Cree XR-E and runtime discussion

How come no one is using the Cree to create long running lights. The brightness on most of my lights meet my needs. But I would love more runtime. I have not seen people heading in this direction. What would a JiL DD with a Cree do?

I also dislike that my lights get warm. I would love the same brightness with less heat too.

Any thoughts?


rob

Re: Cree XR-E

With the multi-level lights, you can have your cake and it it too.

EDIT: One light I plan to build for myself is a DD XR-E on a CR123 and probably a resistor 2 stage switch for less efficient but good low light level.

Re: Cree XR-E

Yup multi level is the way to go. You can get the best of both worlds. It just remains to be seen at what levels you can have them and are they dull enough for your purposes. Just swaping over some of these lights would not give you the same low levels you are used to, so they should be changing the drive levels to compensate.

Re: Cree XR-E

McGizmo said:

EDIT: One light I plan to build for myself is a DD XR-E on a CR123 and probably a resistor 2 stage switch for less efficient but good low light level.

Click to expand...

Hello McGizmo

What reflector do you think about? McR27-L?

Best regards

____
Tom

Re: Cree XR-E

Long John,
If I didn't already have one light with no optics, I would probably make this sans secondary optics. However, I think I would keep it small and simple and use a McR-17XR.

Re: Cree XR-E

McGizmo said:

Long John,
If I didn't already have one light with no optics, I would probably make this sans secondary optics. However, I think I would keep it small and simple and use a McR-17XR.

Click to expand...

:thanks: very much. It hears interesting

Best regards

____
Tom

Re: Cree XR-E

fleegs said:

How come no one is using the Cree to create long running lights. The brightness on most of my lights meet my needs. But I would love more runtime...

Click to expand...

That's a good question. Due to the eye's logarithmic sensitivity, double the light output doesn't visually appear as double the brightness. However double the run time is perceived as an obvious linear doubling of that characteristic.

One answer is there's a natural "onward and upward" tendency to emphasize pushing LED output ever higher, especially in a specialized group like CPF. Whenever a higher output emitter comes along, everybody is interested.

It's similar to a performance-oriented automotive forum when a higher horsepower engine appears. Maybe the increase is due to efficiency improvements, and maybe if throttled back it would deliver more gas mileage, but high output (horsepower or lumens) is sexy and viscerally interesting.

However as already stated, variable-output lights make it a moot point. Whenever variable-output XR-E lights become widely available, you'll have the best of both worlds.

Re: Cree XR-E

Multi level lights are what I am talking about. The lights I have seen that are multi level and use the Cree are brighter at all those levels compared to their luxeon counterparts. Even the proposed P1D-CE is brighter at the lower level. Why? If you are using a low level, you want low. If not you go to med. My guess it's a cost saving if you use the same circuit. But why design it that way. The Ion is going to do this too.

Why wouldn't you turn down the juice to make a longer runtime?

For example, Don designed the A19 XR-E but ran it at 825. Why not run it at 700 or 600 and get a brighter light than a NG500 but with longer runtime. Since the current drive setup at 825 doesn't cross over into beating out my bright lights (ROP, M4)., it puts it in the med bright lights (U60, PD). In that category I don't need the extra brightness I need the runtime with a balance of brightness.


What do you think?


rob

Re: Cree XR-E

Two things:

The Cree is new, and it is BRIGHT. We are flashaholics, and we want bright and cutting edge. So ... in time we will see reason kick in and some long running lights will appear. I guess.

Then ... A lot of lights already meet our runtime requirements. A McLuxIII-PD has 90min on high and 42h on low ... pretty decent ... so an increase in brightness is an interesting solution for all those who do not need more than 90min on high but have to overcome urban light pollution. For example.

Both options - more brightness and more runtime - are nice to have. And both will be on the market.

bernie

I agree with member fleegs above, and think that for many of us, long run times are more important than
extra light output.
Before the Cree came out with the XR-E, I do not remember ever seeing any posts from users complaining about their 'pocket rockets' not being bright enough. However extra run time is something we will all take, thank you very much.

I think a good 'low' is just as important as a good 'high'. There is nothing worse than being blinded by the first level when awakening from sleep.

And I hope as new drivers come out , the designers keep this in mind.

Re: Cree XR-E

Kiessling said:

So ... in time we will see reason kick in and some long running lights will appear. I guess.

Click to expand...

Yes, I think we often overlook the need for good runtime using lower level light. We usually don't see the big significance of this untill we need it! I think we will see both multi level lights and some long running lights with lower output next year. More fun for everyone

fleegs said:

How come no one is using the Cree to create long running lights.
rob

Click to expand...

