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Burning without a lens and why you should NOT do it.

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Tonight I made up a 5A driver out of an old LM338K I had lying around. It's big and bulky, but gets the joj, at least for bench testing anyway. I had the 940nm diode I've been playing with running at 2.1A and could actually feel it when I got my finger really close. So I figured, "why not try and burn something without a lens." I'd heard it can be done.

So I tried a bit of black plastic from a DVD burner and it burned pretty well. :D So then I thought why not try something more difficult to burn like a piece of wood. Well it did burn a little spot, but I had to get it pretty close to the diode.

Then all of a sudden it stopped burning. Looking at the front of the diode, I could see a little bit of smoke had gotten onto it. In a last ditch effort to try and save it, I sprayed some SLX alcohol on there, but it had almost no effect. The diode still works, but it's horribly inefficient. :cryyy:

I think what happened is when enough of the black smoke had gotten onto the facet, it overheated whatever coating was on there and burned some of it off.

So the moral of the story is always use a lens if you're going to try and burn something. This was a cheap diode and so it could have been much much worse.
 

Eudaimonium

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Yeah, getting any particles near the diode's face is a very bad idea. Especially if it's an open type diode like LOC or C-mount, it's going to get permanently ruined.

If it's not, it's gonna be a major pain the a$$ to clean the diode's window from the burnt particles, depending on what you were burning with it.

I remember doing all that in my starting days, before I knew better. Fun times. You don't know how dirty can a diode get before you lit a match with it. With no lens.
 
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DrSid

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Well .. I would say that we at least learned from your mistake .. but honestly, I doubt anyone would be that .. well .. mistaken .. to do it anyway.
Anyway, I feel sorry for you loss :beer:
 

Atomicrox

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Had this happen to me with an IR laser (closed diode). Lighted a match from a couple mm away... it never fully recovered :/
 

Cyparagon

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The more general rule is "keep your optics clean." Yes, the output facet of a c-mount counts as an optic.
 

ryansoh3

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Sorry for your loss.

It's interesting how burning something very close to an open diode can permanently kill it instantly.
 

Blaster

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Well .. I would say that we at least learned from your mistake .. but honestly, I doubt anyone would be that .. well .. mistaken .. to do it anyway.
Anyway, I feel sorry for you loss :beer:
i wouldn't have thought to do it in first place but part of the hobby is doing different things, sorry as well ....and as the quote days we learn by mistakes ...
 
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I remember reading some threads here where someone even damaged or ruined their lens by getting dust or something on the lens and it burned into the lens, I know your talking about the diode window here but the same can happen to your lens. I live in a very dusty environment so I keep a dust cap on it when not in use.
 

Blaster

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I remember reading some threads here where someone even damaged or ruined their lens by getting dust or something on the lens and it burned into the lens, I know your talking about the diode window here but the same can happen to your lens. I live in a very dusty environment so I keep a dust cap on it when not in use.
I remember reading the same post ,so its always a good idea to keep your laser lens covered or keep them in a dust proof area like the aluminum cases you can buy.
 




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