Need advice on Regulated Lux3 3D-M*g mod.

I need some advice on building a regulated M*g 3D light. I know that it seems contrary to all the 3-cell direct drive mods that everyone's doing, but I'd like a regulated light that'll run for more than just 1-2 hrs at full brightness. Just another note, I'm using a 3D host because I already have 3 of them and they are cheap and plentiful around here (a mini-M*g 2AA & 3D combo package cost $28+tax CAD (~$22US) at Costco here). 4 or 6 cell C/D bodies (I don't think I've seen any 2-cell bodies) cost considerably more and are only available at a few specialty shops (otherwise I would have already bought a 2 or 4 cell and used a BB or DB driver). I'm also working with TV1K & TX0K Lux3s (although I do have 2 L-bins now).

Here's my goal for this 3D build:
- current regulated at 700-750mA
- be cheap to run (read: Alkalines, and I know NiMHs are cheaper in the long run, but it's got higher initial cost)
- run on K-bin Vf LuxIIIs
- minimize costs

So far the only viable solution is to use a Wiz2 buck/boost convertor set for 750mA. I'm sure it's a great circuit, but it's not exactly cheap ($30.25+S/H). The cost of the Wiz2 alone almost equals the cost of LuxIII + O-sink + 3D body. Are there any cheaper alternative drivers that I could use?

I was initially thinking of using a Fatman or BB driver to just boost it when the voltage dropped and hoping that those drivers would just run in direct drive mode when Vin>Vout, but when I actually read up on both drivers, it looks like I might smoke the driver & the Lux3 instead if I fed them too much voltage. Then I checked the Nexgen which has an overdrive limit of 0.7V which was better, but when I measured the voltage off 3 fresh alkalines, it was like 4.65V, quite a bit over 3.51-3.75V Vf of a k-bin. And the Nexgen was only $2 cheaper than a Wiz2, so I might as well get the Wiz2 and not worry about the Vf or batteries. But I'm back at the cost issue again. Is there no economical way to build this up?

As a side note, anyone know of a good way to remove an Arctic Alumina epoxied emitter from an O-sink without killing the emitter? (I already AA'd 2 of my k-bins without really thinking) I was thinking of freezing it for a couple hours and try to pry it off with a screwdriver (seems to work for epoxied heatsinks on video card GPUs). I might just swap my K-bins out (save 'em for something else) for L-bins and DD it if there's no economical way to regulate them.

*Edited to reduce current requirement and added cheap to run.

....." But I'm back at the cost issue again. Is there no economical way to build this up?"...

When I started in this ...ummm... adventure I was wanting to do the same thing. From my experience, 3 cells is exactly the wrong amount for regulation. I've never tried the Wiz though. As I understand it, the reason for regulation is to have constant brightness throughout the life of the battery charge. You probably ain't gonna like this, but the BEST solution for 3 cells is to use nimh cells in direct dirve or lightly resistored. Their voltage/current vs amount of charge is remarkably constant. Meaning they give virtually constant brightness until they run dry.
Also, alkaline cells have a high internal resistance, meaning when the Lux pulls current from them, they sag to match the Vf of the Lux. The nimh internal resistance is much lower so they don't sag as much. Fortunately, 3 nimh cells almost perfectly matches the Lux Vf.

