU, it might even be advantageous from the point of view of ground commonality between 7i76 logic and the PC.

I was wondering about that. The FX170 has a 12VDC wall wort PSU. The 5VDC for the toolerator3000 comes from the USB on the FX170. Could I use the USB port as a 5V source for the Mesa as well? (with a USB BOB) It connects with a Ethernet already but I don't think the Ethernet supplies 5V

EDIT: something like this?

If you are using a 7I76E, I would power the 7I76E from the 24V field power
that way the machine and PC are electrically isolated:

That is +24 --> 7I76E TB1 1,2,3,4 and TB3 21,22
24V GND --> 7I76E TB1 8 and TB3 23,24

P3 unconnected or used as 5V _source_ for toolerator

LutzTD wrote: It connects with a Ethernet already but I don't think the Ethernet supplies 5V

Reading the manual ( www.mesanet.com/pdf/parallel/7i76eman.pdf ) it seems that with the correct jumper positions you can run the 7i76E from the same 24V for both logic power and field-IO. You need to be fairly sure that the jumper is in the right place before applying 24V to TB3, however. Alternatively, the board should run happily in USB power, within the current limits of USB.

I did not know what "field power" meant. I thought it was for powering devices like the encoder and the home switches, but wasnt sure. I have not hooked up the Mesa yet. This is why I like to draw everything first. Let me update my drawing again and remove the 5V altogether on the Mesa PCBA.

EDIT: like this?

I need to get the Mesa PCBA from the package as the schematic and the manual do not show where the Jumper 1 location is for sure. But here is the config to use 24VDC for logic on the Mesa 7i76e from what I can understand of your posts