Testing a Cree XHP50.2 J4 3A led

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Phlogiston
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[following on from this post]

Texas_Ace wrote:
Phlogiston wrote:
Texas_Ace wrote:
Or another rather interesting option would be to have a pad for an FET on the mcpcb for heat sinking and then use an opamp LD3 style driver to control it. By having it on the MCPCB the heat sinking should be good enough to allow it to handle it. […]
Alternatively, could there be a special FET MCPCB that would mount to the driver side of the LED shelf?

[…] with a couple of small bolts keeping the FET MCPCB in place […]

The problem with this is that it would not work with all hosts, only those that have a thick enough shelf to allow a screw to be used to mount the bottom side mcpcb among other issues. […]
I was thinking about having the bolt head hold the LED MCPCB down against the shelf, and the nut hold the FET MCPCB up against the other side of the shelf. The hole in the shelf wouldn’t need to be threaded, so the shelf wouldn’t need to be thick enough for that.

Admittedly, there are other issues, as you say: at least one extra wire taking up even more space in the driver cavity, for example, and there’s a risk that the bolt head would experience clearance issues with the reflector.

Just chucking ideas around, basically Smile

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It is a reasonable idea for a purpose built light that would work, the only issue I see is universal retrofit abilities.

You could actually make something like that with an oshpark printed pcb fairly easy. While not ideal it should be good enough to vastly improve the heat dissipation so it can handle almost any single LED on the market right now. Particularly if you stay away from the 50% range where heat dissipation is highest.

My thinking with a MCPCB mounted FET is that it should fit almost any light fairly easily with just 1 extra wire needed. It might have to use a lfpak33 fet but that should be ok. You could use parallel FET’s but that would get more complex.

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Texas_Ace wrote:
It is a reasonable idea for a purpose built light that would work, the only issue I see is universal retrofit abilities.

You could actually make something like that with an oshpark printed pcb fairly easy. While not ideal it should be good enough to vastly improve the heat dissipation so it can handle almost any single LED on the market right now. Particularly if you stay away from the 50% range where heat dissipation is highest.

My thinking with a MCPCB mounted FET is that it should fit almost any light fairly easily with just 1 extra wire needed. It might have to use a lfpak33 fet but that should be ok. You could use parallel FET’s but that would get more complex.

Wouldn’t it be less than ideal putting both high heat sources, led and fet, in the same location? Wouldn’t be better to keep the fet in the driver cavity and add a small smd heatsink potted to the fet and the closest body contact point?

As to my earlier question regarding buck driver voltage, I suppose the only way to safely test would be while watching a scope and thermal image simultaneously…

Edit: or the “squeeze it in your fingers til it burns” approach might work. This is how I did some testing on the t25c driver. Actually, I might just put that driver back on the bench for a voltage out test. . Big Smile

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Texas_Ace wrote:
It is a reasonable idea for a purpose built light that would work, the only issue I see is universal retrofit abilities.

You could actually make something like that with an oshpark printed pcb fairly easy. While not ideal it should be good enough to vastly improve the heat dissipation so it can handle almost any single LED on the market right now. Particularly if you stay away from the 50% range where heat dissipation is highest.

My thinking with a MCPCB mounted FET is that it should fit almost any light fairly easily with just 1 extra wire needed. It might have to use a lfpak33 fet but that should be ok. You could use parallel FET’s but that would get more complex.

I like that OshPark PCB idea Beer

I see what you’re getting at with the universal retrofit now, though, especially if you were switching to different FET package sizes to make it / them fit. Once you had a supplier for the new LED+FET MCPCBs, you could buy them to use in any size-compatible light, and no worries about space in the driver cavity either.

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LightRider wrote:
Wouldn’t it be less than ideal putting both high heat sources, led and fet, in the same location? Wouldn’t be better to keep the fet in the driver cavity and add a small smd heatsink potted to the fet and the closest body contact point?

As to my earlier question regarding buck driver voltage, I suppose the only way to safely test would be while watching a scope and thermal image simultaneously…

Edit: or the “squeeze it in your fingers til it burns” approach might work. This is how I did some testing on the t25c driver. Actually, I might just put that driver back on the bench for a voltage out test. . Big Smile

Having both heat sources in the same place while not ideal is not going to make much if any difference compared to mounting the FET to the bottom side of the shelf. The heat still has to travel through the shelf in order to make it to the body either way. The mcpcb is FAR better at dissipating heat though so it should be able to easily handle the heat from the FET and keep it from overheating.

