# 1" diameter - 12volts DC- 400 lumens direct drive possible?



## lightime (Jun 29, 2009)

My first post so... Hi all!!!

I want to apologize in advance if this is a ridiculous question 

Ok, so I am VERY confused. I have just recently gotten into led's and at first I was looking at "normal" led's (the ones that cost a few cents and can be wired straight to a 12 volt DC car battery by using a tiny resistor)....then I found the SSC-P7 and CREE MC-E etc...these seem to be a little more complicated to wire straight to a 12 volt car battery but seem to be MUCH brighter.

I have 1" diameter to play with and about .5" depth and I want to acheive about 300-400 lumens without needing any kind of power supply, driver etc...to hook up to a 12 DC volt car battery. Is this possible at all?

I thought about doing 8 or so normal led's with resistors but I'm not sure if I can reach that lumens target. Again I am confined to a 1" diameter, .5" depth, and 12 volt DC system. What are my options?

PS. I do not want to be able to control brightness, strobing or anything like that just straight on or off.


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## lightime (Jun 29, 2009)

*Most simple way to hook up a SSC-P7 in a car...*

I am new to led's so please bare with me. What is the simplest way to hook up a single SSC-P7 in a car (12 volt dc, fluctuates between about 12 volt and 13.5 volt when running )? I only want to be able to switch it on and off and achieve max reliable brightness.

Thanks in advance for any help.


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## mds82 (Jun 30, 2009)

*Re: Most simple way to hook up a SSC-P7 in a car...*

you need to purchase a constant currant power supply. this will help regulate the power from whatever input to the correct voltage and amperage for the LED.


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## DM51 (Jun 30, 2009)

*Re: Most simple way to hook up a SSC-P7 in a car...*

Welcome to CPF, lightime.

I'm merging your 2 threads as they are closely related.


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## lightime (Jun 30, 2009)

Thanks for the replies. Where can I get a power supply for hooking up the SSC-P7 in a car where the voltage will vary from about 12 volts to 13.5 volts?

Will a single P7 be brighter than say 10 normal led's wired together? Is it possible to reach 400 lumens with around 10 standard leds wired together? 

Thanks


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## Wiggle (Jun 30, 2009)

The "normal" LEDs you talk about are probably not even within an order of magnitude to the P7/MC-E output wise.


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## blasterman (Jun 30, 2009)

First, you'll need a driver to regulate the variable car voltage. No big deal.

However, you'll need a way to handle the heat any 400 lumen emitter (P7, Bridgelux, MC-E etc.) will generate.


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## lightime (Jun 30, 2009)

Can I use this: http://www.dealextreme.com/details.dx/sku.26110 (18V 5W Cree Circuit Board for Flashlights) to power a P7 with 12 volts input? If yes, how much power would a P7 plus sku26110 draw when on?

Or is this better:

http://www.dealextreme.com/details.dx/sku.13557 ... if so why?

Thanks


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## blasterman (Jun 30, 2009)

I don't believe either supply near enough sufficient current to run a P7.


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## Marduke (Jul 1, 2009)

It may be simplier to direct drive 3 or 4 XR-E's on a largish heatsink.


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## lightime (Jul 1, 2009)

Blasterman, if you read the reviews on the page of sku13557 http://www.dealextreme.com/details.dx/sku.13557

It says it puts out 650mA. What kind of lumen would that produce with a P7, what about a Cree XRE Q5?

How efficient would one of those drivers be?

Thanks!!


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## lightime (Jul 1, 2009)

Marduke, thanks for the reply...I want to use only 1 single LED. Thanks!!



Marduke said:


> It may be simplier to direct drive 3 or 4 XR-E's on a largish heatsink.


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## Marduke (Jul 1, 2009)

Define single LED... 

The P7 is a multi-die emitter. Using a single die LED, it is practically impossible to get anywhere near your target brightness.

Since you considered 10x5mm's, I figured several highpower would not be an issue.


