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Author Topic: Couple of funnies - revisited  (Read 92 times)
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MarkW
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« on: January 21, 2021, 02:58:03 PM »

Back in Mar 2020 I started a post wherein I questione d PWM and M30 problems.

I'm happy to let you know that I figured out the "double M30" problem we discussed already. In the Edit Pro/Epilogue config pulldown there was an Epilogue line of text showing an M30 and some comment that I can't remember just now.    I deleted that Epilogue text string and all is good.

The PWM is still bothering me a bit.  When I issue an M3 command and watch the PWM output with my o'scope I see that there are PWM pulses output from the Pokeys57C NC at 1% of the PWM freq BEFORE I even hit the fire button or move an axis.   This happens regardles s of the PWM frequency . It just happens to light my laser at the lower PWM freqs and I noticed it lites my diode because my control board is spec'd at between 500 and 1KHz.  When I get above 2KHz my control board doesn't light the laser (that I can see). 

My tickle is set to 0 (even went negative number with no differenc e) as you recommend ed yet the Pokeys board still outputs a 5uS wide pulse (at 2Khz PWM freq).  Why?  Min power is set to 0. Max is set to 97%. 

Is there a way to set a minimum output in the Pokeys board that I haven't discovere d?  I'd like to set to zero.

I'm chasing this because I'd like to run my PWM freq at the laser control box spec of 500-1000Hz without the dang laser lighting up when I issue an M3 command alone.  Also trying to improve my raster engraving of lighter gray parts of my image.  Different discussio n/investigation.  Trying to optimize machine first and this "1% always on" bothers me.

Mark


* 5uSec 2KPWM.jpg (3799.58 KB, 4032x3024 - viewed 2 times.)

* JandK.jpg (3528.84 KB, 4032x3024 - viewed 3 times.)
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MarkW
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« Reply #1 on: January 21, 2021, 08:25:43 PM »

A couple of other interesti ng things I've noticed.  Some of the Engine/Planner Config parameter s don't seem to change my observed results at all.

The PWM Period does in fact change the PWM frequency observed on my scope.  So that's good news.

Now the bad news.

Changes to the MinPWM(Tickle), MaxPWM, and MinPWM(PowerOn) have no effect on my laser function. I set Tickle to 10.  No changes seen.  I set MaxPWM and MinPWM to 50 and 10 respectiv ely.  The PWM waveform on my scope show expected pulse widths for values higher than 50 and also lower than 10.  Confirmed by my diode current meter and visual observati ons of the light intensity .  So it appears that these limits are not affecting my Pokey board output signal. Something else is controlli ng max and min power.

Next, I stumbled around in the SpindleLi b-Laser script.  Just looking.  These lines below from it seem to me (uneducate d in programmi ng) to set the max power to 100%, pwm freq to 5KHz and sets the channel to 4.  These are contrary to what I'm trying to use: channel 2, max power at 97 and 1KHz for PWM freq (0.001 period).   Do I need to edit the script to use my values.  (the ones I set in Engine/Planner Config table)

p = Profile("rtPWM");
global LaserAxis = p.GetInt("Axis",8);
global LaserMaxP ower = 100;  //max power = 100%
global LaserPWMP eriod = p.GetFloa t("Period",.0002); //for 5khz tickle 
global LaserPWMC hannel = p.GetInt("Channel",4);

That's enough for tonight.

Mark
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ArtF
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« Reply #2 on: January 22, 2021, 10:07:10 AM »

Hi Mark:

I will do a check to see what might be going on..

As I recall, the lines below were necessary just to initializ e the scripting .
The second part as in the line LaserAxis = p.GetInt("Axis",8); translate s to
LaserAxis is ( Get the value stored under "Axis" and if there isnt one, use 8.)
So the setting for something like PWM tickle..s hould override the default when its set.
 Ill check to see why it may be giving you a minimum instead of zero..


p = Profile("rtPWM");
global LaserAxis = p.GetInt("Axis",8);
global LaserMaxP ower = 100;  //max power = 100%
global LaserPWMP eriod = p.GetFloa t("Period",.0002); //for 5khz tickle
global LaserPWMC hannel = p.GetInt("Channel",4);

l
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MarkW
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« Reply #3 on: January 22, 2021, 10:11:58 AM »

Thanks Art.  This morning I edited the script and changed those values. I noticed no differenc e in my observati ons.   So I changed then back to original.

Mark
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