If you like regulation and want to use alkalines (like I do to both counts), you're better off using a higher battery voltage and a downconverter than a lower battery voltage and a boost converter. Again, it's because of the high internal resistance of the alkies causing a voltage drop (and wasting power doing so) when the load is placed on them.
Here's an example. I wanted a 2D Lux III light that was regulated, bright and reasonable runtime. I tried using a couple different boost converters set at one amp. The results were less than optimal. 15 minutes runtime or so. If I dropped the current to 500mA, it got some better, but not really. I finally tried an 8AA to 2D battery adapter and a downconverter. I got TWO AND A HALF HOURS OF REGULATED RUNTIME at one amp. Now we're talkin'. I got to thinkin' some more about it and realized there was still enough headroom to run a Lux V at about 6.5<>7 volts. I haven't run any real runtime tests with the lux v, but I'v used it quite a bit and can't see any dimming yet. I'm guessing about an hour or so. Think about it. An hour of regulated light from a Lux v in a 2D light......Wooo Hoooo.
Sorry for writing you a novel. I'm just trying to help.
P.S. with the 3D host (do you need special glasses to see it? /ubbthreads/images/graemlins/hahaha.gif ), a 9AA>3D adapter would give even more runtime with the downconverter setup. BTW, it seems like there's no way to get around spending money on these things. Oh well /ubbthreads/images/graemlins/ohgeez.gif

Hi, AvroArrow.

I do think what UncleFester suggested for DD is a good option, though I have not used the Downboy for any of my mod(which I strongly suggest you run the idea with someone experienced to double check this /ubbthreads/images/graemlins/blush.gif), I do suggest the following:

-Get 3 3AA to D adpaters from Waion,
-Downboy 1A(Shoppe, blank + add on resistor, around $16)
-use 9 Alkaline or Nimh


Good luck!

I'll second that.
But use a george80 buck regulator.
I have had Great luck with these tanks. /ubbthreads/images/graemlins/happy14.gif
Plus they fit perfect inside the backside of a D cell Osink with a little epoxy. /ubbthreads/images/graemlins/crazy.gif

Good luck /ubbthreads/images/graemlins/smile.gif

When I do m@g mods, I like to keep things simple. I don't like to use PVC to adapt batteries nor AA to D adapters. It's just something else to worry about.

I've done 2D mods using the NexGen converter. I don't know what happened in Uncle Fester's mod, but I got a lot more than 15 minutes of runtime.

The trouble with running a buck converter like the DownBoy is that once the combined voltage of the batteries drops below Vf (including the voltage sag) the light will drop into direct drive mode. Of course, this is probably a non issue when you're running a ton of AA cells.

The trouble with running the NexGen is that it will go into safe mode when you try to get an amp to the luxeon from a 3v power source. For this application, you'd be better off with a BadBoy, although I don't know if 2 D cells, NiMH or otherwise, can supply the necessary current to do this. I know it will work at 700mA though.

OK, to the chase. If you want a regulated light running on 3Ds, then go with the Wiz2 converter. It will run the batteries down to a total of 2.5v. The wiz2 is a bit more expensive than the BB or DB converter, but AA to D cell adapters aren't cheap either.

On the other hand, you could jam 4 C cells into the 3D light and run the buck converter. Using a piece of PVC pipe as a spacer is more simple than using AA to D converters. It's cheaper too.

Ooooh oooooh oooooh. Chop has a good idea. 4C cells in a 3D light with a buck (down) converter. The PVC is 1 inch sch40 pipe. A 10ft stick of it is a few bucks. You can get a little bit more headroom from the georges 80 downconverter if you short its reverse polarity diode, D1.

I need to try that Wiz2 converter on a 3 cell setup. It COULD be just the ticket!

Whoa, lotsa good advice here.

UncleFester,
Yes, thowing money at it seems the simplest solution. /ubbthreads/images/graemlins/wink.gif I like the DD w/NiMH, but the only thing that worries me is that there's no way to control the current going to the lux3. I was doing some testing and I was measuring 1.8A at the lux3 /ubbthreads/images/graemlins/eek.gif (I have a semi-modular setup, using 3pin molex connectors for easy swapping, so it's easy to measure it) from 3 fresh alkaline Ds. I realize that it will sag after a few minutes, but still. And I've been reading up on Vf shift over time, so this will only get worse over time. Since NiMH have even less internal resistance, wouldn't I be waaay overdriving it in DD? I suppose I could add a simple resistor to limit it, but that seems so terribly inefficient and wasting the potential of the lux3. Also, I don't have any NiMH D cells or D cell charger (read: more $$$) but I've got a box full of alkaline Ds. /ubbthreads/images/graemlins/icon3.gif

What do you mean by more headroom if I short the reverse polarity diode on George's convertor?