They heard your wish: http://candlepowerforums.com/vb/showthread.php?t=141841

I can certainly see your point. I currently EDC an HDS and I have my primary setting on 21 lumens, and that is about what I need about 75 percent of the time. The rest of the time I usually run at even less lumens, with the 60 lumen setting rarely seeing any action at all (more often than not just to show somebody).

This new fenix sounds pretty good, I would like it even more if it had a setting in the 20 to 30 lumen range, that is where it would be best for me.

I too would like to have the low level on the new Fenix Cree set at 20~25 lumen. I have a bunch of other lights for finding my way to the bathroon, map reading ect. As it is I would be forced to use 70 lumen to perform many tasks...so in the end I`ll get less runtime. I also wish it started out on low (25) then went up, 70, 135. This is how I would get the max run time in real world use.

Re: Cree XR-E

fleegs said:

My guess it's a cost saving if you use the same circuit. But why design it that way.

Click to expand...

Being the XR-E is so "new", I imagine it'll take a little while for the design of XR-E specific driver circuits to catch-up (and reflectors/optics, as far as that goes). It's currently easy enough to just drop an XR-E onto a Lux board, and wallow in the "wow".

But hold on... they're comin'!

I think there are a few reasons why we're concentrating more on brightness
than runtime right now with the XRE's

1) They are so new, that they are still very much a novelty and we're nearly
all excited about the dramatic increase in flux and want to see
evidence of it.

2) There are many led "evangelists" who are looking to persuade their
hotwire buddies that hotwires are fighting a losing battle in terms of
efficiency as leds get better and better. The XRE is another nail in the coffin
for hotwires and another huge filip for led enthusiasts.

3) The XREs available are not yet the highest bins. Its only once we have
seen the highest bins reach their full potential that we might start settling
down a bit and looking at the more practical point of view of longer runtimes



Having said that the imminent Titanium builds that Don will be producing DO
have 2 levels and the higher level is 520ma, so he is achieving a balance between runtime and output.

I started asking the same question last week. You can read the replies I got here : https://www.candlepowerforums.com/threads/141427

easilyled said:

3) The XREs available are not yet the highest bins.

Click to expand...

Could someone give a rundown on the XR-E bin order. I have seen P2, P3, P4, Q2 & Q3s mentioned. I assume Q is higher than P and 3 is higher than 2. Is that correct? P2 = lowest bin, Q3 highest? (at least that I have seen referenced)

Thanks,

David

Yes, you got it.

These numbers do not include lumen loss due to heating, and do not include losses due to the reflector or bezel lens, just the LED.

A CREE XR-E P2 bin, takes 350mA to produce 67.2-73.9 Lumens
A CREE XR-E P3 bin, takes 350mA to produce 73.9-80.6 Lumens
A CREE XR-E P4 bin, takes 350mA to produce 80.6-87.4 Lumens
A CREE XR-E Q2 bin, takes 350mA to produce 87.4-93.9 Lumens
A CREE XR-E Q3 bin, takes 350mA to produce 93.9-100.4 Lumens

The thermal resistance of the CREE is 8 C/W, so you will need to derate the lumen output accordingly. (lower C/W is better)


Now, the CREE XR-E is 162% brighter at 700mA, (my testing shows 182% with agressive heatsinking) but we will use their graph, so...

A CREE XR-E P2 bin, takes 700mA to produce 108.9-119.7 Lumens
A CREE XR-E P3 bin, takes 700mA to produce 119.7-130.6 Lumens
A CREE XR-E P4 bin, takes 700mA to produce 130.6-141.6 Lumens
A CREE XR-E Q2 bin, takes 700mA to produce 141.6-152.1 Lumens
A CREE XR-E Q3 bin, takes 700mA to produce 152.1-162.6 Lumens

Re: Cree XR-E

fleegs said:

........
For example, Don designed the A19 XR-E but ran it at 825. Why not run it at 700 or 600 and get a brighter light than a NG500 but with longer runtime. Since the current drive setup at 825 doesn't cross over into beating out my bright lights (ROP, M4)., it puts it in the med bright lights (U60, PD). In that category I don't need the extra brightness I need the runtime with a balance of brightness.


What do you think?


rob

Click to expand...

Rob,
I designed the A19 XR-E but I didn't make these assemblies or choose the drive level of the GD driver used in them. I agree with you that if all you need is a 40 lumen light for instance then drive a higher flux LED at a lower current and enjoy the double bonus of longer run times and greater efficacy..