Now you can have a custom aluminum pcb made for the fet separately but it would add a fair amount of cost.

This option is far from ideal anyways and the best idea is to put the effort into a good buck driver. Also moving to 21700 cells would be a very wise idea as it would give more room for a larger driver.

The opamp driver is simply an easy way to drive high currents if you can heat sink it well enough.

If guns cause crime, then pencils cause misspelled words.

In general, the art of government consists of taking as much money as possible from one party of the citizens to give to the other. -- Voltaire (1764)

Texas Avenger Driver Series

My LED Test series - XP-L2 V5  - Nichia 219C 90+ CRILatticebright "XM-L"XHP35 & PWM efficiency - XHP50 - XP-L V5 - XM-L2 U2 - XP-G3 S5  - XP-L HI V2 - Oslon Square & direct comparison to Djozz tests - Nichia 319A - Nichia 219B 9080 CRI - Nichia 219C D320 - Nichia 229AT

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Phlogiston wrote:
I like that OshPark PCB idea Beer

I see what you’re getting at with the universal retrofit now, though, especially if you were switching to different FET package sizes to make it / them fit. Once you had a supplier for the new LED+FET MCPCBs, you could buy them to use in any size-compatible light, and no worries about space in the driver cavity either.

Yes, that is the idea. I always try to aim for the most universal solution to a problem so that the work can be used over a wide array of situations. Never been a fan of 1 off custom solutions unless there are simply no other options.

If guns cause crime, then pencils cause misspelled words.

In general, the art of government consists of taking as much money as possible from one party of the citizens to give to the other. -- Voltaire (1764)

Texas Avenger Driver Series

My LED Test series - XP-L2 V5  - Nichia 219C 90+ CRILatticebright "XM-L"XHP35 & PWM efficiency - XHP50 - XP-L V5 - XM-L2 U2 - XP-G3 S5  - XP-L HI V2 - Oslon Square & direct comparison to Djozz tests - Nichia 319A - Nichia 219B 9080 CRI - Nichia 219C D320 - Nichia 229AT

Complete collection of all my LED tests

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djozz I don't understand what you mean by lower Vf is more efficient.  Is this a general property of LEDs?  Yes for the same current it's using less power (and in some ways maybe it's better to plot power instead of current), but without understanding output and binning is there something else to this?  For two LEDs with different Vf hooked up to the same battery and same linear current regulator, the one with the lower Vf will use less power at the LED but it just means more heat will dump into the driver instead. Of course that's not the LED's fault.  

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Flintrock wrote:

djozz I don’t understand what you mean by lower Vf is more efficient.  Is this a general property of LEDs?  Yes for the same current it’s using less power (and in some ways maybe it’s better to plot power instead of current), but without understanding output and binning is there something else to this?  For two LEDs with different Vf hooked up to the same battery and same linear current regulator, the one with the lower Vf will use less power at the LED but it just means more heat will dump into the driver instead. Of course that’s not the LED’s fault.  


I meant exactly what you say, if a led compared to another led has the same output at the same current but with lower Vf, it consumes less power and so is more efficient.
And as you say, it is not the led’s fault but in a typical flashlight situation with lineair driver, that advantage is completely gone because you just burn up that voltage gain. But in a boost or buck driver you do see something back of the higher efficiency.
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Last night I apparently was bragging too much about the expected throw of my direct drive XHP50.2 thrower. I just measured it at a modest 70kcd. So not the 200 I was expecting, the big hotspot looked a lot brighter than it actually was.

But perhaps that was to expected, with the die size and dome this is not a thrower led.

If a HI version would come out however, that has about 1.8 times the throw, in the BLF thrower with 12cm reflector the led would do 900kcd at 3500 lumen. So we will have to extend that thread for as long as possible Wink

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Posted the mod in the what did you mod today thread:
http://budgetlightforum.com/comment/1094056#comment-1094056

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Direct drive on 2 freshly charged litokalla 26650s = 14.5/15a of juice showing on my clamp meter. Suprised it didnt pop it. Host got very hot but no immediate problems

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mattjk wrote:
Direct drive on 2 freshly charged litokalla 26650s = 14.5/15a of juice showing on my clamp meter. Suprised it didnt pop it. Host got very hot but no immediate problems

If the host got “very hot” that probably means the LED got to 100 or 150C…
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Aww Man!

