If there are caps on the input. I bet the intent was to be-bounce mechanical limit switches. Or at least to filter the switching noise so that the frequency content is well below the software de-bounce sampling rate.
I've struggled with how best to de-bounce switches for a long time. There is no best answer. RC filters are not a bad option. On Wed, Nov 18, 2020 at 1:35 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Wednesday 18 November 2020 13:56:37 Gene Heskett wrote: > > > On Wednesday 18 November 2020 13:07:18 Chris Albertson wrote: > > > That is what you do, look at the shape with no load. the 10X probe > > > did that. > > > > > > I have to admit my experience with encoders is mostly wth directly > > > connecting to microcontroller pins. No need to opto-isolate if > > > everything is driven from the same driven power. > > > > > > IIt would seem then that those optical couplers are hard to drive > > > and maybe they were designed to be driven by mechanical limit > > > switches. In any case I don't see a reason to use an optocoupler > > > when the device you are connecting in an optical coupler. I think > > > if you drive the motor encoder from the same power and gund at the > > > BOB you are good. > > > > Just try to buy a bob w/o them damned things. If you don't want them > > you have to rip em out. > > I'll take that back. This particular Sainsmart board, the ST-V3 was used > specifically because it doesn't have any opto's on it, but it still has > 5 gawdawful bright leds to tally the inputs, and from the placement of > the led's, I'd have to say they are powered by the logic 1 status of the > input. And I'd assume that the output back to the 5i25 P2, is for those > 5 inputs, interrupted by a 74HCT14 Schmidt trigger. So, the logic 1 > would be anything over about 2.6 volts but haven't checked the data > sheet for sure. So that means there is a pretty good load on that > encoders logic 1 state if it lighting up a grain of sand led blindingly > bright. Thinking a bit outside the box, I am tempted to put those 1500 > ohm resistors in series with the inputs. I cannot find it, but every > input reads 97.5 nf if I give the meter enough time to settle. leads > open its 0.17nf. And I just found the 97.5nf caps that I think are the > real problem. I bought two of these and have the 2nd one in my hands > right now. I have several others in service here already, bought > specifically because there's no opto's on 'em. The only bob I've found, > other than the discoed C1G rev 4, that doesn't have them. In the > morning, set up my hot air kit and get rid of the caps on those 2 > inputs. They are grain of sand monolithic types on the bottom of the > board. I'm betting that will fix it. > > Are Mach setups normally plagued with enough noise to need that > filtering? > > [...] > > 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) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
