Opto spindle Encoder 2 or 3?

I have a lathe I am upgrading from Mach3 to linuxcnc. At present it has 1 opto spindle signal/pulse. I am obviously going to add at least on more, for threading do I need 2 or 3?

My segmented wheel looks like this (its not mine but the wheel is exactly the same)


I was looking at this diagram for a 3 opto setup and noticed that the opto's A and B are offset from each other - is this a software setting in LinuxCNC or do i have to achieve this through electronics connected to the Opto?


Any help appreciated
Thanks

As you have the disk you need to separate A and B optos 90° as in picture. So only A or B need to be mechanically placed so you get this pulse separation. Do you have the CAD file for the disk? If not draw it and play around for A / B placement.

Cheers
Bengt

Ah I see, brilliant - thank you!

Here what I have done, tested but not implemented.

When you say 90 degrees? The left side of my picture shows A being fully off or 0 and B being fully on or 1, yet the waveform picture seems to have A as fully off or 0 and then B as at the very leading edge of on or 1....

Once I start fiddling with this is there any way to verify they sensors are in the correct spot?

thanks again
Steve

Best is 2-channel oscilloscope to play around with.

Oscilloscope - eek! Never had one of those or even used one. I don't even know anyone who has one to borrow.

There's no other way?

thanks
Steve

Why not try using CAD to get you mechanical positions för A and B, look at my 2:nd picture.

Cheers
Bengt

Here a hint on how I did it.

Hi Bengt, thanks again fo the reply. Sorry to be a pain, but I am new Linuxcnc and the spindle encoder is the part I was worried about when upgrading from Mach3.

In your last picture you have posted a cad diagram with the A and B pulse being binary opposite to each other e.g A being 0 and B being 1. I would have expected the pulse diagram to look like this:



Whereas the pulse picture I posted shows A as 0 and B as on the leading edge of 1.


I would then expect the cad drawing (borrowed your drawing I hope you don't mind) to show the B location to be on the red line.


In effect your picture A and B seem to be 180degrees out of phase with each other rather than 90degress.

Obviously 90degrees out of phase would make positioning the sensors quite difficult, but positioning them in a binary opposite fashion as you have would be a lot easier. However I notice you have tested this and it seems to work OK with linuxcnc?

Also what setting did you use for this configuration?

Again thanks for taking the time to reply - any assistance is greatly appreciated.
Steve