AuroraLite,
Not a bad idea but it's actually more expensive than getting a Wiz2. 3x 3AA-to-D + DB1000 = $33+SH. Plus, loading the 9AAs is gonna be a major pain. I'm making one for my parents, so it's gotta be simple to reload.

3rd_shift,
I looked at the George's CC5W but it costs more then a DB1000 and there's a Vf+1V requirement to maintain regulation. The u/nFlex looks really cool, but I don't need variable brightness, nor the added cost.

Chop,
I'm trying to keep it simple (and cheap) too since I'm giving one to my parents, and maybe another to a nice relative. /ubbthreads/images/graemlins/grin.gif I actually considered getting a boost driver and running 2 Ds and a dummy D-cell, but that chops down the total runtime by 1/3. I may have to revise my requirement to 700-750mA instead of 1A. I've done more reading about this and driving it at 1A is really getting into diminishing returns in terms of brightness, with major sacrifice in runtime. I think your 4C w/PVC pipe ($2-3) + DB750 ($16.5+SH) suggestion is the best bet so far. The only downside is the lack of full regulation throughout battery life, and shorter total runtime. According to the spec sheets on Energizer's site, alkaline Cs have 8350mAh and Ds have 20,500mAh total capacity, so 4x8350=33,400mAh for Cs and 3x20,500=61,500mAh for Ds /ubbthreads/images/graemlins/eek.gif. Nearly twice the potential capacity. I may end up getting a Wiz2 for my own 3D if/once I get past the price, but for my parents' mod, the 4C+DB750+pipe looks like the ticket.

Thanks for all your help and suggestions guys. That's what I love about this place, there's always someone willing to help out a newbie with useful info in this addiction... umm... I mean... hobby. /ubbthreads/images/graemlins/grin.gif

An LDO linear regulator will fit the bill when it comes to driving a Luxeon III from 3 cells. The efficiency is reasonable (starts out at 70% with alkalines, 85% with rechargables, and gets better), and only needs Vf + 0.1V to stay in regulation. So if you're using rechargables, and the Vf of your luxeon is 3.6V at 1A, then it will stay in regulation till the batteries are down to 3.7V, which is about 70% of the NiMH battery life. After that, it drops in to direct drive, and things slowly get dimmer as the batteries drain.

Avro
Evan has another good Idea. When the battery voltage is above the Vf, the extra voltage will be dropped across the regulator. That times the current through it is the dissipated (lost)power in the regulator. As the batteries wear down, the voltage across the regulator reduces. At the point where the battery voltage meets the Vf at the programmed current, the lost power goes to zero. That's the same as direct drive.
The difference between the battery voltage and the Vf will be the total headroom. When they're the same, there's none left for regulation. With the 8AA (alkaline) setup I mentioned there's 12-3.7=8.4 Volts of headroom, ignoring the sag in the batteries. The 1V over Vf of the georges80 you mentioned is the headroom needed. The protection diode I mentioned is a schottky meaning it loses something between .1 and .3 Volt so shorting it won't gain much. I don't know, but the DB converter might need some headroom also. Keep in mind, when the a donwconverter goes out of regulation, it effectively goes into direct drive so you still get power into the Lux.
Most converters in the Led flashlight world have a constant current output. With the constant Vf of the Lux, that translates into a constant power output. If the Lux Vf is 3.6V and the current is one amp, the power in the Lux is 3.6 W.
Here's why the high battery voltage works the goodest. Power lost in the battery when loaded is is described by the current squared times the internal resistance in the battery. I^2 X R(batt). For the sake of argument, let's say the converter is perfectly efficient (100%). Power is also described as voltage times current. P= V X I. Algebraically rearranged, P/V=I. We know we want 3.6 Watts of power in the lux. None is lost in the converter so power out is power in. Let's get the battery current. 3.6W/12V=300mA or 0.3A. Remember power lost in the batteries is described as I^2 R(batt). The R(batt) for the AA cells isn't a ton more than the R(batt) of the D cells. The current with the AA setup is 0.3A. Now lets look at 2D setup. 3.6W/3V = 1.2Amps
Again, for the sake of discussion, let's assume the R(batt) for the two types is the same @ .5 Ohm(I'm too lazy to do the research).
8AA
8 X .5 Ohm = 4 Ohm
.3^2 X 4 = =.09 X 4 = 0.36 Watts lost in the batteries resistance
2D
2 X .5 Ohm = 1 Ohm
1.2^2 X 1 = 1.44 X 1 = 1.44 Watts lost in the batteries