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## lightime (Jul 1, 2009)

Sorry, I am new to all this. I meant a single P7, Q5 etc...

At this point I think I am just looking for the most efficient ways to power say a 650ma to 1000ma single multi-die with a 12-14 volt DC input.

I think the most efficient is the "buckpuck" but it is expensive... I'm not sure how it compares to the sku13557 from dx as far as efficiency? is there anything as efficient as the buckpuck for less $$?



Marduke said:


> Define single LED...
> 
> The P7 is a multi-die emitter. Using a single die LED, it is practically impossible to get anywhere near your target brightness.


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## Marduke (Jul 1, 2009)

The most efficient would be 4x XR-E's direct drive without even a resistor. An MC-E prewired for series would essentially do the same in a more compact package.

It might help if you actually explained your circumstances.


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## lightime (Jul 1, 2009)

Basically I am limited to a max 1" diameter lens to place the led itself so I can't use more than one. I am trying the get the most light while staying with this diameter and 1000mA or less. This will be installed inside a car in a rack that holds some audio equipment so that is why I need to use about 12-14 volt input.

Thanks again for all your input.


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## Marduke (Jul 1, 2009)

Well, your heatsinking is extremely limited in that space, so continued operation is not possible at full output.

4x XR-E's would fit space wise, but for any setup you need to go thicker for heatsinking.

12W of power is a lot of heat to dissipate.


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## lightime (Jul 1, 2009)

How thick would the heatsink have to be? what type of plate could I mount the 4 XR-E's to? Do I still need some type of driver or how do I wire them?

Thank you again.



Marduke said:


> Well, your heatsinking is extremely limited in that space, so continued operation is not possible at full output.
> 
> 4x XR-E's would fit space wise, but for any setup you need to go thicker for heatsinking.
> 
> 12W of power is a lot of heat to dissipate.


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## Marduke (Jul 1, 2009)

How thick would depend on how long you will be running the setup, and if any other cooling is present. LED's are like computer chips, heat will destroy them and you need cooling.

Either 4x XR-E's or one MC-E would be wired in a series configuration. No driver required, and you can possibly get away without using a resistor.

You could also use 3x XR-E's and a drop resistor.


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## bshanahan14rulz (Jul 1, 2009)

direct drive, provided you have a non-automotive 12v source. if automotive, please use voltage regulator. automotive 12v is dirty.


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## Marduke (Jul 1, 2009)

bshanahan14rulz said:


> direct drive, provided you have a non-automotive 12v source. if automotive, please use voltage regulator. automotive 12v is dirty.



Which is why it would be nice to know the details of the application...


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## lightime (Jul 1, 2009)

I'm not sure what other details you would need? The led/assembly will be mounted in a audio equipment rack in the trunk of my car. It will mostly be used with the engine off but occasionally with the engine on. I'd like to be able to run it for several hours at a time. I am pretty much stuck with 1" diameter for the lens. I'd like to keep it under 3-4 watts draw so that I won't drain the car battery soo quickly.

Maybe I should have started with my 3-4 watt max draw goal and worked from there? I really just wanted a simple/cheap way to hook up a single one of these multidie emitters in a car environment without the need for a huge heatsink. Again, I am new to all this so thank you again for all the input guys.


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## Marduke (Jul 1, 2009)

You can't really get that brightness at that power.

You also cannot get away from the need for thermal management.


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## lightime (Jul 1, 2009)

How much brightness could I get at 3-4 watts with a xre q5 or similar? Maybe I am better off going with my original plan of using 10 or so 5mm leds?


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## Marduke (Jul 1, 2009)

10 5mm LEDs will be vastly dimmer. At 3-4 watts, you are looking more at 250ish lumens with a modern emitter.


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## lightime (Jul 1, 2009)

That's what I figured so that's why I'm trying to figure this out. What's the simplest/cheapest way to hook up a modern emitter to a car electrical system using 3-4 watts for 200 or so lumens? Would something like this work on a single xre http://www.instructables.com/id/Super-simple-high-power-LED-driver/ or would this waste too much power?


