Gene, What you want is not a diode but a differential line receiver. Not surprised at all that when you look at one half of the signal you see a lot of noise. The receivers will eliminate the common mode noise problem near completely. You Cat-5 cable is already set up for this kind of signal with four twisted pairs.
If you do get a diode the kind to buy are called "TVS Diode", TVS = "Transient Voltage Suppressor" they are made exactly for this job and will absorb much more energy than a Zener. They are easy to find and cheap. You should not use them for noise, they are for circuit protection. On Wed, Mar 8, 2017 at 1:21 PM, Gene Heskett <ghesk...@shentel.net> wrote: > On Thursday 02 March 2017 14:02:30 Gene Heskett wrote: > > > On Thursday 02 March 2017 13:53:32 Kurt Jacobson wrote: > > > There should be a flat rubber gasket with holes for the three > > > mounting studs. If not I guess it would be a good idea to use some > > > sort of "goop" to seal the interface and keep coolent from getting > > > to the encoder. > > > > > > Kurt Jacobson > > > 505-303-1933 > > > Sent from Mobile > > > > Goop, Go2, same stuff I think, but Go2 comes in a much handier to use > > container. I'll do that to mine when I mount them. Thanks Kurt. > > > > Cheers, Gene Heskett > > It turns out that black bit that looks like a skirt on the rear housing > pan, is in fact a separate piece, a soft plastic like gasket, so I > didn't add any goop. > > But, I have the nuts tightened on the switches, and the panel all wired > up, and power on the jog wheels, losing 11 millivolts in each conductor > on the trip out over 14' of stranded cat5 wire. The noise is just at > borderline when the motors are powered up. > > These encoders aren't active drive to whichever rail they are headed for > on the scope and only make 3.75 volts for a logic one, and that impinges > of the upper noise margin some. > > I don't have wire conductors enough to make up a differential receiver, > so I'm inclined to run them past a small capacitor hooked to ground to > absorb some of the noise right at the 7i90's GPIO input. > > And even bigger question is that there is a huge spike on the leading > edge of the uprising edge, and it switches from the A channel to the B > channel depending on which direction I am cranking the dial. Obviously > there is a need for additional bypassing of the power rails right at the > wheels +- terminals or very close. I haven't made any connections to the > 7i90 yet as the peak voltage of these spikes is about 6.75 volts. > > Peter C. W.; would a 1n914 type diode (I have at least 50 of those, not > all tested and good, be fast enough if installed to clamp the data lines > at 1 vbe, about 5.75 volts, well above above the 5.04 volt 7i90 supply > rail? Or is allowing about 5.75 volts at a GPIO input playing with > fire? Or do I need to locate a 4 pack of some 4 volt zeners? More > wasted time as I know the shack doesn't have any such critters. > > Thanks all. > > 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> > > ------------------------------------------------------------ > ------------------ > Announcing the Oxford Dictionaries API! The API offers world-renowned > dictionary content that is easy and intuitive to access. Sign up for an > account today to start using our lexical data to power your apps and > projects. Get started today and enter our developer competition. > http://sdm.link/oxford > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Announcing the Oxford Dictionaries API! The API offers world-renowned dictionary content that is easy and intuitive to access. Sign up for an account today to start using our lexical data to power your apps and projects. Get started today and enter our developer competition. http://sdm.link/oxford _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
