wiring PLC digital outputs to VFD

[Brijm]

Guys I don't think he was necessarily intending to use an external power supply on the drive terminals. I think he was doing something like this

7 VAC

X----------X

OUT0 5

X-----------X

quote]

That was my assumption as well. If he wired 120V to the system, then I imagine he is still trying to put the smoke back in.... Hence the silence on the update.

 

[unsaint32]

I am so sorry for not updating until now. I got so busy that I could not even touch this issue. I had decided to use interposing relays as all of you had suggested. Thank you so much. The reason I wanted to try my original method was that I found out the PLC had relay outputs. What Brstilson had described was exactly what I was describing. I still think that it would have worked since the relay contacts are just dry contacts, but I didn't trust my knowledge enough to connect VFD's COM terminal to PLC's VAC/VDC terminal. Thank all of you again.

 

[OkiePC]

The reason I wanted to try my original method was that I found out the PLC had relay outputs. What Brstilson had described was exactly what I was describing. I still think that it would have worked since the relay contacts are just dry contacts, but I didn't trust my knowledge enough to connect VFD's COM terminal to PLC's VAC/VDC terminal. Thank all of you again.

I had a feeling it was something like this, or that if you wired the power from the 12vdc of the drive as the source for the triac module it might actually work. I was grinning reading the thread.

Thanks for the punch line...not as exciting as Lancie's but thanks anyway.

 

[unsaint32]

if you wired the power from the 12vdc of the drive as the source for the triac module it might actually work.

12vdc for the triac module? Did you mean to say relay output module?

 

[OkiePC]

Yes.

I got that from an early post, someone assumed you had triac modules.

I thought you were going to take the +12vdc from the VFD to the AC output card AC common terminals and use the triac outputs to switch the 12vdc signals going back to the drive.

I am not sure what would happen. Maybe nothing. Maybe it would have worked. Maybe a little of both. I think no smoke though, nor damage.

If you had applied 120vac to the PLC card output common and the drive terminals, that is a whole 'nother smelly story. Probably a sizzle maybe a pop, some small fire and little smoke, unmistakable smell.

It was all a misunderstanding gone astray awaiting a part number I think.