Help! Where is a good place to "browse" Driver/LED parts on the internet?

Looks legit to me. The more heatsinking the better, but your primary problem is really going to be the [thermal] interface between heatsink and host.

I 100% agree. But, aluminum is notably cheaper and readily available, which does make it attractive to me. Also, while I am certainly no expert, it seems the thermal conductivity of brass runs about 64 and aluminum runs about 118. If I need to solder, I will likely elect to use brass. If I can get away without soldering and simply use an aluminum heat sink (with thermal grease?) “stuck” onto the back of a decent LED base plate, I will probably go with aluminum.

You assume correctly, I do not have access to my own lathe or milling machine. However, my brother is a skilled mechanic and has a number of useful tools such as metal cutting jig saw, bench grinder, and various small hand grinders (some of which are air driven and quite powerful). More to the point, he has the experience and talent to use them for shaping combustion engine components such as intake and output ports. So, within reason, I think he can help me create almost any shape required out of relatively soft material such as either brass or aluminum.

Since I live in Japan, I am able to get Eneloop Pros at a fairly reasonable price. (More accurately, the price difference between Regular and Pro is very slight, and I have even seen Pros for less than Regulars on occasion. I currently uses Pros exclusively. But, I can get either one if necessary. I simply have no experience nor knowledge about driving any “flashlight battery” at anywhere near the current you are suggesting…

Can you “guesstimate” what kind of current would be required to drive 3 x Cree XLM-U2s with a direct driver board such as the BLF17DD?

Well, once again you answered my latest post while I was still writing a reply to your previous post. Thanks for the quick responses!

I was thinking in terms of using genuine silver thermal grease such as what the computer “overclockers” use between their CPUs and heatsinks. I believe it has excellent thermal properties. I was thinking to apply such grease between the LED mounting board and the aluminum disc (assuming there is no risk of shorting something out). Also, I believe I have plenty of room for two more “layers” of 1/8” aluminum, so I could also smear some of that grease between those layers… Just how hot is this thing likely to get? Will it fry an egg? :slight_smile:

As you say, the interface between the heat sink and host is going to be a true problem. I can make it as tight a fit as possible, but the host body material is quite thin, and it is covered in some kind of ancient black material (bakelite?)

Your choice of TIM isn’t a big deal, the same thing applies here as everywhere else: any decent TIM will do fine if you apply it properly. XM-L2 & etc have an electrically isolated thermal pad. Electrical conductivity between the MCPCB and heatsink is not a concern.

Without proper heatsinking of course it will fry eggs. Maybe you do not currently have any power LEDs? Or nothing on your “bench” where you can observe it outside of an assembled flashlight. A well driven power LED will become burning hot in an instant without adequate heatsinking. (It will be burning hot immediately when powered on.)

Coming back around to the real problem… It does not appear that the head of this flashlight is covered in bakelite. That’s the critical area since your heatsink will be interfaced there. Epoxy is a terrible conductor of heat compared to metals, but I suspect you may end up playing with epoxy due to the ridges. You could also look into using solder to fill the ridges - that’s significantly better than epoxy.

So far, the following driver seems to be the most “interesting” to me:

It is a LD-2C 3A 1/2 Cell Driver and has been reviewed by HKJ.
It is available at the Outdoor Store.

It seems like it “should” work…

Input voltage: 3-4.5V, 5.5V-8.4V

Group of modes:
3 Modes: High (3A) - Medium (900mA) - Low (150mA)
2 Modes: High (3A) - Low (150mA)
1 Mode: High (3A)

I would most likely use it only in single mode, but apparently it is fairly easy to change modes.

I don’t think you can build a monster light with that driver. It can’t handle high voltage or high current… so no high wattage… so no shocking wall of light.

I still don’t get why you would want a driver. It is hard to get lots of current with 1 x 3.6 V or 3 x 1.2 V., so, not needing to be efficient, you probably want two lithium ion batteries in series, or two parallel pairs in series, without a buck driver. You don’t need modes or exact regulation or voltage conversion, but just to keep the current in the right ball park. So a resistor or some steel wire will meet all the requirements with minimal cost, space and complexity. Wire is probably a bit better than a resistor, as you can cut it until you get the desired current and its resistance increases as it gets hot. Very thin copper wire might melt, but steel should take the heat with no problems. The steel already in the antique flashlight might even do all the regulation you need.

