HY VFD DCM connection

[Neale]

I most definitely don't want to upset anyone, and I appreciate the difficulty of dealing with questions on the forum when you don't know the background of the person asking. In particular, very few participants here understand the first thing about electrickery and questions tend to be of the general form, "Where do I stick the red wire?" However, in my case with a degree in electronic engineering, many years playing with building amateur radio kit, and having built a couple of CNC routers and done a brain transplant on them more than once, I had looked at the UCBB output circuitry (usefully given in its manual, although the AXBB manual didn't seem to do the same thing) and noted the output MOSFET 2A/50V rating. I was really just looking at whether someone had internal (literally) info on the HY VFD ground isolation. I would have been reassured to hear something that backed up the checks I was going to do anyway (and which suggest that there is ground isolation on the DCM and digital input pins). I'm one of those people who find it difficult to accept a "do it this way, don't do it that way" without a technical explanation. Even if many people asking questions here do want exactly a "tell me how to do it, don't bother explaining!" approach!

If I were doing this job from scratch, I would have designed in a relay (for belt and braces rather than necessity) and allowed space for it in the control box. However, as this is a brain transplant job, adding a relay as well as having two boards to replace the one original would be a bit of a fiddle that I would rather avoid. I'm using the UCBB rather than AXBB because I want to retain the 24V signalling in the control box rather than go to 5V.

Jazz - out of curiosity, I'm assuming that you have used the UC300/HY VFD combination, so how would you normally switch the HY digital inputs? Depends on BOB used, maybe?

Oh, and if you want a laugh at my expense - after installing the UC300/UCBB and wiring it all together, installing the latest version of UCCNC (and even noting a minor bug in the diagnostic screen display) and configuring it, I can't get the steppers to move... I've probably forgotten a ground wire somewhere or something stupid like that. There's nothing like confessing to a problem like this to make the answer leap out at you, so I'm off to the workshop with my oscilloscope to find this week's stupidity!