Scaling an Index pulse - Mesa 7i76

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21 Sep 2016 02:21 #80703 by michalskig
Is there any way to scale an encoder index pulse? The driver on my spindle motor upgrade provides me with a configurable encoder signal from the drive, but it still outputs a single pulse per revolution and since I am geared up 2:1 that would only provide LinuxCNC with the indication of half the actual spindle speed. Is there any way with the hostmot2 encoder component to scale that pulse 2x or am I limited to only adjusting the A/B pulse count to 2x per revolution and using the A phase as my index pulse and only run one direction?

My other option would be to program a PIC to issue 2 pulses for every one received but my PIC programming skills are extremely rusty so a HAL solution would be much simpler.

Converted Sieg X3 Benchtop Mill
5i25/7i76 on a Mitsubishi drive for spindle
3x G203V driven steppers (for now, acquiring servos and drives for the next upgrade)

Thanks for any help! - Greg

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21 Sep 2016 04:51 #80705 by andypugh

Is there any way to scale an encoder index pulse? The driver on my spindle motor upgrade provides me with a configurable encoder signal from the drive, but it still outputs a single pulse per revolution and since I am geared up 2:1 that would only provide LinuxCNC with the indication of half the actual spindle speed.


Encoder velocity is measured using the A/B phases. The index is only used as a reference for starting spindle-synchronised motion, which on a mill means rigid-tapping mainly. Index might also be used a a reference for spindle orientation if you have a tool changer, but even then, many tool holders are symmetrical enough to work in both index positions if it is exactly 2:1

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21 Sep 2016 12:19 #80716 by michalskig
Thanks. I thought in looking at the block diagrams that the index triggered a clear of the count, I didn't consider that the index was only used for orientation. This makes my life a lot easier!

Sorry for the double post - I thought I may have screwed up the CAPTCHA but then when I posted the second time I saw the moderator approval note but obviously since it was in limbo I couldn't delete/edit. Thanks!

Greg

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