What do I need to drive 50,000mcd LEDs

[prosper50]

Hello everyone! Brand new to this forum, so thank you in advance for your assistance.

I was looking aroun the net for LED lightbars (offroad application, etc.), and they are amazingly expensive ($999+).

I went to ebay and bought about 50 ultra bright white LEDs thinking that maybe I can put something together for a lot less. The LED specs are as follows:

10mm
water clear
3.4-3.8V
15 degree viewing
50,000mcd
Forward Current: 30Ma
Peak: 100Ma
Reverse Voltage: 5V

The auction comes with 50 resistors in order to operate at 12V, but my question is, is there any type of device (driver) that would be best in order to properly power the LEDs (either in series or in parallel). Like I said, I'm tying to make some kind of light bar... probably two rows of 25 LEDs... so they would all be operating at the same time.

I know that the LEDs put of heat as well as any possible driver. I know that heatsinking is vital, so I will properly take care of that aspect.

Any specifics would be appreciated (brands, models, specifications, etc.). Also, if something needs to be custom built, I am OK with that as well. I have an electronics background, but I'm pretty new to the specifics of this new high intensity LED technology.

THANK YOU ALL!!

-Dave

 

[John_Galt]

First, :welcome:

Second...
Throw out those 50,000mcd LED's. these are low power LED's that may only produce that amount of light for a few hours before fading dramatically, if driven above a few milliamps.

Buy yourself a chunk of aluminum, and some fins for heatsinking. You'll want to buy some high power LED's, from Cree, SeoulSemiconductors, etc.

But first ask yourself this...
1) Do I want to go for maximum brightness, or for colors to look more realistic out doors. If maximum output, then look for LED's that have a color temperature, usually rated in degrees Kelvin, of 5,500+. If you want colors to look more realistic, at the loss of some output, look for LED's that have a color temp. of 3700-5500*kelvin.
2) What kind of beam shape do you want? A spot pencil beam to ligh things up far away; a full flood, illuminating everything within 20-30feet? Or a mixture of both.
I would say go with the Cree XR-E Line up of LED's, because they have a good output, are available on stars, for easy mounting and soldering, and have a wide array of optics available on the market.
3) How much do you want to spend? Making a good waterproof housing that has enough mass and cooling fins to hold your electronics and LED and optics can get expensive. Electronics can also be expensive. If this is for a vehicle, you are going to need a good "constant current" driver that has an input range voltage of 12- ~15v, to accommodate voltage fluctuations during different operations. (Constant Current, as opposed to a Pulse Width Modulation driver, which basically flickers the LED's on and off rapidly. If the flicker is slow enough, it can be seen often enough to be annoying.)
I would suggest taking a look at mountain biker forums for some ideas on construction of the housing, and what type of LED's to use (mtbr.com).

 

[carbine15]

+1 for high power LEDs. More light, better light, longer life (if heatsinked) and more efficiency.

 

[prosper50]

Hi guys!!

Thank you for the input! Oddly enough, I did start out at the Cree website before heading to ebay. I liked Cree's lineup of LED solutions. The only thing is, I didn't want to go top-shelf for my first LED experiment. I know that through the maze of driver options, LED options, current considerations, heat issues, etc., I will likely destroy something in this first round. Not to mention the fact that I need to experiment with light-bar size, shape, location, LED configuration, etc... for my particular application. I'm going to be taking this apart and re-assembling it a few times, and again, I know some parts won't make it. However, I would completely agree that Cree's solutions would be excellent for a final product.

My purpose for going to ebay was to get the biggest quantity of the brightest CHEAP LEDs available. While I could only find a quantity of 50, I am assuming that this will be good for a first test. I was just curious what solutions might have been recommended on how to get them the brightest, without destroying them right out of the gate. This will indeed be for an automotive application, so I would definitely need some kind of constant current device to compensate for the fluctuating current of the vehicle. I also wanted to stay away from PWM. ;-)

If there was some kind of cheap solution for this first trial, I'm all for it. I just didn't know what it was or where I could locate it. I have machining background, so I can easily manufacture a finned aluminum housing/heatsink for the entire device, I just wanted to get something up and running first.

So, knowing that Cree is the way to go for the final product, is there any suggestions for a constant current device that could drive the LEDs that I listed to their brightest potential without running the risk of burning them out as soon as I throw the switch???

