This is like Mission impossible type stuff… Scaru, if something goes wrong. Can I have your flashlights? :bigsmile:
He, screw it. I just placed another order there for 10 of them but this time with DHL shipping to hopefully speed everything up. :D
+1
The way I understand it is the phosphor coating varies from LED to LED (hence differences in tint) however it is down to the quality of the crystal itself beneath the coating, thus there should be no correlation (that I can think of) in forward voltage between different tints and even brightness bins.
Is this true? Will a few mV forward voltage difference cause LED’s to blow? 
The problem is the steep current vs forward voltage curve for LEDs. Voltage goes from 2.5V 3.5V(ballpark) while current soars from 50 mA 3000mA. It’s not quite linear but close enough so that 1/10V 300mA with the lowest vF led getting extra current meant for 6 others. We already push our LEDs much harder than in commercial applications and this may be a bit too much. The common heat sink might help normalize them but with so much current supplied and no regulation my guess is that one will turn blue and die and then another then the rest. I don’t know this will happen but I suspect it will. It’s a neat experiment though.
In principle, I agree completely. The V/I curve of an LED does not lend itself well to parallel direct drive… In practice, however, I’ve found it to work much better than the theory would suggest. A small group of LEDs from a single lot have proven to have remarkably similar Vf and V/I values - at least in my experience. I’ve had much better luck with parallel arrangements than the math would suggest should be possible.
There’s risk, for sure, but I’ve seen it work on many occasions…
PPtk
Haven’t had enough LED’s to measure, but what’s the forward voltage variations for XM-L LED’s?
By datasheet (at 700mA drive current) typical is 2.9V and max is listed as 3.5V. That’s about 21% from typical to max. There’s no minimum listed at any drive current and the max is only listed at 700mA. Probably not a bad rule of thumb to think typical plus 21% and minus some unknown percentage as a range.
Scaru, you should buy around 3-5 times as many LEDs as you need and try and match them for Vf.
While, I could do that I am simply going to buy the 7 I need and replace them as they die. ;) Because as I understand it the worst that could happen is one of them gets to much current and dies, then it would be a 6 led light.
wow, you have a built in fail safe/ redundancy right there 
Looking forward to the results, way to go with pushing the boundaries of what’s possible/ sane!
In rock climbing its called “zippering”. You fall and an anchor pulls pitting more strain on the next until it fails… mostly happens on aid pitches with body weight only placements. Here, if one led does fail, the rest would probably poof before you can say “Jack the Clipper” so the best bet is don’t let the first one fail. Match the Vf’s.
Question: Do you match them with a low current test or screw the stars to a sink one at a time for a 3A test?
Ideally you want to match the Vf curve over the full operating range, but that ain’t gonna happen. So you match them for the worst case condition of full power…
Amazing :bigsmile: How did I miss this thread?
The boards arrived as did the LEDs.
And here it is next to a triple.
Can someone tell me whether I'm understanding the wiring right? I drew a red line to show the connections (or what I think are the connections).
i seriously hope you are planning on making more than one of these…. i think there is a lonely solarforce host in my collection that would go nicely with one of these
Can you use a meter to bell out the continuity so you know what way the layout is?
Smart, going to do that now!
Red line looks right.
Your connection diagram is not correct. You have the top copper artwork in PDF format inside of the zip file that I sent you to give to the circuit board fab shop.
Here it is:
And here are the connections in colors (Red+ Black-):
PPtk