Thank you for the great work! IgorT.
Your graphs are textbooks for me.:wave:
Thank you for your comments! Much appreciated! If it wasn't for all the feedback i doubt i would have the motivation to do it all.
And the explanation on test load is COOL.
I experienced two of 1.2W 445nm of 850mA v5.
I'm waiting drlava's v6 that could kill 445nm LD.
Wow, those must be some freak diodes you have there! The best of my three in the multi-plot needs 1A for 1.2W..
EDIT: Unless you did what i tried to explain in that warning and actually set them higher due to unmatching dummy Vf?
With v5 you are referring to the last FlexDrive version, yes?
I'm asking cos later you mention v6, which if i am not mistaken is not really FlexDrive v6 but MicroBoost v1. Don't confuse the two, they are completelly different beasts.
The MicroBoost is very close to what i've been using for over two years by now and made around 150+ of by hand, except that Lava's version is pot-adjustable (i only used fixed resistors) and has numerous safeties built in, to make it virtually fool-proof and user-friendly, which makes it suitable even for beginners to use as long as they follow the instructions... (my driver is much simpler in design as it was only made to work, and not necessarily to be friendly to anyone :evil
But in terms of their capabilities and limits they are almost the same, which is why i remembered to mention the warning for when a MicroBoost is used close to it's limits.
But i fear i didn't explain it well enough the first time and started going in circles, once i wanted to elaborate.
Let me try again:
VERY IMPORTANT FOR ACCURATE CURRENT SETTINGS ON THE MicroBoost DRIVER (TAKE 2):
If using a MicroBoost driver close to it's limits one HAS to do it with the dummy's Vf AS CLOSE AS POSSIBLE to the actual Vf of the diode (or a slightly lower dummy Vf just to be on the safe side!) while powering the driver from a PSU set to 4.2V (or a FRESHLY CHARGED battery if no PSU is available, but this is the less preferable option)!
The reason for this is, that when powered so close to it's limits, the driver can and will drop in current slightly (or even a lot) from where it is actually set to, as the battery voltage decreases (that's why i recommend using a PSU for this step) or if the voltage it has to put out increases (= if the Vf of the dummy is higher than that of the final load - the LD)....
In practice this means, that it is possible you unknowingly set the driver higher than intended, if you use an insufficient power supply or a dummy with too high a Vf - in both cases the driver may be struggling to put out your desired current and you actually end up setting it to 1.2A instead of 1A while you only see 1A flowing through your dummy load with a Vf of 5V (example). That's because the driver may be unable to push the current it's actually set to, through the dummy with a too high Vf.
Once you would then put this same driver onto an LD with a 4.5V Vf, the driver would suddenly be able to deliver the entire current it was set to, and pump it through the diode (which could potentially be dangerous depending on how big the difference is).
A similar thing could happen if you used a partially charged battery, forced the driver to push 1A through a 4.5V dummy, but then you put a freshly charged battery into the laser and the diode is suddenly at a higher current than you thought you set it to. That's why setting a driver from a PSU set to the very maximum a Li-Ion can produce is preferable...
I believe this explains the issue slightly better now... :angel:
The reason i am even mentioning this is because i've seen it happening a few times on my drivers and once on the MicroBoost when i was pushing them close to their limits.
But the issue manifests itself differently when the current is set by fixed resistors vs. a pot.
If you measure the driver's feedback voltage you can calculate precisely which resistors you need for 1A. If the driver then doesn't put out 1A through the dummy it can be either because the dummy Vf was too high or the supply voltage too low (or you're simply trying to run it over the limit). But since the fixed resistors set the current exactly to 1A, there is no danger once this driver is soldered to the diode - if it can, it will put out exactly the current it is set to and no more / if it can't the current will simply be lower than set on the LD which again isn't dangerous.
But when the same driver is adjustable with a pot, the user may not necessarily know what they actually set the driver to. If you're setting it too close to the limits you can run into the trouble i explained above.
Luckily these 445nm LDs are tough bastards and 1.2A instead of 1A won't necessarily hurt them (too badly)...
But still i believe it is best to be sure about where you have them set.
I will do some more tests to figure out where these limits i keep talking about actually are, but i can already say i really like the MicroBoost drivers. It's quite amazing how many parts Lava managed to put on there while keeping them small!
