First Casualty: dead BDR-209 diode

[IWIRE]

That is not a bad idea to have one scoped to see where they are with these diodes. I think I will shoot one over to Lazeerer and see what he comes up with.

Thanks DTR. That would be nice to know for certain. :beer:

 

[Jstr]

I agree, thanks DTR,I was hoping something useful would come from this discussion.

Also this is what I mean by proven when talking about the microboost.

I have built around 50 of these @ 700mA with the microboost without issues.

My current setting was probably too ambitious. But let me know what you think about the driver spiking as a result of the battery voltage dropping and the (Vout*I out/V in) surpassing 1.2

 

[rhd]

Yep, I think your theory about battery voltage sag contributing to the problem makes some sense.

I would be interested to know how much safety is built into Lavas formula. Also, the formula would have to factor in a decision about acceptable ripple. It would be interesting to know what that ripple level is.

Really, what we should do, is collect a whole bunch of drivers and send them to one member with a good scope to test at a couple different common setups. To my knowledge, something that standardized and comprehensive has never been done on LPF. To be honest, few drivers have even been scoped individually.

 

[IWIRE]

Please accept my condolences during your time of loss
Thanks for sharing it, hopefully the insight gained will help future builds.

I think I used a flexdrive in my build with this diode. There is a thread on it somewhere. Not sure why I chose that drive, must have made sense to me at the time. I remember someone commenting it may not have been the best choice in drives.

I know I set it to .666ma, I'm getting 1w output and it still lives. A few days ago I was shooting it through a diffraction grating taking pictures, it does seem to have a long run time with out overheating.
I'm thinking this was just too high a current for this particular diode. Might have been fine with another diode.
Hopefully we get some good drive info from this.

 

[Jstr]

Please accept my condolences during your time of loss
Thanks for sharing it, hopefully the insight gained will help future builds.

I think I used a flexdrive in my build with this diode. There is a thread on it somewhere. Not sure why I chose that drive, must have made sense to me at the time. I remember someone commenting it may not have been the best choice in drives.

I know I set it to .666ma, I'm getting 1w output and it still lives. A few days ago I was shooting it through a diffraction grating taking pictures, it does seem to have a long run time with out overheating.
I'm thinking this was just too high a current for this particular diode. Might have been fine with another diode.
Hopefully we get some good drive info from this.

Thanks, IWIRE. I saw your build thread, and it was one of the reasons I chose the flexdrive. (also the microboost is backordered on Illumn, so I did not really have a choice) Great build, btw. Have you posted the pics, yet?

And yeah, I consciously made the decision to run it hard, which was a mistake. But I still find it really annoying that in the end it was the battery's fault. (I know the problem was definitely rooted in the way too high current)

Anyway, lesson learned- charge your batteries!

I'm really interested in the scope test to hopefully confirm that at high currents and output voltages, the input voltage sag causes dangerous spikes.

 

[IWIRE]

It's an honest mistake. Sounds like we are both fairly new to this hobby It's hard when you finish a build and want to see it work.
I'm bad about paying attention to detail until I finish the build.
Then I just grab whatever battery is handy and a lens laying on my bench and fire it up :crackup:

Something I have been doing when pushing a diode. I first hook the diode up to my PS and get an LPM reading to see what the diode can take. I forget about whatever magic output I'm hoping to achieve and set the current to what the diode wants.
Whatever the output is, it is what it is. I've had really good luck doing it that way. Seems like every diode is a little different.

No I haven't posted the pics I took.
I'm still practicing :beer:

 

[Jstr]

I have yet to master the beam shot, too. But that's a very nice one of the beast in your sig! Did you use smoke for that one? I don't, and it never turns out quite how I want.

That's smart, using a PS first. It's much safer than hoping your diode matches exactly with DTR's tests. Unfortunately, I have yet to invest in a variable PS or an LPM. I looked into getting a PS, but the good ones are ridiculously expensive, and I would almost never use it other than when testing a diode, which happens rarely enough.

As for an LPM, I would love one, but I am hoping for a new version of the radiant x4 that can read up to 6W, I'm sure you can guess why. I don't know how close we are to seeing that, however, or if it will be as cheap. I would also jump on a good one if it came up for sale here.

Anyway, I put in a summary at the top of the OP for those who do not want to read everything. :beer:

 

[IWIRE]

That's what I'm trying to master. Beam shots. My beam shots suck.
My PS is just a cheap fleabay one but it works good enough for me

I agree with you on the LPM. Diode outputs are getting crazy.

