danger laserpower setting in DSP from Lightobject

Discussions and help on this commercial controller.

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danger laserpower setting in DSP from Lightobject

Postby a542002 » Wed Feb 01, 2012 11:03 am

Hi all
I just wana let evrybody know who uses the 2012 DSP from light object
dont set the max power setting for the laser higher as 60% any setting higher will damage or destroi the laser tube if you set your job power setting to more the 40% because the DSP does not take the laser current as a measurement.
I only reailze this after my tube was pretty much gone because for cutting I used the job setting of 75% but only after inserting a mA meter in the return circuit from the laser tube, was is the right way to measure the current what goes to the tube, I did see that the current by 75% for job setting was way up over 20mA ( actually it did go to 40mA) and this was what distroid my tube only after about total of 5 hour cutting with 75% and 250 hour engraving with up to 15%.
the first sign is power loss especially at high pixel settings.
Now I have to wait for the replacement.
greetings
walt
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Re: danger laserpower setting in DSP from Lightobject

Postby bdring » Wed Feb 01, 2012 1:06 pm

No two setups are going to give the same current at 100%. Therefore controllers allow you to setup what 100% means. You determine what percent of full scale on the power supply gives you the max rated current of the tube. You then enter that into the settings for the controller. If that number is 68%, the controller will output 68% when you tell it to output full power and 34% when you ask for 50% power.
Bart
"If you didn't build it, you will never own it."
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Re: danger laserpower setting in DSP from Lightobject

Postby twehr » Wed Feb 01, 2012 1:45 pm

bdring wrote:No two setups are going to give the same current at 100%. Therefore controllers allow you to setup what 100% means. You determine what percent of full scale on the power supply gives you the max rated current of the tube. You then enter that into the settings for the controller. If that number is 68%, the controller will output 68% when you tell it to output full power and 34% when you ask for 50% power.


Bart,

Not sure which controllers you are referring to (or I am misunderstanding your post - always a possibility for me). While the DSP's do allow you to enter a MAX power output into the Manufacurers Settings, they work this way. If you set the max to 60% and you enter a job setting of anything larger than that (75, 90, 100 etc.) then the job is actually run at 60% (PWM setting). If that happens to equal 100% actual output for your tube, then 60% = 100%. It never lets the PS go over the stated max (PWM). In other words, it limits the PWM setting, but does not scale it.

Running 50% will not necessarily provide half (of full) power. This is because, in my experience, the PS are not linear, much as we wish they were. The actual power delivered is based on the current (mA) through the tube. On my setup, 58% PWM = 100% tube power (18 mA). 29% PWM is about 38% (just under 7 mA) tube power. The only way to know what power you are putting out is to build a chart that correlates the PWM setting to the mA through the tube. My table of settings is included here are an example (not as a reference for anyone else).

Tims PWM Table.png


Anyone can read the full write up I did on the subject of the PWM power settings.
tim
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Re: danger laserpower setting in DSP from Lightobject

Postby bdring » Wed Feb 01, 2012 1:51 pm

I said the "controller" will output xx%. There are a lot of things that affect true laser power hitting the work piece. I was primarily addressing the issue of over driving the tube.
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Re: danger laserpower setting in DSP from Lightobject

Postby a542002 » Wed Feb 01, 2012 1:59 pm

sofar thats all correct but to confusing for the ordinary guy, believe me I was there
greetings
walt



bdring wrote:I said the "controller" will output xx%. There are a lot of things that affect true laser power hitting the work piece. I was primarily addressing the issue of over driving the tube.
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Re: danger laserpower setting in DSP from Lightobject

Postby twehr » Wed Feb 01, 2012 2:04 pm

bdring wrote:I said the "controller" will output xx%. There are a lot of things that affect true laser power hitting the work piece. I was primarily addressing the issue of over driving the tube.


It is probably too early in the morning for my brain to attempt to work correctly, but it still sounds to me like you are implying some kind of scaling taking place. There is no scaling based on the max settings taking place anywhere in the DSP chain (designer, control panel, or controller). It is simply an upper limit.

What am I not getting from what you are saying?
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Re: danger laserpower setting in DSP from Lightobject

Postby bdring » Wed Feb 01, 2012 2:12 pm

I am saying the DSP controller can help you from over driving your tube.
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Re: danger laserpower setting in DSP from Lightobject

Postby twehr » Wed Feb 01, 2012 2:17 pm

bdring wrote:I am saying the DSP controller can help you from over driving your tube.


That is absolutely correct. Guess I was reading something into the example %s you were giving. Sorry for any confusion.
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Re: danger laserpower setting in DSP from Lightobject

Postby Speedythinker » Wed Feb 08, 2012 7:56 pm

To clear things up here, I used a scope observe the waveforum and played around with the frequency.
Depends on your power supply, the frequency of the PWM provides an excellence controlling on the power % even if you have 100% set on the system default.

In my case, I set PWM frequency to 50,000HZ and the otuput of the 40W PS never go beyond 18mA. Plus, it provide fine output with 95%,..90%, 85%,80%....

I won't call "danger" here. I would say "hands on"

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Re: danger laserpower setting in DSP from Lightobject

Postby twehr » Wed Feb 08, 2012 8:13 pm

Speedythinker wrote:To clear things up here, I used a scope observe the waveforum and played around with the frequency.
Depends on your power supply, the frequency of the PWM provides an excellence controlling on the power % even if you have 100% set on the system default.

In my case, I set PWM frequency to 50,000HZ and the otuput of the 40W PS never go beyond 18mA. Plus, it provide fine output with 95%,..90%, 85%,80%....

I won't call "danger" here. I would say "hands on"

Marco


Marco,
Is that specific to the newest version of the system or will it work on mine as well (2010)?
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