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Author Topic: PWM signal not showing correctly  (Read 6150 times)

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Re: PWM signal not showing correctly
« Reply #10 on: August 30, 2012, 08:18:33 AM »
Wow, ...what are the scope settings on ?  I had my scope dialed to .1 and .2mv on both knobs...if that makes sense. Is a 20mhz scope sufficent to see these waveforms ?

Yes, i can say again, that i get nothing even close to this out of mach3..and all of this is why i cannot get the laser to output to different power levels.
The other thing i was thinking of is that the version i installed is too old maybe ? The version i have dont have the pulley ratio boxes on the ports and pins settings popup..its on a separate link lower down , and the speed of the spindle box is also not on the front screen as i have seen on others ...might this be why i have all of these problems ?
Re: PWM signal not showing correctly
« Reply #11 on: August 30, 2012, 09:00:54 AM »
No, mine is not even anything close to the pwm screengrab that you have attatchd. I`m starting to think that my version of mach 3 is very old. I have seen that the ports and pins setup tab dont have the pulley setups on it. This can only be seen by clicking another link further down from ports & pins. Also the spindle speed is not on the 1st screen either. I have looked for this box to try see what the spindle is running at, but its nowhere to be seen. This version was installed over a year ago, which make me believe that the pwm section might have not been working correct in this version.

I`m 1st going to try to see if i cant get all to work by tackling the easy things first before i try the z axis motor option. The pwm seem to be working great if it works with the s word commands in the gcode.

Can you possibly tell me what your scope settings were ?

Thanx again for your time and input.
Much appreciated
Andre
Re: PWM signal not showing correctly
« Reply #12 on: August 30, 2012, 09:01:49 AM »
Sorry, i have sort of double posted my message

Offline Hood

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Re: PWM signal not showing correctly
« Reply #13 on: August 30, 2012, 10:00:49 AM »
Should your scope not be on 5v/div?
Unless of course you have a 10x probe.
Hood

Offline Tweakie.CNC

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Re: PWM signal not showing correctly
« Reply #14 on: August 30, 2012, 11:56:06 AM »
Hi Andre,

My scope was set...

Y = 0.5 V/cm (10x Probe)
x = 0.5 mS/cm

(The PWM waveform is 5 Volt peak to peak with a pulse repetition frequency of 1 kHz).

Tweakie.

addition...   This post may be of interest to you http://www.machsupport.com/forum/index.php/topic,12444.msg155403.html#msg155403
« Last Edit: August 30, 2012, 11:58:08 AM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: PWM signal not showing correctly
« Reply #15 on: September 03, 2012, 01:20:48 AM »
No progress. I have been at it all last week, but i just cannot get a nice pwm signal. Now i know i `m getting some kind of signal out of the pwm pin, as i do get a trigger to fire the laser. When i disable the pin output, the laser stops working, so i`m at the right pin.
I dont want to stare myself blind on the pwm signal as it is propably working correctly as i do get an output, but it will be nice to know that it does work and i can look further down the line. I dont think my scope can read the signal correctly. Its already more than 15 years old , so it might be faullty. I`m going to try and dowmload  pc scope software and see if that doesnt work....i`m becoming obsessive of the pwm signal :-)

Another thing that lead me to believe that the scope is faulty, is the fact that i`m also battling to see a normal radio control pwm signal....i can parcially see it , like only half of it ..never a nice clear all the way across the scope, but just enough to know that its there.. :-(

Thanx for all the feedback and info so far.
A

Offline Tweakie.CNC

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Re: PWM signal not showing correctly
« Reply #16 on: September 03, 2012, 03:56:31 AM »
Hi Andre,

It's just a thought but are you able to adjust the laser intensity (set different current settings) from your GCode by using say S25 and S75 etc. ??

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: PWM signal not showing correctly
« Reply #17 on: September 03, 2012, 04:28:45 AM »
Hi

No, doesnt work. I have tried it ...always 100%  ...although the spindle speed box is showing the correct speed as picked up by the cnc code, but the laser output is not responding to it ...always just 100%

The other thing i`m thinking of is that the hobbyCNC board might be the problem. I have sent mail to Dave Rigotti to ask him bout it. I dont know how the signals work inside the pc printer port, but it might be that the board interferes with the pwm signal inside the pc.

THX
A

Offline Tweakie.CNC

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Re: PWM signal not showing correctly
« Reply #18 on: September 03, 2012, 05:56:59 AM »
Sounds to me like you do not have a PWM signal on that particular pin of else you have a conflict of pins.
If you attach your .xml file (Mach folder - the profile you are using - [usually Mach3Mill.xml] but it must be renamed to post - I suggest Andre.xml) I will take a look.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: PWM signal not showing correctly
« Reply #19 on: September 03, 2012, 06:03:03 AM »
Hi

I will download the file and post tomorrow. I have actually read the file that report on the status of the ports and pins. There it had some error messages on the step pins, but the motors ran fine, so i assumed it meant nothing. Also, i had followed the setup instructions from the hobby cnc documentation on what pins to use. It specifically stated what pins to use for the direction and step.

Thanx
Andre