bigchelis was saying in a CPF thread that you can’t just meter-read the lux values with tight beam throwers. It needs to be measured and the reading needs to be number crunched through a conversion factor to get the “real” lux value.
3.8A !!! Wow thats a lot, did the LED survive?
How does it do in the field? thats what really matters.
Maybe too much current, the heat is sagging it. If you have some dry ice you could cool the head/pill portion. :heart_eyes:
Maybe you could measure at 20m. Could you throw the beam into the air and see if the focus is correct, ie focussed at infinity? There is a possibility that it is focussed at say 30m only.
It can withstand 2-2.5A with proper heatsinking, and short bursts. But output sags at those current levels, depending on how long its left on. The OPs 3.8A is the most I have seen.
More likely OP already converted the lux based on distance, since he mentioned 78KCD for the xml, which I would imagine OP used conversion instead of measure at 1meter. so 55Kcd is more likely rather than 5.5 million cps.
3.8A will not be 2x the 2A XRE many have pushed to using solder to copper. To get XRE over million cp mark need 2A + 10 inch reflector. One can not beat the law of physics. Pushing to 3.8A if not killing the led will likely offer reduction in lux due to heat build up, even copper has its limits.
If he got over 5 million cps, he would not have made this statement: “My initial conclusion is that installing XR-E into very wide reflectors is a waste of time.”
Installing a XR-E into a larger diameter reflector is definitely not a waste of time. Maybe the wholes too big or the excessive current (as was already mentioned) is the problem.
If the XM-L was driven to spec and the XR-E is driven to spec the XR-E will throw further.
@ all: See what ma_sha1 wrote.
@ gcbryan: I am thinking the same but was tired.
Reason to test with that current? I had the driver installed in the host and that driver is a b!tch to install a 17mm driver into.
Plus I wanted to see result for myself. I am one of those guys who had to pee on the electric fence fence myself. Getting told how it hurt wasn’t enough.
I am still battling to figure out what is going on exactly but I think I’ll throw it in the deep freezer (–28 ° C) to confirm it is due to heat sag.
Then I’ll try changing the batteries in the light meter and the DMM to ensure they are good.
Then maybe I’ll do a direct drive under ambient temps to see what the led is pulling “naturally”
But I also have a birthday for a 5 year old and some family stuff to do today so it wont be until much later that I update this.
You need a certain minimal distance for measuring lux for two reasons:
- To close and not all area of the optic is in play, the surface brightness is not yet covered the whole aperture.
Giving to low numbers in lux measurements. (Something with F-number and etendue.)
- The rays might cross eachother before they form a collimated beam.
Measuring lux before or in the crossing gives unreliable numbers.
Thats where the rule of thumb comes from; measure at distance at least 10x the diameter of the optic.
To really know what the light is doing; measure from several distances, for example 5 meter intervals, as soon as two or more measurements result in the same candela (when calculated back to 1m), you know that you’r measurements is sound.
For your experiment, I really think you are overdriving the XR-E beyond the point of diminishing returns.
Can you measure the lux@1m without the reflector?
That would tell you how the led is performing.
The measurement with and without reflector together tell you how the XM-L reflector works for the XR-E, by using the formula for throw. Thats the best way to evaluate this experiment, otherwise its just guessing…
I just noticed 10 minutes ago that the led is a bit off center.
I was meticulous when mounting it so it must have happened when soldering the wires to the pads.
I guess I was too tired after all.
Funny thing though is that it does not show up in the beam if shining it on something more then 2,5 to 3 meters away. And that is part of the reason that I did not notice during last night after finishing the mod. I never shone it on something that close I guess.
Here is a picture of the mistake I made.
BTW: Did a test to see if I could live up to my name. No dice. Seems the led runs cool enough that it can survive a 15 minute run even when inside in ambient 22°C air no fan just sitting on a table.
@ waltherK:
The measurements were made at 5 meters and 10 meters and 12 meters. All add up to about 55 kCd calculated back to 1 meter.
Did a measurement just now at 1 meter that shows about 37 kCd.
Took it outside to see if there was problems with focus. Seems to my eyes that the beam converges at about 90 meters (this is really hard to tell and could be a optical illusion my eyes pick up) after which it starts to disperse.
Hope I am using the correct terms here - please feel free to assist me if I am not. That spot does not move when moving the reflector in or out. It simply disappears.
