sweet thanks gene I will take your advice and connect the pc chassis to the main ground.
I think I will continue to use my grounding blocks for now though as there are about 20 ground cables to connect up and that is getting a bit much for one bolt I think. hopefully I don't have a problem. I will let you know if I do haha regards Andrew On Sat, May 30, 2020 at 2:00 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Friday 29 May 2020 21:22:09 andrew beck wrote: > > > thanks guys > > > > just one question about all this gene > > > > why do you suggest breaking the ground off the the computer > > powersupply cable and connecting a ground from the pc chassis to the > > machine main ground? > > > > does the grounding that goes through the cable now good enough? > The computers 3rd wire should remain if its the ONLY ground connection in > the whole system. But since we power gear thru EMT tubing, and that also > includes a generally better ground, the power cord to the computer > should have that 2nd or 3rd ground removed, and the computers ground > taken back to this common bolt by a direct from its chassis ground wire, > UNLESS the computer is mounted to and mechanically connected to the > frame of the machine and this frame is grounded to that common bolt. > > Anytime you can lift just one of those wires from that bolt, and still > get ground continuity because its grounded someplace else too, is bad > kharma, find that "other" ground and disconnect it. Once, done well, is > enough. A shielded cable where the shield is grounded at the far end > can inject many volts of noise, enough to blow the interface card. > Disconnect that far end. That bolt should connect to the power > wirings "static" ground, and the only allowable cross connected point to > the powerline neutral is in the main entrance box. You don't care if a > nearby lightning strike might cause that bolt to be 200,000 volts from > ground for a microsecond during that strike, but the +5 volt line will > be 200,005 volts, or 5 volts from what it considers its ground might be > at that exact instant. You will be damaged ONLY if some other point in > the circuit breaks down and some of that lightning bolts energy actually > flows thru your system to get to that better ground. Block it with air, > the more the merrier. > > > regards > > > > Andrew > > > > On Fri, May 29, 2020 at 11:53 AM Leonardo Marsaglia > > <ldmarsag...@gmail.com> > > > > wrote: > > > > Connect all grounds to this bolt, checking that they are not > > > > grounded at the far end. By doing this, you are establishing a > > > > single point ground that is the zero volt reference for the whole > > > > system. Connect this bolt to the building static ground, the bare > > > > wire in most power cabling. > > > > > > > > Connect the machines frame to this bolt. > > > > > > > > Connect the - rails of all supplies to this bolt. > > > > > > > > Connect the - terminals of all cards to this bolt. > > > > > > > > Break the 3rd pin off the computers supply cable and connect the > > > > computers chassis to this bolt. Power the computer not from the > > > > wall, but from the same power feeding this box. > > > > > > > > Connect the shielding of all shielded cabling to this bolt. Do not > > > > connect the far end of this shielding to anything that is > > > > otherwise grounded. > > > > > > > > By making sure these grounds are not connected anyplace else you > > > > are breaking any ground loops which can and will act as antennas > > > > to insert noise into your control signals. > > > > > > > > By having this single point ground, a nearby lightning strike can > > > > inject a 100k volt pulse into the system ground as what would be > > > > called a "ground bounce", but the system will not see it as noise > > > > nor be damaged, because everything is bouncing in unison. > > > > > > > > Regardless of what that bolt does during the strike, the 5 volt > > > > supply remains at 5 volts to this bolt, and the 24 volt supply > > > > remains at 24 volts to this bolt. > > > > > > > > And when the storm is done, your chances of having anything > > > > damaged is reduced to the vanishing point. > > > > > > Thanks for this Gene. It's more than useful to remember how to > > > properly ground logic circuits to avoid external noise and dangerous > > > voltage spikes. > > > > > > El jue., 28 may. 2020 a las 20:35, Gene Heskett > > > (<ghesk...@shentel.net>) > > > > > > escribió: > > > > On Thursday 28 May 2020 18:36:10 andrew beck wrote: > > > > > hey gene > > > > > > > > > > sorry for the slow reply > > > > > > > > > > just getting to this grounding thing now. > > > > > > > > > > currently I have single large copper block with a lot of holes > > > > > in it for terminals, this is connected to the earth(ground) wire > > > > > that goes back to the whole shed main ground wire rod in the > > > > > dirt > > > > > > > > > > all my servo drives and vfd main grounds go back to this point > > > > > as do all motor grounds etc. this is how heidenhain set up the > > > > > machine originally and they have a whole grounding schematic > > > > > showing how it all works. I have basically copied that. > > > > > > > > > > I have 2 meanwell 24v powersupplies that have the ground wire on > > > > > the input side also connected to ground. the output side (phase > > > > > and neutral) are floating relative to ground and not connected > > > > > to ground at all I think. as the meanwell switching powersupply > > > > > output should be isolated from the input. I think this is > > > > > correct > > > > > > > > > > the computer cord ground wire is currently connected to this > > > > > same large copper block. > > > > > > > > The sheer bulk of that copper bother me a bit because it can > > > > function as an antenna. A single bolt, tightened well into the > > > > chassis with all the connections stacked up on this bolt will be > > > > quieter. > > > > > > > > > my computer