LS 1W, Heat & 2AA Step-Up Current Regulators
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Charlie:
Longer lasting, longer running, and NiMH tolerant.
I'd like to believe that you were thinking of me and my heavy use of NiMH's (which you avoid like the plague) when you discussed Silviron's thermal runaway problems with his copper direct drive Luxeon driven by 3 @ 4/3 A NiMH's.
Your brightest LGI's appear to eat up alkalines in their initial 1/2 hour of run time (although they remain bright for two hours) and you're understandably hesitant to run NiMH's in them for fear of thermal runaway. I think you did me a favor.
(The cynical might speculate that your decision to keep the brighter of your babies was serendipidiously mutually beneficial.)
Longer lasting, longer running, and NiMH tolerant.
I'd like to believe that you were thinking of me and my heavy use of NiMH's (which you avoid like the plague) when you discussed Silviron's thermal runaway problems with his copper direct drive Luxeon driven by 3 @ 4/3 A NiMH's.
Your brightest LGI's appear to eat up alkalines in their initial 1/2 hour of run time (although they remain bright for two hours) and you're understandably hesitant to run NiMH's in them for fear of thermal runaway. I think you did me a favor.
(The cynical might speculate that your decision to keep the brighter of your babies was serendipidiously mutually beneficial.)
star882
Enlightened
Try IC based DC/DC convertors.
Craig, what is your idea?
Craig, what is your idea?
brightnorm
Flashaholic
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- Oct 13, 2001
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<font size="2" face="Verdana, Arial">lemlux,
Would you Please explain "forward voltage" (in layman's terms). Thanks
Brightnorm
Brightnorm:
I used the term "forward voltage" because it is listed in the various Luxeon spec sheets. I believe it simply means the voltage actually delivered to the Luxeon. The spec sheets suggest that the average white Luxeon wants to draw the following "forward current" at the following "forward voltages" at 25 degrees C:
fV fC
3.4 350
3.3 250
3.2 150
3.1 100
The spec sheets don't show how rapidly the forward current appetite of the Luxeon increases as voltage increases beyond 350 mA. The tolerance level for forward current decreases as temperature increases.
The spec sheet also says that individual white LS 1Watts can draw the recommended 350 mA forward current at forward voltages as low as 2.79 V and as high as 3.99 V.
A Luxeon that wants to draw 350 mA at 2.79 V will want to draw a potentially fatal current at 3.6 V. Alkaline AA's can't deliver much more than 900 mA for a short time at any voltage. 3 NiMH AA's can deliver 2000 mA or so at around 3.2 volts.
My guess is that my LGI's are drawing between 500 to 600 mA at 3.6 volts on NiMH's which is just where I'd like them to be.
I would also think that a Luxeon that wants to draw 350 mA at 2.79 V would work very attractively with 2 AA lithiums. Without good heat sinking a luxeon at this end of the spectrum might get in trouble with 2 new luxeons.
Whatever I've said that is correct supports circuit designs that control current. It also supports my contention that I'm well served having the relatively dim LGI's.
I used the term "forward voltage" because it is listed in the various Luxeon spec sheets. I believe it simply means the voltage actually delivered to the Luxeon. The spec sheets suggest that the average white Luxeon wants to draw the following "forward current" at the following "forward voltages" at 25 degrees C:
fV fC
3.4 350
3.3 250
3.2 150
3.1 100
The spec sheets don't show how rapidly the forward current appetite of the Luxeon increases as voltage increases beyond 350 mA. The tolerance level for forward current decreases as temperature increases.
The spec sheet also says that individual white LS 1Watts can draw the recommended 350 mA forward current at forward voltages as low as 2.79 V and as high as 3.99 V.
A Luxeon that wants to draw 350 mA at 2.79 V will want to draw a potentially fatal current at 3.6 V. Alkaline AA's can't deliver much more than 900 mA for a short time at any voltage. 3 NiMH AA's can deliver 2000 mA or so at around 3.2 volts.