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CRX wrote:
Aww Man!

!{width:80%}[img]http://i.imgur.com/U0OskkJ.jpg[/img]!

You can do that with MCE’s too! Wink

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It’s not a desired effect. Blew it with two 14250 cells LOL . Bad reflow.

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I’m going to keep running it at max power see how it goes i didnt even put a driver in and all springs are bypassed 22 gauge wire so no resistance

Reflow very important to have an excellent thermal path. Also soldered the sinkpad the brass pill (i have a copper pill too but the xhp70.2 is going on there when i can get one!)

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mattjk wrote:
I’m going to keep running it at max power see how it goes i didnt even put a driver in and all springs are bypassed 22 gauge wire so no resistance

Reflow very important to have an excellent thermal path. Also soldered the sinkpad the brass pill (i have a copper pill too but the xhp70.2 is going on there when i can get one!)


Just because it has a good thermal path doesn’t mean it has good cooling.
Also, unless you use a superconductor there is going to be resistance.
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I’ve got 3 of the 5000K 50.2’s in my latest scratch build, pulling 21.12A from a pair of Sony VTC6’s for 11,696 lumens. The cells were at rest at 4.13V at the time of the test. The KaiDomain triple reflector makes for a decent hot spot, just a hint of a dark spot but I probably don’t have em perfectly located height wise. I’m using 20Ga Teflon wires, cut out the area’s around the side of the reflector where the pads are for clearance, have filed down centering rings.

They rock, for sure!

Dale

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Enderman wrote:
mattjk wrote:
I’m going to keep running it at max power see how it goes i didnt even put a driver in and all springs are bypassed 22 gauge wire so no resistance

Reflow very important to have an excellent thermal path. Also soldered the sinkpad the brass pill (i have a copper pill too but the xhp70.2 is going on there when i can get one!)


Just because it has a good thermal path doesn’t mean it has good cooling.
Also, unless you use a superconductor there is going to be resistance.

You have taken my post to literally by no resistance i meant there is no FET/springs to reduce the current thus its a low resistance as it possibly could be.

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mattjk wrote:
You have taken my post to literally by no resistance i meant there is no FET/springs to reduce the current thus its a low resistance as it possibly could be.

You could use 8 gauge wire like I do, that has less resistance than 22 Wink
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djozz wrote:
Flintrock wrote:

djozz I don’t understand what you mean by lower Vf is more efficient.  Is this a general property of LEDs?  Yes for the same current it’s using less power (and in some ways maybe it’s better to plot power instead of current), but without understanding output and binning is there something else to this?  For two LEDs with different Vf hooked up to the same battery and same linear current regulator, the one with the lower Vf will use less power at the LED but it just means more heat will dump into the driver instead. Of course that’s not the LED’s fault.  


I meant exactly what you say, if a led compared to another led has the same output at the same current but with lower Vf, it consumes less power and so is more efficient.
And as you say, it is not the led’s fault but in a typical flashlight situation with lineair driver, that advantage is completely gone because you just burn up that voltage gain. But in a boost or buck driver you do see something back of the higher efficiency.

It also means that with a regulated driver(either boost, buck, or linear) the more efficient lower Vf led will stay in regulation longer and half a volt means something there.

Another great test thread Djozz!

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Rufusbduck wrote:

 It also means that with a regulated driver(either boost, buck, or linear) the more efficient lower Vf led will stay in regulation longer and half a volt means something there. Another great test thread Djozz!

 

Boost or buck?  yes and and no.  Without enough voltage difference between source and load you just shouldn't be using a buck.  With too much, you shouldn't be using linear. Once you get to where a buck (or boost) works well, further marginal differences in voltage won't matter, and it becomes a big advantage of a buck. In the transition though I'd turn this around as a disadvantage.  Lower Vf led's are bad because they require a buck, and because without one the setup on the whole becomes more and more inefficient. 