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## Gryloc (Jul 1, 2009)

Things are getting chaotic here, it seems, and I see you getting discouraged and wanting to resort to 5mm LEDs. Here are some options for you, simplified as best as possible. More accurate numbers can be used after you make a decision. 

So, wait, you could obtain 400 lumens using only 4W of energy if you use 4 R2-binned XP-E emitters in series running at a 350mA of current each (or 4 in parallel at 1400mA total). You could cram 4 normal sized emitters together in a 1" diameter space as well. A M-binned MC-E should do the same but in one small emitter package. You do not need 10W to create only 400lm of light unless you use old Luxeon III emitters, or possibly a huge cluster of 5mm LEDs (but the diameter would be much bigger than 1 inch).

Try a MC-E wired in series. Use a small value resistor to drop that little bit of voltage when the car is running (13.5V), but the light will dim a little bit when the car is off and you are running off the battery for a while (but the light will be plenty usable). Are you sure that the heatsink or the enclosure cannot be any larger? 1" round by 0.5" deep is such a tiny space!

Actually, 4W will still be a bit much for such a small place and small heatsink, unless this heatsink is bolted to a large piece of steel or aluminum. However, if you cut all this down to a single XR-E emitter (and a current regulator circuit), you will get nearly 100 lumens and the LED will get pretty warm, but if you are using this at night, it should stay cool enough to not damage the emitter. 100 lumens is pretty nice. Maybe two emitters and 2W may easily work depending on your heat spreader...

If you find 100 lumens to be enough, maybe you should just toss in a cheapy 5W-10W light bulb. It is a tiny place to work with but in this power range, I think you can get anywhere from 75 to 150 lumens of light. A bulb is cheap, and easy to find. The replacement bulbs found in high-mounted brake lights are pretty bright, or just use your typical 12V brake light bulb.

Don't bother with 5mm LEDs, multiple 5mm LEDs make for a more complex solder job than using a single high-power emitter, plus the cheap ones are not as efficient! I mean that if you want 400 lumens of light (and a huge cluster), then it will still draw 8-20W of power (assuming 20-50lm/W). There will still be heat, but divided evenly among each little LED. 1 inch diameter cluster of LEDs may fit 16 or so 5mm LEDs, and I think that cheaper ones only put out 2-4 lumens or so, so that means a max of nearly 70 lumens, right? Plus the light is cold and blue-tinted. Some high-power emitters are much warmer colored in comparison. Your cheap light bulb will have the most pleasing warm light of them all.

What do you think? In such a small space, to get meaningful output from a power LED will mean a bit of heat to dissipate. Just for quick calculations, figure out how much light you need, and divide it by 80 lumens/W, and that will give an approximate power consumption in watts (new R-binned XR-Es have an efficincy of over 100lm/W at 350mA or ~1W). We can get more detailed after you make a decision on the light level you want. If the power level will be too high, then might as well switch to a light bulb. Assume maybe 15 lm/W for them -and bulbs don't mind the heat at all. If battery life is a concern, then a big car battery may not mind an extra 6-9W or so for a while. Are you driving your PA system off of the battery, too? If so, you should have a nice battery system already.

-Tony

EDIT:
BTW, you could drive a single die emitter (like the XR-E or XP-E) at 3-4W and get a bit more than 200lm like mentioned above, but I was just assuming situations where you used 1, 2, or 4 emitters at 1w each, where there is a good balance of output and efficiency. As you drive LEDs at a higher level of current (say 700mA or 1000mA), the efficiency will be less than at 350mA or ~1W. An MC-E uses four dies and can be treated like four separate LEDs (equivalent to four XR-E or XP-E emitters in one small package). Drive a MC-E at only 2W and get even better efficiency!


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## lightime (Jul 1, 2009)

Thanks for the reply Tony. You got it...I am pretty much going crazy here with all the info.  The 5mm cluster seemed like the "easy" way out but since I have extremely limited soldering ability that is pretty much out.

