On Sunday, 27 March 2022 14:31:16 EDT Chris Albertson 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-Ard > uino%EF%BC%885pcs%EF%BC%89/dp/B08977QFK5/ref=sr_1_17?keywords=c+optical > +sensor&qid=1648405019&sr=8-17> > I didn't see anything there that was both fast enough and small enough.
I have no clue hor fast, but tearing down a gimpy mouse with get you 2 that are small enough. @ near identical mice would get you 4 and you'd likely have a spare. Most mice die from broken solder joints where the finger switch meets the pcb. And those mice interrupters are micro sized in comparison. Makiing the optical disk isn't that hard, I've done it several times. Getting the slot widths correct is the major problem. > Best to use a thin aluminum plate to make the interrupter disk. I've used .032 brass sheet, as it can be chemically blackened to discourge false triggers from the edges of well finished, shiny holes. So can the alu for that matter but its a flat black, and glossy is actually blacker. Black however is relative, you'd be far better to make sure its a flatter than a plate of pee before engraving it, and use an engraving bit so the edge reflections are well away from the receiver cell. Far more effective to reflect the light away than to paint or chemically blacken it. Purposely dimming the ir led would also help. > 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 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, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