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AlexGT wrote:
I have an Acebeam K60, if I install this led and according to the graph I would lose around 600 lumens but gain more throw? Doesn’t sound like a bad trade. Love

If you sliced the dome off your xhp70 you would also get a little less lumen’s, but more throw.

Then I wonder if the new xhp50.2 is an upgrade or pretty much the same?

One advantage the xhp50.2 may have over a sliced dome xhp70 is less of a donut hole. Then again, I think the K60 has an OP reflector so it’s not likely to ever get a donut hole. On a SMO like my L6, the xhp50.2 may have a slight advantage.

Do you guys know off hand if a sliced dome xhp70 has a smaller or larger hot spot compared to a dome-on xhp50?

My Convoy L6 thread with XHP70.2, Texas Avenger FET driver, Narsil v1.2 ramping firmware, lighted side switch and cut down SMO reflector. Lots of amp draws on stock driver as well.
http://budgetlightforum.com/node/54477

My Supfire L5-S thread with XHP70, Texas Avenger FET driver, NarsilM v1.0 ramping firmware and lighted side switch. My mini L6! http://budgetlightforum.com/node/55746

6 NarsilM user videos
http://bit.ly/narsil-vid1

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There is a donut hole on the Thorfire S70 and also on the new Eagle Eye X9, both use the XHP-70 and both have heavy orange peel reflectors.

Dale

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The XHP-50 and 50.2 fit on the XM-L footprint and can use the XM-L reflector. The XHP-70 is a much larger emitter physically, albeit not as large as the MT-G2. So comparing the 50 to the 70 is not an equal comparison. The 50.2 version has less gap between emitters but not as tight as the XHP-35 so there are still some issues. The 50.2 utilizes a phosphor covering much like the XP-G2 and as such it would be difficult to do a clean de-dome. Slicing the dome may well yield better throw but the center of the hot spot would still suffer from the gap between dies.

Dale

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The XHP-70 can do substantially more lumens than the 50 or 50.2 variant, as well.

Dale

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So your saying swapping in the new xhp50.2 is not gonna be any kind of an upgrade over a sliced dome xhp70.

Well, that’s a bummer.

Maybe the new xhp70.2 will be a real upgrade.

My Convoy L6 thread with XHP70.2, Texas Avenger FET driver, Narsil v1.2 ramping firmware, lighted side switch and cut down SMO reflector. Lots of amp draws on stock driver as well.
http://budgetlightforum.com/node/54477

My Supfire L5-S thread with XHP70, Texas Avenger FET driver, NarsilM v1.0 ramping firmware and lighted side switch. My mini L6! http://budgetlightforum.com/node/55746

6 NarsilM user videos
http://bit.ly/narsil-vid1

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Well, it’s maybe not as straightforward as that. Depends on several factors. And for the record, whether or not the XHP-50.2 shows a donut hole is reflector dependant, it can still show that just maybe not as bad.

I got the new Eagle Eye X9 today and there was visible donut hole from the XHP-70 beam. I was about to put in an 50.2 and thought about slicing the dome off the 70. That made all the difference in the world in this particular light and it’s still making just over 3000 lumens at 4.84A so I’m thinking I might leave it just like this. Since djozz showed that the 50.2 maxes out around 5000 lumens and some 10A, it’s doubtful that it will best the 70 in this light without more extensive modification.

So there are always mitigating factors that make it more complicated than simply the emitter.

Edit: Maybe some expansion on my reasoning would help. The XHP-50.2 is similar in structure to the XP-G3. I don’t like the G3 for it’s beam profile and am finding a large similarity to this G3 in the 50.2. Sometimes it’s not all about power, given an ugly beam profile with odd color shifts the power levels aren’t winning it over for me. That’s just me though, and just my singular experience with my triple in a single triple reflector. I might find I love it in a different light or different reflector. Won’t know that until I try and I have a single 50.2 to play with…

Dale

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I have a dumb question about the LED. I want to reflow one and can’t figure out where is + and – Facepalm

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Tom_182 wrote:
I have a dumb question about the LED. I want to reflow one and can't figure out where is + and - :FACEPALM:

Dang dunno offhand, but check the CREE datasheet and usually there's a mark on the underside to indicate anode or cathode side - I always forget which is + and - and always looked it up. Finally wrote it down, but my notes are @home frown. I sanity check all the new LED's now - used to be easier.

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