Current setting for LS3 driver board ?

Does anyone remember the current the LS3s was set for ?

Was anything else besides the emitter different to a LS2 ?

TIA

Klaus

the current is set to 330 ma (.15 ohm resistor) and the only difference from the LS2 board that i can see (i have taken mine apart) is the emiter.

Hence that's why it was referred to as "underdriven at 2.5 watts"

Thx all

LOL @ Chris - Except yours /ubbthreads/images/graemlins/grin.gif How would you set it now given all that you/we learned about the LT1618 lately - again at 667ma or lower ? Any recommendations / suggestions for a 17670 LiIon / 5W LS setup ?

Klaus

I have a home-made LS3 that I made around the time the real LS3 came out biased at 667mA. I didn't have rechargeable Li-Ions then but now that I do it does work quite well. I would probably not go much above that on 17670's, maybe 750mA tops if you want it to stay in regulation for a decent amount of time.

CM

Thanks Chris,

I was even expecting you to propose a lower setting due to the recent posts re 123 power draw and such including your Spice simulation of the LT1618 - I´ll probably crosspost in that thread and ask Doug to chim in - maybe you could do a similar simulation than you did for the 123 setup ? My gut feeling is that probably the LT1618 with one Li-Ion driving a 5W LS might have a lower sense-making treshhold even than 700ma. Sense-making defined as a good compromise between energy usage and brightness.

Klaus

[ QUOTE ]
Klaus said:
Thanks Chris,

I was even expecting you to propose a lower setting due to the recent posts re 123 power draw and such including your Spice simulation of the LT1618 - I´ll probably crosspost in that thread and ask Doug to chim in - maybe you could do a similar simulation than you did for the 123 setup ? My gut feeling is that probably the LT1618 with one Li-Ion driving a 5W LS might have a lower sense-making treshhold even than 700ma. Sense-making defined as a good compromise between energy usage and brightness.

Klaus


[/ QUOTE ]

Klaus, your gut and mine have the same feeling. Furthermore, I don't see a 1X123 successfully driving a 5W at 667mA and being in regulation even from the start.

Thx Doug for chimming in - but doesn´t the use of a single Li-Ion change the picture a little ? It should be able to provide higher currents at less voltage drop and therefore be not as challenging to the chips input current limits ? I´m just **speculating** here though and you and Chris will hopefully set me straight.

Let me make my sometimes confused writing a bit clearer - you and Chris discussed the 1/3W LS ~ LT1618 ~ 123cell setup quite nicely in the other thread - now my **new** follow-up question is about a 5W LS ~ LT1618 ~ Li-Ion.

I would hope that using the same methods you both had been demonstrating there and which I obviously lack you could come up with some proposal for a good compromise current setting where the chip still runs in some **happy** mode and doesn´t get taxed beyond the sense-making boundaries.

Thanks again

Klaus

Klaus, for your proposed setup, I would think that 500mA would be a good "sense making" balance.

Thx Doug,

one more question though - would I **guestimate** somewhat correctly that using one LiIon vs 2x123 should give not too different results as the higher voltage of the 2 123 cells will get dragged down to a not much higher level than the single Li-Ion while the Li-Ion will still be able to supply higher currents without as much drop ?

Interestingly the KL4 circuit will run at the same brightness level with both setups while drawing approx 50% more current from the LiIon - I´m not so sure about the LS3 / LT1618 setup due to the drivers input current limitations and it might make more sense to use 2 123s though - even when the use of rechargeable Li-Ions is very tempting for a DIY LS3 for me too.

BTW - I think I´ll go with that 500ma setup then and hopefully I´ll find a LS which is nice and white at this drive level.

Klaus