Thanks for sharing your information.
It's another step closer to success.
I'll REP you tonight if it will let me
:beer:

 

[rhd]

That is not a bad idea to have one scoped to see where they are with these diodes. I think I will shoot one over to Lazeerer and see what he comes up with.

Did you ever end up scoping a Flex or MicroBoost?

Here's an interesting post in the thread regarding the New Open Boost that supports the theory I discussed here in this thread. To make sure there is no confusion for anyone casually reading, the scope results in the thread I'm linking to are NOT for the Flex / MicroBoost: http://laserpointerforums.com/f67/o...-cell-tested-working-89556-7.html#post1314858

That linked post explains the results, but here's the nutshell. The newest Open Boost revision very cleanly boosts to an output of 5V @ 2.3A (a simulated 445 9mm), but when the same driver design boosts to 6.6V @ 850mA (a simulated 16x BR), the output has a very substantial ripple. This is notwithstanding the fact that driving 6.6V @ 850mA involves substantially lower output wattage than driving 5V @ 2.3A.

While it's a different driver, the underlying principals should be the same, so it would be very interesting to see if similar results show up when the Flex / MicroBoost is scoped.

 

[IWIRE]

I agree rhd, it would be interesting. I have a flex and microboost I would be willing to donate for testing by a respected forum member. They can keep the drives just share the results on the forum.
It would be nice if it was ARG since that's who scoped your drive. The testing would be consistent.
But any test by any respected member would be better than no test.

 

[AngelG]

Are we/you sure that these "unknown" diodes are made to withstand so high currents ?
I remember reading somewhere that Sony has invented the SLD3237VF diode for 12x writing speed.
SLD3237VF is rated to 200mW CW / 400 mW pulsed current.
To extrapolate:
12x <-> 200 mW ==> 16x <-> 280 mW, let say 300 mW CW at 300 mA. I don't know why do we think it's rated for more by the manifacturer. For very short pulses (30nS) it should withstand 600 mA, so let assume for longer pulses (50% duty) it could withstand 450 mA. And this is the absolute maximum. I think that even at 450 mA CW you're killing it albeit slowly, because it's rated to work 5-10k hours.
Death report1 at I >=650ma, Death report1 at I >=600ma
I'll repost this on another BDR209 topic because I want more people to think on it.

 

[Alaskan]

Seems we run our 16X 405nm laser diodes at a kill current, I know mine eventually died when pushed to almost 900mw output. I doubt I had even 45 minutes of total run time on it.

 

[Pman]

This is an old thread but I'll still comment that I have found with these diodes that you cannot just go with what your variable DC power supply can push the diode to. I think I have gotten every bdr to hit over 1W with the power supply but it's a totally different story when it comes to a driver and batteries. The highest output one I have right now is 880mW and I wouldn't go higher. Don't count out the 12x one. It has shown to me to be more robust overall and part of that may have to do with the larger 5.6mm size.

 

[Alaskan]

I had my 16X 405 UV, if I can say that, diode in a pointer and my LPM showed about 884mw output. What I liked about this diode, although the beam was extremely faint due to our eyes only being about 1% as sensitive to this wavelength compared to green, is that as a single mode diode at such a short wavelength, the spot could be focused down to a very tiny burning point of light, even 20 feet away I could still focus the beam small enough to burn, none of my other laser pointers could do that. Single mode at this power, coupled with the shorter wavelength and low divergence sure is nice. Only complaint is how faint the light is and yes, don't look at the spot, very very bad, especially at this wavelength!

 

[AngelG]

I build my LD drivers myself. But it's true that they could kill the diode if the current is not stable or if there are pulsations. Also, when there are short strong pulses and long wires, the wires could act as coil and produce high back EMF which can kill the diode, because Vr is often <= 2V.

Somebody has killed his diode trying to supercool it. He observed increased optical output before that.
One theory is thermal instability in the drivers he used;
Another: We assume a constant current driver is being used.
What happens inside the crystal (my theory): Vf of the LASER diode increases while the temperature is going down. This leads to more power being unloaded inside the crystal (Pc=I*Vf). But the crystal temperature is not equal: some areas are cooled by contact with the holder, other areas are overheating. When the total Vf is increased, the hottest areas start to conduct increased current compared to the coldest. When the excessive current is already applied, the hottest areas start melting....