My guess is that my LGI's are drawing between 500 to 600 mA at 3.6 volts on NiMH's which is just where I'd like them to be.
I would also think that a Luxeon that wants to draw 350 mA at 2.79 V would work very attractively with 2 AA lithiums. Without good heat sinking a luxeon at this end of the spectrum might get in trouble with 2 new luxeons.
Whatever I've said that is correct supports circuit designs that control current. It also supports my contention that I'm well served having the relatively dim LGI's.
I think you have a few of my efficiency numbers wrong.
I state on my web site that Badboy is:
typical 85% efficient and drops in efficiency around 2V and below. At 2V the efficiency is down to 72%.
For a 2AA setup, most energy is gone when the two batteries drop to 2V. So, my converters start very high and drop slowely in efficiency as the battery demand goes up and battery voltage goes down.
If you look at Badboy output regulation is held to within +/- 1mA of load current over the complete regulation period.
If you really want high efficieny, try a Madmax 1675 which starts at 94% and drops down to 78% at the low end (1.2V).
I don't think you can get more efficient than direct drive, but, my converters come pretty darn close.
-Wayne
I state on my web site that Badboy is:
typical 85% efficient and drops in efficiency around 2V and below. At 2V the efficiency is down to 72%.
For a 2AA setup, most energy is gone when the two batteries drop to 2V. So, my converters start very high and drop slowely in efficiency as the battery demand goes up and battery voltage goes down.
If you look at Badboy output regulation is held to within +/- 1mA of load current over the complete regulation period.
If you really want high efficieny, try a Madmax 1675 which starts at 94% and drops down to 78% at the low end (1.2V).
I don't think you can get more efficient than direct drive, but, my converters come pretty darn close.
-Wayne
I have two of Mr. Bulk's dimmer LGI's. They are about 80% as bright as his brightest on new alkalines. This appears to be a blessing in disguise as I suspect that it means that they are at the higher forward voltage end of the spectrum.
These two LGI's never get very warm on new alkaline batteries and don't seem to get any warmer with 3 AA 1800 mAh NiMHs. (The blessing in disguise is that I don't suffer thermal runaway with NiMHs.) Nonetheless, both battery loads deliver a brighter, whiter beam than either my 416 mA BadBoy yellow or my 500 mA ARC LSS. The BadBoy Yellow seems to get a little warmer than the LGI, and the hand warming capabilities of the 500 mA ARC LSS have become legend over the past week.
I noted that Dat2Zip has stated that the Badboy is (edit) 85% efficient on fresh batteries and 72% efficient on run down batteries. I assume that the circuit he designed for the ARC Hybrid has similar efficiency. It would appear that the (edit) 15% to 28% lost energy is dissipated in heat. Those 3AA direct drive units with forward voltages high enough to avoid thermal runaway should enjoy long lives and runtimes.
I tried the LGI with 2 lithium cells and a dummy and found it not only much dimmer than the other lights mentioned, but also considerably dimmer than a jBechtoe 4 Nichia 6400 cluster in a PR base designed for 4.5 to 4.8 V when driven with 4 @ AA alkaline cells run down to 4.9 V. This supports my deductive logic that these two LGI Luxeons have relatively high forward voltages. It also disinclines me to get a CMG Reactor or an Inretech drop in for 2AA lights unless/until the manufacturers are able to reliably source Luxeons with below average forward voltage requirements. I'd rather spend the extra money on 500 mA BadBoy Green's when they're available.
These two LGI's never get very warm on new alkaline batteries and don't seem to get any warmer with 3 AA 1800 mAh NiMHs. (The blessing in disguise is that I don't suffer thermal runaway with NiMHs.) Nonetheless, both battery loads deliver a brighter, whiter beam than either my 416 mA BadBoy yellow or my 500 mA ARC LSS. The BadBoy Yellow seems to get a little warmer than the LGI, and the hand warming capabilities of the 500 mA ARC LSS have become legend over the past week.
