I have 3 DC power supplies in the drive side, a 5vdc, a 24vdc, and a 170vdc.
The 5vdc power supply on the 0v side reads 37.6 ohms with the 0v and 5v sides connected to the 7i77 5v plug. The 7i77 is the only thing it powers up. When I unplug the 7i77 0v reads open so there is a path through the 7i77 5v to ground. The 24vdc power supply is for the limit switches and push buttons. It reads open from 0v to ground. The 170vdc power supply is a bridge rectifier with a large blue cap and a power resistor. See the photo in the link of the current panel. I can't tell which side should be 0v but both sides measure 0.65M ohms to ground. I don't know if that is reading back through the bridge rectifier or the drives. It only powers the three axis drives. Current panel layout http://gnipsel.com/images/bp-knee-mill/bpel06.jpg JT On 1/4/2016 10:48 AM, Bertho Stultiens wrote: > On 01/04/2016 05:34 PM, John Thornton wrote: >> Well I grounded X2 to the main ground and when I started LinuxCNC and >> started to home I got the flurry of sserial errors. So I thought about >> it for a bit and maybe the ground from the computer case to the ground >> block was creating a ground loop so I took it off. Started LinuxCNC and >> immediately go a flurry of sserial errors which locks up LinuxCNC. Mind >> you this is with the 7i77ISOL card between the 5i25 and the 7i77 which >> is supposed to block any noise in the sserial communications. The X2 to >> ground has to go... >> >> I do have a 7i92 to test out... > My guess is that you have more than one (ground-)loop. You also need to > check how the 0V (DC) line interacts with other devices/converters etc. > wrt. ground and see whether any of them also hook-up to ground somewhere > along the wiring, PCBs or supplies. > > The second type of loops can be (entirely) in the 0V (DC) connection(s) > where multiple paths, with different impedances, impair the integrity of > the signal lines. You need to check how the different DC supplies > interact with the connections as they are. The problem often becomes > visible when you have both high- and low-power devices connecting and > running on the same supply and have the 0V (DC) connected so that it > (can) create(s) a loop. > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
