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DIY Thermal LPM for under $50

^ What are you using as sensor, and what's its coating ?

Different coating materials can make A LOT of difference .....
 





Digi-Key - 102-1672-ND (Manufacturer - CP60133)

That's my sensor. I am using a Rustoleum paint (RustOleum.com)

I went to Home Depot and that's what the guy recommended for the most absorptive black paint.

Unfortunately, I actually think that my 445 is damaged... :( Because my 405 will read around 620mW, my green will read about 130mW, and my LOC will read about 175mW (set up at 380mA). Sad face.
 
The sensor looks good enough for powers over 50mW or similars, probably don't read very well lower powers (few junctions), but it must not give you problems, at that power ..... about the paint, i don't know, i've looked at the shops online here in Italy, but found nothing with that brand and name ..... i suppose it's matte black, not glossy (reflective), if so, a thin layer on the sensor must do a good job.

About the absorption curve of that paint, perhaps it's not available in any place (or maybe i'm just searching it with the wrong terms, i don't know) ..... can be good, but the only way for see if it's really good, is to check with other wavelenghts, from lasers already metered, sorry.
 
The only thing that concerns me is that the 405, 508mA diode is putting out more power than the 445nm, or at least that's what the meter says... so... sad face.
 
OT, but take the lens off your 445 and look at the unfocused output on a wall. A normal output will have 4-6 (seems to vary per diode) discernible lines in the output. A messed up one that still lases will have a lot more, and look like a bunch of thin lines. If the output looks normal, you should probably verify the driver is set at the right current.

Though I have to ask, are you comparing the same currents? 500mA to a 405 will put out more power than a 445 at 500mA.. Due to the fact that the 405's have a higher Vf, and therefor your actually putting more wattage into the 405 than the 445, even at the same current.
 
Yeah... it has that, which is odd... but I can double check it.

Further, I am *not* comparing the same currents... the 445 is supposedly set at 900mA... which I guess I can check later. I didn't want to have to take it apart but I guess I have to....
 
Yeah that's a fairly normal beam profile. Your driver probably isn't putting out anywhere near 900mA then.
 
Hmm. So I changed out the driver (better driver in my opinion), modded to put out about 1050mA. I am still only reading like 410mV. Something's off....
 
The only way you are going to callibrate your LPM is with
a known calibrated LPM... Not with Lasers of unknown
output...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
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I can, however, calibrate it to within reasonable accuracy (+- 100mW for higher powered lasers) by estimating the power of a couple of lasers (based off of their current) and then calibrate it so they are all equally close to their "actual" value.

The calibration I have so far gives me around 620mW for my 508mA 405 (regular glass Aixiz lens), 178mW for my LPC (378mA, acrylic), and 137mW for my Rayfoss greenie (makes sense that it's underpowered).
 
Well, that's what I am going to do once I have the circuit all set up and finished (right now it's sitting on a breadboard, I am going to transfer it to a custom-made PCB, put it all in a project box, get a panel display, etc).
 
Ah, ok I thought you already had it sorted out because your already calibrating it. So, you would have to re-calibrate it again once you get it on your custom PCB? :thinking:
 
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Well Not sure if you noticed but that picture you posted of your beam profile is horible. Not in a sence of how the 445nm looks defocused witch looks normal to me but the fact that you had black burned spots on the window.!!!:eek:

THis can reduce your power quit a bit and probebly is what caused your laser diode to degrade and damaged it.!!!


Becarfull next time with any of your diodes.

How did this happen.? If you know of course.

You Most likely wont be able to clean that off. You will mess it up even more if you try because of how bad it is so i would not even attempt it unless you dont care and you have spare diodes to use if it does.
 
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