Thanks again everyone!!! This is a GREAT site - I've learned a lot already just from mulling around the posts!!

-Dave

 

[John_Galt]

To test out your design options, before you commit to spending a lot of cash, maybe get a few Cree LED's in neutral and cold color temps, and a few different optics to try out.

Buy a length of 1/8th or 1/4 inch aluminum bar, some thermal paste, a driver, and test fit your optics to see what type of beam pattern you like best.

That way you'll have direct comparisons between LED's, and optics.

Have fun building it, what ever it turns out to be, and remember, post pics!

 

[JohnR66]

To add to John's fist post, the 50,000mcd rating is overstated even when new. If these were truly rated, they would be brighter than the Nichia GS and they ain't even close. My own tests put them at around 40% of Nichia GS intensity.

They fade at an alarming rate as well. At 30ma, these are down to around 1/3rd light output in 192 hours. Using a light meter, I tested LEDs from various ebay sellers with the same result. You get what you pay for.

If you're going to use 5mm LEDs, at least get good ones. IMO, if you need more than 9 5mm LEDs in a project that is to project light in one direction, then use quality power LEDs.

 

[prosper50]

Excellent Information - I just wanted to thank you John, John, and Carbine for your input.

I spent a bunch of time today looking around the net at the various recommended high-power LEDs (1W, 3W, 5W), and their respective power drivers, and I have one final question...

It seems that a lot of the common configurations, even on the Instructables.com website, only give specifications for one or two high-power 100Ma or 200Ma LEDs per driver (in both serial as well as parallel configurations). Obviously, if my ultimate goal is to create an offroad light bar, I will need a few more than a half dozen, even considering the high-power nature of these LEDs. Is there any source of information, or any guidelines, for connecting more than just a few of these devices per driver, or are numerous drivers necessary in order to facilitate a higher quantity of LEDs? I know that ultimately this answer will depend on what LEDs I use, their specs, what driver is used, etc.... but in general are these high-power drivers limited to powering just a few LEDs??

Thanks again, and as always, I appreciate the expert insight!!!

-Dave

 

[Kestrel]

if my ultimate goal is to create an offroad light bar, I will need a few more than a half dozen, even considering the high-power nature of these LEDs. Is there any source of information, or any guidelines, for connecting more than just a few of these devices per driver, or are numerous drivers necessary in order to facilitate a higher quantity of LEDs? I know that ultimately this answer will depend on what LEDs I use, their specs, what driver is used, etc....

I don't know if this will be of any help to you (I'm not a modder), but you might find the following thread interesting: The 'gold standard' of multiple high-power LED configurations, the Data Bank 70.

Post 78 provides a slight bit of add'l info regarding your interest.

 

[spencer]

For a light bar that will be driven off of an automotive power supply (12Vish dirty power) there are some good options for drivers. The hyperboost can run about 15 high power LEDs from a running vehicle (14.4V) at 1000mA per LED. I have been looking at it to do the same thing you want to do.

 

[lolzertank]

I don't know if this will be of any help to you (I'm not a modder), but you might find the following thread interesting: The 'gold standard' of multiple high-power LED configurations, the Data Bank 70.

I'm not sure if calling the Data Bank 70 a "gold standard" is appropriate given that the LEDs are direct driven from A123 cells.

Mr. Beambastic would be a better example, though 10+ MC-E drivers are certainly not cheap.

 

[Kestrel]

I'm not sure if calling the Data Bank 70 a "gold standard" is appropriate given that the LEDs are direct driven from A123 cells.

Mr. Beambastic would be a better example, though 10+ MC-E drivers are certainly not cheap.

Yeah I know it's not exactly what the OP was looking for, but thought it might have provided an idea. :shrug:
I figured that there might have been some other high-power builds out there that would be more applicable that folks might post on - the OP might have not run into the Big Lights thread yet and so I was wondering if this ground had already been covered by someone?

 

[lilmarvin4064]

for what you want to do, I would consider this housing...

Cooler Master : part # : ECC-00388-01-GP
Mouser Electronics: part # : 794-ECC-00388-01-GP

http://ecd.coolermaster.com/english/products/images/ECC-00388-01-GP.jpg

...and install 3 Cree MCEs. much more simple. 2100 lumens?

Not sure on the drivers. I prefer Luxdrive and Taskled drivers.