48V DC LED wiring for a new build; XM-Ls, etc.

tagger

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We're about to start construction on our new home. I'd like to design the lighting, and, inspired by threads like http://www.storageforum.net/forum/showthread.php/7919-Wiring-a-house-for-LED and the fantastic input of those like jtr, I'd like to run some numbers by you pros and get any feedback you may have.

First some assumptions: we'll assume that I want LEDs. In particular, we'll assume that I want a “purpose-built LED” solution, as jtr has referred to it, for a variety of reasons, including the desire to run things optimally in order to maximize efficiencies. We'll assume that I have an acceptable (to my wife and I) physical design, which involves strips in dropped crown-molding (“mini-soffit”)-like configurations, run around the perimeters of rooms (or portions thereof) where LEDs are bounced off the ceiling (indirect). There are a couple of variants, and, in the kitchen, a direct down-lighting design prevails, but one that will still take the form of “strip”. Putting those assumptions together, one option for component LEDs are the Cree XM-L's that jtr mentioned, that were newly released in 2010 as he was writing, and have now been around a couple of years. Now the picture is becoming clearer: I'm interested in buying some aluminum plates (or other substrate / cooling-configuration) and spacing the emmitters on them myself, as the given room/application dictates. We'll assume that I have some electrical experience, but no real LED experience. We'll assume that we're not the pickiest people when it comes to temperature / color, but I'm considering some of jtr's advice about throwing in a color here and there to help with the color (though I'm not sure, as bright as each XM-L is, if that's still a great option, as the spacing may be greater than with lower-power LEDs and the color variations may become visible, but more on details later). Finally, we'll assume that I'm _not_ interested in dimming. I will in some cases bank the lighting for 2 or maybe 3 brightness configurations, but that's it. However, there are some instance in which I'd like 3-way switching, so to speak, and I think I'd like to run the switching, if possible, with signal-wire, to the wall switches, which would be momentary switches of some sort (no state). More on this later.

I'd like to run things at 48V DC - just under the 50V threshold for obvious reasons, but high enough to minimize line loss if I need to take the DC any great distance. I'm open to transformer options and configurations, and, of course, have access to all the insides of the walls, can put boxes wherever I want, etc. Likewise, I'm confident that I can easily find physical housing for drivers. I know that if I use #12 Romex then my 5% drop distances for 4, 6, 8, 10 Amps are, respectively, 132, 90, 64, and 52 feet, which are all acceptable in my application. I will, of course, take distances and transformer locations into consideration when making final wiring choices. I'm not convinced that using a single transformer for the whole house's DC lighting is the best way to go, and I'm ok with having a few regional transformers, say, each on their own little 10 or 15-Amp circuits (A/C, from the panel to the tranformer at 120V), to provide the DC to a given, say, few-hundred square-foot region of the house.

For a given room / application I have an approximate lumen requirement, albeit, since I'm not the most familiar with lighting, my calculation is based on incandescent equivalencies. E.g., in one room, I'd like the equivalent of about 2 75-Watt incans for whole-room lighting. No work areas or anything. This example happens to be a bedroom, in which we'll have reading lights at the bed. So, that's about 2360lm. If the XM-Ls are 250lm at 1Amp (I'm not sure if that's exactly right, but approx.), I might need about 10 of them to do the job. Possibly 5 along one wall and 5 along another, spaced a couple feet apart would do it, right?