I can bolt it up to a fairly nice chunk of steel behind the .5" of depth so I think I can deal with the heat. I really wanted to use one of these newer emitters rather than a standard light bulb and I wanted to stay under 4watts total. So I guess that leaves me with either the MC-E or an XRE. Considering I was willing to settle on the brightness of 10 5mm leds I think I will be more than happy with 100-200 or so lumens. So does this mean a single XRE might work for me? if so what do i need to hook that bad boy up 

Thanks again for all your help.


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## Gryloc (Jul 1, 2009)

I will make this kinda quick (in comparison to my last post). I am doing some quick testing with an LED pressed against a 1" round piece of aluminum that is maybe a little more than 5/8" thick (all I have at the moment). I want to see what temperatures the heat spreader gets (not a good heatsink because it has very little surface area with no fins) at different power input levels. I have a small thermocouple probe sandwiched in there (meaning the contact isn't the best, so the LED die will be warmer than the metal base). I will report which power level is way too much (too high of temperatures for the LED). This isn't a pretty test, nor the most accurate, but it is something that will provide a few useful numbers to work with.

Anyways, with 1-4W of power, you can get a useful range of light. I am basing my numbers from now on from jtr1962's wonderfully informative post collection here. It is based on many previous lumen measurements and I have used these for years and I am excited to see new tests done. I love using actual numbers instead of assuming... So scroll down about halfway until you see a test on the "*Cree 7090 XR-E bin Q5*". I can imagine if you get an XR-E emitter, it will be a Q5-bin or better because they are a great value! You will see a table below showing each lumen measurement at each current level. The column showing power is useful also. Keep in mind some electrical power is used when producing light, so not all power that goes in comes out as heat (but it is a nice safety factor to assume so). Also, between each LED you handle, the forward voltage at a certain current level may vary by a few tenths of a voltage. So one emitter that requires 3.4V at 700mA and another 3.45V or 3.5V maybe. This will affect power in a bit, so your results will vary some. Jtr's numbers are good enough for your project designs.

So, you got lumen amounts compared to power inputs. This is for a single die XR-E emitter. If you use a quad die MC-E emitter wired in series, then just multiply the voltage, power, and lumen outputs on that table by four (current stays the same). With a MC-E, you can use an even lower current levels than the single die emitter and get a bit more light output.

So, choose between 100 and 200 lumens and think about what you want. The XR-E can make this light output using between 1.12W and 2.75W (respectably). The MC-E can do the same using between 0.86W and 1.8W. The MC-E is about 4 times more expensive than the XR-E, but it is up to you. With a bit of steel behind the heatspreader, you might be able to use more power, but we will have to figure it out later. I wont be able to post again until very late, so think about it.

-Tony


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## lightime (Jul 1, 2009)

I really appreciate you taking the time to test that for me if it holds up with something like that it would be excellent.The xre q5 is what I have been looking at. Maybe down the road I will do something with an mc-e but for now lets stick to the xre q5. Would it be possible to figure a setup for the xre q5 at 100 or so and a setup for 200 or so....that way I could perhaps try both.

If we could shoot for the 200 with the xre q5 that would be great, I would be willing to settle on a bit less but I would be *thrilled *with 200.

Thanks a million :bow:


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## blasterman (Jul 1, 2009)

The Cree XR-E Q5 / R2s are easily the most efficient/practical way to solve this problem. In terms of raw lumens per power used they are near the top of the food chain.

In fact, you could damn near hit 400 lumens with three cool white R2s driven at about an amp total and less than 12volts if my math is right. And, if you can solder in a tight space, you could keep the footprint to less than an inch.

However, I have to stress again that you are going to need a good deal of space to radiate that amount of heat. Please note the amount of radiating area LED MR-16's use to hit trivial lumen levels of 160 or so, and most of us criticize those gadgets for not having enough heat sink area, and they are out in the open. 

