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CNC 445nm 2W laser cutter problems

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Hello. I am working on a laser cutter for a class project. I have built a laser driver for my laser diode but it will not burn anything. I am running .27A through the diode with a measured potential of 5V which should output 1.5 watts. The laser diode is placed inside a Aixiz housing with a G2 lens. My circuit schematic is uploaded, except that the potential is from a power supply and not 9V, and R1 is 6 ohms. I would be grateful is someone can spot what is wrong with my setup, because it seems like this laser should be able to burn something. Thank you.
 

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Encap

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Please make a Welcome post in the Welcome sub-forum and introduce yourself --tell something about yourself and add you location to your profile first if you expect any real help on LPF
 

Alaskan

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Why aren't you using a constant current regulator instead using a voltage regulator? Are you using a A or M140 laser diode? Does it appear to have a bright beam output? Did you focus the beam down to a small burning spot?
 
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My circuit is a constant current regulator. The laser diode I am using is a M140 which does have a very bright beam that is focused to a small point. I've let it sit for a minute or two focused on one spot but burning occurred.
 
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1st of all what diode are you using? 0.27A is probably too low for a blue multimode diode and you running it right at above threshold.you need over 1A for those diodes for cutting

edit:i see you are using an m140.if it is the m-type you can run it up to 1.8A if it is the a-type don't go above 1.5A

edit2:also i noticed you mistake the electrical watts with the optical output watts which are completely different.the 1.5w you calculated has nothing to do with the optical output of your diode
 
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Alaskan

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Here's a data sheet for it: https://www.onsemi.com/pub/Collateral/LM317-D.PDF

The LM317 regulator has current limiting built in to prevent it going too high as a protection to the device itself, but didn't realise it could also have an adjustable current limit too. Don't see how yet without digging into it more, but the spec sheet indeed indicates it can. If it is just wired to rely upon its default bulk current limit through the device, it would also protect a laser diode too, as long as the current fold-back point of the regulator isn't higher than what the laser diode can withstand. What are you trying to burn with that beam?

Hope your regular has a soft enough start when turned on to keep from hitting your laser diode too fast with voltage each time, can be hard on them over time.
 
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lasersbee

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Hello. I am working on a laser cutter for a class project. I have built a laser driver for my laser diode but it will not burn anything. I am running .27A through the diode with a measured potential of 5V which should output 1.5 watts. The laser diode is placed inside a Aixiz housing with a G2 lens. My circuit schematic is uploaded, except that the potential is from a power supply and not 9V, and R1 is 6 ohms. I would be grateful is someone can spot what is wrong with my setup, because it seems like this laser should be able to burn something. Thank you.
That LM317 is only rated at 1 Amp... You would need
a large Heatsink at it's max rated output current.

You would be better off using an LM338 which is rated
at 5 Amps. It will still need a heatsinh above 1 Amp.
http://www.ti.com/lit/ds/symlink/lm138.pdf

Or get a proper Constant Current pre-built adjustable
Laser Diode driver off eBay...


Jerry
 
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Alaskan

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Aha, due to tht, maybe the diode running at close to half it's power output capability.
 

WizardG

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Aha, due to tht, maybe the diode running at close to half it's power output capability.
I'd say a LOT less than half its output capability:

From the OP, "I am running .27A through the diode..."

That's barely at threshold for these diodes.
 
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Thank you to everyone who helped me out. I have my laser working now, just working on the programming for my project now.
 

diachi

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That LM317 is only rated at 1 Amp... You would need
a large Heatsink at it's max rated output current.

You would be better off using an LM338 which is rated
at 5 Amps. It will still need a heatsinh above 1 Amp.
http://www.ti.com/lit/ds/symlink/lm138.pdf

Or get a proper Constant Current pre-built adjustable
Laser Diode driver off eBay...


Jerry
Seconded on the LM338, very useful if you're taking this route and need the current. Pretty sure they're available in a TO-3 package for better heat dissipation too, although I have them in TO-220.

They're functionally the same as the LM317 so they're easy to get going and there's plenty of documentation out there on them.

Thank you to everyone who helped me out. I have my laser working now, just working on the programming for my project now.
That's great! Thanks for updating us. Hopefully you'll come back and show us the finished project. :)
 




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