Cheap Chinese Laser Question...

bharbour
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Cheap Chinese Laser Question...

Post by bharbour » Wed Nov 08, 2017 6:01 pm

...I bought a cheapie 2.5watt 450nm laser off of eBay. The specs for the driver says that it'll operate from 0 to 20Khz...TTL I'm assuming. I've got an Arduino Uno running GRBL 0.9j on my CNC machine and I'd like to vary the output of the laser from barely on (for focusing) to full power.

I've been reading tons of info, but have yet to understand fully how to do the above. Does 20Khz into the laser driver equal 100% power?

Thanks in advance...
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

cozmicray
Posts: 115
Joined: Mon Feb 03, 2014 10:13 pm

Re: Cheap Chinese Laser Question...

Post by cozmicray » Wed Nov 08, 2017 11:24 pm

perhaps have your Mom do a web search for grbl laser?

Applying voltage to ttl trigger turns laser ON
by PWM (pulse width modulation) of that trigger
one can get 0 to 100% laser power

see
https://jtechphotonics.com/

massive amount of info at

Other - (etchers, drag knifes, lasers)

https://www.shapeoko.com/forum/viewforum.php?f=24

can't find it there --- perhaps you shouldn't be playing with lasers

Universal gcode sender can GRBL and use built in GRBL firmware for laser

GRBL WIKI MAY HELP

https://github.com/gnea/grbl/wiki/Grbl-v1.1-Laser-Mode

https://blog.protoneer.co.nz/grbls-pwm- ... d-spindle/

bharbour
Posts: 413
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Location: Mobile, AL
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Re: Cheap Chinese Laser Question...

Post by bharbour » Thu Nov 09, 2017 2:00 pm

"perhaps have your Mom"...LOL. I saw your same response somewhere else on the forum, and I get your gist. You assume no one's searching for information and it probably pisses you off. You could be right, and you could be wrong. You're an interesting fellow for sure. Let me ask a question of you...who helped you learn?

Well my Mom did search. And I completely understand the relationship to the TTL turning the laser on and off, and that PWM can control the laser from 0% to 100%. What I didn't understand is the relationship between the output frequency of the Arduino and the frequency of the laser board and what the resulting laser power might be.

"can't find it there --- perhaps you shouldn't be playing with lasers"...LMAO!!! You're right! I'm not going to 'play' with my laser until I understand it. That's the point of asking the question isn't it?

It appears to me, and I might have missed something, that the JTechphotonics info is slanted to their driver board and a particular input frequency. The other links, I've looked at them and I think I understand the GCode part of it.
cozmicray wrote:perhaps have your Mom do a web search for grbl laser?

Applying voltage to ttl trigger turns laser ON
by PWM (pulse width modulation) of that trigger
one can get 0 to 100% laser power

see
https://jtechphotonics.com/

massive amount of info at

Other - (etchers, drag knifes, lasers)

https://www.shapeoko.com/forum/viewforum.php?f=24

can't find it there --- perhaps you shouldn't be playing with lasers

Universal gcode sender can GRBL and use built in GRBL firmware for laser

GRBL WIKI MAY HELP

https://github.com/gnea/grbl/wiki/Grbl-v1.1-Laser-Mode

https://blog.protoneer.co.nz/grbls-pwm- ... d-spindle/
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

bharbour
Posts: 413
Joined: Wed Aug 06, 2014 3:40 pm
Location: Mobile, AL
Contact:

Re: Cheap Chinese Laser Question...

Post by bharbour » Thu Nov 09, 2017 3:25 pm

I found a really cool stand alone circuit based on a 555 timer that is a variable frequency PWM oscillator. The timer switches a MOSFET on and off so that it can handle higher currents...like in switching a laser on and off.

https://www.instructables.com/id/555-Ti ... ontroller/
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

halfnormal
Posts: 227
Joined: Thu Nov 21, 2013 6:44 am
Location: Flagstaff AZ

Re: Cheap Chinese Laser Question...

Post by halfnormal » Thu Nov 09, 2017 5:56 pm

bharbour wrote:The specs for the driver says that it'll operate from 0 to 20Khz...TTL I'm assuming.
The frequency is how sensitive the driver input is. More pulses, higher sensitivity. Each pulse is turning the laser on. More/longer pulses, the more the laser is on, the more power is output.