via the 5i25 currently supplies 5v logic power to > > > > > the 7i76 > > > > > > > > Thats fine, but if using a std bob on the other 5i25 port, do NOT > > > > enable the jumper for that port as the bobs std grounding will > > > > short circuit that, you must supply a separated 5 volts to that > > > > bob, or plug in a usb cable to steal it from the pc's usb > > > > circuitry, > > > > > > > > > and one of the 24v meanwell powersupplys supplies the 24v field > > > > > io for the 7i76 > > > > > > > > I have all supplies - outputs tied to ground. It might work 99% > > > > of the time without it, till the first nearby lightning strike... > > > > With all that grounded, it will probably keep right on working > > > > after the strike. > > > > > > > > > my encoder problems started when I connected up the servo drive > > > > > simulated encoder output to the 7i76 encoder counter. I haven't > > > > > connected the 5v and 24 v grounds together. they did work for > > > > > awhile but don't now > > > > > > > > Tie the -'s to the ground bolt. Then do a full powerdown on the > > > > whole thing, with about a 10 count in the dark, then boot > > > > everything back up and test it. And report what you get now... > > > > > > > > > I have a 7i89 and 7i84 coming soon and will need a external 5v > > > > > powersupply anyway i think so will change when they arrive here > > > > > from america. > > > > > > > > > > anyway I read your reply and got a bit confused could you read > > > > > my email here and let me know what I need to change and why I > > > > > should do it this way just so I understand. > > > > > > > > Basicly, your lack of a common ground has possibly allowed > > > > voltages well above the breakdown voltages of the chips on these > > > > cards, between the - connections and a real ground. They all have > > > > what can look like an SCR as an isolation tub under each > > > > transistor its built from, and these SCR's can upset the whole > > > > thing if they get turned on. Thats why the count to 10 or more > > > > powerdown is done, giving these SCR's time enough at a low enough > > > > voltage to turn them off, at which point the circuit looks more > > > > normal and may even work. If not, then something has been damaged > > > > on the card and it should be replaced or tested and repaired as > > > > needed by Peter. His turnaround time from CA to WV here in the > > > > states has been very good. Its several thousand miles. But if I > > > > recall correctly, you are not exactly local. > > > > > > > > > regards > > > > > > > > > > Andrew > > > > > > > > > > On Thu, May 21, 2020 at 9:31 PM Gene Heskett > > > > > <ghesk...@shentel.net> > > > > > > > > wrote: > > > > > > On Thursday 21 May 2020 01:57:06 andrew beck wrote: > > > > > > > hey peter > > > > > > > > > > > > > > I had a look and the unless there is a shorted out pin in > > > > > > > the servo drive connector itself I think the wiring is all > > > > > > > good. > > > > > > > > > > > > > > and I highly doubt the servo drive has problems all I did > > > > > > > was connect the 24v back into the servo on pin which is how > > > > > > > it has been running for the last ages. > > > > > > > > > > > > > > anyway how do you recommend commoning the grounds? > > > > > > > > > > > > > > it is as simple as connecting the field power 0v ground with > > > > > > > a wire to the logic power 0v ground? > > > > > > > > > > > > Yes, but how you do it can be very important. > > > > > > > > > > > > In your control box, install a longer bolt, #6 or #8-32 to the > > > > > > chassis. 4mm if metric. > > > > > > > > > > > > Connect all grounds to this bolt, checking that they are not > > > > > > grounded at the far end. By doing this, you are establishing > > > > > > a single point ground that is the zero volt reference for the > > > > > > whole system. Connect this bolt to the building static ground, > > > > > > the bare wire in most power cabling. > > > > > > > > > > > > Connect the machines frame to this bolt. > > > > > > > > > > > > Connect the - rails of all supplies to this bolt. > > > > > > > > > > > > Connect the - terminals of all cards to this bolt. > > > > > > > > > > > > Break the 3rd pin off the computers supply cable and connect > > > > > > the computers chassis to this bolt. Power the computer not > > > > > > from the wall, but from the same power feeding this box. > > > > > > > > > > > > Connect the shielding of all shielded cabling to this bolt. Do > > > > > > not connect the far end of this shielding to anything that is > > > > > > otherwise grounded. > > > > > > > > > > > > By making sure these grounds are not connected anyplace else > > > > > > you are breaking any ground loops which can and will act as > > > > > > antennas to insert noise into your control signals. > > > > > > > > > > > > By having this single point ground, a nearby lightning strike > > > > > > can inject a 100k volt pulse into the system ground as what > > > > > > would be called a "ground bounce", but the system will not > > > > > > see it as noise nor be damaged, because everything is bouncing > > > > > > in unison. > > > > > > > > > > > > Regardless of what that bolt does during the strike, the 5 > > > > > > volt supply remains at 5 volts to this bolt, and the 24 volt > > > > > > supply remains at 24 volts to this bolt. > > > > > > > > > > > > And when the storm is done, your chances of having anything > > > > > > damaged is reduced to the vanishing point. > > > > > > > > > > > > Stay well Andrew. > > > > > > > > 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) > > > > If we desire respect for the law, we must first make the law > > > > respectable. - Louis D. Brandeis > > > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > Emc-users@lists.sourceforge.net > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > 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) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