Ok, off the sopabox. having blathered about that for long enough, I really do want to try the Wiz2 thng.

For giveaway lights, I would believe your best bet will be 3D cells with a small amount of resistance (something like 1/2Ohm). Yes, there is some I^2R loss in the resistor. Keep in mind that Lux III light will STILL make usable light with batteries that won't even make a stock Muglite run at all. If it's not perfectly efficient, it's not the end of the world.
Allright, I'm about dried out for now. Have fun.
/ubbthreads/images/graemlins/thumbsup.gif

evan9162,
This LDO linear regulator that you mention looks really interesting (it looks like it's waaaay cheaper DIY solution than a buck convertor). I did a search and found some really detailed info (most of it sounded like EE stuff, a bit over my head) about it being essentially a managed resistor. One question I do have is what's the difference between a LDO linear current regulator and a buck convertor? They both control the current feeding the LED when Vbatt>Vf, and then drop off to DD-mode when Vbatt=<Vf. And it looks like I'm gonna have to contact andrewwynn and Mr.Al about their circuit because it looks like the ticket for running 3 alkaline or NiMH cells. /ubbthreads/images/graemlins/grin.gif And I'd actually like to try building my own LDO regulator, seems kinda fun.

UncleFester,
Thanks for the headroom explanation, it's making sense for me now. And your example situation is basically illustrating that a buck setup is more efficient than a boost setup, right? I was originally going to DD the lights with a light resistor (I got a bunch of 0.8ohm resistors) because it was simple and cheap, but after reading about Vf shift over time, I'm a bit reluctant for fear of frying the Lux3s. In reality, this probably won't happen for a least a couple hundred hours of use, but if I'm really paranoid about Vf shift, I could just use a higher value resistor. And I'm still trying to figure out how to measure the actual Vf of the Lux3s I have so I can get an appropriate resistor. Took me a while to figure out that the DMM had to be in-line/series with the Lux to measure the current it's drawing. /ubbthreads/images/graemlins/thinking.gif

So it looks like I'm gonna try the LDO route if I can figure it out, otherwise like you said, for the give-away lights maybe I'll just fall back to the simple resistor and call it a day. Gotta save up for that Wiz2-937 for my own... hmmm... wonder if the Wiz2 could drive 3 lux3s for 3x(lux)3x3(cell) mod. /ubbthreads/images/graemlins/grin.gif

Avro.
Is your username taken from this ?

You catch on FAST. Congrats on doing the legwork.
A managed resitor is a perfect description of a low dropout linear regulator.

The difference between the buck regulator and a linear regulator is that the buck is more efficient because it converts current and voltage where the linear has the same current both going in and going out. The power lost in the linear regulator is the current through it multiplied by the extra voltage (headroom) that appears across it.

Those .8 Ohm resistors will work fine. They should be at least one Watt power rated though. My recommendation is to go ahead and build one of these. You'll like it. You can hand select the resistor to get one amp. Then you can measure the Voltage across the Lux to determine its Vf. I think Lumileds rates their Vf at 750mA. I understand your concern abut overdriving the lux, but a lot of guys here beat the snot out of them and they keep coming back for more. Some overdrive with fresh batteries isn't really much of an issue.

