controlling A DC spindle with mesa 7i92

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21 Sep 2018 06:44 #117837 by Clive S
Thank you that is very helpful, I will look into it and do more research

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23 Sep 2018 16:03 #117898 by Clive S

To know what these pins and parameters mean you need to look at the PWM section of the hostmot2 manual page


I am sorry I need more help with this. I have put this in a custom file:-

#PWM Generator signal/setup
setp hm2_7i92.0.pwmgen.pwm_frequency 180
setp hm2_7i92.0.pwmgen.00.output-type 1
setp hm2_7i92.0.pwmgen.00.scale 10
setp hm2_7i92.0.pwmgen.00.enable true

But I don't know how to proceed further to get the pwm signal out of the bob to be able to feed it into the converter board that will give me the 0-10v.. I assume the "s" command in the midi will change the frequency of the signal.

I have searched the forum for examples but not found any.

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23 Sep 2018 16:12 #117899 by PCW
PWM modulation varies the duty cycle of the signal (not its frequency)

Normally you would want to set the PWM scale to the maximum RPM value (at 10V)

Then you link the hardware PWM value pin to motions speed command (in RPM)

net spindle-speed motion.spindle-speed-out-abs => hm2_7i92.0.pwmgen.00.value

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23 Sep 2018 18:50 #117901 by Clive S

PWM modulation varies the duty cycle of the signal (not its frequency)


Yes of course Peter I got my words mixed up. But thanks for pointing that out.

Now with the below, I see the PWM signal on gpio 001 and it changes with the midi "s" so my next job will be to connect to the spindle board.

#PWM Generator signal/setup
setp hm2_7i92.0.pwmgen.pwm_frequency 1500
setp hm2_7i92.0.pwmgen.00.output-type 1
setp hm2_7i92.0.pwmgen.00.scale 5000
setp hm2_7i92.0.pwmgen.00.enable true
net spindle-speed motion.spindle-speed-out-abs => hm2_7i92.0.pwmgen.00.value

As always I am grateful with the help and time.

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23 Sep 2018 20:20 #117906 by PCW
Note that you may have to invert the PWM polarity depending on what the PWM--> analog converter expects

You may also find that the spindle speed is all the way up when LinuxCNC is not running, normally this is fixed by using the spindle-on signal from motion and having the proper polarity on the relay or SSR that enables the spindle.
The following user(s) said Thank You: Clive S

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