Surefire 6P White Luxeon Module.

[vcal]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Go, Go Gadget Flashlight:

The runtime tests I have done are with 2 AA batts, and they aren't too bad. NiMhs were even better than alkalines (high current demand). Both run just about an hour at constant brightness (350 - 400 mA).
<HR></BLOCKQUOTE>

Was that an LS operating on 3 NimH cells?

 

[Go Go Gadget Flashlight]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by napalm-2002:
dont lose faith guys he'll figure it out and i hope it will use both batts!<HR></BLOCKQUOTE>

Thanks for the vote of confidence. However....

I took a long hard look at the step-down circuit and I couldn't figure any way to fit it in the 6P. Sorry guys.

On the other hand, GlowBug's request for the AA version (3v) had the side benefit of inspiring me to try the Luxeon/LM2621 combo with a single 123 and "dummy" 123. Works great!

Here's a beam shot of the original P60 bulb and the Lux2621 module (running on one 123).

And here's the module itself. White Luxeon, LM2621 step-up, and heatsink all fit in place of the stock Surefire lamp/reflector assembly.

Here's all the parts that GlowBug will get to run on 2-AA's or a single 123.

The module draws 0.7A while the original P60 draws 1.05A. My module should run about 1.5 times as long as the P60. And, at constant brightness. The step-up does a great job of maintaining voltage all the way down to about 1.6v input from the 123.
Current to the Luxeon ranges from 360 to 440 ma until the battery starts to die. The 6P body does an excellent job of heatsinking, keeping the Luxeon happy the whole time.

The Luxeon is rated at 18 lumens (I think) and the P60 at 65. So, obviously, it's not as bright, but it is LED white, nearly indestructable, and constant brightness.

 

[BKO]

Very cool!!
I`ve got an old SF 3p thats just begging for one of those!

How much do you want for one?

Bill

 

[Brock]

I was just going to say, hey then I could get out my old 3P and just put it in there

You know it sounds like you made a Arc LS, single 123 and the Luxeon Star, but in a Surefire case. Hummmmm..... I like the sounds of it. Are you going to sell them?

 

[Go Go Gadget Flashlight]

I was thinking the same thing myself. I also wondered how different the E1 and E2 are in the size of the lamp assemblies. Anybody have an Executive and a 6P or 3P to compare it to?

I may sell them, but I dread the price. I don't know what the best price for the Luxeon's will be.
Assuming $14 +Ship for the Luxeon, $20 for the step-up, $2 for misc parts, and about 4 to 6 hours to build one adds up quick!

Not to mention, I'm currently behind on my commissioned jobs.

I'm working on a Nichia 6P bulb and a DB-Nichia for two of our members. It'll be at least a week before I can think about any other "jobs".

 

[JoeyL]

Hi Gadget!

I'm not sure what dimensions you're asking for. The E1 and E2 have the lamp only, while the 6P/R have the lamp and reflector as a unit. I have both, so tell me what dimensions you need.

I went ahead and fit a Luxeon LS into the head of an E1, but with no step-up or voltage regulator. (there just isn't room).
This was a tough project, because I drilled out the stock reflector which is solid metal.
Also, I had to play around with the dimensions of the remaining circuit board to get it past the internal threads of the bezel while being able to rest it on the lip of the reflector remaining, and still contact the body of the battery holder for a heat sink.

The performance is probably nothing like the unit you made for the 6P. But, it lasts over 6 hours on a single 123. The first hour drops slowly from 310 ma down to 180 ma but stays at 160 for 4 more hours. It is still much brighter than the E2 nichia conversion with new batteries.

Also, it's nice and small and the E1 body has a good switch already. I'm pretty happy with it.

I still would like to put in an order for one of your units, though.

 

[Harrkev]

For LED use, how does one control a boost regulator???

When I did a search, most parts (those from Linear and Maxim) seem to want to control the output voltage. However, for and LED, this worries me. If you are not careful, you get thermal runaway.

It always seemed more useful to control the output CURRENT through the diode. However, there are precious few chips that can handle this. One chip that I saw that was made for white LEDs was from Maxim. However, this chip was intended for backlighting uses (PDA, cell phone, etc.). Therefore, this chip required both a Vcc (battery) supply, and a separate logic supply (3.3V or 5V) in order to control the thing. I do not know if it would work without this supply.

Do voltage-mode supplies work OK?
Has anybody tried a current-mode supply?