I guess the claim could be made that the buck converter is more efficient. But that efficiency gain is for the whole package, not just the converter which may or may not be more than a boost converter.

The problem I had using a boost converter goes like this:
The converter pulls on the batteries, causing their output voltage to drop(because of their internal resistance). Remember the converter wants to maintain a specific output power. To do this, it pulls (or tries to) more current from the batteries. When the current increases, the voltage drops even further, causing even more current...... Those poor akaline cells fall flat on their face.

If you want, you can measure current by putting a small value (.1Ohm works well)in series with your load or (or battery if you're measureing it) and reading the voltage across it. Ohm's law. V = I X R. With .1 Ohm, i Amp will read 100mV or .1V.
Well, you're probably tired of me by now.
Have fun

[ QUOTE ]
AvroArrow said:
evan9162,
This LDO linear regulator that you mention looks really interesting (it looks like it's waaaay cheaper DIY solution than a buck convertor). I did a search and found some really detailed info (most of it sounded like EE stuff, a bit over my head) about it being essentially a managed resistor. One question I do have is what's the difference between a LDO linear current regulator and a buck convertor? They both control the current feeding the LED when Vbatt>Vf, and then drop off to DD-mode when Vbatt=<Vf. And it looks like I'm gonna have to contact andrewwynn and Mr.Al about their circuit because it looks like the ticket for running 3 alkaline or NiMH cells. /ubbthreads/images/graemlins/grin.gif And I'd actually like to try building my own LDO regulator, seems kinda fun.

So it looks like I'm gonna try the LDO route if I can figure it out, otherwise like you said, for the give-away lights maybe I'll just fall back to the simple resistor and call it a day. Gotta save up for that Wiz2-937 for my own... hmmm... wonder if the Wiz2 could drive 3 lux3s for 3x(lux)3x3(cell) mod. /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]


An LDO linear current regulator uses a transistor to control current. Any voltage difference between the LED voltage and input voltage is dropped in the transistor, and dissipated as heat. Thus, large differences make the setup more inefficient, and make the pass transistor heat up more (requring heat sinking). But, given 3 cells and a single Lux III, it's a great setup that has pretty decent efficiency. Input current from the power source, and current to the LED are the same.


A buck converter, on the other hand, uses an inductor and capacitor to switch the power on and off to the LED. The inductor and cap smooth the power to the LED. Voltage differences between input voltage and LED voltage result in the input current being lower than the current to the LED.

With a perfect buck converter, power drawn from the batteries equals power to the LED. So, if LED Vf=3.5V, and current=1A, and you drive it with 7V, then input current would be 500mA.
However, there are losses in a buck converter - a DownBoy converter is about 85% efficient, so in the above example, you'd be drawing around 590mA from the power source.


An LDO regulator is pretty easy to build, depending on your electronics knowledge. I have a design that uses a MOSFET pass transistor for very low dropout voltages (headroom) - the thread is here:

MOSFET-based LM334 regulator

You could probably build one for $5. If you're really interested, I might be convinced to build a couple for you for $5 each.

4.5 V is the biggest pain as a Vbatt source to run Lux.. as many of us have painfully found out.

I would definitely try the LDO solution.. evan has a great circuit.. and MrAl developed one that is simpler to control.. i've made a version for my nanos that works phenomenally well and it costs about $2 to build.. i've sold 'diy kits' that include all the parts for like $5 if you have enough room inside your mod you can put the chips on prototyping boards so the soldering is a cakewalk.

the higher the Vbatt the lower the efficiency is the main issue.. however they get very efficient as the battery dies... the average works out very nice in the cases i've worked on.

I really like the cost of a DIY LDO ckt.. very hard to beat for make it your own.

-awr

UncleFester,
Close, same company, different jet. Thanks for noticing, most non-airplane buffs never even heard of Avro (or A.V.Roe). /ubbthreads/images/graemlins/smirk.gif (that's not my site BTW)

Thanks for the pat on the back. I try to learn on my own first before asking for help. Stays in my brain longer when I figure it out for myself. And thanks for the explanation on the buck & LDO convertors. I bought the 0.8ohm resistors after doing the calculations with jtice's LED resistor calculator program. Very cool and useful piece of software.

