I hope those are NZ $ and not US $ <lol> ________________________________ From: andrew beck
Hey guys will this work OK? I think it's the same as the one from amazon https://www.trademe.co.nz/3531064367 And I'm thinking I may need two discs. One above the other so I can use a index sensor on the top layer. Or maybe stick a proxy sensor on it. Looks like they have a 6mm gap between the slots in the sensor. Do you think a 1mm wide gap gap would be ok maybe in a 2 mm thick sheet? On Mon, 28 Mar 2022, 07:35 Chris Albertson, <albertson.ch...@gmail.com> wrote: > Forgot to include a link. You can buy the bare sensor but also you can buy > them on PCBs with connectors attached and ready to go. > amazon.com/Measuring-Optocoupler-Interrupter > < > https://www.amazon.com/Measuring-Optocoupler-Interrupter-Detection-Arduino%EF%BC%885pcs%EF%BC%89/dp/B08977QFK5/ref=sr_1_17?keywords=c+optical+sensor&qid=1648405019&sr=8-17 > > > > Best to use a thin aluminum plate to make the interrupter disk. Make the > slots 50% duty cycle, You need three sensors for quadrature with index. > The above sensor should directly interface to Measa or a parallel port or > some microcontroler. > > > On Sun, Mar 27, 2022 at 10:02 AM Chris Albertson < > albertson.ch...@gmail.com> > wrote: > > > THis goes to 10K RPM? that is 167 revolutions per second. 400 slots > > means 70 KHz signal. > > > > Can you design an inductive sensor that does 70KHz but is also sensitive > > enough for near zero RPM? Optical sensors can work up to 1MHz with no > > problem as they don't have any inductanve. You can buy a "C" space > > sensor for a few dollars > > > > In either case, optical of inductive, you want a 50% "slot" where there > is > > as much metal left as cut away Then the "edges" of the square wave are > the > > same in either direction. The 50% duty cycle in effect doubles the > > sensor resolution. > > > > Why? Think about the signal when the direction changes. You have two > > sensors in quadrature and lets say one is being blocked and one is not, > I > > think you want the turnaround to take as long for each sensor. > > > > > > On Sun, Mar 27, 2022 at 2:22 AM Andy Pugh <bodge...@gmail.com> wrote: > > > >> > >> > >> > On 27 Mar 2022, at 08:09, andrew beck <andrewbeck0...@gmail.com> > wrote: > >> > > >> > And is bigger dia better for higher resolution? > >> > >> Probably not, as it will perhaps have more scope to oscillate at 10,000 > >> rpm. > >> > >> Don’t neglect the purely mechanical design of this fast-spinning part. > >> > >> Have you considered optical sensors rather than inductive? > >> > >> What will be counting the pulses? > >> > >> LinuxCNC can lathe-thread with one sensor. > >> But rigid-tapping is different as it needs to accurately detect the > >> reversal point. So you need three channels for index and full > quadrature. > >> > >> Work out what error you can accept in the reversal point detection (as a > >> fraction of thread pitch) and you can get a feel for how many slots you > >> need. > >> > >> > >> > >> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
