7i76E to VFD

It looks a little awkward as the VFD seems to only support separate FWD and REV command inputs, and the 7i76 expects ON and REV.

Initially I would suggest connecting the 7i76 TB4 pin 6 (ENA+) to VFD STF and TB4 pin 5 (ENA-) to VFD SD.

Then worry about spindle reversing later....

tecno wrote:

These are 12VDC relays so feeding 12VDC via red wire and connect Forward and Reverse relays SD / STF and SD / STR.
Input to trelay board to TB4 - 8 dir+ to Forward coil and TB4 - 7 dir - to Reverse coil.

Can this be correct?

It doesn't sound right, but I don't know how your relay board works.

TB4 ENA+ and ENA- are a solid-state switch that is closed any time that the HAL pin "spinena" is set. There is no PWM output unless this pin is set.
TB4 DIR+ and DIR- are another solid-state switch that is directly controlled by another HAl pin (spindir?)

So I think you need a SPDT relay controlled by DIR to select a VFD terminal in series with a SPNO relay controlled by ENA.

I don't think that you can easily use those relays, as they appear to need the coils to be driven in a bipolar way.

Well, it is difficult if you limit yourself to using spinena and spindir.
If you run one of the relays from GPIO then it is fairly easy.

Actually, I think it can be done with the relays you have and without using GPIO. I was mis-reading the data sheet.

I will try to draw a diagram at lunchtime.