I'm currently replacing the motion controller in my router with a UC300ETH+UCBB board. Previous motion controller had an on-board relay for the VFD control which used a n/o contact to connect "For" to "DCM". DCM is the common ground for the digital inputs on the VFD. However, the UC300/UCBB combination does not have a relay. The UCBB digital outputs use a MOSFET to short the output to board ground, which is fine for things like the stepper drivers. I don't really want to have to install a separate relay board, so wonder if I can connect DCM to the UCBB ground and "For" on the VFD to a UCBB digital output. The main issue here is whether it is safe to connect VFD DCM to ground in the control box.

The HYmanual I have is no help on this one!

Anyone have experience of switching an HY VFD like this? I'm sure that there are plenty of UC300/HY VFD systems out there...

Thanks in advance,