I have been searching around the web looking at so many different model numbers for the Cree XHP50 and 70. Places like digikey and mouser, just to name a couple, have so many it gets frustrating being a noob at this flashlight modding! My questions are How do I chose a good XPH50/70 for Kelvin and also for driving them at 6 volts using a driver? I see so many of the XHP’s rated at 12 volts, but I also see the specs showing both 6 volts and 12 volts to drive them. That being said, I want a 6 volt in both the XHP50 and 70, that will have a pure white color around 5-6000K, and be the proper size for flowing on the copper heat sink pads that are sold at various places. One last thing is when I do finally know what I need to order with these Cree emitters, would using the Artic Silver Ceramique 2 be a good choice for these high powered emitters to the heat sink?
MTN has a bunch of options, pre-mounted on copper. The 2C or 3A will be 5-6000k.
Artic Silver 5 thermal compound works great, haven’t tried ceramique. From a quick search they seem to have similar performance when cooling computer components.
The reason I was asking these questions is because I was getting ready to place an order with digikey and wanted to buy a couple of these XHP50 and 70 emitters. Thanks for the reply! I guess I will order some Ceramique 2 and believe it will be a good thermal compound!
Hi Rufus! So in other words I can buy these Cree emitters that are rated at a maximum of 12.4 forward voltage, and drive them at 6 volts? I’m really a little confused as I thought I needed the Cree emitters that were rated at 6 volts to get around the 4,000 lumen light output? Perhaps you can explain this where I can understand better. I am always trying to learn more each day! Thanks again!
The Cree XHP series is a LED with 4 3V emitters
You can run 4 in series then you need another board and 12V
If you use the XM-L2 bosrd you automatically bridge 2x2 diodes so they run 2 parallel strings with 2 in series resulting in 6V operation
Hello Lexel, Now it makes sense to me! Thanks for that info! So any Cree 12.4 volt forward max voltage can be mounted onto a board such as the XM-L2, or any board for that matter, as long as the board will bridge 2 diodes in parallel then 2 in series for 6 volts as you mention? So it seems to me that Cree makes the XHP50/70 where each diode is run in series and connect the diodes so that they can be driven both with 6 and 12 volt configurations? Or am I confusing myself? lol
I would like to know what you guys think would be the best option for driving either a XHP50 or XHP70 emitter. I see that for the XHP50 emitter, it is rated at a maximum of 2.8 amps @ 6 volts, but I have read through this forum where people drive these emitters over the rated maximum specs. That being said, should I get a driver that is rated at 6 volts/ 2.8amps? Or can I get one with a higher current output and be ok?
So in other words the main factor is the heat issue? So I am assuming that with these copper heat sinks, the heat is transferred enough to allow for over-driving these emitters? So when you speak of a temperature step-down, is this some type of circuit that is built on the driver boards? Sorry for all the questions, just trying to get more knowledge! So basically I would be fine driving an XHP50/70 at maximum rated values, but can drive them harder depending on the heat control.
There are drivers with external PTC to monitor temperature and step down max current if its too hot.
Direct Thermal Path copper boards reduce the temperature a lot as the heat has a lot less resistance than on normal aluminium boards where is also a dielectric insulation below the LED pad in the middle.
Don’t flow it directly to a piece of copper, you should buy an emitter that is already mounted on a star like the sinkpad or noctigon ones from mtn electronics.
OK, I understand a little better now! So I can order an emitter that is already flowed on the sink pad and purchase a driver that has this PTC on board. OK, now would it matter what size sink pad or octagon I would get? Also, Do I solder the heat sink pad directly to the main heat sink that will go into the end of the flashlight? I guess I could call this mtn electronics place and ask them for the best driver with PTC for the emitters I will purchase! I am guessing that this PTC stands for Protected Thermal Circuit? Thanks again guys, much appreciated!
There are drivers with external temperature probe or some with a sensor on the driver board
The DTP MCPCB with LED on top gets enough thermal paste to make enough area contact to the host for a good thermal flow
and fixed with screws (Convoy C8)
or hold in place by the reflector (Jetbeam Jet-1 MK or Skilhunt H03), with enough force to press it tight on the LED base,
or glued with thermal epoxy(Wuben I333).
Most people use thermal paste and screw the star into a heatsink, or they use a thermal adhesive like arctic silver thermal adhesive.
You can solder the star onto something, but IMO that’s a pretty big hassle to make sure the entire bottom of the star is contacting the heatsink, thermal paste is a much easier option.
Nice shots of the different flashlight outputs Lexel! And thanks for your comment Enderman!
So by screwing down these noctagon/heat-pads to the main heat-sink using thermal paste will allow for changing the heat-pads with emitters on them correct? I would think when using a thermal adhesive, that will be a permanent fix to the main heat-sink!
Has anyone here tried using like a double-sided thermal tape? Just curious! I see they have them in 2mm thickness, but not sure if that would be as good as using a thermal paste?
Lexel, can you suggest a good driver for the XHP50 that has the PTC/DTP-MCPCB that I can purchase?
Yup, screwing down with thermal paste is less permanent than using thermal adhesive which is really hard to remove.
Double sided thermal tape doesn’t work very well for high heat devices like LEDs because thermal transfer is worse than thermal paste and it is thicker (when you scerw down with thermal paste it ends up being extremely thin)
So basically I would be fine driving an XHP50/70 at maximum rated values, but can drive them harder depending on the heat control.