Understaning PWM

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10 Jul 2021 15:00 #214183 by PCW
Replied by PCW on topic Understaning PWM
The PWM scale should be set for the spindle RPM at 100% PWM duty cycle

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10 Jul 2021 15:48 #214187 by hairyMug
Replied by hairyMug on topic Understaning PWM
changed the settings but still goes to max speed when enabled...

> I'm going to try using the "halscope" (another thing to figger out ) to verify correct PWM output as it might be the "spinx" board reference voltage hookup...

Thanks!

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10 Jul 2021 16:15 #214189 by PCW
Replied by PCW on topic Understaning PWM
You also need to get the polarities of the PWM and enables signal going to the SPINx1 correct

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10 Jul 2021 17:30 #214197 by hairyMug
Replied by hairyMug on topic Understaning PWM
definitely the spinx as the signal from the 7i96 looks good...
I switched the "wiper" and "ref" but it only knocked the rpms to 6800...
Going to try flipping the PWM and see if that helps... but at least I see light at the end of a long tunnel..

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10 Jul 2021 18:53 #214206 by hairyMug
Replied by hairyMug on topic Understaning PWM
No matter what I do, it refuses to work and, using the docs for PWMGEN, there are parameters that are not there in this PWMGEN object...
I've switched all I can possibly switch wire-wise... I GIVE UP!

Being a glutton for punishment, (and I have to get my spindle controlled), my VFD supports a rs485 interface so I'm going to look at that as an alternate method of spindle control...
I am hoping to find some info on the rs485 interface of the 7i96...

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10 Jul 2021 21:01 #214214 by PCW
Replied by PCW on topic Understaning PWM
Did you verify:

1. +5V to +15V on SPINX1 SP+ relative to SPINX1 SP-
2. SPV = 0V when unconnected to 7I96
3. SPINX1 PWM connected to 7I96 TB2 pin 3 (PWM+)
4. SPINX1 DIR connected to 7I96 TB2 pin 5 (DIR+)
5. SPINX1 /ENA driven by a SSR output (OUT+ to SPINX1 /ENA
OUT- to GND)

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12 Jul 2021 10:45 #214386 by andypugh
Replied by andypugh on topic Understaning PWM

No matter what I do, it refuses to work and, using the docs for PWMGEN, there are parameters that are not there in this PWMGEN object...


You are maybe looking at the wrong pwmgen.

For the Mesa cards, the pwmgen is (badly) documented here:
linuxcnc.org/docs/2.8/html/man/man9/hostmot2.9.html#pwmgen

The software pwmgen is here (you probably don't want to use this one, it's largely for the parallel port)
linuxcnc.org/docs/2.8/html/man/man9/pwmgen.9.html

And, for completeness:
linuxcnc.org/docs/2.8/html/drivers/pico-ppmc.html

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12 Jul 2021 16:39 #214410 by hairyMug
Replied by hairyMug on topic Understaning PWM
all voltages spec'ed by PCW are as stated...
Thanks for the alternate doc link Andy...

I have a feeling the PWM (as well as DIR) polarity need to be reversed as when I start, the VFD shows REV rotation...
>> It's a cross between and elephant and a rhino... Ele-if-I-no...

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12 Jul 2021 20:22 #214424 by hairyMug
Replied by hairyMug on topic Understaning PWM
ok; It turns out the enable signal needs to be inverted.
So, I went to pncconfig tool and said to invert the output...
It generated:

setp hm2_7i96.0.ssr.00.out-00.invert_output true

Which promptly created a startup error... Silly me, I thought something this easy would work...

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12 Jul 2021 20:29 - 12 Jul 2021 20:50 #214425 by PCW
Replied by PCW on topic Understaning PWM
Umm, no

The SPINX1 enable signal is active low so you wire
OUT0- to GND and OUT0+ to the SPINX1's /ENABLE signal,
so when SSR 0 is on (true in hal) , the SPINX1 /ENABLE
signal is low and the SPINX1 is enabled.
Last edit: 12 Jul 2021 20:50 by PCW.

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