Smoked my spindle - likely my fault

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12 May 2024 19:46 - 12 May 2024 19:57 #300469 by moretoyswins
Sorry, if the title offended anyone. In my defense I am a little upset, not with LinuxCNC or the 7i96s. It is more than likely it is something I did wrong due to my lack of understanding.
Last edit: 12 May 2024 19:57 by moretoyswins.

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12 May 2024 19:54 - 12 May 2024 19:57 #300470 by moretoyswins
Sorry, I did not realize my original message got truncated, I am at my LinuxCNC machine using a touch screen and virtual keyboard. I had written more including the make model of spindle, AMB 1400 FME-P DI.

As to the -ve voltage I was of the understanding that setting hm2_7i96s.0.pwmgen.00.offset-mode to true would give me the 0-10v
Last edit: 12 May 2024 19:57 by moretoyswins.

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12 May 2024 22:56 - 12 May 2024 22:57 #300478 by PCW
No, that is not correct. If you have a 0-10V input you
should not apply negative voltages.

What I would do is this:

7I96S SPIN+ --> +12V
7I96S SPIN- -->  GND
7I96S SPINOUT --> SPEED CONTROL

Then set the spindle OUTPUT_SCALE to 12V/10V * 25000 = 30000
and spindle MAX_OUTPUT to 25000

(and offset mode false)
 
Last edit: 12 May 2024 22:57 by PCW.

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13 May 2024 00:20 #300484 by moretoyswins
Thank you, I will try that now!

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13 May 2024 02:28 #300485 by moretoyswins
Sorry for the delay, life got in the way.

Long story short test with a DVM were positive, could not test spindle due to the late hour.  At "m3 s25000" I am putting out between 9.98v and 9.99v, I hope the fluttering does not effect the Spindle performance.
 
I ended up with:
OUTPUT_SCALE = 12.27V/10V * 25000 = 30675

The issue is the power supply, currently I have one PSU that supplies both +-5v, +12v, the other PSU I have is 48v for Steppers.  the issue is you can only adjust the 5v side, the 12v is only "approximately 12v".

From the manufacture's documents:

Accurate voltage regulation is not guaranteed if the load does not draw the minimum current.

Looking at the block diagram the reason becomes clear: only Channel 1 (5V) is regulated via a feedback loop. Channel 2 (12V) is open loop and unregulated.So you have to adjust the 5V output with the potentiometer while your intended load is drawing its usual current... and you will get "approximately 12V" on the other output.Also the 12V output will fluctuate depending on current draw on the 5V output.

Of course you don't find these things out until you go digging.

The 12v side does fluctuate between 12.26v and 12.27v, I used the latter in your formula.

There may be a separate 12v PSU in my future, if I can make space in the controller box, which is currently packed.  Should have started with a bigger chassis, but I choose to use an old PC case.

Thanks for all the help, on to the next issue and I will have to test Spindle in daylight hours.


 

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13 May 2024 03:42 #300486 by PCW
Even a few % variation in spindle speed is not of much concern.

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13 May 2024 03:53 #300487 by moretoyswins
I'm sorry I failed to state my concern clearly. My concern is not how fast the Spindle turns but whether the fluctuation in voltage will adversely affect the electronics in it.

Thanks again for all your help!

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13 May 2024 04:11 #300488 by PCW
0.1% voltage ripple is not of any significance for spindle control.

Even 1% will probably be filtered to much less
by the speed control input circuitry.


 

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