You can run the driver below the frequency stated but you would have less control. 20000/255 = 78.4 10000/255 = 39.2 As you can see, at 20khz there are 78 pulses per 1 increment in GRBL as opposed to 39 pulses at 10khz.

I hope this helps

I also want to add that a "good" powersupply will protect the laser better than a cheap one and will last longer as well. Cheap ones are not too forgiving to the "oops" factor.

bharbour
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Re: Cheap Chinese Laser Question...

Post by bharbour » Thu Nov 09, 2017 7:23 pm

Thank you for attempting to explain this!! When you say that I would have less control, are you saying I'd have less power? Half the power at 20Khz I'd have at 10Khz? Is the number 255 the same as setting s255 in GRBL1.1f?

Or by control do you mean the higher the input frequency the greater the resolution? If the frequency was low enough, and the laser was at low power, and you had very fast movements, you could get dashed lines instead of continuous lines.

I've got a spare Ardunio Uno that I'll load up with GRBL 1.1 tonight and will try the laser with that. I'm currently at 0.9j on my CNC machine.
halfnormal wrote:
bharbour wrote:The specs for the driver says that it'll operate from 0 to 20Khz...TTL I'm assuming.
The frequency is how sensitive the driver input is. More pulses, higher sensitivity. Each pulse is turning the laser on. More/longer pulses, the more the laser is on, the more power is output.

You can run the driver below the frequency stated but you would have less control. 20000/255 = 78.4 10000/255 = 39.2 As you can see, at 20khz there are 78 pulses per 1 increment in GRBL as opposed to 39 pulses at 10khz.

I hope this helps

I also want to add that a "good" powersupply will protect the laser better than a cheap one and will last longer as well. Cheap ones are not too forgiving to the "oops" factor.
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

halfnormal
Posts: 227
Joined: Thu Nov 21, 2013 6:44 am
Location: Flagstaff AZ

Re: Cheap Chinese Laser Question...

Post by halfnormal » Thu Nov 09, 2017 9:23 pm

bharbour wrote:Or by control do you mean the higher the input frequency the greater the resolution?
Yes you are correct that the resolution will be greater/finer.

255 is the S setting in GRBL. It relates to the PWM output. I should also clarify that the PWM frequency is a fixed value in GRBL. It can be changed in the software and recompiled if needed.
I do not remember what it is off hand but it is the standard everyone uses for laser control.

I think you are starting to understand how it all fits together!
Last edited by halfnormal on Thu Nov 09, 2017 9:30 pm, edited 1 time in total.

bharbour
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Re: Cheap Chinese Laser Question...

Post by bharbour » Thu Nov 09, 2017 9:29 pm

Thanks again!!!!
halfnormal wrote:
bharbour wrote:Or by control do you mean the higher the input frequency the greater the resolution?
Yes you are correct that the resolution will be greater/finer.

255 is the S setting in GRBL. It relates to the PWM output.

I think you are starting to understand how it all fits together!
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

halfnormal
Posts: 227
Joined: Thu Nov 21, 2013 6:44 am
Location: Flagstaff AZ

Re: Cheap Chinese Laser Question...

Post by halfnormal » Thu Nov 09, 2017 9:32 pm

Check the post above for a quick edit and a better explanation of the GRBL PWM.

cozmicray
Posts: 115
Joined: Mon Feb 03, 2014 10:13 pm

Re: Cheap Chinese Laser Question...

Post by cozmicray » Fri Nov 10, 2017 4:29 am

Please I hope you have some laser protection glasses!
much better than white cane later


Most better controlable lasers have diode module
and driver board
---- turn 12V to voltage laser diode needs
---- trigger laser power

you never gave us any detail on your Cheepy laser?
details may show what trigger requires

I started with micro switch
switch closed --- applying 12V to trigger --- Laser ON
switch open --- no voltage on trigger --- laser OFF

Pulse WIDTH modulation
wider the pulse -- longer laser is ON --- more overall output

the driver reads the trigger pin at a frequency
up to the specified frequency.
If you try to switch it faster that that it won't work right

I use pin 12 and gnd of arduino / grbl
to trigger on laser driver

Pin 12 can be controlled by GRBL firmware to switch laser
via g codes

but if you like, build all the circuits you want,
but micro-controller (arduino) has more than enough
function to do it all???

If cheepy is like J photonics unit or any with driver board
most are controlled the same
see
https://jtechphotonics.com/wp-content/u ... c-V1_2.pdf

:?:

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