OK. It thought it was the best so far, that I have found. It appears to deliver 3A (not enough?) and handle either 1 or 2 Li-Ion cells. (As I mentioned, in my case, I am thinking in terms of 6 Eneloop Pros (using two 3 x AA serial D-Cell adapters in series for around 7.2 volts).

But, I confess to being completely ignorant on such matters… Any suggestions for a more appropriate driver? (Depending on its total height including components, I might run into trouble. Given my current Concept Sketch) I really only have about 6-7mm in available height.)

I guess I don’t want a driver, if I don’t need one. I simply do not understand enough to be able to visualize how such a thing would work without any driver of any kind. But, not using any driver would certainly resolve any space (height) issues.

Can you point me in the right direction where I can learn enough to understand what you are saying in your post? I have no idea what the “resistor” you talk about does, or why it is necessary.

Sorry, but please help!

Do you understand basic electricity concepts? Volts, Amps, Watts (Power), etc? You’ll never have a real grasp on this sort of thing if you do not, that’s just how it is. If you DO understand the very basics then you can pigyback LEDs on that (they are special). Take a look at my posts in these two short threads:

Also be sure to go back and at least skim lagman’s thread I referred you to earlier.

If you want “help” (guidance) and not “being told what to do” you’ll need to do two things:

  1. increase your understanding of what’s possible and how this works
  2. make some decisions as to what kind of light you want this to be

For example, your tentative choice of the LD2C… it can supply 3A to a single LED. Something like 9W of output power. That’s all it’s been tested to do. That’s like one regular EDC flashlight for most of us, nothing impressive at all. You said you wanted powerful, I assume the equivalent of an everyday carry flashlight is not what you were thinking of.

EDIT: And FWIW I don’t 100% agree with Fritz t. Cat. Your host probably won’t do well with continuous direct drive (DD) at high current. I’d say the best thing is to implement a DD driver with turbo stepdown if you wanted to get close to “true” DD performance but be able to operate the light for more than 60 seconds at a time without damage. Even a showoff light has to stay on for a couple of minutes sometimes.

Please kindly take a look at this new concept sketch:

Once I had a “working design” (concept) for the LED and optics, I started looking into Drivers. The LD-2C 3A 1/2 Cell Driver seemed to be good enough for me… and, it has a relatively short overall height of 7mm. So, I started looking at ways to make it fit, and came up with a less than perfect, but hopefully functional concept of using a 1/16” thick disc, backed by a 1/4” thick doughnut. I am still thinking in terms of aluminum, but will consider brass or even copper (although, I believe copper is quite expensive).

Most drivers seem to be fairly small in diameter, but many of them are quite tall in height. If I end up needing to use a taller driver, then I am thinking in terms of shortening the optics to make more room. The LED will be directed at the original antique glass lens, so modern optics are actually fairly useless anyway. But, I hate to not have any kind of reflector, since I presume considerable light would be “lost” (not directed towards the front) without one. On the other hand, while less than ideal, I think I can “get away” with shortening the optics; making them much less efficient but still hopefully useful.

Having said all that, everything is still completely up in the air, and there are many potential trade-offs. If I were to give up on my desire to use “standard” D-Cells (D-Cell size adapters), clearly I would have plenty of room. If I were to give up on the adapters, I would probably run a single protected 26650. (I am not very fond of the idea of using Li-Ion cells in series.)

Anyway, I am certainly learning a lot as I go, so please keep up the kind comments and advice. I certainly need all the help I can get!

Combining the stock optics with any other optics or reflectors will probably make you unhappy.

I might lean towards a single MT-G2 running DD (w/ a DD driver) on 6xAA Eneloops. (Sitting right behind the stock optics)

You have this thing in hand? What was the spacing between the stock bulb and the glass lens?

Can you get a focused beam out of an LED by handholding the stock lens?