So, from how I'm looking at this, the limited space actually places a heat sink limit and hence is the bottleneck.


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## lightime (Jul 1, 2009)

yup, that is exactly my issue...that's why I'm willing to come down to say 100 to 200...I am assuming that since I won't be driving it as hard it won't generate as much heat and like I said I was going to settle on a 1" array of 5mm led's so this has to be much better than that. I'd like to just run a single xre q5 for somewhere between 100-200 lumens. 



blasterman said:


> The Cree XR-E Q5 / R2s are easily the most efficient/practical way to solve this problem. In terms of raw lumens per power used they are near the top of the food chain.
> 
> In fact, you could damn near hit 400 lumens with three cool white R2s driven at about an amp total and less than 12volts if my math is right. And, if you can solder in a tight space, you could keep the footprint to less than an inch.
> 
> ...


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## Gryloc (Jul 2, 2009)

blasterman, I just want to quickly correct you. You said you can achieve 400lm if you drive three R2 emitters at 1000mA. That is far from true. Check slightly past halfway here (Cree 7090 XR-E bin R2). To achieve 400 lumens using three R2 XR-E emitters, then you will only need to drive them at 400mA each (~4.02W total). If you attempted to drive all three at 1000mA, expect up to 810 lumens!

Anyways, I enjoy doing stuff like this! I ran a quick test by mounting a warm white SSC P4 onto a 1" diameter round aluminum bar that was about 5/8" thick (deeper than your requirements). I used some Arctic Alumina thermal paste between the star and the metal cylinder. I also sandwiched a small thermocouple probe between the two metal surfaces. Because the contact was not that good due to the thermocouple wire, the temperatures should be slightly lower (not by much). I ripped this emitter out of an IKEA lamp, and I estimated that it had an efficiency of 50-60lm/W, so more of the input power will be converted to heat than your more modern Q5 or R2 binned XR-E. This will work as a slight safety factor. Some pressure was maintained on the star MCPCB board containing the LED emitter by using some narrow strips of high temperature Kapton tape. The tape is strong, very thin, and sticks well to most materials in high temperature environments. The tape may have insulated the heatspreading aluminum cylinder a small amount.

So, I powered the LED emitter at varying current levels using my CC/CV power supply. I used some slightly common current levels, and determined the input power by multiplying the current by its forward voltage at that current level. The aluminum bar sat on top of a piece of cardboard, sitting on my folding card table top. There was a little amount of air moving around the room from the ceiling fan about 10 feet away. After setting the current to a certain level, I waited about 10 minutes or so (I didn't keep very good track due to being distracted by the CPF ). However, the temperatures looked like they stabilized somewhat. I hope to re-run this test later when I can watch the time better. Earlier today I was kind of rushed because I had to get to class. Below are my results...


```
Room temperature:         25 C  (78 F)  
   150mA  3.03V  0.454W   27 C  (82 F) * 
   350mA  3.28V  1.148W   49 C (121 F)  20.9 C/W
   500mA  3.35V  1.675W   58 C (137 F)  19.7 C/W
   700mA  3.49V  2.443W   73 C (163 F)  19.6 C/W
  1000mA  3.69V  3.690W  100 C (212 F)  20.3 C/W

*did not let stabilize fully
```
I seen a thermal resistance of 20 C per watt rise in temperature using my limited heatspreader setup. I believe this is only case-to-ambient thermal resistance (Rc-a). The Emitter has a thermal resistance of 8 C/W, and the MCPCB star may add another 5 C/W, right? So you are up to 33 C/W thermal resistance from junction to air (Rj-a). Can someone double check me? Thanks

It is difficult to measure junction temperature, but Cree made a chart to find suitable operating conditions. If you open up the XR-E datasheet here (pdf), you can see on page 7 a chart on the left ("Thermal Design") that tells you what are the safe operating conditions for the emitter. Using the 20 C/W line (case-to-air), the temperature at the operating current level must lay somewhere to the left of the line. Do not forget that my emitter is less efficient, and it also has a higher forward voltage at each current level. Still, the 700mA level seems safe (~2.5W). Assuming you go with a 700mA drive level, expect up to 185lm with the Q5-bin, and 210lm with the R2-bin. With heat brings a slight decrease in output (only a temporary degradation) of up to %20 (see page 6 of the datasheet). Extra heat can hurt the already less efficient emitter when you drive it at higher current levels. The efficiency of an underdriven MC-E may mean higher output levels and less heat to degrade the output. However, in real world application, your eyes may not see the difference.

