On Wednesday 08 March 2017 16:21:03 Gene Heskett 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
Addendum, DigiKey has no zeners below 4.7 volts. Which is odd, because years ago the semi people claimed that was both the highest voltage, and the most stable voltage for a true zener. Anything above 4.7 volts was in fact not a true zener, but an avalanche diode and would drift low with time because that damaged the junction given enough time and current even if the current was so low that heating was only a few degrees. In my repair work over the last few decades, I've never found a zener rated at more than 12 volts that wasn't by the time I tested it, well out of tolerance low. One 10 volt was actually dumping at just over 5.75 volts, which actually was the cause of the circuit malfunction. It had not been powered down except for power failures in about 20 years then as it handily predated my coming on board in 1984 by at least 15 years then. I am tempted to take, since I've a couple bags of them, about 6 of these 1n914's in series, which would give me a softly regulated 3.4 to 3.6 volts if I feed the top with 5 volts thru a 47 ohm resistor for forward bias, and fork an additional 1n914 off toward each data line. That, and a small ceramic cap to ground to absorb some of the motor switching noise ought to clean it up quite a bit. Too beat tonight, but I'll cobble up something on a perfboard tomorrow for testing. 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