 

[php_44]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Harrkev:
For LED use, how does one control a boost regulator???
.....
Do voltage-mode supplies work OK?
Has anybody tried a current-mode supply?<HR></BLOCKQUOTE>

You are correct that a boost regulator chip that regulated current would be more useful than one regulating voltage. However, I've built a couple of boost supplies that were voltage regulated and they work well. I simply look at the LED voltage curve (either from a data sheet, or by actually testing a LED), and set the regulator 0.5 to 0.7V higher than the LED voltage. Then choose a LED current - say 50mA, and use a small resistor (0.5v/.05A)=10ohms resistor to limit the current through the LED.



The method boost convetrors regulate voltage is to compare some fraction of the output voltage (set with a two resistor voltage divider) to an internal reference voltage (typically 0.3 to 1.5V) and keep the two equal. The Maxim ICs which were made for LED backlight use have a small (0.3V)reference voltage and regulate by comparing the voltage developed across a small current sensing resistor in series with the LED. Again say (0.03A)*(10 ohms)=0.3V. You can do the same with ANY boost regulator IC - but for most you loose efficiency because their internal reference voltage is more like 1.5V. So (0.03A)*(50ohms)=1.5V. But now probably 1/3 of your battery energy is going into the 50ohm resistor, instead of just a few percent with an IC using a low ref voltage. If you choose a very high boost voltage and string 6-8 LEDs in series - even a 1.5V reference begins to become efficient.

 

[Go Go Gadget Flashlight]

JoeyL,

I'm not all that familiar with the E-series. I've seen pics, but no details of the head.

I remember Brad's LED bulb for the E2 and how it is like a pancake with a bulb sticking up.

Is the reflector of the E1 removable?

If you (or someone else) could take some pics looking into the bezel and looking into the body, I could get a better idea of what might fit.

If the black round part of the Luxeon won't fit in there, then I won't be able to make a module for it....

 

[BKO]

Gadget,forget about the SF "E" series LS retro-fit--The E1/E2 SF lights have an integated bezel and reflector--one piece..

SF "E" dimensions.
ID at threads--.76in-bezel to-body.
ID of bezel--.85in..

The SF "P" series LS mod is definatly the way to go IMO.

-----------------------------------------------Bill--

 

[PeLu]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by php_44:

You are correct that a boost regulator chip that regulated current would be more useful than one regulating voltage.
<HR></BLOCKQUOTE>

It seems to me that most (regulated) LED light manufacturers start with constant voltage and when they develop advanced models they go over to constnt current. With Nichia LEDs their relatively high dynamic resistance helps, and in your case you even add some resistance.
With LEDs with lower dynamic resistance (like the Luxeon) it's not that easy, when you want to avoid a serial resistor.

And sensing volatge may be as low as 0.05V, of course needing some more effort.
Using LEDs in series looks better at a first glance, but has several drawbacks:
It is even more complicated to heatsink them and to keep them at the same temperature.
(talking about 5mm LEDs)

 

[Harrkev]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by php_44:

but for most you loose efficiency because their internal reference voltage is more like 1.5V.
<HR></BLOCKQUOTE>

Yup. What I was thinking was running a rail-to-rail op-amp directly off of the battery supply. Then, I could use a small precision (1 or 2 ohm) current-sense resistor. The op-amp could amplify this small voltage to use as feedback for the regulator. The problem with this is that the input voltage to the op-amp would be right at one of the rails. I am not sure if it could handle it. I also don't know is if this would be more efficient than using a voltage-mode regulator.

Do most commercial light regulate the voltage or current?

Any comments?

 

[JoeyL]

Hello,

Yes the reflector in the E series is solid metal and very well imbedded into the bezel case. No way to get the lens out either. It appears glued in.

Gadget, I can't get photos onto the website now, but I could e-mail to you if interested.

Instead of making the hole in th bezel bigger, the alternative is to take off the lens, which looks like a truncated cone, remove the black cylindrical plastic lens holder, and epoxy the lens directly to the LED and circuit board. Then you can trim the lens down to the required size. My problem was trying to keep the lens well rounded.

This cuts down on light output slightly, but it seems minimal.

Sooo, if you still want to try it out, it can work. An E2 could have enough room for the regulator with a single 123. The E1 could be a real challenge.

 

[php_44]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Harrkev:
I was thinking was running a rail-to-rail op-amp...1-2 ohm sense resistor...<HR></BLOCKQUOTE>



If you were using a Luxeon unit and running it at around 300mA - you could directly use a 1 ohm sense resistor with some of the Maxim boost IC's supporting a 0.3V reference. If you were looking at a few Nichia discrete LED's then amplifying the voltage produced by a 1 ohm current sense would be great. You'd only need a gain of 10-50 depending on the boost chip you used.