I noted that Dat2Zip has stated that the Badboy is (edit) 85% efficient on fresh batteries and 72% efficient on run down batteries. I assume that the circuit he designed for the ARC Hybrid has similar efficiency. It would appear that the (edit) 15% to 28% lost energy is dissipated in heat. Those 3AA direct drive units with forward voltages high enough to avoid thermal runaway should enjoy long lives and runtimes.
I tried the LGI with 2 lithium cells and a dummy and found it not only much dimmer than the other lights mentioned, but also considerably dimmer than a jBechtoe 4 Nichia 6400 cluster in a PR base designed for 4.5 to 4.8 V when driven with 4 @ AA alkaline cells run down to 4.9 V. This supports my deductive logic that these two LGI Luxeons have relatively high forward voltages. It also disinclines me to get a CMG Reactor or an Inretech drop in for 2AA lights unless/until the manufacturers are able to reliably source Luxeons with below average forward voltage requirements. I'd rather spend the extra money on 500 mA BadBoy Green's when they're available.
Wayne:
I've edited the 85% correction to my earlier post.
My preference is for the BB constant output rather than the MM longer run and higher initial brightness.
BTW, my BB does display a perceptible slow fade at the end of the NiMH charge. I was under the impression that it would drop off a cliff. I wonder if Charlie sold me his MM thinking it was a BB Yellow.
I remain comfortable in my assertion that I'd rather pay $37.50 @ for your BB Greens than $20 for an un-selected 1W LS drop-in running 2@ AA lithium 1.5V cells.
As I continue to play with these lights I've loaded 2@ NiMHs and 1 @ lithium AA in one of my LGI's. Brightness improves as expected and heat output (as measured by my cheek) remains below that of the BB Yellow and the ARC 500 mA LS.
I've edited the 85% correction to my earlier post.
My preference is for the BB constant output rather than the MM longer run and higher initial brightness.
BTW, my BB does display a perceptible slow fade at the end of the NiMH charge. I was under the impression that it would drop off a cliff. I wonder if Charlie sold me his MM thinking it was a BB Yellow.
I remain comfortable in my assertion that I'd rather pay $37.50 @ for your BB Greens than $20 for an un-selected 1W LS drop-in running 2@ AA lithium 1.5V cells.
As I continue to play with these lights I've loaded 2@ NiMHs and 1 @ lithium AA in one of my LGI's. Brightness improves as expected and heat output (as measured by my cheek) remains below that of the BB Yellow and the ARC 500 mA LS.
carbonsparky
Enlightened
Would you Please explain "forward voltage" (in layman's terms). Thanks
Brightnorm[/QB][/QUOTE]
When you apply power to a semiconductor(in this case the LED) the semiconductor will have a voltage drop across it(forward voltage drop) that stays somewhat the same no matter how much current(with in reason) you push through it. This voltage drop can be measured by measuring the voltage on the led. With leds you must limit the current to a safe level by dropping any extra voltage(voltage above the forward voltage of the led) in a resistor or another semiconductor. The sum of the voltages in a circuit must equal the supply voltage. Some of the smaller led lights (photon 2) drop the extra voltage by actually loading the batteries down enough to get the correct voltage and current.
Brightnorm[/QB][/QUOTE]
When you apply power to a semiconductor(in this case the LED) the semiconductor will have a voltage drop across it(forward voltage drop) that stays somewhat the same no matter how much current(with in reason) you push through it. This voltage drop can be measured by measuring the voltage on the led. With leds you must limit the current to a safe level by dropping any extra voltage(voltage above the forward voltage of the led) in a resistor or another semiconductor. The sum of the voltages in a circuit must equal the supply voltage. Some of the smaller led lights (photon 2) drop the extra voltage by actually loading the batteries down enough to get the correct voltage and current.
