On Tuesday 08 May 2018 08:06:37 andy pugh wrote: > On 8 May 2018 at 12:53, Gene Heskett <ghesk...@shentel.net> wrote: > > Is there a possible violation of the single point ground? Some cable > > shield grounded on both ends for instance? > > The internet says that that might be correct for 2.5Mb serial data.
For unbalanced signals? Small Maybe, but I suspect yours are balanced. > https://www.edn.com/electronics-blogs/the-emc-blog/4417778/Questions-o >n-cables-for-EMC-mitigation > > > Or a possible failure of the supply's output capacitors? ESR from > > their aging comes to mind. And switchers do tend to abuse those > > caps. > > This PSU is just a bridge rectifier and some big caps. Unregulated > straight off the mains. I wish mine were that simple. AC isolation pretty much demands transformers. So I use toroids, amoung other advantages, they don't broadcast huge magnetic crap. You can stack as many as your mounting bolt is long without noticeable cross coupling. A piece of insulation shim to keep them from shorting is all you need. But keep heat in mind if stacking. And your mains are about 230 volts IIRC. That's more than any of the stepper drivers can tolerate, but thats not germain here I don't think. Are your drives all on a common supply bus?, or does each drive src its power straight off the caps with individual wires? If a common bus, split it into individual wires so the currents can only see each other at the common points at the supply. If already so, try a 1 u-f mylar cap at the big caps common points. If that helps, the big caps are developing high ESR. Replace them, or leave the 1 u-f installed forever, its good practice. > I think that any noise has to be PWM noise from the other drives. That would be my assumption too, Andy, but I'd get out the 100mhz dual trace scope and verify it. And this is a case that demands its grounding be defeated, and measurements all made from that single point ground bolt, so you may have to power the scope from an isolation transformer in order to make that valid. Else the ground loop in its own power cord _will_ make it lie to you. -- 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> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
