Spindle speed sensor - tried out solutions and few questions

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bbatarelo
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Spindle speed sensor - tried out solutions and few questions

Post by bbatarelo »

Hi all,

can anyone recommend a model/make of sensor that can be plugged directly into acorn's headers (meaning it grounds 24V to com) that has been tried out and known to work without a hassle? I believe it should be hal effect probe.

Also, on the spindle side what is the solution for the component being sensed? A protruding piece of steel or a magnet afixed to spindle somehow?

On Acorn side, just as a curiosity, does Acorn just blindly display rpm from sensor or does it actually use that information as a feedback when adjusting 0-10V levels in order to achieve desired rpm?

Thanks,
Bruno
tblough
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Re: Spindle speed sensor - tried out solutions and few questions

Post by tblough »

Acorn uses a 5V differential output quadrature encoder for spindle speed. It is used in rigid tapping operations to sync the spindle rotation with the z-axis movement. It will also display the actual spindle speed on-screen. Centroid uses an open-loop control for spindle speed on all if it's controllers. You will need to calibrate your spindle motor controller to the Acorn's 0-10V output but the Acorn does not use feedback to adjust it's signal level. With better spindle controllers that have span and limit adjustments on the incoming analog signal, you can usually get within 10rpm of the selected speed.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
bbatarelo
Posts: 36
Joined: Fri Jan 10, 2020 6:25 pm
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DC3IOB: No
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Re: Spindle speed sensor - tried out solutions and few questions

Post by bbatarelo »

tblough wrote: Tue Oct 26, 2021 7:35 pm Acorn uses a 5V differential output quadrature encoder for spindle speed. It is used in rigid tapping operations to sync the spindle rotation with the z-axis movement. It will also display the actual spindle speed on-screen. Centroid uses an open-loop control for spindle speed on all if it's controllers. You will need to calibrate your spindle motor controller to the Acorn's 0-10V output but the Acorn does not use feedback to adjust it's signal level. With better spindle controllers that have span and limit adjustments on the incoming analog signal, you can usually get within 10rpm of the selected speed.
Hi Tom, I know about the encoder, but it is also possible to wire up just a simple 24V rpm probe according to documentation (and also to lose the rigid tapping ability). My questions are focused on that route.

Bruno
tblough
Posts: 3071
Joined: Tue Mar 22, 2016 10:03 am
Acorn CNC Controller: Yes
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100327
102696
103432
7804732B977B-0624192192
DC3IOB: No
CNC12: Yes
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CPU10 or CPU7: No
Location: Boston, MA
Contact:

Re: Spindle speed sensor - tried out solutions and few questions

Post by tblough »

Not that I know of.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
cnckeith
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Re: Spindle speed sensor - tried out solutions and few questions

Post by cnckeith »

most use a hall effect sensor that triggers once pre revolution. Franco sells one that we tested with when we added this plc feature. (note: as the documentation says this technique can only be used for RPM display and does not support threading or rigid tapping for that the machine requires a real spindle encoder as tom mentions above.)

Acorn does not close the loop between RPM sensor and analog out 0-10. there is a calibration procedure to perform when setting up a VFD which provides accurate results.
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
Gear we use but don't sell. https://www.centroidcnc.com/centroid_di ... _gear.html
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