As I said earlier, 9-10W of output is just a good regular flashlight. Definitely not a hotrod, and with the terrible beam pattern you are currently headed towards…

Hard to say how much I understand electricity, it is certainly not my strong suit. I am better at life sciences, and have a pretty good grasp of simple chemistry. Physics (especially as it relates to the natural world) is highly understandable to me, but I quickly get lost in the math. I have some knowledge of the basic electrical formulas, but don’t really “understand” them.

I have looked at it, and I will look at it again. I think I now have some understanding of the different types of drivers that are available.

I understand you very well, and I greatly appreciate your considered method of “educating” me. While I am willing to “do what I am told,” I am always interested in knowing “Why?”

Of course, “impressive” is a relative term. I was first looking at optics for 5 x XML LEDs and got the impression that I needed around 5A for that. That made me think that 3A might be “adequate” for 3 x XLM (1A per LED?) Please kindly suggest a specific driver that I should be looking into. Since I want (potentially) to run on 7.2v that seems to limit my choices somewhat. But, more likely, I am still simply not yet looking in the right place(s).

The simplicity and low space requirements are attractive to me. However, in my opinion, to be effective even a “hot rod” must be street legal and “drivable” (not subject to rampant parts failure). I would want this flashlight to be able to be “used” to a certain extent. A turbo timer might be the solution. One lower mode might work. Perhaps simply lowering my expectations a little (Do I really need a “wall of light?”) might make the most sense. If I can get somewhere near the brightness of a Skyray King, I will be quite satisfied, I think. (Certainly, no one is going to expect that kind of brightness out of such an ancient looking flashlight.)

Thanks again for all your kind help.

Do you currently have an SRK? Maybe that will help with this discussion! “Authentic” SRK’s are driven at 2A per emitter I think, so around 6W per emitter (ballpark), or 18W total. (6A total * whatever the forward voltage of the LED is at that current.) Hotrod SRK’s are generaly driven at around 4A per emitter or greater. At 4A with the increased Vf you’re talking about 14W each, 42W total. Do remember that getting double the actual output (measured in Lumens) is not going to appear twice as bright. I do not know what the scale is, but it’s not linear. To have something which looks twice as bright as 500 lumens you might need 1500 lumens or more, I don’t know exactly.

If you think in terms of Watts it will help you avoid fallacious thinking. Watts in, Watts out. No free energy.

Maybe I need to scale back my idea of what’s impressive. You’re right, any kind of nice, clean, bright beam coming out of your antique flashlight will be impressive.

…OTOH a shocking level of brightness would be sweet! It is a hotrod after all.

Please do take my advice and look into what your current optics will do. IMO you could waste a lot of time and effort planning with mistaken ideas about how the optic will behave.

CREE XM-L2 emitters are rated to take up to 3A each so keep that in mind. A few of the more extreme guys on here have had theirs over 6A, some even 7A or more! If you get the heat away from the emitter effectively, you can do the same. I’m not sure if that is possible in your selected host, but 1A to each emitter is definitely a yawn. I think I’ll agree with wight about leaning toward a single MT-G2 emitter. It is easy to get your hands on, will be insanely bright, just like you wanted, and you don’t have the complexity of trying to shoehorn multiple emitters and optics into the old host. Keep the lens from the host flashlight, don’t add any optics. That should leave you more space for a driver and hopefully a decently sized heat-sink.

Thank you very much for these words. I appreciate your “voice of experience.” This is why I have been posting those concept sketches. I am hoping you (and others?) will quickly notice any major flaws in my “thinking.”

Sounds good. First I ever heard of a Cree MT-G2 emitter. I see that they are readily available on eBay and look wonderfully powerful.

Actually no. It is with my brother. He will be cutting the metal parts. Right now, all I have is a rough idea of the current space occupied by the current “pill” (antique bulb assembly). The entire bulb assembly is easy to remove, giving a completely open area between the glass lens and the positive terminal of the D-Cell. At the moment, I believe that that space is approximately 40mm dia. x 25mm depth. Once I have final concept sketch, I will ask him to verify all the measurements in detail, and perhaps even “dummy up” some “parts” of the right size to make certain that everything will really fit.

