XHP35: measured luminance and forward voltage

Basically there are lots of ways to skin a cat.

But cooking it up so everybody likes the taste is another matter altogether…

That thought might gross some folks out, so let me say this. In the old days of this country the mountain men were hunters and trappers, had their choice of virtually every animal to eat. I’ve read in quite a few different places that the wiliest old mountain men preferred Cougar meat over all other.

I don't think that's a fair summary. It makes it seem as if it all gets to the same endpoint and that's not true.

DB custom I'll try to be a little more clear. The mtn-max basically produces one single output current (just checked). So imagine it makes 6A (you can buy for whatever you want). Then it uses a standard direct drive style control to PWM that, sending pulsed current to the LED for reduced modes. But the LED always sees 6A or nothing, just in pulses. an XML is brightest at 6A but it's not efficient at 6A, pulsed or not, it's still 6A and that's not efficient.


What you want is a buck where you can actually dynamically change the current setpoint. The LM3409 can do that but it requires an analog voltage input. What I proposed and we're doing, and I don't know maybe was already in the design too, certainly TA also always thought it should work that way, so I might not have added much except getting the cap value right for it and nudging him to get back on it, but anyway.. what this setup does is use PWM from the mcu and filter it through a cap to make a steady controlled voltage to control the IC current setpoint with. The buck should deliver a steady current for your selected mode (with a very low ripple voltage too at least in good circumstances).

That means in low mode, it's only pushing low currents through the LED, not high currents like the MTN MAX. For the very lowest modes it will probably still need some PWM to help it, but it will already be efficient at that point.

Well they do all reach the same end point, they all light up an LED without burning it up.

The same way you can deep fry, roast, broil, grill, smoke, boil a cougar to make edible meat.

Sure they will not taste remotely the same but they are still cooked meat in the end.

Most people would never know the difference between any of the drivers we are discussing from a purely technical standpoint. The only thing some might notice is the tint shift on the non-PWM versions. By eye you would not notice the difference in output with any of them.

true enough. They may notice the battery life though. I use my lights hiking and biking. 20 mins extra on that 30% mode sometimes makes a difference.

Battery run times will be longer from the more regulated circuitry and the light will probably last longer due to the more efficient nature.

Thanks Flint, I knew that but of course… forgot. I don’t deal with it much as I typically use the FET direct drive for maximum output.

I have more recently bought a few lights with regulated circuit for just those reasons. They tend to be pricey lights though. Like the small Nitecore MH20GT. Very nice little light. Pricey. I’ve also gotten a couple of review lights lately that promise regulation, the nifty Rofis TR20 with an angle head tube style design and the zanflare z1, another tube light with interesting feature set. Still have to break down and photograph the TR20 for a review, but so far I’m finding it a pretty nice light and the adjustable angle head feature is something that, paired with the strong removable magnet at the tail, could come in very handy indeed.

Regulation, gonna have to figure all that out and build me up a nice XHP-35 version. I have a few bare emitters, gotta figure out what driver to use and then decide on how to build the host. Looking at what TA is doing, have some big metal on hand so just have to design it. :wink: (Reckon I’ll have to try Narsil as well.)

I agree, assuming the pattern is Lambertian is an approximation. A very good one for domeless emitters and good one for most domed emitters. For a domed emitter I might make an adjustment based on the actual angle profile like you suggest. I actually have measured the angular profile of a lattice bright emitter domed and domeless and they were very close to the profiles for the XPL and XPL HI profiles, respectively.

I don’t think Cree’s output numbers are very very accurate. For example, I’ve measured the XPL HI V2 1A to be brighter than other V2 emitters with different color temperatures. Some of this of course could be the difference in how our lux meters sense different wavelengths. Also, djozz’s measurements are commonly above Cree’s quoted numbers. Their numbers do just represent bins after all, so I wouldn’t expect them to be spot on for all emitters.

I have couple of xhp35 lights a Ultrafire F13 with a 1A boost driver and a Jaxman X1 with a 1.5A boost driver, I like the X1 very much maybe 1800 lumens OTF and a throw of at least 700m and it doesn’t get as hot like some of my other lights.

That sounds very nice indeed.

