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spindle speed configuration, odd PWM range

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02 Jan 2019 19:20 #123351 by tonydiethelm
Hi all,

My spindle control was bought from China and came with an annoying lack of documentation. :D heh.

Speed control is done via a potentiometer. With my trusty multimeter, I measured the control voltage swinging from 0-2.5V. Ok.

So I set out to configure my spindle speed in LinuxCNC. It shouldn't be hard, it's just the worlds sparsest Look Up Table.

Oh, my breakout board does 0-10V output.


Trying for a direct route, I set...

speed1 0 - PWM1 0
speed2 12,000 - PWM2 0.25

A quarter of 10V is 2.5V, that should make a rough speed control from 0V/0RPM to 2.5V/12000RPM. Close enough for me! It doesn't work.... It just outputs 0V for everything. :/

So, I go for an indirect route....

speed1 0 - PWM1 0
speed2 48,000 - PWM2 1

That should make a rough speed control from 0V/0RPM to 2.5V/12000RPM, and I just.... won't go above 12,000RPM? And that totally works, so it's not a problem with the board or its Vout capabilities. It works fine. But it's weird.

So... it's working, but I don't know why it didn't work the first way and I'd love an explanation. But I can live without one.

And yeah, I could have just built a little voltage divider. Eh. Effort. I'm lazy, that's why I built a CNC machine to do my carpentry for me. :D

Is there anything here that I'm not seeing? Is there a danger of higher voltages getting applied to my speed controller?

Thanks all!

:D

Tony

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06 Jan 2019 13:18 #123599 by pl7i92
can you show a image of the control Board
it might be a regular 0-10V

But you can also get a Regular PWM2Analog device or build your own with a Regulator pot to go down to 2,5V

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06 Jan 2019 20:57 #123639 by andypugh
What appears in the HAL for each way of doing it? (That is what really matters)

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