 

[Andrew124C41]

(Edit) Summary of thread: I set the current too high (765 mA), but the diode was fine until the battery voltage sagged and put the flexdrive out of it's specs range, and that is the believed cause of death. Even with initial input voltage of 4.2V, the flex was technically already out of it's range at that current, but it did not kill the diode until a good 20 min of battery drain. (it was a 3100 mAh battery, so at an estimated 4.0 V, maybe??). So, hopefully we will get some scope data on this driver and confirm this theory.

(Original post)

Hi guys,

The purpose of this thread is to isolate the cause of death and hopefully add to the limited information available on this diode. I welcome any thoughts and comments that might provide helpful insight.

*There is not much to see other than sinner's spectacular handiwork, so I will not post pics unless necessary.

Build:
- MS-SSW-III host (check it out here)
- Flexdrive set to 750 mA
- 1x18650 orbtronic cell + blank 18650
- G-2 lens
- DTR silicon wire


What Happened:

So, I recently got this diode from another member here (who got it from DTR) because I have been wanting a 405nm build for a while. Unfortunately, the diode died before I could even add it to my sig.

The sinner host seemed great for extended duty cycles, and (while it worked, it never even got warm).

The build part was pretty standard, just soldering some wires (slowly, I admit). I stuck the flexdrive in the pill, heatsinked with copper wire and protected by electrical tape- thankfully I just used tape to secure the driver in the pill. All, assembled, it worked great. Nice, visible 405nm beam. Really great divergence, too, I was surprised. I used it sparingly at first, keeping cycles to ~1 minute on/off (I had to, it burned everything it touched).

BUT, then I wanted to get it warm to see realistically what the duty cycle should be. I timed it, and 3 minutes 15 seconds into the test, the diode suddenly stopped lasing. No warning, just LED'd (I assume this is the correct term). I immediately clicked the clicky switch off.

When I turned it back on, I saw that the diode was still emitting a faint light, but the divergence was terrible- at 10 yards, the focused spot was about the size of printer paper and barely visible in complete darkness.

I opened up the pill and lowered the current by ~70 mA. Same result. I haven't done anything more to it since then, but soon I will disassemble. But first, I need to clear up some issues.


What I suspect could be the problem:

I have two theories, and I do not think the diode is to blame.

Either a). I soldered the driver poorly, which caused the output to gradually increase, which destroyed the diode from current overload.

Supporting Evidence: I noticed while setting the current that this was in fact occurring. The current would start out consistently (I tested several times) at 765 mA and VERY slowly it would climb. I barely noticed- I thought it was just slight fluctuation. But then I conducted a longer test. After 7-8 minutes at least of constant run, the current came up to 784 mA when I stopped, again, after 8 minutes of constant run because the test load was getting pretty warm.

Refuting evidence: The diode died very suddenly, without any signs of dimming or heat (when I felt the host immediately after, it was barely warm). If it was current overload, one would expect dimming at least. Although my soldering is not professional by any means, it's not exactly easy to mess up assuming you're careful and patient, and my job looked solid- I was very thorough. Also, the current ramp-up was extremely slow, and the power graph on DTR's site showed the peak (power) at around or above 850 mA.


Or b). the host has a weak contact point in the tailcap, which caused a current inrush every time the clicky was pressed, which eventually caused a spike that killed it immediately.

Supporting Evidence: While I was setting the current, every once in a while, I would click it and the multimeter would still read zero. I had to click it again (twice, to be "on"). Then, with the diode connected, the problem persisted. At points, it seems I had to click it several times to get the mechanism in the right spot. This was pretty annoying, but I did not think much of it. The clicky is metal, and the spring inside it *feels* (I have not opened the clicky) like it is not secure, as in when the host moves, the metal button rattles. The sudden manner of death seems to fit this(?). I have read multiple accounts of bad clicky switches and also that not having secure contact points can kill diodes.

Refuting evidence: It's a sinner host . And it worked for a little bit. I can't think of anything right now.


Anyway, thanks for reading. Please share any thoughts, ask questions, whatever. If nothing else, I want to know if I can still use the host, driver, or both as is, or if I need a new tailcap, maybe. Cuz, well, it sucks to lose a diode, and doubly so to lose a diode, driver, and host together. I also hope that when I get the money, I can buy a new sled, get the diode from that, buy a diode press, extract the old diode, and press in the new one (if I trust myself to do that much).

Hopefully the information in this thread will add to the info available for this diode, though I doubt that the diode itself was to blame, given its performance with others.

Have you changed the lens....you know, fooling around switching from a 3 element to a G2. I ask because mine had not died yet but is on the way out. I think you get any thing near the window and thats it....they crack and start the ball rolling....well, realliy lights out.