And, if I'm paying about 6.5-cents per kwh right now, and wanted to compare, then my 2x75-watt incandescents would cost me 10-cents a day, or $35.59 a year if run 10-hours a day. Roughly, at 100lm/watt, I guess I'd be running the LED equivalent at about 25 watts (compared to the 150-watt incandescents), which calculates out to 2-cents a day or $5.93 a year. I know, I'm leaving out the consumption of the drivers, but if constant-current drivers run about 96% efficiency, I'll just let it go for the calculation for now. If my house was over-simplistically scalable and the whole-house load was 15-times this, then we're looking at a $1.20/day or $444.90/year difference (savings). I see XM-Ls on ebay for $60/10pcs ($6/pc) (is this a decent price? I haven't looked at vendors yet). If my whole-house scenario was over-simplified and I decided that I needed about 150 of these little guys, that would come to $900. The power-supply(s), wiring, boxes, mounting, etc. might all add up to a couple thousand (very rough). So I'm looking at a few thousand, perhaps, not including labor and soffit-building, etc., which I intend to do. So the ROI would be about 6-10 years. Well, big error, of course: I'm assuming that a bunch of incandescents and conventional wiring would cost $0, but that would just reign the ROI in a little. And if my LEDs last 15 years, then I only have to replace them at under $1000, likely, in 15 years, and the ROI on that is 2 more years, for another 15 years of life, presumably. Again, assuming that incands were 0$. I can handle that. I'd net more than $2k in the first 15 years, and then neigh $7000 over the next 15 years.

About switches... in a couple of applications I'd like switches at each end of a room/hall. I don't like state switches, and I'm not fond of touch-switches. I'd like a mechanical momentary switch. I haven't looked hard for one yet, but will soon. Any advice on a switch? Any advice on how to deliver a switch signal to the driver (I'd prefer to signal post-transformer, I think, but perhaps there's reason to consider 120V switches, even if I go with a momentary switch, or possibly low-voltage switches that go to latching relays on the 120V circuit?). Do I need to breadboard my own solution, complete with debounce and whatnot? My electrical experience of this sort is quite rusty, so I'd love it if there was a prefab solution I could make use of here.

An aside: I do have plans for PV-solar someday, but it might be 150' from the house, so I have to figure out how to carry it up high-voltage/low-current, and in big wires, to reduce loss; I'm sure it's still easier to step down to 48-V than it is to transform A/C, so, when the time comes, I'd like to have a way to patch that source in directly (that is, from the batteries). I don't think this will be hard, but if I'm transforming in the wall somewhere, I have to keep in mind how to get the new source there in the place of the AC; I may be able to just use the existing romex to do it, and be fine, and just bypass the transformer there, possibly replacing it with step-down circuitry. This isn't the most important piece of the puzzle, just something I'd like to think ahead on a little bit.

Now for color (temperatures, CRIs, etc.) I have XLampXML_HVW.pdf, the poop sheet which characterizes their “cool”, “neutral”, and “warm” white options, and I can take some jargon-filled advice from other threads about what “good” color might be, and I can, as advised, order some stuff and see what it looks like before ordering the big bundle, but does anyone have any basic advice for this product in particular, to get me started. Devoid of any advice, I'd probably try an assortment, but would stick closer to the warm end of things than the cool end. I like incandescent color alright, and the photographer in me likes anything between white and warm for portraiture, but I really am fairly liberal here; not even the CF “green” bothers me as much as it does some people (I wouldn't shoot portraits under it, but I can live with it). Of course I don't want green hues, but, I'm thinking I might have a pretty easy job of choosing here; my design will reduce glare problems, and my lax color attitude might lead to happiness with anything in an acceptable spectrum. Color-crats have it harder in life, I'm sure.

And finally, cooling: I really like the idea of running some water in tubing to which the LEDs are mounted. I know copper would work best, but it's not practical or cost-effective. I know PEX is more insulative, but cold well water in PEX should still help deliver off the heat a bit, if I can figure out how to mount the things well. I have a couple of options for what to do with this water, but, for the sake of argument, just assume that it gets fed, thus pre-warmed, into our water-heating system. So, an assumption is that maximum efficiency occurs when light usage and water demand are in concert, or if water-demand is somehow constant. Since we're doing in-floor radiant, demand may be somewhat constant, if we go open-loop. But most likely we'll run closed-loops through heat-exchangers. In this case, we'll have to rely on the coincidence of water-demand and light-demand, but that may work out pretty well, actually. Any advice on doing something so unconventional would be greatly appreciated.
 

ddrueding

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1. Welcome to StorageForum!
2. Your project sounds fascinating. Not unlike something that I was trying to do while remodeling a while ago. (Didn't do it due to time constraints, but still interested)
3. JTR is the guy around here who knows this stuff, but I haven't seen him in a while. Last I checked he had some other interesting projects going on.

All your math seems (very roughly) accurate. I would probably factor in a 30-50% loss due to layout and other room configuration issues, this was a big deal in my house at least.
For the switching side of things, I ended up going with a 120v standard system called Insteon. Works great, but means you would need a transformer for every load after the switch.

As far as capturing the heat for water cooling, I had the same idea myself. PEX is not much cheaper than copper once you factor in the cost of the fittings and tools. Also considering the copper pipe is rigid enough to actually serve as the strip for mounting the LEDs themselves (using some kind of electrically insulating thermal adhesive pad or thermal epoxy). The only warning I would put on this is that pipes with water flowing through them make noise. You may not want noise in every room every time the hot water is turned on. I would consider a closed-loop with a low-flow pump and heat exchanger into the underfloor heating loop. On second thought, this could actually be the same loop; target temperatures are about the same and the LED soffits are within the insulated envelope of the house anyway.
 

tagger

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2. Your project sounds fascinating. Not unlike something that I was trying to do while remodeling a while ago. (Didn't do it due to time constraints, but still interested)
I know -- your thread back then is one I've studied, and was a chief inspiration for this post! Thanks! I was a little disappointed to see the project fizzle, by the end of the thread; hopefully you have a chance to get back to it sometime, or do a project like it in the future.

3. JTR is the guy around here who knows this stuff, but I haven't seen him in a while. Last I checked he had some other interesting projects going on.
I confess that I'm interested in his input; if he's not around, then oh well. What "projects", here in storageforum.net or somewhere else? I'll resist stalking him, though. :)

Insteon. Works great, but means you would need a transformer for every load after the switch.
Oh, so did you wind up with LEDs? I thought you were turning to fluorescents at the end.

As far as capturing the heat for water cooling, I had the same idea myself. PEX is not much cheaper...
Yeah, I shouldn't throw copper out the window too quickly. I had thought of putting it in the actual floor loop, on the return side, after the water is cooled, but it's still not cooled very far. Probably it would work, but I wondered if I couldn't greatly improve the life expectancy of the LEDs by keeping them as cool as possible. I think I could orchestrate a low-flow solution, even a passive one that relies on convection (I have two stories on hand). Thanks for the thought!
 

ddrueding

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I know -- your thread back then is one I've studied, and was a chief inspiration for this post! Thanks! I was a little disappointed to see the project fizzle, by the end of the thread; hopefully you have a chance to get back to it sometime, or do a project like it in the future.

I intend to. But we were moving in and I needed a quick and dirty fix.

I confess that I'm interested in his input; if he's not around, then oh well. What "projects", here in storageforum.net or somewhere else? I'll resist stalking him, though. :)

Last I talked to him he was working on LED bike lights. I think it was in a thread around here somewhere.

Oh, so did you wind up with LEDs? I thought you were turning to fluorescents at the end.

Nope. When I realized that the heater in the house wasn't usable, and that we didn't have the money to install the system I wanted, I just put in 5" 75W halogen cans. They do keep the place toasty (at a price).

Yeah, I shouldn't throw copper out the window too quickly. I had thought of putting it in the actual floor loop, on the return side, after the water is cooled, but it's still not cooled very far. Probably it would work, but I wondered if I couldn't greatly improve the life expectancy of the LEDs by keeping them as cool as possible. I think I could orchestrate a low-flow solution, even a passive one that relies on convection (I have two stories on hand). Thanks for the thought!

I'm sure you could find specific data on those LEDs on temperature vs. lifespan, and I suspect that keeping them under 40C (100F+) would be just fine. I can't imagine even the supply side of your underfloor exceeding that temperature often (if at all), and if you have a very direct (efficient) link from your LEDs to the copper, the temperature delta there can be kept to a few degrees.
 

tagger

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I suspect that keeping them under 40C (100F+) would be just fine. I can't imagine even the supply side of your underfloor exceeding that temperature often (if at all), and if you have a very direct (efficient) link from your LEDs to the copper, the temperature delta there can be kept to a few degrees.

Actually, 125F is pretty common on the supply side, and the return, in some conditions, may not be as far from that as one might imagine. However, the flow would be just about right (and noiseless), and likely I could indeed keep them very close to 40C. They'd probably do a handy job of pre-heating the water before it gets back to the source! One really important advantage would be that I'd remain so far above the dew point that I wouldn't have to worry about condensation. Running cold water through pipes in the soffits could be a problem in certain cases.
 

ddrueding

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On the PDF under "Thermal Design" it shows that ambient can be 70C so long as the thermal resistance between the LED junction and ambient is kept below 7°C/W. Of course keeping it lower than that will help the lifespan of the LEDs, but that is a lot of headroom.

Also, under the "Lumen Maintenance Projections" note it says not to go over 2A if you want to keep 95% of brightness after 6000 hours. It states a 35,000 hour lifespan, but not how bright they will be at that point. I would probably use more LEDs at a lower power setting just to make sure they can achieve your expectations.
 

ddrueding

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It also seems that the unit was designed for 700mA (most of the graphs use that as a reference), but efficiency numbers (like 100lm/W) are typically at much lower power settings.
 

Bozo

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You might want to consider multiple transformers, as you mention. Having a fault in one fixture putting the whole house in the dark would be a real pain.
 

jtr1962

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I didn't catch this thread because I haven't been around much. Mom was hospitalized in late February. Thankfully she's doing OK now but I needed to take on pretty much all the responsibilities of the household for a while. That doesn't leave as much time for sites like this.

Anyway, I'll start by suggesting a transformer in every room. It's easier to purchase such transformers because the wattage ratings will be smaller than a whole-house transformer, and you avoid a single point of failure. Also, you can match the transformer voltage more closely to the LED string voltage. I also suggest you go with 24 volts instead of 48 volts. Easier to find drivers for 24 volts than 48. Even 12V is viable. Remember that the entire point of LED lighting is efficiency. This means even if you light a room stupidly bright, say 10,000 lumens, you're only looking at 100 watts of power, give or take. Even using 12V, this is only about 9 amps accounting for driver losses. Even the thinnest Romex can deal with this.

Next issue is heat. The better LEDs such as the XP-G, XM-L, and the new XT-E convert better than 1/3 of their input power to light at lower currents. This means if you're feeding the LEDs 100 watts, you might only need to deal with 65 watts of heat. If you don't mind using more LEDs (which helps make the light distribution more even), you might even approach 50% efficiency, meaning only half of what goes in comes out as heat. In any case, given the surface area you'll have for dissipation, there is no need for liquid or even forced air cooling. My guess is junction temperatures will remain low enough to ensure at least 50,000 hours of service. This is "good enough". Remember you probably don't want to design for the LEDs to last forever until LED efficiency has plateaued because you'll eventually want to replace your emitters with more efficient ones. 50,000 hours will ensure you won't need to consider replacements for 10 years or more. By then LED efficiency will have come very close to being as high as it will ever be. A secondary benefit of this will be that junction temperatures will be very close to ambient because very little input power will come out as heat. This should ensure very long life of the replacement LEDs, perhaps on the order of several hundred thousand hours.

Color temperature and color rendering are the next issues. At this point I don't recommend mixing whites with reds or ambers for improved color rendering. For starters, unless you put a red/amber with each white, the end result will look horrible. Second, you can find LEDs with "good enough" color rendering these days. I've finding that neutral white XP-Gs look quite good even though they're not specified as "high-CRI". If you prefer 3000K, "incandescent" type light, you can go with high-CRI XP-Gs. Another high CRI option option is the Nichia 219, which is finally available to us hobbyists in a very nice 4500K. As already suggested, buy a few of each possible candidate which has specs you like, and try it. There is no substitute for actually seeing the LED in use.

More later once I get some feedback on what I've already written.
 

ddrueding

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Good to have you back jtr, and I'm glad everyone is alright. Without dimming, what are the opinions of putting the switch on the 12v side or using normal household switches on the 110v side and having to use separate transformers for each load?
 

jtr1962

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I think it makes more sense to just switch the transformers on the 120VAC side. If you switch on the 12V side, the transformer still draws power even when the lights are off.
 

jtr1962

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I'm tempted to say the same ones I used in your and my chandelier projects but those might not be useful here if the number of LEDs in the string needs to be less than three or more than six. Truth is I haven't really looked at what else is available in a while. For the purposes of this project, a decent quality generic 12V or 24V supply might suffice as the most cost-effective solution on the AC side. The current of each LED string would in turn be regulated by constant current DC-DC drivers similar to the ones I make for automotive use.
 

ddrueding

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I don't mean to derail tagger's thread, but I'm still missing some chunks of knowledge. (Thanks for your patience!)

120v AC -> Light Switch -> 12v Power Supply -> LED DC-DC driver -> LEDs

Is that right? If I don't need dimming, what are the most important factors for the driver? How to compute the number of LEDs in a string and how many strings?

Now that we have an efficient heat pump in the house, it would be great to not use these inefficient 75W halogen heaters all the time.
 

jtr1962

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I don't mean to derail tagger's thread, but I'm still missing some chunks of knowledge. (Thanks for your patience!)
120v AC -> Light Switch -> 12v Power Supply -> LED DC-DC driver -> LEDs
Yep, that's pretty much how it would work. The point of using one constant voltage supply for an entire room, versus individual 120VAC drivers for each LED fixture, is it makes the wiring if you have a bunch of fixtures in a room much simpler (i.e. most of the wiring is low voltage). By using an individual DC-DC driver for each fixture you're only using low voltage wiring in that fixture. And you can also easily dim most DC-DC drivers via a potentiometer or microcontroller. If you only have one fixture in a room, then a single 120 VAC driver probably makes more sense.

Is that right? If I don't need dimming, what are the most important factors for the driver? How to compute the number of LEDs in a string and how many strings?
I'd probably say the current rating is the most important factor. Better to overdesign a bit and use a driver capable of, say, 2 amps, if you plan to run your LEDs at 1 amp. Overdesigning will allow the driver to last longer and run cooler. In LED systems, it's actually the driver electronics which are usually the weak link. And of course the LED driver must be rated to run at the raw DC voltage you plan on using.

As for LED voltage, if possible it should be fairly close to but perhaps several volts less than the raw power supply voltage (i.e. 12V, 24V, etc.) because DC-DC drivers are more efficient when the LED string voltage and power supply voltage are close. For example, using a 12V power supply one of my automotive drivers is about 84% efficient driving a single LED, 90% efficient driving 2 LEDs in series, and 95% efficient driving 3 LEDs in series. The voltage of LED strings can be roughly estimated by allowing 3.3V per LED. In the case of a 12VDC supply, the maximum number of LEDs in the string can't exceed 3 unless you use a boost driver. With a 24 VDC supply you can usually go to 7 LEDs per string, especially using LEDs with a low Vf such as XP-Gs. With a 24VDC supply and 7 LEDs, DC-DC drivers can be 97-98% efficient.

Now that we have an efficient heat pump in the house, it would be great to not use these inefficient 75W halogen heaters all the time.
Agreed. A big disadvantage of using ceiling-mounted incandescent lamps as space heaters in much of the heat ends up in the attic where it's wasted. It's more efficient to just use a regular resistance heater if you don't have a heat pump.
 

ddrueding

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Agreed. A big disadvantage of using ceiling-mounted incandescent lamps as space heaters in much of the heat ends up in the attic where it's wasted. It's more efficient to just use a regular resistance heater if you don't have a heat pump.

That is one of the reasons I got cans that are designed to be surrounded by insulation, and then surrounded them with insulation. Most of the heat goes down (it can noticeably heat whatever is underneath it within minutes).
 

ddrueding

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ddrueding

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The main things I'm interested in is light levels, colors, heat dissipation, etc. so I do need to get the same stuff that I plan on deploying elsewhere.

Though that does look like a cool (and ridiculously cheap) system.
 

tagger

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THANK YOU!

I finally caught-up reading all of these great posts. Thank you so much for chiming in, jtl; with all this input, I think I can make a great educated decision on some tester LEDs to purchase and hook up, and be able to shop for some power supplies, drivers, etc. You mentioned, jtr, in another thread, making drivers.. do you still do that? If I spec'd out for each room what I wanted in terms of exact LEDs, the number of them in series, and the line voltage (which would be obvious at that point), could I hand that info to you to build a driver? Or would you recommend something off-the-shelf; I'd just have to isolate the appropriately-spec'd one? I haven't looked a lot at drivers, either making or buying, yet. I do have some electrical experience, and studied electrical engineering in college (oh so long ago), though I develop software for a living now; so, in short, it's not totally foreign to me. But I know enough to know that even a simple driver might not be so simple. There are of course things like this out on the web, which certainly suggest simplicity is sometimes in order.
 

jtr1962

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You mentioned, jtr, in another thread, making drivers.. do you still do that? If I spec'd out for each room what I wanted in terms of exact LEDs, the number of them in series, and the line voltage (which would be obvious at that point), could I hand that info to you to build a driver?
I still manufacture drivers. Once you settle on specs, let me know and I'll see if something I have is suitable. It should be as I make automotive LED drivers but the chips I use can operate way above 12VDC if necessary. In fact, most of them can operate to at least 30 VDC, a few even to 60 VDC.
 

tagger

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I'll probably stick to 24V. I think that'll be sufficient, and I'm not running long lines, as I was originally thinking I might, in which case the line-loss was a consideration. So I may be interested. What would you say, in your humble opinion:), do your drivers bring to the table that off-the-shelfers can't?
 

ddrueding

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Ended up with 12 of the Triples. I've attached a picture. It looks like I can just run a pair of solder bridges to run them in series?
Triple-LED.jpg
I also have a pair of the LuxDrive BuckBlock 2100mA drivers (PDF).

So if I put in 12v, I can run 4 series of 6 and be running them at 350mA? I don't think I'm doing the math right....
 

jtr1962

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I'll probably stick to 24V. I think that'll be sufficient, and I'm not running long lines, as I was originally thinking I might, in which case the line-loss was a consideration. So I may be interested. What would you say, in your humble opinion:), do your drivers bring to the table that off-the-shelfers can't?
I'd say my drivers have a proven track record at this point. I have several thousand running in an automotive environment with relatively few failures. An automotive environment is much more severe than a household environment. My drivers don't cost any more than anyone else's either.
 

jtr1962

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What are people's (specifically JTR's) thoughts on this 60W dimmable LED power supply?
That seems like a good power supply but since it's constant voltage instead of constant current I'm assuming using a dimmer will lower the output voltage. This means the dimming feature will only work if you don't use DC-DC drivers in between the power supply and the LED. Basically, you would need to just run the LEDs in strings with a simple resistor to limit current.
 

jtr1962

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Ended up with 12 of the Triples. I've attached a picture. It looks like I can just run a pair of solder bridges to run them in series?
Yes, that would work just fine.

I also have a pair of the LuxDrive BuckBlock 2100mA drivers (PDF).

So if I put in 12v, I can run 4 series of 6 and be running them at 350mA? I don't think I'm doing the math right....
Actually, 2 series of 6 if the input voltage is 12 VDC, 4 series of 6 is it's 24 VDC. Each 2100 mA driver can drive 6 LED strings in parallel at 350 mA per string. With 12VDC you're limited to 3 LEDs per string, or one triple wired in series. With 24 VDC you can go to 6 LEDs or two triples.

The only caveat is to make sure all the LEDs you're using are from the same bin (which yours are), and also more or less at the same temperature, to ensure the current gets distributed evenly.
 

ddrueding

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jtr1962

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Sorry, I'm a bit confused. Since I'm doing 12v, I'll just focus on those bits:



4 triples like this?
View attachment 492
That one wouldn't work at all on 12 VDC. It would work fine on 24 VDC. Each string would get 1050 mA.


So 6 strings of one triple each?
View attachment 493
Yes, 6 strings of one triple each per driver. I assumed when you said "series of 6", you mean a series of six triples. I think that's where the confusion came in. Anyway, connecting them like this will work just fine. Based on the B10 bin, you should get at least 100 lumens per LED at 350 mA, or 1800 lumens total for all 6 strings on each driver.
 

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Those are both bad configurations to use. You can't control the current in each string. You could end up with too much current one or more of the strings due to variation in Vf.
 

ddrueding

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Those are both bad configurations to use. You can't control the current in each string. You could end up with too much current one or more of the strings due to variation in Vf.

I suspect that is why he wanted to make sure they were from the same bin and operated at the same temp. Even with those under control, do you think there would be too much variance in Vf? What configuration would you recommend?
 

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I suspect that is why he wanted to make sure they were from the same bin and operated at the same temp. Even with those under control, do you think there would be too much variance in Vf? What configuration would you recommend?

I used to have the same line of thought as SD but that was back in the days when LEDs have wide variances in Vf. Nowadays it's likely Vf from the same bin will match to within 0.1V or better. An alternate arrangement is to connect each triple in parallel, and then use two groups of three triples in series (you can equalize things further with the optional connections shown in red):

Parallel_Triples.png

This configuration is generally more immune to variations in Vf than the one you proposed.
 

ddrueding

Fixture
Joined
Feb 4, 2002
Messages
19,511
Location
Horsens, Denmark
That looks easy enough, wire is cheap. I just need to think through the physical topology.

I'll be mounting 6 triples and a single LuxDrive BuckBlock on the flat side of a heatsink that is 24" long, 4.23" wide, and about an inch tall.

What do you think of this? Everything is to scale but the wire.
Component-Layout.png

Thanks so much for the help!
 

jtr1962

Storage? I am Storage!
Joined
Jan 25, 2002
Messages
4,168
Location
Flushing, New York
That looks good to me. I'm estimating the heat sink will be dissipating 25 or 26 watts (this assumes about 1/3 of the the power to the LEDs comes out as light, the rest as heat). The heat sink will get warm, but probably not too hot to touch, and the LED junction temperature should be just fine. Don't forget pictures when you're done!

I may ultimately make an LED setup to replace the flourescents in my work room down the road (in a few years). My LED projects in the relatively near future include the dining room chandelier and modding some outdoor halogen lights that look like this with LEDs. I'll probably need to project about 3000 to 4000 lumens forwards to match the output. I'm not yet sure if the small housing is up to dissipating the heat. I'll probably use the new Cree XB-D because it's has the lowest cost per lumen and "good enough" color rendering for outdoor lighting.
 

ddrueding

Fixture
Joined
Feb 4, 2002
Messages
19,511
Location
Horsens, Denmark
Got it built, but having an issue. All the LEDs all turn on for just an instant when I plug it in or unplug it, but the rest of the time are off. Need to start testing stuff. Any suggestions?
 

tagger

What is this storage?
Joined
Apr 18, 2012
Messages
10
I'd say my drivers have a proven track record at this point. I have several thousand running in an automotive environment with relatively few failures. An automotive environment is much more severe than a household environment. My drivers don't cost any more than anyone else's either.

Ok, I'm going to order some LEDs in the next couple of weeks to emulate a single solution for our new build. It'll be a series of 8 single LEDs. I'll send a drawing and the LED choice(s); how will I go about providing payment and shipping information to order a constant-current driver? And will you be able to make a transformer recommendation, too?
 
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