Surefire L1 (Cree) runtime ?

LEDBE
Chao's L1 runtime graph is the Surefire L1 Cree. Has there been a change in Surefire L1 Cree?

Bill
 
Just in case anyone was interested in the charts:

Thanks Chao :thanks:

Chao said:
Got them today :twothumbs, new Cree L1 is just a little bit longer than E1L, the new TIR optics is very cool, produces round hot spot and useful sidespill.


...7/12 updated..........................
L1 runtime-high level
2007L1runtime.jpg


...7/14 updated..........................
L1 runtime-low level
2007L1runtime-low.jpg
Click to expand...
 
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Chao's runtime graph on high mode will have more meaning when we find out what the approximate lumens are on high. We know that the approximate mA drain from the battery is 660mA's or so......As I am writing this it does seem that the L1 Cree should have a flatter runtime in regulation. The circuit is no doubt a boost circuit with maybe 500mA's or less to the led, not a difficult load for the circuit to produce with the mild mA drain from the SF CR123. Maybe we should ask Chao to repeat his runtime test?

Bill
 
The runtime graph looks even nicer! Cool :cool:
Looks like a very nice site there ... and good beamshots. Saved to HD :D
bernie
 
Bullzeyebill said:
Chao's runtime graph on high mode will have more meaning when we find out what the approximate lumens are on high. We know that the approximate mA drain from the battery is 660mA's or so......As I am writing this it does seem that the L1 Cree should have a flatter runtime in regulation. The circuit is no doubt a boost circuit with maybe 500mA's or less to the led, not a difficult load for the circuit to produce with the mild mA drain from the SF CR123. Maybe we should ask Chao to repeat his runtime test?

Bill
Click to expand...

So why do you think the L1 doesn't have a flat regulation curve?

It seems its possible based on other lights and this is confirmed by the current. I've seen graphs of 2 cell Surefire lights and its pretty flat (u2).

I've read that if you supply an LED with a constant current the light output shouldn't vary with heat, its the Vf of the LED that varies with heat. So is the driver not a constant current driver?

I just thought of one reason, maybe Surefire's regulation strategy includes how it falls out of regulation, like they don't want to have drastic changes in brightness so they want to knee of the curve to gradually curve off.

I'm not an expert on regulation or buck boosts so I wondered if someone had insight on why surefire chooses not to have a flat runtime curve for this light, (or possibly any other 1 c2123 light).

If the low is a digitally controlled circuit then why that first initial drop off in the first minute or so. I assume that will happen every time to activate low after the light has been sitting for a while. Kind of like flashing unregulated incandescent lights where it is really bright for the first second of so on depleted batteries. This seems more a design flaw because its a big change in brightness at first and is not good when you want to maintain your night vision.

Considering the cost of the light and Surefire's attention to detail in construction and operation that is easily seen from a mechanical perspective of their lights, I can only assume that the runtime curve is intentional. Does anybody have any guesses about why?

~CPEng
 
I have never noticed a brighter flash when turning my L1 on low. If it's there it's just not enough for the brain to register (or at least my slow brain). Now if you want to see a startup flash you should see my Fenix L2Dce.

Geoff
 
~CPEng, not sure why runtime graph is not flatter. The L1 does run a constant current regulated boost circuit. The current at tailcap is about 640 or so mA's with fresh CR123, increasing over time. Inefficient circuit? Poor heatsinking. Heat will cause a drop in output. Prior L1's only ran about 350mA's or so to the LED. Maybe design specs were not changed for boost in current that new Cree L1 got, except that isn't really true because they did change the orientation of the regulator in the body. Maybe regulator is too close to battery. We do know that the L2 on high (lux V) has a terrible discharge curve. Some of the newer E series LED lights now have a regulated low that is driven by a constant current regulator, while the L1 has a resistorized low. Maybe resistance at tailcap of L1 is a problem. I am really shooting in the dark here.

Bill
 
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Flying Turtle said:
I have never noticed a brighter flash when turning my L1 on low. If it's there it's just not enough for the brain to register (or at least my slow brain). Now if you want to see a startup flash you should see my Fenix L2Dce.

Geoff
Click to expand...

Yeah I guess what I meant is the light will drop 20% soon after you turn it on on low. I don't have an L1 so I'm just going by whats on the curve. But to think about it a 20% drop in output is hard to see. From a practical perspective I guess its not important but from an engineering perspective looks like there could be improvement.

Thanks to answers from BBill I guess it still has the resistor in the tail cap which makes sense because I only saw one contact from the tail cap to the body. So unless it sends a signal to the electronics embedded in the main power supply signal the only thing it can do is resist the power supply with a resistor.

Just writing this made think that maybe the L1 circuit is designed to run partially regulated on low with that resistor which adds that extra design criteria not easily seen by individual runtime graphs but rather looking at the system as whole. So maybe a flat runtime on high was compromised to make the low circuit with a resistor run partially regulated. Just a thought, have no data to back it up though.

Does the L2 have a resistor in the tail cap as well? I assume it does because after looking at pics it doesn't seem to have two contacts between switch and body. On flashlight reviews he tests L2 (06 version). The regulation on high looks alright, flat until drop off. The low looks a lot like the L1. So if they share the switch design I can see it making sense why the low has that initial drop off.

Sorry for the long post. Just curious.

~CPEng
 
Seems similar to this as well.
Only difference is Chao's used SF123 cell while light-reviews.com used Energizer CR123 cell.

runtime_high.gif
 
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