Trying to get this thing to work

[Doddy]

Right, I've polished my crystal ball and predict from the image you've provided that the controller is labelled Z-DQ, lower right?

Have a look at the following.

https://hackaday.io/project/6776-304...g-machine-mods

And see if any of that is relevant.


EDIT:

I've re-read the earlier posts - part of what OP is asking for is to be able to read the RPM - not, as most of us use, setting the RPM from Mach3. Jazz did spot this with his dialogue on spindle encoders.

If OP just wants manual control for the spindle, but with an indicator for the spindle RPM, then you need to figure a way to attach a rotary encoder (this can be as simple as a slotted/reflective opto-coupler mounted near the spindle with a bit of reflective tape on the spindle) - to generate a 1-pulse per revolution signal. From here, either an external device to display the spindle speed or determine an input pin on the controller PCB, and wire that signal to that input, such that Mach3 can read this signal state. If you can get as far as this then I'm quietly confident that there's Mach3 experts here that can advise on getting this to display spindle RPM (I stopped using Mach3 a while ago and only ever used it in a display-commanded RPM, rather than display-actual RPM configuration)