This is from another thread


X1 XHP35 HI D4 1A, boostdriver, Keeppower 26650 protected, approximately 700m

I actually think your method might be more accurate than an integrating sphere. Integrating spheres will have some angular non-uniformities in their responses anyway.

You could of course also measure the angular profile one one power level if you're really ambitious.

Anyway 2600 lumens is defiitely impressive. So for throw that should be equivalent to about 1670 xp-l lumens just dividing by the area difference. I'm not sure how an xp-l hi at 6A does. Probably right about there I guess.

Throw per watt, the xp-l only needs to get 1336 (multiplying again by 24/30 as a rough figure) to be even. Obviously the xp-l hi can beat that handily at 6A (24 watts).

Basically, at a more sustainable power level of 10W for either, the xp-l will get a brighter spot downfield, while the xph35 will get a bigger spot downfield. At max power they'll be about the same brightness, with xhp-35 still bigger, but also draining batteries faster to produce the light in the extra area.

It all depends where your measurement errors and uncertainties are, both methods can be done less or more accurate.

An example: the method of the OP and derived fine-tuning discussed later, heavily depends on a good quality well-calibrated luxmeter and requires some thinking about what the influence is of the diameter of the detector, while on the other hand in an integrating sphere method the luxmeter’s calibration is not very relevant but the calibration light sources often are uncertain.

Oh and by the way, wow, that Vf is linear. I'm thinking using about an 0.8 ohm 2 watt fixed resistor and a FET would maybe work pretty great as a near (but safe) direct driver. In other words just use any direct driver and heat sink a resistor on the led lead onto the case.

The lux meter is always relevant, in regards especially to how it samples the light spectrum. I suspect for high bin led's this could maybe explain the high readings.

Actually I doubt that, in my testing an XP-L HI is lucky to even match 1300 lumens. Highest I have seen so far a bit over 1200 lumens, usually closer to 1100-1200.

Which actually makes sense. Maxed out XP-L V6 models are generally around 1600-1700 lumens. The V2 is 28% lower flux bin, so thus by the math it should put out around 1200 lumens all else being equal.

Assuming we have an accurate lux meter, a potential advantage of this method is it might be easier to measure the absolute output without needing to calibrate the apparatus.

Texas_Ace, are those LED lumens or OTF lumens?

OTF lumens for the most part, although I have not measured a known good HI model without a light yet.

Although it should be 28% lower then the V6 which seems to max out around 1700-1800 even at the emitter from others tests.

Based on measurements I’ve done, the XHP35 HI measured is closer to the dedomed XPL V6 1A in throw than most XPL HI V2 tints.

In an EE X6, I measured 70Kcd with a XPL HI V2 3B and 94Kcd with a dedomed XPL V6 1A. This was at direct drive currents with a 30Q cell, about 5.5A and 6A, respectively. With the X6’s reflector area of ~630mm^2, the effective luminances of the LEDs are 111 and 149 cd/mm^2, respectively.

Using the method in the OP I measured the luminance of the dedomed XPL V6 1A at 5.5A to be 141 cd/mm^2, which is consistent with the measurement in the X6. The XHP35 measured had a luminance of up to 135 cd/mm^2, which is significantly higher than the XPL HI V2 3B. The XPL V2 1A is another story though; I’ve measured it to be ~20% higher in lux than other V2 tints, but it has a noticeable bluish tint.

In an unrelated topic the results from my build on the MaxToch Shooter 2X came up, thought the actual numbers from that might be relevant here.

This is copied and pasted out of robocop’s thread on the Shooter 2X…

“I took some measurements of voltage and amperage at the the emitter , and when I put the bezel/reflector back in it went on a little differently. So I checked lux again and got a surprise! 326.25Kcd for 1142.37M throw. Pretty much where the de-domed XM-L2 started out but with considerably more lumens. Sweet!

0.06A at 10.80V for ~89 lumens
0.55A at 12.22V for ~783 lumens
2.87A at 14.75V for ~2346 lumens

She’s singing along nicely!

And the LD-2 driver is very efficient apparently, with tail current readings at .06, .57 and 2.89A earlier (cells were higher charged then)”

(edit: used a clamp meter with a loop of wire between the negative lead and mcpcb for amperage, direct readout from the mcpcb for voltage, in the light)