Lathe spindle speed/index from working mach3....

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02 Jan 2019 03:47 #123307 by pbreed
My lathe spindle has an optical interrupter wheel with one slot twice as wide as all the others.
This worked weel on mach 3, but I'm trying to convert to linuxcnc.
I'm using a parallel port....

How do I configure this?
Is it even possible?

Thanks!
This is my first step into linuxcnc world, I have the axis moving, just trying to get spindle feedback....

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02 Jan 2019 12:20 #123315 by pl7i92
this will give you the Signal
encoder_0.phase-Z <== spindle-phase-Z

this needs to be done in the HAL of the mashine if you start from Stepconf wizard a NEW mashine Config anbd config the input to the Spindle index and Z phase
in the Drop down menu
you can COPY past this to the HAL file you already generated

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02 Jan 2019 12:34 #123320 by pbreed
Sorry I don't exactly understand....
The reuse of - is confusing....

In the drop down menu I create an input for the parallel port pin...
(Currently have that set to spindle index)

is encoder_0.phase-Z one variable....
(encoder_0.phase-Z) or is it two (encoder_0.phase)-(Z)
same question for the other side of the <==

spindle-phase-Z is this one, two or three variables?
Where does one go to learn the HAL language?
Are hal variables automatic?
are there fixed names that tie things in stepconfig drop down to hal variables?

Sorry to be slow...

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02 Jan 2019 12:49 #123321 by Clive s

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02 Jan 2019 13:04 #123324 by pbreed
The OP had the line:

<== what does <== do?
It appears nowhere in the basic-hal doc.
<= appears, but not <==

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02 Jan 2019 13:17 #123325 by Clive s

pbreed wrote: The OP had the line:

<== what does <== do?
It appears nowhere in the basic-hal doc.
<= appears, but not <==


The <= etc are not used by linuxcnc and do cause a lot of confusion, and are only there for human readability

They are put there just to show the direction of the flow.

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06 Jan 2019 19:06 #123619 by andypugh

pbreed wrote: My lathe spindle has an optical interrupter wheel with one slot twice as wide as all the others.


When you say "twice as wide" do you mean "twice as long"?
How many optical detectors are in the system?

It is common to have several slots detected by one sensor and then one long slot that reaches far enough to trigger a second sensor.
But, in theory, it would be possible to detect a missing or longer pulse to provide index. Automotive crank position sensors often use a missing-pulse indexing scheme.

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07 Jan 2019 02:36 #123664 by pbreed
Only one sensor....
48 or so slots, one of the slots is twice as wide, hence the single sensor detects the index by noting that one pulse is 2x as long.

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07 Jan 2019 10:41 #123687 by andypugh
That's interesting. ad you say that Mach3 worked with that?

My impression is that Mach3 only uses one pulse per rev, so perhaps only the long pulse was being passed to Mach3? Can you see every pulse in Halscope?

Is it possible that the original Mach intallation was using something like a Smoothstepper, and that that can handle an missing-pulse index? I have just done a bit of web-searching and have found no evidence that native mach3 can handle a multi-pulse encoder.

The simple answer would be to make a new encoder disc with a conventional index. The elegant and future-useful answer would be to add missing-tooth index to the LinuxCNC encoder counter. Were you looking for a software project, or were you wanting to make the lathe work :-)

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07 Jan 2019 10:52 #123691 by tecno
Once upon the time Mach could do that trick with multiple pulses and extended slot for index. I was one of the guinea pigs helping Art F with different indexing formats.
Only Pport used as there where no external boards.

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