Most cheap commercial lights I've seen have no boost circuit, or one that runs "open loop" with a circuit tweaked to not overload the LED with fresh batteries.



There's some expensive commercial lights that use current feedback. I saw one that sort of cheated by sensing the current through an amber LED with lower voltage drop than the array of white - thus affording the use of a larger sense resistor to get a corresponding larger sense voltage - while the total voltage drop of the resistor plus the amber LED was equal to the drop of the parallel connected white LEDs. I think a lot of commercial lights use voltage feedback - it's less complicated though not optimal.

 

[Go Go Gadget Flashlight]

Thanks guys for the info on the E-series lights.

Looks like way too much work as I have minimized the module as much as possible already (for my skills anyway).

 

[PeLu]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Harrkev:
Do most commercial light regulate the voltage or current?<HR></BLOCKQUOTE>

Almost nobody does mention that, but the few I know about started with regulated voltage. ActionLight V2 will have regulated current.

 

[bikeNomad]

This is my first post here, so: greetings!



I've been looking at doing a LED design for bike lighting for some time, but am also interested in flashlights.



I'm puzzled as to why people here seem to only discuss (unless I've missed it) step-up (boost), step-down (buck), and SEPIC switching regulators when there's an obvious solution for step up/down usage that's compatible with existing IC parts:
The inverting regulator! Since we don't have to have a common positive ground, we can look at battery minus as a negative supply and produce a positive output (referred to battery positive). This is exactly the same as a step-up but the output capacitor is referred to battery positive (and of course the output is taken across the output capacitor).


You'll have to voltage-shift the sense voltage, of course, but this can be done with a single-op amp and four resistors (which can also give you the gain you need to make a voltage regulator into a proper current regulator).


Given that there's some great step-up chips with power FETs on-chip, and that this circuit only requires a single inductor (vs. the SEPIC's double inductor, or flyback's transformer), why not use it?


(And I would definitely use current regulation, not voltage regulation with the LS!)

 

[Go Go Gadget Flashlight]

BikeNomad,

Would a circuit like you suggest be simpler, cheaper, smaller? What's the benefit?

You're way over my head unless I can see a schematic! Even then, I may not get it.

I'd definitely prefer to use current regulation, but I have yet to see a circuit that works that way besides an inefficient LM317.

Enlighten us! Please!

You might start a whole new trend here!

Welcome aboard!

 

[bikeNomad]

The main benefits of using an inverting regulator with current feedback:<ul>[*]The (absolute value of the) output voltage can be above or below the input voltage using an inverting regulator. So you can power a single 3.42V white Luxeon Star LED from two (one if you do it right) to N NiMH batteries, and not worry about what happens when the batteries get down around the voltage of the LED(s).
[*]Using current feedback, you're treating your LEDs better. Looking at the Luxeon data sheet, you'll see that the Vf (forward voltage) ranges from 2.55V to 3.99V due to manufacturing variations. If you wanted to make a unit that didn't require trimming for a specific LED, you'd have to deal with this variation. If you use current feedback, you could just set the output at 150-350mA (depending on brightness desired) and leave it there.
[/list]

Given that many of the integrated switching regulator chips are supplied in very small SMD packages, it should be possible to make a more or less universal LED power supply that will work from a wide variety of power sources and with a wide variety of LED hookups.


I'm considering making such a circuit for my own use and the use of LED experimenters.
However, I'm uncertain how to package this. I'm guessing that replacing low-value SMD resistors to change the current output is a non-starter for many people. Making it so that the current value can be set by an external voltage divider is dangerous: if you have a 350mA max output, 5% variation means 17.5mA. Perhaps a high (350mA)/low (40mA?) range jumper would work, along with an external divider for brightness control.

 

[PeLu]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
The main benefits of using an inverting regulator with current feedback:<HR></BLOCKQUOTE>

OK, you mentioned the advantages, but not the disadvantages:

1. For most applications the negative output is not a problem.

2. Inverters have the highest peak currents of all usual converters, resulting usually in a lower efficiency. And your input and output capacitors have more 'work' because of the comparable 'nasty' waveform. And the output voltage is not 'supported' by the input voltage, which also decreases efficiency.

Anyway, what counts is the result and we are waiting for your design!