Hi everyone,

I think I've read about 40 different forum entries, watched a dozen videos and I still can't seem to figure this one out.

I'm trying to connect my rnrmotion mach3 bob to the VFD. The VFD in question is this one:https://www.omc-stepperonline.com/download/VFD%20manual%20datasheet.pdf

So far I've ascertained that I need to wire (from the bob to the vfd):

AVI - AI1
ACM - GND
10v - A0 (jumpered for 10v output so it is pushing the correct voltage over to the bob)

There are two GND pads on the VFD, and I'm not sure if they are internally common so I have bridged them.

I've also wired from output 2 over to X1 on the VFD (which is set to "forward" by default)

The VFD is also set to accept an input from an external terminal, and I'm quite sure my pin/port settings are ok for the spindle.

I have absolutely no idea what I'm missing here, though I suspect it's going to be frustratingly obvious. Has anyone got any ideas for things I should be checking? Is my wiring right? Any help would be appreciated!

have you seen in the manual that the VDF input are in basic setting NPN not PNP.

J1 on the VDF is to change this.

Yep I did change the jumper to NPN as well (which I forgot I did, then wondered why when I switched it back to pot control it wouldn't work).

I'm starting to think it may be easier to use the 485 pins and get a converter to do it through there. I'm not sure if there's anything else I've missed in programming for the VFD (changed input to external etc) but I suspect there's maybe an issue with one of the pads. Because it's PWM I can't measure it with my multimeter.

A0 is not a power supply, it outputs an analog voltage for metering that indicates a parameter like frequency or motor voltage. Have you actually measured 10 volts coming from that terminal? I checked the VFD manual and don't see how it could be forced to a constant 10V.

I can't find a manual for your rnrmotion mach3 bob. Its 10V terminal most likely does need to be connected to a power supply. The VFD P12 terminal is a 12V supply. Even though that's a bit it's probably OK to connect it to the BoB 10V terminal. A BoB manual should answer these questions.

have you found this:

https://buildyourcnc.com/FAQ/14900

Two 1N4148 diodes in series with the P12 power supply will drop the voltage at the BoB board to approximately 10 volts.

You could also use something from the 1N4001 series (1N4001 to 1N4007). The difference is the voltage rating which isn't not an issue in this use. They have a lower voltage drop so you would need to use three in series.