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Author Topic: PWM questions for CO2 Laser  (Read 7172 times)

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DaveDoesIT

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PWM questions for CO2 Laser
« on: September 16, 2008, 01:15:20 PM »
Hi All,

I would like to use the PWM output to drive a CO2 Laser intensity and I have some questions.

The Laser expects a PWM 5V, 5KHz, 100mA signal ranging from 1% to 95% with 50% mark:space as 50% intensity.

I have done a search of the group but largely no answers found. I have also checked the Help .pdf and I could find only one mention of Kernel speed.

I can get by with 9 steps of intensity so using 5KHz signal for the Laser, 45KHz Kernel speed is required.

I cannot run DriverTest as I do not as yet have the controller installed. I need to make sure Mach3 will do what I need before I tear out all of the current electronics and buy Geckos etc.

Kernel speed:
  What governs which Kernel speed I select?
  Why not just select the fastest?

What is the output voltage of the PWM signal?

If the output voltage is higher than 5 volts, how do I reduce that?

What is the output current of the PWM signal.

Will I need a current limiting resistor to limit that to the 100mA max?

If so, how do I calculate the value?

{EDIT}
I just tried to set the PWM Base freq. to 5000 and Mach3 converts that to 4166. That's almost a 20% reduction in freq. How can I set it to display and use 5K? I tried changing Kernel speed and using 6000 but it still goes back to 4166.
{/EDIT}

Thanks for any help you can give.

Dave
« Last Edit: September 16, 2008, 02:17:06 PM by DaveDoesIT »

Offline Hood

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Re: PWM questions for CO2 Laser
« Reply #1 on: September 16, 2008, 01:30:42 PM »
You can run the Drivertest even if you have nothing connected to the parallel port.

Usually you select the kernel speed by what you require to get your motors running at the speeds you want, setting faster will probably do no harm as long as your port can handle it, I know my lathes computer was not happy on 60KHz and wouldnt even run the motors at 100KHz so you may find that your port is not happy at higher kernel speeds..

As for the rest of the questions I am afraid you will have to wait for someone more knowledgeable about the PWM as I have never used it so never looked into it.

Hood

DaveDoesIT

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Re: PWM questions for CO2 Laser
« Reply #2 on: September 16, 2008, 02:09:06 PM »
You can run the Drivertest even if you have nothing connected to the parallel port.

Hi Hood,

Nope, I get a box pops up and says, "No driver sensed installed. Run driver test" I click the OK button and nothing happens. I opened a dos box and ran it form there and same thing. I am using win2000 I will go try the XP beast.

Dave

Offline Hood

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Re: PWM questions for CO2 Laser
« Reply #3 on: September 16, 2008, 02:13:46 PM »
Did you install the driver when you installed Mach? sounds like you opted not to install it. If thats the case then just reinstall Mach again over the top of itself and choose the driver this time.
Hood

DaveDoesIT

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Re: PWM questions for CO2 Laser
« Reply #4 on: September 16, 2008, 02:24:37 PM »
Did you install the driver when you installed Mach? sounds like you opted not to install it. If thats the case then just reinstall Mach again over the top of itself and choose the driver this time.

Hi Hood,

Nope same again. "Load Driver" was definitely checked and the DriverTest program ran during the installation. When I ran it stand alone I got the same thing. Well I got nothing actually which was the same thing. {grin}

Dave

Offline Hood

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Re: PWM questions for CO2 Laser
« Reply #5 on: September 16, 2008, 02:26:09 PM »
try using the special driver
Hood

DaveDoesIT

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Re: PWM questions for CO2 Laser
« Reply #6 on: September 16, 2008, 03:50:33 PM »
try using the special driver

Hi Hood,

Not sure about the special driver but I completely uninstalled Mach3 which I had installed in Folder under Program Files.

I then installed and let it install in the Root and rebooted and now I can run DriverTest.

Having done so I am now not sure what it did or tells me. It showed some pulse speeds at 25K but what was I supposed to look for or do? When I started Mach3 it was still set to 25K.

I have to say this is pretty frustrating and unintuitive stuff.

Dave

Offline Hood

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Re: PWM questions for CO2 Laser
« Reply #7 on: September 16, 2008, 04:29:45 PM »
Dont know what you find unintuitive, you double click the drivertest (with mach shut down) it takes over and you see a line, if its smooth your good, if its full of spikes you have problems. If you dont see anything you have problems.

Hood

Offline Hood

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Re: PWM questions for CO2 Laser
« Reply #8 on: September 16, 2008, 04:34:12 PM »
Heres the drivertest on my home computer, its not great but is fine, if the spikes were huge then its time to worry :)
Hood

DaveDoesIT

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Re: PWM questions for CO2 Laser
« Reply #9 on: September 16, 2008, 07:58:50 PM »
Dont know what you find unintuitive, you double click the drivertest (with mach shut down) it takes over and you see a line, if its smooth your good, if its full of spikes you have problems. If you dont see anything you have problems.

Ahh, I see the problem, the DriverTest.exe included in the current setup file is for Mach2. This was a clean and full install to a new Folder on the Root.

THAT's what I call unintuitive. :O

Dave