I've read about the disadvantages of using alkalines, but these are for mom and dad, so keeping it simple and cheap to run (in their eyes) is important. I'm gonna be investing in some NiMH Cs & Ds later on for my own use. I just have to get around to ordering them online as the only commercially available NiMH Cs & Ds are Energizer Rechargables, both rated at 2100-2200mAh. Yes, 2200mAh NiMH D cells. Kinda ridiculous when I can get 2500mAh AAs for cheaper. Thanks for the tip on measuring Vf. I read about someone else measuring across the lux and people were suprised that he didn't fry the lux. I'm more willing to measure across a resistor since I don't have to worry about frying a $.25 piece. Why would I get tired of free helpful advice and information? Thanks!

evan9162,
Thanks for explaining the difference between the buck & LDO convertors. That buck convertor that you're describing sounds like a Pulse Width Modulation type device, right? I'm sorta familiar with PWM as I've gone through 2 not-so-well-designed PWM based fan controllers for my computer before switching to a more robust and reliable rheostat based controller.

My electronics knowledge and ability is... okay with regular sized parts, but I don't think I'm up to soldering SMD sized parts onto a quarter sized PCB. /ubbthreads/images/graemlins/blush.gif I think I may have to try to convince you to build me a couple. /ubbthreads/images/graemlins/grin.gif

andrewwynn,
Yes indeed, 4.5V is a royal pain in the butt to drive a lux as I am learning right now. /ubbthreads/images/graemlins/icon23.gif MrAl and your circuit design was the first hit when I did a seach for LDO current regulator. That's a very cool squashed bug design that you did. And the size of that nano driver... /ubbthreads/images/graemlins/ooo.gif I think I may buy a couple DIY kits from you too since you say it can be done relatively easily on a prototyping board. That I can handle. Dime sized PCB... not yet. This way, I can hopely get a couple of real working units off of evan9162 and a couple more to build myself that may or may not work, depending on how good a job I do, all for the price of 1 DB. /ubbthreads/images/graemlins/grin.gif Thanks a bunch guys!

allright,:Thread Hijack:
Avro. What makes you think I'm not an airplane nut? My favorite plane is the XB-70. Always has been since I was a kid and probably will be forever. You probably know about its history. It's sad about #2.
I saw the Vulcan fly at an airshow at (then) Bunker Hill Air Force Base in Indiana. It was an incredible experience.
I'm familiar with the British manufacturer Avro Aero. I didn't know about the plane Avro Arrow. Clever. Did they ever fly one, or did the program get killed before that? (They only flew two XB-70's, thanks to our friend Robert McNamara) Hijack mode off

For Mom and Dad, you'll be fine with 3D alkalines and the .8 Ohm resistor. I think I remember your having a K bin Lux. A lot of people run them direct on 3 cells without resitors and they seem to do fine. Your .8 Ohm is a safety net.
The 2100mA Hr D cells you mentioned are probably AA's with an adapter on them to make them look like D's. Wouldn't be the first time.
Using a resistor to measure current: I use a .1 Ohm because it's convenient to calculate the current and it introduces very little loss in the circuit being measured. You put it in series with whatever load you want to measure and read the voltage across it. Teh voltage across the .1 will be one tenth the actual current. (2.5A =.25V). The .1 Ohm probably has less loss than the current scale on you dmm. You can put it in series with your current limiting resistor (and the LUX) to measure the current through the Lux and its resistor. If you want to adjust the current, I would say to find some batteries that have had their initial charge worn off a litttle and find the right current set risistor to set the current to one amp. When it's at one amp, you can measure the Vf across the Lux if you're interested. Again, I'd just put that .8 Ohm in there. I'm sleepy and giving up for the night.
Keep shining

