On 7 November 2015 at 15:18, Jan Kandziora <j...@gmx.de> wrote: > Am 07.11.2015 um 10:26 schrieb Colin Law: >>> >>> When you connect the ground line to data-, you have a different current >>> on the common ground/data- line because the ground line also carries the >>> supply current. So there's no way the receiver can successfully >>> eliminate line noise. Instead, it picks up supply current noise. It just >>> doesn't work. >> >> Does that argument hold in the case of parasitic power, where the data >> and common lines do carry the same current? >> > Your argument is good as you have two data wires and no ground > connection in that case. The same when the slave circuits are powered by > local batteries. > > *BUT* this only works when the host ground is *not connected* to earth, > not even by a noise filter. > As soon it is, your circuit isn't symetrical > anymore as one of your two data wires (the "ground") is tighter coupled > to earth than the other, and subsequently picks up noise more eagerly. > Which destroys the loop's cancellation effect.
Don't follow that. We are talking about series mode inductive loop pickup not common mode (or at least I am). Provided it is only earthed at one point (which should be the case for all 1-wire circuits) I don't see it makes any difference to the series mode pickup. I am not an expert in this area by any means though so am happy to be further educated. Cheers Colin > > You can try to minimize that effect by mounting your twisted pair > (again) on a pole and avoid shielding at any cost. > > > Kind regards > > Jan > > > > ------------------------------------------------------------------------------ > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------------------------------ _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
