On Saturday 26 December 2015 14:09:51 John Thornton wrote: > I found this on amazon > > http://www.amazon.com/UT-211-Port-powered-Mini-size-PhotoElectric-Isol >ator/dp/B00GI9GS58/ref=sr_1_3?ie=UTF8&qid=1451156759&sr=8-3&keywords=se >rial+isolator > > Not sure how I might isolate the VFD from the chassis at this moment. > Well I could machine some delrin standoffs... I have a machine shop. > > I will need the control transformer to get power for the monitor or > just plug the monitor into the wall outlet and power the PC with 240v? > > JT > At that price, John I'd put one of those in just for the PC's own protection, and it might well break a ground loop at the same time.
But verify the speed as I haven't a clue how fast the modbus runs. Opto's tend to have a speed limit, often below 500 kilobaud. > On 12/26/2015 12:51 PM, Bertho Stultiens wrote: > > On 12/26/2015 07:36 PM, John Thornton wrote: > >> You misunderstand, all those components are internally grounded I > >> did not ground any of them. I just showed that the shell on each > >> component is bonded to the ground connection on each device. > > > > Ok, now the real question is whether you can see the difference wrt. > > to my drawing. > > > > The trick is that there should never ever be two or more paths for > > the current to flow, even if it is just an earth connection (or GND > > for that matter). > > > > The isolation barrier I drew is the low-to-high-power separation. It > > should be kept physically separated everywhere until you join the > > power and earth connections at the power supply input. > > > > The real problem I see is the connection of the VFD controller to > > the computer's serial port. Apparently, the computer and the VFD > > controller both have the GND connected internally to earth. > > > > I am pretty sure that the computer's GND is connected to the earth > > (chassis) of the computer (most PCs have). > > > > The VFD controller probably has the same connection, where the > > modbus serial port's GND is connected to the VFD controller's earth > > (chassis). > > > > If so, then you need to break that loop by electrically isolating > > the serial port. > > ---------------------------------------------------------------------- >-------- _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
