On Friday 29 May 2020 22:36:43 andrew beck wrote: > actually just another question here gene > > so following along that analogy you made with the single bolt for all > ground wires. if I connect the pc case to the bolt and also the 0v > from 24v dc outputs, > > does that mean that I don't have to connect between the mesa 7i76 > field io 0v and logic power 0v? I think it does.
No, they are to be connected to that same bolt, or in your case to the same block. Those cards are NOT grounded by their mounting screws, so in order to function, they must also have those "grounds" connected. If you can measure low ohmage continuity to ground from those terminals on the mesa cards when that wire is not connected, then you've a ground loop someplace, find it and break that connection. Both the - line from the 5 volts, and the -line from the 24 volts connect to this bolt. You want this bolt to BE the entire systems common ground point. This is then called a STAR ground. > just triple checking as things get expensive if I get them wrong and I > don't want to go down that track I don't want you to go there either. One other thing. If you are controlling any relays from the 7i76D's, outputs, be sure to add a diode, between the field power +12 or +24 terminal faced so that any voltage above that +12 or +24, is shunted away from the 7i76D output and dumped back into the +12 or +24 supply. Otherwise the inductive kick which can hit shocking values from the relay coil as its being turned off, will blow that 35 volt rated output of the 7i76D. Probably about the 2nd time your code turns that relay off. :( The exact same idea applies to any "inductive" load, like a solenoid air valve enabling a coolant mister. Known as a flywheel diode in the parlance of electronics. It doesn't have to be a high powered diode, I keep a bag of 1N914's at $3 for a bag of 20 around for that. But test it, I've been known to get duds from such sales. Stay well and safe Andrew. > regards > > Andrew > > On Sat, May 30, 2020 at 2:14 PM andrew beck <andrewbeck0...@gmail.com> > > wrote: > > 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 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