I will ask my brother to try that. I presume that an easy method would be to take a “bare” LED flashlight (without any lens or reflector) and try beaming it through the lens?

I certainly will change course to avoid the “terrible beam pattern.” Would you please kindly suggest a specific DD driver that could put out the necessary wattage from 6 Eneloop Pros?

Thanks for the excellent advice. I am having trouble “digesting” everything, but I feel I am making some real progress towards understanding how to achieve my goals for this little “project.”

I certainly now prefer the idea of a MT-G2 emitter, and will proceed to update my “new design” (concept sketch) around that…

All suggestions welcome. Do you have a specific driver to recommend for the MT-G2 emitter?

I’d look at IOS ( and get one mounted on a Noctigon. Hank @ IOS is a trusted source for emitters (they are not marked as to the efficiency bin so it’s easy to lie…).

Yes, that should be fine. The information we really want here is where we get a focused, square beam out of a regular power LED such as an XM- or XP- series emitter. It would also be good to know if there is a position (somewhat closer to the lens) where a pleasant wash of light is produced.

My new-ish A17DD-SO8 driver is the smallest big-power DD driver we have right now. It should give the same performance we’ve seen out of the BLF17DD series of drivers. The [small amount of] testing which has been done so far seems to back that up. I have not done an MT-G2 build with it, but it’s ready for that.

Understand that a DD driver will put out whatever it can get. I haven’t looked at the charts (combine HKJ’s data with djozz’s data I linked to previously), but as I recall a 7th Eneloop might be a nice thing. If you could do an 8x carrier with a dummy that might be nice. That might be too much power though, I’d have to check.

My brother has what he believes to be an “authentic” SRK that uses 3 x XML. While not necessarily “insanely” bright, it certainly seems to be a very bright flashlight.

I have have no idea how many amps it draws. Neither one of us are true “flashlight modders” (so far). We only make fairly minor modifications and/or improvements to the low cost flashlights we purchase from China.

I will try to bear this in mind.

I was also willing to accept the presence of ugly artifacts in the beam. But, as I am beginning to gain at better understanding of what may be possible, I am leaning towards increasing my goals with regards to “impressiveness.”

I could not agree with you more. Cost remains a consideration, but I am becoming increasingly flexible on that, as I begin to become more aware of what I might be able to achieve by spending that “extra” money. For example, I am now leaning towards using all copper heat sinking material. As I understand it, aluminum has approximately twice the thermal conductivity of brass, and copper has approximately twice the thermal conductivity of aluminum. I realize that ultimately the heat must be dissipated from the heat sink, through the flashlight body, and out into the “external world.” But, there may be some advantages to having a heat sink that heats up very quickly: it should help me gain a better understanding of the ultimate heat dissipation requirements, and lesson the chances of damaging the LED during early testing.

Do you know of any source that sells the MT-G2 on a copper “star?” (I have noticed that some of the more expensive XMLs are sold mounted on such a star.

I have no hesitation in accepting you advice on this matter, and have changed my thinking (planning, conception) accordingly.

Thanks again for all your excellent advice and many efforts to assist me.

You can estimate how much resistance you need to get 3 amps. or so. It will be on the order of an Ohm. Start with twice that. You can get a multimeter cheaply. Measure the resistance of some steel wire with the meter. Use thinner or longer wire to get more resistance and less current. Then measure the current with the battery, the wire and the LED on a heat sink. Move the contacts nearer together on the wire until you get a good current. Assemble the flashlight and measure the tail current. It it is too small, take it apart and shorten the wire. If you leave the original spring and switch, they will add significant resistance and you may not need any steel wire at all. If the current is still too low, start bypassing the tail spring and other steel parts with copper until it works right.
You can use resistors, but they may not be readily available locally in the value and power capacity you want and their resistance is probably constant with temperature or may even decrease with temperature, because they have carbon in them, which is a sort of semi-conductor. Metals increase in resistance with temperature, which will (slightly) stabilize the current against changes in battery voltage. My direct drive Smiling Shark SS-5039s work fine with just the original stray resistance or even less than that.