Bizarre simpledrive II driver problem

Something incredible happens to your lasers. As dkumpula told you, this 2500mA driver is not optimal for 100mA diode (its range of operating current is just above the error of the current setting for v2500), especially since you for some reason do not want to use LASORB. The v2500 does not have a quality control system for the supply voltage, but it has a 330uF filter capacitor, which is sufficient in most cases. Really, I do not know what's going on with your setup, maybe your driver was corrupted by the previous owner and needs to be calibrated maybe something else

For good cable management and EMC there are no barriers

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are we talking about the power supply wires or the wires that feed the laser diode being a twisted pair

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no, I am going to using a lasorb , I did not have a spare for the other one and was using a switching diode till I could get my hands on another lasorb for that wavelength, I have one now for the 490 blue, my boss gave me one, and I am going to mod the driver I have with your instructions, when the original 490 failed it was just running and died, I was not doing anything with it but shining it into optical calcite. I can post pics of that if you want

I was just confused by not getting any feedback from you, and wondering when I will get the 490nm diode.

I fully intend to mod the driver and I now have a suitable lasorb, just waiting on a diode.

The 520nm laser diode has always had a lasorb on it and it's working just fine,

and to clarify a bit more, I was comparing the startup noise with a lasorb compared to a high speed switching diode and posted the pictures of the waveforms, I knew there was a risk to the 505nm diode with this test comparison and I know why it failed. I think I mentioned that the 505 had a lot of hours on it as well.

I have not followed the whole thread but is there any possibility of a back reflection blowing the diode? Calcite does strange things to light. Some diodes are very sensitive.

Yeah, kecked makes a good point. My builds frequently have the diodes pointed directly at the face of a PBS cube and I believe I have seen sensitivity for 520nm and 405nm diodes to this arrangement. I have attempted to compensate with by making the angle a bit off from 90 degrees and sourcing cubes with better AR coatings. That said, these diodes are known to be sensitive so lasorbs and other precautionary measures are prudent.

Also in case there was some confusion, BBE and DTR are not the same person. They live on opposite sides of our ‘little blue dot’.

David

I never thought of the back reflection, and thank you for clearing up the confusion it was DTR that said he was replacing the diode and he is not responding to stuff I send to him, I was confused thinking BBE was DTR, sorry for that,

The back reflection I know can damage video projectors as well, I found it fascinating that the calcite fluoresces in the beam path but otherwise does not do that with UVA or UVC
Attachment 54196

The long open-can reds (single-mode 660 nm diodes) from back in the day were *notorious* for blowing up due to back-reflection. They had a max output of around 300 mw, but at that level the intra-cavity flux was something like 10X higher (so ~ 3 watts). Given how small the emitter was on those things, it's no wonder they were so sensitive. They were already operating right at the threshold of catastrophic damage to the emitter face. So yeah, a single stray beam going back to the diode was all it took. Instant LED. It didn't even have to be a perfect reflection. Catch a stray bounce from an optic, or even from a polished metal mount, and you were suddenly cursing up a storm. I once killed one from the reflection off the blade of a flathead screwdriver! (D'oh!)

Lasorbs were great for preventing static from killing those diodes, and they worked really well to help smooth out the spikes we'd see from some of the shitty drivers we used to use back then, but they couldn't save the diodes from back-reflection. In the end everyone learned to align everything at 10% power and only crank it up once you were certain that everything was perfect and the case was sealed.

A little side note about Lasorbs: they must be installed as close to the diode as possible. For sure no more than about an inch away. If the total length of the current path from one end of the lasorb, through the diode, to the other end of the lasorb is more than about 5 cm, the diode can still be killed by static even if the Lasorb is functioning perfectly.

Bill Benner did some tests back when Pangolin was developing the Lasorb, and he discovered that he could kill a diode with a single static discharge (~ 20KV from an ESD gun) even with a strip of braided copper ribbon directly shorting the two leads of the diode, but only if the braided copper ribbon was more than 5 cm long.

Adam

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Originally Posted by buffo

The long open-can reds (single-mode 660 nm diodes) from back in the day were *notorious* for blowing up due to back-reflection.

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I still use LPC-840 open can 650nm diodes combined with 638nm reds to give a bit more range on the high end of the spectrum. I haven't damaged one of those, but I'll keep this in mind.

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A little side note about Lasorbs: they must be installed as close to the diode as possible. For sure no more than about an inch away. If the total length of the current path from one end of the lasorb, through the diode, to the other end of the lasorb is more than about 5 cm, the diode can still be killed by static even if the Lasorb is functioning perfectly.

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I believe that Bill has said to keep attach Lasorbs no more than 1cm from the diode. I've started attaching mine directly to the diode pins. This is a pain in the butt!

-David

I have been putting them on the diode leads as well

Did you not see my reply to your last message which had the shipping details I sent to your sbcglobal email? Other than that don't see any more recent messages. Anyway you said you were out of funds but really needed the diode and asked if I could send you one to replace the one that got damaged. Since you had a number of past purchases I said I would help you out and send you a free one. It shows delivered this morning so you should have it and can get back up and running.
https://tools.usps.com/go/TrackConfi...99939024476096

I use the brass mounts from dave and glue them to the top. I then bend the leads down to meet the laser diodes leads and then solder the leads for the driver in the center where they meet. I don't but good idea to add electrical tape to make sure the wires don't touch the brass. I like this arrangement as it also stabilizes the leads from the diode. If you pick off the leads at the top by the lasorb you get some stress relief too.

