Nicely done!Sent from my Samsung S10
-------- Original message --------From: Lawrence Glaister <[email protected]> Date:
2022-03-31 11:30 a.m. (GMT-08:00) To: [email protected]
Subject: Re: [Emc-users] Homebuilt encoder Hi Andrew,It has been a few years
since I added a spindle encoder to my lathe. I have a web page describing the
gruesome details that might give you some ideas and some gcode to play with for
cutting the disks. This encoder is still in operation with the data being fed
into a parallel port on an older PIII 700Mhz Del box running ubuntu
10.4.https://ve7it.cowlug.org/spindle-encoder.htmlcheersLawrence VE7ITOn
2022-03-31 10:10, Chris Albertson wrote:> On Wed, Mar 30, 2022 at 11:18 PM
andrew beck <[email protected]>> wrote:> >> 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?> > > > The link does not work for me.> > Ideally the
slots and the space between the slots is the same. But this> only really
matters if> 1) you intend to double the resolution by looking at leading and
trailing> edges.> 2) and when the spindle reverses direction there is a small
error if the> geometry is asymmetric. Maybe the error is too small to break a
tap, I> don't know.> > If the plate is thinck relative to the slot width all
that means is the> alignment most be good, with the IR beam exactly 90 degrees
to the disk.> The Omron senors, when you look inside use a very thin disk, like
brass> shim stock. This minimizes any error caused by misalignment. The very>
high-end sensor use glass disks with vapor deposited aluminum to block the>
light.> > Don't bother with two disks, because alignment can never be 100%
perfect.> Simply drill a hole for the index or make one slot deeper.> > A
trick used in automotive sensors is to have one missing slot. Then> software
resets the counter when the expected pulse does not happen This> saves the
cost of the third sensor but that only matters if you build a> million cars.
IR sensors cost only about $1.> >>>>>>>> On Mon, 28 Mar 2022, 07:35 Chris
Albertson, <[email protected]>>> 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 <>>> [email protected]>>>> 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
<[email protected]> wrote:>>>>>>>>>>>>>>>>>>>> On 27 Mar 2022, at 08:09,
andrew beck <[email protected]>>>> 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>>>>> [email protected]>>>>>
https://lists.sourceforge.net/lists/listinfo/emc-users>>>>>>>>>>>>>>>>>
-->>>>>>>> Chris Albertson>>>> Redondo Beach, California>>>>>>>>>>>>> -->>>>>>
Chris Albertson>>> Redondo Beach, California>>>>>>
_______________________________________________>>> Emc-users mailing list>>>
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https://lists.sourceforge.net/lists/listinfo/emc-users>>>>>>>
_______________________________________________>> Emc-users mailing list>>
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https://lists.sourceforge.net/lists/listinfo/emc-users>>> >
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