I wonder how the temperatures will be affected of the aluminum plate is bolted to a large sheet of steel. I may re-test considering the aluminum is sitting on a sheet of metal I have laying around. 

Oh, I forgot to come up with some options for you like you asked for. Using the Q5-binned XR-E (common and pretty cheap), you can drive it at the following levels and expect the following light output:

```
Current:  Pin:   Output*: Case: Junction: Deg**: Deg Output:
   350mA  1.12W   105lm    47C      62C   -10%        95lm
   500mA  1.65W   142lm    58C      79C   -15%       121lm
   700mA  2.38W   185lm    73C     104C   -20%       148lm
  1000mA  3.50W   237lm    95C     140C   -30%       166lm

-Max junction temperature is 150C, so operating at 1000mA is cutting it close!

*This is the measured output of the emitter assuming the junction temperature
is close to 25C (tough to accomplish in most real world applications)

**Subtract from Output. The output degradation percentage is based on a 33 C/W 
j-a thermal resistance to find junction temperature, then using the graph on 
page 6 of the datasheet. I assume a 25 C air temperature.
```
That temporary degradation hurts a lot. Usually we don't see that much degradation in our flashlights due to our better heatsinking and far lower thermal resistance. The lumen figures are also "bulb lumens", so see further losses due to the additional optics and lenses you use. Physics stinks, eh?

Well, I need to get some sleep... I have a feeling that I left some hanging thread ends in this post. I guess I will clarify any questions of yours in another post. I will try to return during this busy week and holiday and see how I can help you along. There are others ready to help, obviously. Just consider the links I gave to Jtr1962's threads. Nothing beats actual measurements. We can assume all day, but if you use those numbers, it can help you figure out how many volts will be dropped at a certain current level, the light output in lumens, and the input power which can be compared to my crude power vs temperature table.

Cheers,
-Tony


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## lightime (Jul 2, 2009)

Tony, great info there and again I thank you soo much for your effort. To think that I was about to purchase 10 5mm led and settle for that  I was soo overwhelmed with info that I really had no idea which way to go. Thanks to your info/testing along with the others who chimed in I feel I have a much better understanding of how I will do this. 

Like you said nothing beats actual testing so I just ordered a couple xre q5's (my soldering skills, if you can call it a skill have been pretty much limited to wires so I need a few in case I mess up) and I'm going to use the lm317 + resistor to test it in my application (in the equipment rack in the car with the best heatsink I can get in there) at 350, 500, and 700... maybe even 1000 if all goes well. Based on your testing it looks like I should be good to go at the very least with 100 lumens from a single q5...sure beats the heck out of a dozen 5mm leds and is much easier to install. lovecpf

Once I determine whether to go 350,500, or 700...My next question would actually be what driver to use. From what I have read the lm317 + resistor would be very ineffcient. I'd love to know how to figure out how ineffcient it would be just out of curiousity.

After doing tons of searching here at cpf and running around on google I beleive that my only solution to actually drive this will be something like a "Buckpuck"....kind of pricey but looks like it would work. Is there anything else that I could use as a driver?

Thanks again!


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## PapaLumen (Sep 2, 2010)

http://www.dealextreme.com/details.dx/sku.26110 is a very cheap driver which would suit. puts out up to 1.2A though, but many people run their xr-e's at this current. Ive just recieved two of them for two xr-e torches im am making.


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