thank you!
Wow, thank you for this in depth look Marc E! I really appreciate it, this helps a lot. I have looked to the data sheets to find this information before, but admittedly never went to the "back end" of them (P.28) and looked, thats why i probably never found the information i was looking for. although if i did see the items you shared, i probably wouldn't of understood what they are depicting anyway, without an explanation like you provided. So, thank you very much!
It seems you have this figured out now. I’ll add a little bit more.
In order for the xhp35 to be tightly packed, Cree actually joined the edges of the core in such a way that there are no wires connecting them. See below.
This gives them virtually no gaps between the cores and you get a better result (tighter beam, less artifacts). There are only 2 electrical contacts on the rear.
The xhp50 and 70, on the other hand, have the cores separated. The 50.2 and 70.2 have the same gaps, but the yellow phosphor is just spread all over minimizing the gap appearance.
It’s cores are wired such that 2 of the cores are in series and the other 2 cores are in series. You then have 4 connectors on the back. The MCPCB is what determines if it will be 6v or 12v. It can connect the 2 series cores in parallel for 6v or it can connect the 2 series cores in series and you get 12v.
The newer 3v version of the XHP50.2 has the cores internally wired all in parallel and only have 2 electrical connections on back. This is why it’s 3v only.
Keep in mind that these 4 core leds (xhp50 and 70) are basically just 4 smaller 3v leds combined. You can see the combinations in the second picture I posted.
Thanks "JasonWW" and others for your explanations and to those who ask interesting questions.
The discussion and diagrams clarified LED characteristics that previously confused me and understanding them makes this hobby more interesting.
Thank you Jason for your enlightening posting!
Wow, that's awesome info Jasonww, thanks for all that info. I appreciate it. Never realized the 50 & 70 were just a combo of 4 smaller leds!
You guys like that, huh?
Here’s a couple more pics showing more detail on the Cree Xtreme High Performance leds. This is a 50.2 below. The 70.2 is similar. Both are 2nd generation.
Ignore the tiny wires cut above and missing below. They don’t flow the main current. They are something to do with anti-static or something. I can’t remember off hand. The led still functions with the tiny wires cut. (The true positive and negative may need to be swapped around in the image above. I chose them arbitrarily for demonstration purposes since I could not see the mark on the backside.)
Now the 1st generation xhp50 and 70 had positive and negative lead wires coming out of each core. I added some black marks next to the leads since they are difficult to see. (Please excuse the low-quality image)
Here is a 5050 MCPCB that can be used in 6v or 12v.
In stock form it is not passing any current. If you want it to be 6v you would add some solder to the pads where the blue arrows are pointing.
If you want it to be 12v you would add a solder bridge across the yellow arrow pad.
All leds have some indicator on the top or bottom to show polarity to make sure you solder it correctly onto the MCPCB.
(The original pics are not mine, I found them online a long time ago. The MCPCB pic was outlined by the someone else, also.)
I have one question which requires experts to advise: Which metal flashlights incur high risk of lightning when outdoor during a thunder storm?
From own assumption: copper is the worst, followed by brass, stainless steel; aluminium should be quite safe, and the least dangerous metal is titanium. But I am not sure about my assumption.
I guess it is just common sense not to bring out any metal flashlights during a thunder storm, and to hide them inside our backpack if we are hiking in the open.
I don’t know if your joking or serious.
Jason WW, I am serious. Really want to know.
I just note that many flashlights are made of titanium, copper and brass. In fact I have just bought two Astrolux FT03 Mini brass and copper flashlights. I think they should not be used outdoor when it is raining.
But what about the common aluminium flashlights, and those made of titanium, which I assume are not attracting lightning much. Please correct me if I am wrong.
Just avoid ones with magnets in them, like in the tailcap. That will suck lightning to you like fat kids to a candybar.
It should not be an issue. Unless your holding a metal rod well above your head in an open area, I don’t see how holding a flashlight would have any effect as far as drawing a bolt of lightning towards you. Just my opinion.
Magnets? He said he was serious.
If you keep the flashlight in close to your body at waist height, the lightning will likely strike your head first and flashlight will be safe. If you use an umbrella that will help keep your hand and the flashlight dry.
I am living in Singapore, which is reputed to be the “capital of ligthning” of the world.
I am curious to note that people mention on the BLF whether a certain flashlight can be used in the rainstorm, or submerged in the water for how long; but I have not seen any discussion on lightning risk. That’s why I have asked for experts’ opinions.
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JasonWW 
, You are a GEM here at BLF. You have helped me several times, THANK YOU :+1:
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Yes and not everybody has the luxury of being able to stay indoors every time a lightning storm happens. But as pointed out above, unless you’re holding it above your head looking for lightning the body material is not really going to matter. The talk of use in the rain or submerged has to do with the ipx rating. Just about any light discussed here is pretty safe in the rain.
Thanks Oli and Lightbringer for your views. They are reassuring and useful to me.
And don’t call him Shirley…
Experts? Nah. Everyone just seems to yell at each other. Loudest person wins. :laughing: