Maximum sustained current for LSH-P?

[djpark]

I managed to get the LSH-P head and changed the optic to fraen. Now I wish to increase the current to led for brighter output.

What is the maximum current which can be fed to lsh-p safely? I mean about 30 minutes without shutting down, not just for 5 minutes.

I am looking for the advice from the experts or those who have experience.

Thank you in advance.

-- DJP

 

[LitFuse]

I don't know about the maximum safety wise, but you won't see much (if any) benefit in going over something in the mid 600's. I usually add a second .15 resistor to set mine at 667. Anything more increases the heat and lessens runtime without providing much increase in output. If you go higher, it will be brighter, but onlf for the first few minutes.


Peter

 

[Deleted member 684]

I've modified a Arc LSH-P to run at around 600++ ma and it ran for less than 1 hour before dropping out of regulation. I would say it's around 30 mins of "Sun mode" and another 30 mins of "Late afternoon sun mode" before plunging into "moon mode"

Did I mention that it got really really hot to hold?

 

[stefx]

On my LSL i tried to add a second resistor in parallel and i even bridged the resistor completely: No increase in light output. I even swapped LEDs. It seems as if my LSL is already at maximum and out of regulation with the stock resistor.

Stefan.

 

[LEDSmith]

Change your LED to a Lux III, place 3 x .15 ohms resistors in parallel and you have a super bright, long throw destroyer! Sucker gets hot and burns through the batteries but life is short and you've got to push the limits.

Why play it conservative? Unless you go for the gold, you will just get tired of your low output configuration and want to squeeze more light out of it in the future.

 

[jpeg]

I thought added resistance would dampen the circuit, not make it brighter. What's the theory here?

 

[LEDSmith]

Resistors configured in parrallel, reduces the effective resistance.

 

[shiftd]

i believe the sense resistor everyone talking about is the one that limit the current (or determine it). The original circuit uses .15 ohm to drive the led at about 343 mA current. So if you put another resistor in paralel, it will increase the current no matter what (up to certain limit, of course). So if you put another .15 ohm in paralel, the current should be doubled. However, being semiconductor they are, luxeons does not doubled its light output for every doubling in the current input, more like less than double, about 1.5 times. So there is a trade off there.
Also, if you drive your lux really hard, it will be a toaster there in your LS head that will definately make your lux grow old FASTer. How much faster? that will depend on how much hotter your LS gets.

 

[jpeg]

Who'da thunk...

Thanks LEDSmith... /ubbthreads/images/graemlins/smile.gif

 

[LEDSmith]

The beauty of lux III's is that they are relatively cheap. If it burn's out then I will replace. So far, I have burned through 20 batteries without a noticeable decrease in output. You just have to know when to turn it off.

Once you initially break the factory seal on an Arc, dis-assembly for additional modification is easy.

 

[Wisti]

LEDSmith , why don´t you use one 5 ohm resistor
instead of 3 15ers ?

 

[shiftd]

Wisti, those resistors are more like .15 ohms,instead of 15 ohms. I don't think there is any .05 ohms out there. /ubbthreads/images/graemlins/icon3.gif

Ledsmith, yea i agree with you. Lux3 are relatively cheap and they generally have a good performance. But it would be wasteful to burn them to death. So yea, you have to know when to turn it off.

 

[Wisti]

Thank you , shiftd !
I didn´t see the point .
In Germany we write it 0,15 Ohm .

 

[shiftd]

same thing with asians. /ubbthreads/images/graemlins/grin.gif
it is called zero comma one five there
but here, it is more like zero point one five

because most cpfer are Americans, better learn to accustom yourself to this different notation /ubbthreads/images/graemlins/grin.gif

 

[Wisti]

It´s not the point instead of comma but the missing zero !

 

[bhds]

Interesting thread. I have a question along the same lines. I modded 2 arcs with fraen lenses and TWAKS. One I added a .12 ohm resistor for a calculated current of 750ma and the other I left running the stock current. The one running 750ma seemed to be pretty bright initially and runs very hot. When compared to the arc running the stock current there is almost no discernible difference in perceived light output. Tried it in all sorts of different situations and the only way I can tell the difference between the two is in the heat /ubbthreads/images/graemlins/confused.gif Can anyone explain what I'm seeing? (or not seeing)

 

[THE_dAY]

bhds, i have seen similar results with 667mA and stock 333mA Arcs. i had two modded with TWAK at 667mA and one with R3J at stock 333mA. the R3J had very similar output to one of the TWAK mods but the other TWAK mod was slightly brighter but i think it was due to a good LED. doubling the current on the Arcs does barely anything IMHO. i think the big difference comes through with good LEDs.

 

[djpark]

It is interesting indeed.

I just added 0.18 ohm register to R15 and the calculated current is 611mA with the original LED.

Since I have only one LSH, I can't compare the original and modded one. At first look, it sure looks brighter. However, I don't really see a lot more light than the original.

The tint of LSH-P Luxeon is warm and it can look almost green if I compare with 8mm white. I might change it to Lux-3W.

-- dj