That’s a good way to save a half centimeter or so. I cut a couple lengths of heat shrink tubing to keep everything insulated. Electrical tape eventually comes off in warm conditions in my experience.

David

yeah for some reason I was not getting anything from my SBC E-mail, I usually don't have that problem, I will gig deeper into the settings to make sure that does not happen again, I had gotten earlier replies, so no clue on that, I got this diode in today as you had tracked, thank you so much!
This thread has been interesting as well, thank you!

I started using the brass blocks my self, easer to mount and you don't need to have a press fit in diode so it's possible to pull the diode with out destroying it, I am going to epoxy the lasorb on top and use heat shrink as well

I changed the current sense resistor to .5 ohms and am quite pleased with how the driver functions now, I ordered a few other resistors to convert them over for my low power applications. I am wondering if it's wise to make a sub board with both a .1 and a .5 ohm resistor with a switch to select one or the other, I don't always keep the same drive for just one application, if I had the money ideally I would just have extra drivers
I like that these use a large resistor that is easy to mod, drivers with SMD resistors suck to change out with out a hot air tool.

I have unrelated question but since the brass block style mounts came up, I cant get the optics on them to focus to a point, but the optics from the cheaper round mounts like what DTE sells work great.
I don't know what to call the round mounts? the type where they are press fit in.
the focus I get with the glass ones looks like a tad pole or tear drop(dead sperm cell if you will), I was thinking it was contamination but they look clean and scratch free. optics is not one of my strong points

Yeah, I picked up 10 of the shunt resistors myself, but haven't converted my 2.5A SimpleDrives yet.

Regarding your questions on colimation lenses, we've covered this a few times, but its been a while. First, with regards to Dave's at Lasershowparts brass mounts; you need to take off the focus ring from the rest of the colimation lens in order to screw it in far enough to focus the beam properly. Whether you are talking about G2 lenses or acrylic, these generally need to be screwed in to the point that the lens is almost flush with the brass mount itself. You may be able to do this with your fingernail or a jeweler's flat-head screwdriver.

You also need to ensure that its in tight enough to be centered and won't drift over time when things heat up and cool down. I use plumbers thread seal tape for this. I cut off a length on my bench about three to four inches long and then cut it lengthwise into two or three long strips. I then wrap it around the colimation lens exit side (the one with the notches) counterclockwise (if the exit side is facing you) fairly tight two or three times. Make sure to stop on a full revolution and cut or break the tape at that point. You are trying to make the colimation lens centered with the diode, otherwise you end up with the teardrop focus you were talking about.

Now you will notice that the colimation lens starts to get tighter to install as you get to the point with the plumbers tape. It should be tight enough not to move when focused, but not so tight that you damage the colimation lens 'notches' when you are tightening it. If you bend those notches, you won't be able to screw in the lens enough to focus it. If the lens is still fitting in too loose, add another round of plumbers tape. (I start with two rounds and add another as necessary.) You could also use lok-tight for this final step once you are sure everything is perfect.

Now, getting the lens in place with two or three rounds of thread tape takes more effort, of course and will do a number on your nails. Alternatively, I suggest making yourself a little tool of thin (about 0.2mm) aluminum. Just cut a 1 inch x 4 inch strip and bend it 90 degrees about 1 inch in. This will allow you to screw in the lens without damaging the notches or threads unless you have too much tape on the threads. You may be able to accomplish the same with two micro screwdrivers, but you need really steady hands to keep from slipping and scratching the lens or damaging nearby components.

That's about it. Oh, finally in regards to the 'bullet' modules like DTR sells versus Dave's, its a matter of personal preference. The bullet modules are easier for new builders to work with as DTR solders the wires to the diode leads for you. Using these mounts also allow you to rotate the modules within the SK-12 mounts so that you can match up the slow-axis/fast-axis orientation across your diodes. They are also a bit cheaper.

Dave's brass modules are smaller and mount lower making them more appropriate for small, aesthetically pleasing builds (in my opinion) as compared with a bunch of SK-12 mounts holding bullet modules. Dave's diode mounts also mount consistently flat to your optic plate making accurate near-field alignment easier than the SK-12 approach. Personally, I started Dave's mounts, switched to the SK-12s and then returned to Dave's mounts after a couple builds. All of my builds now utilize Dave's mounts.

I hope this helps!

-David

Sorry, I was not able to visit PL daily

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I was just confused by not getting any feedback from you, and wondering when I will get the 490nm diode.

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Don't forget to set the quiescent current using "zero" pot, it may be unbalanced after replacing the shunt

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I changed the current sense resistor to .5 ohms and am quite pleased with how the driver functions now

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No, we are basically discussing the consequences caused by Lenz's Rule. I'm trying to explain that this rule applies to any electrical circuits, not only for my driver :)

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I have not followed the whole thread but is there any possibility of a back reflection blowing the diode? Calcite does strange things to light. Some diodes are very sensitive.

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Thanks for that info.

I did not need to readjust the bias on the one I modded, it's running great, I was wondering though, the pins for monitoring the laser current, what would the new math be for the different resistor? I am having trouble recalling it even for the stock resistor, are the pins just in parallel with the resistor? or is there some other circuitry in place? I have this ancient wood cased portable meter from 1944 and thought it would be kinda neat to use that to monitor laser current, or skip that and use a programmable panel meter lol.

I am really loving these v2500 drivers modded for 500ma, it is working out so well