445nm laser problem..

Hi guy's and girls..

I have a problem with one of my lasers....

It's a custom build 2.5W with m140 diode inside it. (not sure on the driver used)

The laser takes 2×18650's

I have tested 3 pairs of different battery's and 3 different chargers, but the problem still is there, even after i shipped it back for repair.

I want to know your opinion on what you think what's wrong with it..

when the spot becomes bigger on itself without focussing, i see some green on one side.



Cheers, sm

Never seen a laserdot becomes bigger by itself. Did you check the lens ? Maybe a loose element causes the trouble.

Blord said:

Never seen a laserdot becomes bigger by itself. Did you check the lens ? Maybe a loose element causes the trouble.

Click to expand...

Nah it's not a lens problem.. (i'm sure on that)

The lens can be taken out with ease and is hold in place by a spring..
It's just a custom focus adapter with the lens screwed in.

It's what you see in the video....

First few sec.. you see a normal line, and after that it seems to unfocus to a bigger dot that is deff not 2.5W or unfocused by the lens.

I'm gone try some unprotected cells.
Perhaps the protection is kicking in.

The builder doesn't use protected cells.

If the spot is changing sizes or shapes without any power drop that means you have a loose diode window that has come free of the adhesive. If the window shifts down onto the emitter wires that could cause a power drop. In the video your diode appears to be bright and then drop greatly in power. Like 1/10th the power. Is that what's happening in person? It also looks like the laser is right on the edge of being overpowered. I would bet that if you turned down the current 50mA you would solve this problem. That is what you can hope the problem to be. The diode window problem would require a decanning or re-adhering. I did see one new fellow post recently who can do this kind of precision work.

Have you checked the raw output without a lens? Does it do the same thing?

Hello all...

I appriciate the help so far, but there's a quick thing to say about DIY repairs.
I had sergery on my right hand for the second time, so i can't do any repairs myself, let alone filming this was allready a painfull experience

Anyway's... The video is what you see for real.
It starts (call it normal) in the beginning were you can actually see the laser line and the dot at the end of it.

After a split sec the laser dimms and there appears to be a splash with low output. 1/10

This is a 2.5+W rated 445nm laser.
It's using an LT1084 driver, heatsinked to the main heatsink. It's running at 1.8A, and uses a G1 lens.



It worked before, then it went bad, sended it back.
Loose wire got resoldered.
Recieved it back (what builder say's) in working order.
But it didn't when i fired it up with 3 different pairs of protected batteries.

So all i can do now with one hand is that i ordered a pair of AW IMR 18650 batteries today, to see if his diagnostic is correct about the protective circuit kicking in on them.

I'm 100% sure it has nothing to do with loose matterials inside the diode itself.
Also the lens is fitted inside the custom made focus knob that is easy to remove or check myself that that's not the problem. (nothing special there)

So i'm awaiting my order, and hopefully that's it
But i will let you all know that.
It's just frustrating that i need to smack allot of money on this when i allready paid so much for this wonderfull laser.

Cheers, SM.

So batteries weren't included with the laser?

yobresal said:

So batteries weren't included with the laser?

Click to expand...

Nope...

Too risky...

But the strange thing is that it used to work with the batteries i use.

My order that i placed today, shipped out to me, so hopefully i know more soon.

If it's still not working (seller's advice to try diff batties) then i'm asking the seller to cover shipping back couse i'm not going to pay anymore. ^^

I havn't had any fun with this laser sinds februari 2012.

Hey guys,

I'm the builder of this. It's courteous of Smeerworst not to have mentioned this - but I'm happy to be open about it. When I got this back, there really wasn't anything obviously wrong with it. I decided to use some aluminum solder and give it a super solid case feed directly to the driver, but the unit itself basically worked perfectly.

Anyway, here's my theory on what's going on (and this is a cut and paste of what I sent Smeerworst). Input / critique of the theory is welcomed. I've already told Smeerworst that I've got him covered if there actually is a real problem with the laser.

---

I know what the problem is, the challenge was figuring out why it was happening.

The driver is supplying full current for a few seconds, and then switching into a lower current output. This lower current output is below lasing threshold, so you get the different output that looks like more "splash" (or kind of like single mode output). That's what 445s do below lasing threshold.

The big question, is why. There are a small handful of reasons this could be happening.

The big common reason for this is the use of protected batteries. If the protection kicks in on one cell, current will drop, which means that protection WON'T kick in on the second cell. This means that the second cell continues to provide a lower current, and the driver gets 1/2 the required voltage. As a result, you'll continue to get low output (very similar to what happens if you just used one cell and a spacer). The current this build is designed to run at is enough to trigger protection. Both sets of cells you show in the video are protected. The Eden and the TrustFire cells are both protected, and so are the Soshines.

That's the problem, and luckily it's an easy fix! I never use protected cells. If you use good IMR cells, they're safe chemistry, no real need for protection.

Pop in some non-protected 18650s and your build will work perfectly

Question- What kind of optics ? Im asking because many of the optics i have seen use a spacer and threaded retainers typically begins to move around in the housing. I Locktite the retainer screw on all my optics. At one point i had a handful of lasers that would do the exact same thing in the video. If its not the diode window take apart your optics or replace it with one that works..

No, it's not the optics. This is a brand new G lens. It's not the window either, you wouldn't see the behavior resetting if it was the window.

It's an electrical issue, and I'm 90% certain that the issue is the use of protected cells.

Okay, so if you'll bare with the low production value, here's a video reproducing the issue. Forgive the low quality, I was trying to film and demonstrate at the same time.

In the video is a build using the same driver. It's meant for 2x 16340, which is what I use first. Full output.

Second, I use a single 18650, to simulate the impact of one cell's protection kicking in. The result is very similar to what Smeerworst is experiencing. The dot looks larger, almost like a single mode output from something like a 658.

Edit:
http://www.youtube.com/watch?v=k5emvHohk-0

Very interesting. At first I thought it was a loose lens thing as well (looked like it was shifting not in brightness but in beamshape) but I realized that you're right. That's definitely what it should be. But really, is 1.8A enough to kick in protection on big 18650s?

Wolfman29 said:

That's definitely what it should be. But really, is 1.8A enough to kick in protection on big 18650s?

Click to expand...

I think there are different kinds of protection. In fact, I think some protection circuits are charge/discharge only, and others have over current/don't. I'm not an expert on protected cells by any means though. I'm almost entirely unprotected IMR cells at this stage. But I know that I've often run into issues with the rare few protected cells that I have tried using in laser builds.

We'll know soon, but I'm confident that this is what's going on.

I suppose we will!