Spindle and encoder

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14 Aug 2023 07:32 - 14 Aug 2023 07:33 #277923 by smplc
Replied by smplc on topic Spindle and encoder
Yes, please see enclosed.  Masso provided an 0.128 thick spacer that I used to set the distance of the encoder LED's from the code wheel when the shield was removed.  Is your encoder using the 7i96s firmware and how did it go?
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Last edit: 14 Aug 2023 07:33 by smplc. Reason: Spelling.

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14 Aug 2023 09:34 #277936 by rodw
Replied by rodw on topic Spindle and encoder
The sensors seem a bit off centre. Could it be that they are not seeing solid bars all the time?

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14 Aug 2023 09:48 #277939 by tommylight
Replied by tommylight on topic Spindle and encoder
Does not look like a differential encoder at all.
Looks like a single channel with index.
Thinking of it, now it is clear why the scope looked like that, the sensors are on the edges of both rasters on the wheel.

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14 Aug 2023 10:31 #277942 by JPL
Replied by JPL on topic Spindle and encoder

Does not look like a differential encoder at all.
Looks like a single channel with index.
Thinking of it, now it is clear why the scope looked like that, the sensors are on the edges of both rasters on the wheel.
 


That's what it looks like but I believe this could still really be a quad encoder

I'm thinking that with 2 sensors spaced exactly 1/4 cycle apart you will in fact get a normal quad signal  (B rise in the middle phase A+, eg: 1/4 cycle later). But for this to work the encoder disk must have the marks (white/black) spaced exactly right. 

Given the above you will see when using their encoder wheel generator that the white and black are always the same width. Looking at the last pictures from smplc I see 5 cycles (black/white) per disk. This is right ONLY if the disk is about 1.75 to 2.0 inches (44 to 50mm) diameter. 

Hence the question: Is the encoder disk really that diameter?

Looks bigger than 2 inches to me, but it is hard to judge just with the picture. 
 

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14 Aug 2023 10:57 #277945 by rodw
Replied by rodw on topic Spindle and encoder
It is definitely quadrature. For the OP, you should see the wave form as shown by Masso. docs.masso.com.au/wiring-and-setup/setup.../spindle-rpm-encoder

For the others, the target is created by a pdf generator on their web site to match the sensor spacing and the diameter. Its actually a cool idea.
But it is important to make sure that  scaling to fit is disabled when printing the target as dimensions are critical.

 

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14 Aug 2023 13:38 #277955 by PCW
Replied by PCW on topic Spindle and encoder
OK so that's a 5 PPR disk so 20 counts per turn...

If the OP thought that was 10 PPR (and made it
in the right diameter for 10 PPR) that would explain
some of the issues.
 

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14 Aug 2023 14:32 - 14 Aug 2023 14:55 #277961 by JPL
Replied by JPL on topic Spindle and encoder

If the OP thought that was 10 PPR (and made it
in the right diameter for 10 PPR) that would explain
some of the issues.

 

You cannot select the ppr with their 'encoder wheel generator'. You just set the inner and outer diameter. The software do the rest.
BUT, as rodw mentioned, the scaling is critical. You must make sure that the printed size match the setting you've provided, There's even a square printed along the wheel that you need to measure (20mm x 20mm) to make sure it is 1:1.

The scaling of smplc's disk is in fact what I'm questioning.

But yes, the printed disk the OP is using is definitively 5ppr not 10ppr he mentioned before.
Last edit: 14 Aug 2023 14:55 by JPL.

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14 Aug 2023 15:02 #277963 by smplc
Replied by smplc on topic Spindle and encoder
The encoder should be mounted near the centerline.  The encoder came in a set with a bracket designed with Sherline specifications. 
www.sherline.com/product/masso-optical-e...d-decal/#description  .  I already moved W1, W2 and W3 jumpers to the left before using the Hal Scope.
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14 Aug 2023 15:43 - 14 Aug 2023 15:50 #277968 by smplc
Replied by smplc on topic Spindle and encoder
It'd appear that the disc is 10 Lines per Revolution (LPR) or Pulses per Revolution (PPR) and 40 Counts per Revolution (CPR). The disc came with the encoder and was probably provided by Sherline. The outer line's cord length scales about equal. The code wheel isn't any more eccentric on the pully than the circle size of the spindle bore OD printed on it and scissors cut out with minimal allowance. The encoder isn't adjustable toward or outward from the code wheel diameter. The bracket could be shimmed if needed to move the encoder outward from the code wheel diameter. The bracket would require to be milled thinner if needed to move the encoder inward the code wheel diameter. I would have expected Sherline and or Masso to already engineer the encoder diameter location of the code wheel with the assembly. I can measure with calipers an approximation of the code wheel lines and diameters if needed. I'm curious now what's the dimensional tolerance of error moving the encoder inward or outward the code wheel diameter.
Last edit: 14 Aug 2023 15:50 by smplc. Reason: Spelling.

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14 Aug 2023 16:06 #277971 by JPL
Replied by JPL on topic Spindle and encoder

It'd appear that the disc is 10 Lines per Revolution (LPR) or Pulses per Revolution (PPR) and 40 Counts per Revolution (CPR)
 

No!  If the disc have 5 blacks and 5 whites it is then 5ppr, not 10.

Also, maybe have a look at those previous discussions:
forum.linuxcnc.org/39-pncconf/45140-encoder-spindle-help
forum.linuxcnc.org/39-pncconf/49256-no-c...with-working-encoder

It seems to me that it is not easy to use this encoder because of the less than perfect phasing (quadrature error)

 

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