hi thanks for your response. you are not telling me weather it is a good idea to tie the negative pole to the ground. 'float': does it mean 'none of the wires are connected to the ground'? i can not procure surge arrestors from the US, i am in a far away third world country. my TP cable with without shielding. what value would you recommend for 'filter capacitor after 5v regulator'? i would rather use a large heatsink than an electric fan (pron to failure with time). i have sent you a schematic including the fuse, please comment. thank you again mila --- Greg Herlein <[EMAIL PROTECTED]> wrote: > > possible), you can use the 2 pairs for just the > positive voltage and the > > shield as the ground. O, and don't forget to use > a nice filter > > Be careful of ground loops. If you have two grounds > tied to > earth at two different places, the actual potentials > at each > spot can be different, resulting in a small current > flow across > your ground conductor... and a resulting voltage > drop at one end > across your ground connector. This can driver you > nuts trying to > find problems in your signaling. > > Ethernet uses differential pairs which *should* be > immune to > this, but there may be logic circuits inside the > device that are > affected. > > The current flow can result in galvanic corrosion > too, resulting > in ground connections that get eaten through. :( > > Be careful, think it through. You may want to > "float" the far > end powered device and ground it only through the > ground > conductor you've definded in the CAT5 cable. If you > do that, > remember that a long wire run has appreciable > resistance and > factor that into your fuse plan... you may want to > go with a > smaller fuse, since a short inside your remore unit > may result in > less current than you would get if there was not a > whole long run > of wire involved. Don't skip fusing it though! > > Greg > > -- > general wireless list, a bawug thing > <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
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