I dont have a heavyweight post that can contribute to this thread. But I do have a little story/question related to Avro's problem that I can share as actually I am in exactly the same situation as him!! Spare 3D mag (about 10yrs old, bought in 1 package with the minimag 2AA too!!!) I only use flashlights as EDC or for outdoor adventure activities. And I found out the hard way that lugging a 3D mag around with another set of spare batteries for camping is not the wisest thing to do. Bright, yes, but for long? no. Heavy? VERY... /ubbthreads/images/graemlins/crazy.gif

So I consider building a bright torch just for fun around the city. At first thinking to do the DD Minetrois (Modamag) by buying the trisink, 3 ***K LuxIII in parallel, 9AA-in-3D NiMH. But I have to find a 3AA-to-1D that put the batteries in parallel to keep the overall 1.2V 1D package. Three of them and we get 3.6V in 9AA-3D form. Do you guys think this will work?

But... as you can guess, I calculate the cost... and found out that the cost goes up along the way. The reflectors, three of them, the sink, the luxes, the battery cages... they all adds up the cost /ubbthreads/images/graemlins/icon3.gif

So now im thinking exactly the same thing like Avro. Just build a simple 1 LuxIII solution with 3 alkalines (or NiMH in the future) D cell. I'm thinking to get a ***L bin LuxIII on top of a hotlips-D, direct drive with 3 alkalines. In the binning reference, I get 3.75-3.99v Vf for ***L bin lux. So the question is, will this thing work reliably? any damage to the lux?
On the other hand, what will happen when we DD a ***L luxeon with 3 NiMH, 3.6v? Dim?

UncleFester,
:hijack on: I thought you probably were a plane nut to notice. /ubbthreads/images/graemlins/grin.gif That was sad with #2, a stupid photo shoot! There were 6 Arrows complete, but #6 never got to fly because the program was axed. It was another ahead of its time aircraft. Never fully completed because they couldn't finish the engines in time before being axed in favor of the dud Bomarc missile system. :hijack off:

Thanks for the tips on measuring the Vf, I'll give it a try during my build.

Ny0ng1,
That's what's great about this board, you don't always have to contribute, it's fine to ask questions too because we're all here to learn and have fun blinding people. /ubbthreads/images/graemlins/wink.gif

One thing that you need to check before buying a Hotlips D or D O-sink is the serial number on your old 3D mag. If the serial number starts with a D (e.g. D1234678) then you're okay, but if the serial number is just numbers, then neither heatsink will work. I have an 8-9 year old old-style 3D mag that the heatsink won't fit in because the inner diameter is too large. The old D mags were 37-38mm diameter and the newer ones have 34mm, and both heatsinks are machined to fit the 34mm. The only solution is to get a different heatsink. B2eze makes custom aluminum mag heatsinks, from a 1x to 4x lux configuration. I bought a copper 3x lux heatsink from him to mod my old 3D mag because none of the hotlips or o-sinks will work in it. The other nice thing about B2eze's adaptor here is that it comes with PR bulb base, so you don't have to hack up your switch.

For a L-bin, DD is your best bet for alkalines. I have a bunch of K-bins, which is why these guys have recommeded a resistor because it has a lower Vf. L-bin is perfect for a DD build. I'm not sure about DDing it with NiMHs though because like you said, it's 3.6v, which I don't know if it's enough to start it up.

A 3D mag with 5 x 1/2 D cells, LuxIII and downboy converter works really well.

You can get 1/2 D 2400mah cells relatively cheaply from the battery station ($4.00 ea...I think). These can easily be charged individually in normal multi cell chargers.

Plus at 750ma you're looking at almost 5 hrs runtime.
I've seen broupbuys for 4000mah 1/2D as well but I wouldn't know what direction to point you in for these.

Tim

andrewwynn,

Can you please email/PM me the schematic for the simple LDO that you refer to here? Sounds like a cool thing to try for my 3D LIII mod /ubbthreads/images/graemlins/grin.gif

Will