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
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>

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