DIY spindle encoder problem

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21 Jul 2019 04:47 #140043 by Dinuka_Shehan

This usually means that the slots and teeth should be equal width,
though optical sensor design and sensitivity will also affect the on/off times.

I think equal width is a good thing to aim for, but if its too difficult, unequal slot/tooth
spacing will still work, it will just limit your maximum RPM.


I cut slots with Universal milling machine and aid with indexing head so I can get equal pitch.
But I don't have proper cutter for suit this slot because of that I use fly cutter.
What happen when slot and teeth width precisely not equal.

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21 Jul 2019 04:51 #140044 by Dinuka_Shehan

Note that these assume the slots are 50% open so you get close to square

Then can't I get square with unequal slots and teeth?

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22 Jul 2019 16:17 - 22 Jul 2019 16:17 #140197 by Dinuka_Shehan
Physical width of Teeth and slots

This is the most critical factor. The teeth and slots must be large enough to be
properly recognized by your photointerrupter. My photointerrupter has a slit width of 1mm.
you see in detail what happens when an obstacle moves through the slit
of the photointerrupter. This behaviour has influence to the minimum width of your stripes
and spaces. This in turn means that you have to increase the diameter of your
index disc when you want to have more pulses per turn. And the maximum diameter depends
on how much space you have. As a thumb rule the minimum witdh of your teeth and
also of your slot should be two times the slit width of the photointerrupter.
Much smaller teeth and slots will make you problems in obtaining a reliable signal.
When you run into this problem (you need more pulses per turn but cannot increase the
diameter of your index disc) then choose another photointerrupter with smaller slit width.
Last edit: 22 Jul 2019 16:17 by Dinuka_Shehan.

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22 Jul 2019 17:51 #140207 by PCW
Replied by PCW on topic DIY spindle encoder problem
Right, that is good advice: make the disk as large as possible to
"swamp out" the effects of detector/source edge detection errors
The following user(s) said Thank You: Dinuka_Shehan

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23 Jul 2019 08:43 #140277 by verticalperformance
My DIY encoder. forum.linuxcnc.org/26-turning/33983-maxi...encoder-speed#105521 . Slots were 1.6mm wide at about 32mm radius, with 60 slots in the disc. 3000rpm no prob with parallel port. The index pulse was a piece of white tape on the disc, that tripped the standard Sherline tach encoder.
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27 Jul 2019 15:37 #140751 by andypugh
I am working away from home, so have a big backlog (this message is being sent from an RPi plugged in to the hotel TV)
Equal slot and tooth widths is something to aim for. You can have any number of slots, so choose the slot number to suit your tool.

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27 Jul 2019 19:09 #140760 by Dinuka_Shehan
Thank you for your commitment and help

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