Mesa 7i76D + Omron MX2, spindle speed works, spindle enable does not

Greetings,

I have recently upgraded from a simple router setup to a spindle using an Omron MX2 VFD.

My setup includes a Mesa 7i76D, which I'd like to use to control the VFD via the 7i76D's TB4 spindle connector. I have successfully wired up the analog 0-10V output to control the VFD frequency and confirmed that it's working, i.e. the VFD's diagnostic output shows the correct frequency values as output by the 7i76D.

What I can't figure out for the life of me, however, is why TB4.5 SPINDLE ENA- / TB4.6 SPINDLE ENA+ are not working. The Omron VFD is setup to NPN logic (aka "sinking inputs, internal supply" in the attached picture) i.e. it expects the inputs to be bridged to L, the digital input GND reference. Taking a jumper cable and connecting the input pin to the L pin does trigger the input. I took a multimeter and measured +24V between L and the input pin.

I connected TB4.6 SPINDLE ENA+ to the input pin and TB4.5 SPINDLE ENA- to the L pin of the VFD. Issuing an M3 Sxxxx command in LinuxCNC MDI (or using the GUI buttons) does update the VFD's frequency setting via the 0-10V input, but does not actually turn the spindle on. The relevant parts of my HAL file look like this:


I checkedand it does indeed update as expected when I enable the spindle in the GUI / using GCODE. However, the VFD does not turn on. For those of you who are familiar with the Omron MX2 series: yes, the VFD is programmed to accept the FW / RV commands from the terminal (i.e. AT002 == 01), as is evidenced by correct operation via jumper wire.

As of now, I'm pretty confused and almost sure I'm missing something very obivous, but it's been a long day.

Anyone got any ideas? It'd be greatly appreciated. Thanks in advance!

If bridging the ENA pins starts the VFD but
setting hm2_5i25.0.7i76.0.0.spinena true does not,
That suggests a hardware issue (bad or damaged OPTO for the ENA circuit)

Quite naturally, I figured it out a few minutes after posting, rubber duck debugging and all.

Summary: the output transistor on my 7i76D is most likely screwed. I did not check the IC itself, but I assume it's a quad or dual opto coupler chip, with one of the outputs being faulty (namely the one that is connected to SPINDLE ENA on TB4).

I did not touch the wiring on the VFD side or the configuration at all, but simply unscrewed the connecting wire at the TB4 connector and switched cables from SPINDLE ENA to SPINDLE DIR, and lo and behold, everything works as expected. Just to make sure I didn't go crazy I checked everything back and forth twice to make sure I didn't mix up any wires on the 7i76D' side, but no, the enable pin does in fact not work at all.

I disabled spindle-ccw and adjusted my HAL config to map spindle-enable to both hm2_5i25.0.7i76.0.0.spindir and hm2_5i25.0.7i76.0.0.spinena. This is necessary since the 7i76/7i76D does not output a spindle voltage if the firmware does not receive the spindle enable signal from the host, even though the opto couple still won't switch. This tells me that the firmware is indeed receiving the enable signal just fine (as I already discovered using halcmd earlier), and combined with double checking the wiring reinforces my belief that the particular output got messed up somehow.

I'm probably gonna live with this situation for a while since I don't run the spindle in reverse anyway, but I expect to eventually fix things by replacing the OC IC.


Edit: Thanks for your reply PCW, I see we commented rather simultaneously and (unfortunately) came to the same conclusion. I'll update this thread with some documentation on my approach of fixing the board once I get around to do that. Cheers!