Hi guys,
I suppose I did this mod primarily because it "was there". After doing the L1-PRT's where I would add an aditional 123 cell and go from the stock boost circuit to a Yamaguchi step down circuit (down boy) which seems to be more "friendly" to the two stage resistor switch system, I was curious how the L2 would behave in a similar set up. Although the resistor two stage switch works well with a boost circuit, there are some short comings both in terms of efficiency as well as function near the batteries end of life. Folks who have used their L1's have seen this.
The L2 addressed this issue by breaking new ground and including circuitry that regulates the low level output as well as the high level, both in boost configurations. From a run time graph that Craig just provided, I think it's clear that a good regulation of the low level output has been achieved with the L2's driver. I would also expect better repeatability across the diverse population of Luxeons given a current regulating circuit like the L2 has. The L2 is cool!
Well on to the mod..
Since I removed the circuit from the battery tube, I needed to put the DownBoy in the head. I used the same format of modified PR head and modified E-can that I have used in the L1-PR(T) mods but I used a 5W LED in this case instead of a Lux III. The larger diameter reflector of the PR both tightens up on the reflected beam as well as opens up the angle on the spill beam. Whether this is an advantage or disadvantage is purely up to the user's preference. I like them both. The PR does enhance the throw of the 5W at the expense of the "wall" of light from the stock L2 (KL4 style) reflector.
My primary interest was in comparing the output over time of the resistored step down system VS the fully regulated boost system.
Since my mod contains 3x123, the length of the run times would be expected to be greater than that of the stock L2 2x123. I set the current level of high on my mod at 750 mA and later I determined that the L2 is at 800 mA. I did a Lux-Run on the mod on both High and Low output:
Although the low level is not regulated, the 30 ohm resistance was enough to drop the Vin below Vf of the LED and in the case of the Down Boy, once this occurs, the LED is in direct drive with little baggage, if any, added by the converter. Since the Lithium batteries have a reasonably flat discharge rate, the Lux-Run has a very reasonable curve to it, IMHO. In comparing these run times to those posted on the stock L2, I think a resistored two stage on step down circuit fairs reasonably well. Had I stayed with 2x123 and used a BadBoy with the 5W and a resistored two stage, I believe the superiority of the L2's dual current regulation circuit would be seen.
I offer this information with no implied conclusions to be reached; merely more information to mull over. /ubbthreads/images/graemlins/nana.gif
I suppose I did this mod primarily because it "was there". After doing the L1-PRT's where I would add an aditional 123 cell and go from the stock boost circuit to a Yamaguchi step down circuit (down boy) which seems to be more "friendly" to the two stage resistor switch system, I was curious how the L2 would behave in a similar set up. Although the resistor two stage switch works well with a boost circuit, there are some short comings both in terms of efficiency as well as function near the batteries end of life. Folks who have used their L1's have seen this.
The L2 addressed this issue by breaking new ground and including circuitry that regulates the low level output as well as the high level, both in boost configurations. From a run time graph that Craig just provided, I think it's clear that a good regulation of the low level output has been achieved with the L2's driver. I would also expect better repeatability across the diverse population of Luxeons given a current regulating circuit like the L2 has. The L2 is cool!
Well on to the mod..
Since I removed the circuit from the battery tube, I needed to put the DownBoy in the head. I used the same format of modified PR head and modified E-can that I have used in the L1-PR(T) mods but I used a 5W LED in this case instead of a Lux III. The larger diameter reflector of the PR both tightens up on the reflected beam as well as opens up the angle on the spill beam. Whether this is an advantage or disadvantage is purely up to the user's preference. I like them both. The PR does enhance the throw of the 5W at the expense of the "wall" of light from the stock L2 (KL4 style) reflector.
My primary interest was in comparing the output over time of the resistored step down system VS the fully regulated boost system.
Since my mod contains 3x123, the length of the run times would be expected to be greater than that of the stock L2 2x123. I set the current level of high on my mod at 750 mA and later I determined that the L2 is at 800 mA. I did a Lux-Run on the mod on both High and Low output:
Although the low level is not regulated, the 30 ohm resistance was enough to drop the Vin below Vf of the LED and in the case of the Down Boy, once this occurs, the LED is in direct drive with little baggage, if any, added by the converter. Since the Lithium batteries have a reasonably flat discharge rate, the Lux-Run has a very reasonable curve to it, IMHO. In comparing these run times to those posted on the stock L2, I think a resistored two stage on step down circuit fairs reasonably well. Had I stayed with 2x123 and used a BadBoy with the 5W and a resistored two stage, I believe the superiority of the L2's dual current regulation circuit would be seen.
I offer this information with no implied conclusions to be reached; merely more information to mull over. /ubbthreads/images/graemlins/nana.gif
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