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445 nm diode LEDing? Help!

alexjt

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Sep 2, 2010
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Hi all,

I was working on a 445 nm laser build, and in the middle of it, a tornado hit my place. Damage to the house was pretty minimal (we got very lucky!) but several trees fell on the house, and shook the house earthquake style. Dust everywhere, plus changes in pressure and shaking make me worried something's broken.

I have a pair of A140 diodes and a pair of Microboost drivers. I am testing with one of the drivers set to about 350-400 mA. My test load shows the Microboost putting out the proper current (the test load is 6x 1N4001 diodes and a 1 Ohm, 10 Watt resistor. Yes I know 10 watts is ridiculous. :scowl: It's what I have.) The diode is LEDing on me. I tried swapping with the other diode, but got the same thing.

I'm trying to think of all the things that could cause the diodes to be LEDing on me, but I haven't been able to find a coherent list of possible causes in the forums. Maybe I'm just bad at searching :thinking:

Any ideas?

Thanks!
-Alex
 





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you could always jump in on the group buy i have in my sig ;) but none the less, from what you said i honestly couldn't tell you whats wrong
 

Kevlar

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What is your power source? You have 2 separate builds? What are the specifics of the other builds? Are these your first builds?

We need more information and possibly pictures to help you out more. IMO, it would be pretty rare for 2 A140s to LED on you.
 

alexjt

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you could always jump in on the group buy i have in my sig ;) but none the less, from what you said i honestly couldn't tell you whats wrong


I'm in for one diode, check your thread. I can always use MOAR PARTZ! Thanks for the heads up!

What is your power source? You have 2 separate builds? What are the specifics of the other builds? Are these your first builds?

We need more information and possibly pictures to help you out more. IMO, it would be pretty rare for 2 A140s to LED on you.

Thanks for the post, Kevlar. My Power source is a 3x AAA battery sled for now. Since my original post, I've confirmed it's not the batteries, (I've tested them in another build and they worked fine.) I'm only working on one build, but got an extra diode and microboost. As I said above, I can always use more goodies. :D

These aren't my first builds, I've done a bluray and (a sissy 5mw red pointer for kicks) build to get my feet wet before, and I had been finding these diodes incredibly forgiving compared to others...of course, tornadoes mean business.

On close inspection with a magnifying glass, I found a crack along the edge of the glass on one diode, so that one has gone to diode heaven. (I assume?) Still not sure on the other one yet, but since both microboosts seem to be working, maybe I'll pull my bluray diode out of it's build, set the power down on the microboost, and do a test...Once again, thanks for the post! I appreciate it!:wave:
 

Kevlar

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The crack on the glass doesn't sound good but it doesn't necessarily mean that diode is dead. I would guess it would mess up the beam profile though.

You say you are using a 3XAAA battery sled? Are they primary batteries (1.5V) that ones would buy at any local store? If they are, I'm not sure they are up to powering a 445nm diode.
 

daguin

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The crack on the glass doesn't sound good but it doesn't necessarily mean that diode is dead. I would guess it would mess up the beam profile though.

You say you are using a 3XAAA battery sled? Are they primary batteries (1.5V) that ones would buy at any local store? If they are, I'm not sure they are up to powering a 445nm diode.

A cracked window only affects the shape and limits a bit of the output. It will NOT cause the diode to fail, unless there are pieces of the window bouncing around inside and one of them "cut" a wire.

Three AAA's will NOT give you more than about 500-600mW, but they will give you better than an LED emission. Maybe if they are "crap" batteries or mostly drained, the affect would be more pronounced.

However, with two of them failing I would look at other than the diodes for the problem

In any event, you can pull one apart and try powering it with something better than three AAA's (a li-ion or a bench PSU, etc.) to see if that is the problem.

Peace,
dave
 

alexjt

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A cracked window only affects the shape and limits a bit of the output. It will NOT cause the diode to fail, unless there are pieces of the window bouncing around inside and one of them "cut" a wire.

Three AAA's will NOT give you more than about 500-600mW, but they will give you better than an LED emission. Maybe if they are "crap" batteries or mostly drained, the affect would be more pronounced.

However, with two of them failing I would look at other than the diodes for the problem

In any event, you can pull one apart and try powering it with something better than three AAA's (a li-ion or a bench PSU, etc.) to see if that is the problem.

Peace,
dave

Ok, very good to know! I'll look into testing all the components more thoroughly, I've got a bench psu at work that I'm pretty sure should fit the bill and give more accurate power output in any case.

Here's a question: I know from forum searching that removing diodes from a microboost while power is connected is almost certain to fry them, but is there any way the microboost might be harmed by similar sudden connections/disconnections from a test load or battery source? I have up till now been under the impression that the microboost had a built in protection for this kind of thing...If that's not true, I very well could have fried it. Thanks for the advice!

-Al
 




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