LED project, heat dissipation

[Derek R]

I would like to put 24 150mA smd LEDs in a space approximately 1.5 x 3". The LEDs I have picked out have a die heatsink that I believe needs to be thermally linked to a heat dissipating material.

I have been searching for an easy way to do this (something to put behind the LED, on the board), but I haven't found much for applications this small.

Does anyone have any suggestions on what to use? Does there exist some sort of bracket somewhere that I could easily use? Should I instead look into having a place like 4pcb.com build a circuit board for me instead? Can places like 4pcb.com build heat sinks into circuit boards?


These are the LED's:

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=219044159&uq=636225868333308885
http://www.cree.com/~/media/Files/Cree/LED Components and Modules/XLamp/Data and Binning/XLampML_BL.pdf

Thanks in advance!

 

[BobK]

You should get one of the many LEDs / COB modules that are already fastened to a metal plate suitable to be fastened to a heat sink.

Bob

 

[Derek R]

You should get one of the many LEDs / COB modules that are already fastened to a metal plate suitable to be fastened to a heat sink.

Bob

I'm looking at what they have on Digikey for those, and much of what I'm finding is too large and more powerful than what I want. They also don't have any good yellow/amber options. I need these in white, yellow and red.

Edit: In my first post, this data sheet is more helpful: http://www.cree.com/~/media/Files/C...d Modules/XLamp/Data and Binning/XlampMLE.pdf Page 24

 

[BobK]

Okay. What is the purpose of this? If it is not for illumination purposes, 24 x 150mA is a lot of power.

Bob

 

[Derek R]

Okay. What is the purpose of this? If it is not for illumination purposes, 24 x 150mA is a lot of power.

Bob

A motorcycle tail light. I want it to be bright but also rather diffused (over several LEDs spread out).

I'll be building a circuit to fit in my front and rear turn signals. In the automotive section I got some help with building a circuit to allow me to use red dual-brightness bulbs in the rear turn signal housings to sync with the brake light, while disabling the higher brightness (brake light) when the turn signal flashes. Now that they're all put together, I don't like how the bulbs inside of the turn signals look like a single bright point, when I'd rather they be a more diffused lit up area. That would be just as visible to drivers behind me but easier on their eyes. The front and rear turn signals will have yellow/amber flashers, the front will have white running lights, and the rear will have red running lights that double as brake lights by increasing brightness.

 

[BobK]

Okay. The datasheet shows a pattern for a stripe to connect to the heat tab on the bottom of the LEDs and vias to carry away the heat. These would go to another side of the board which is solid copper except for the vias. So you will need a double sided board with vias. Then the copper on the opposite side can be connected to an additional heat sink if necessary. And you will need to use reflow soldering.

Bob

 

[(*steve*)]

You might also consider using aluminum cored circuit board.

 

[Derek R]

Hmm, sounds like using those LEDs would take a lot more time and thought than I had hoped. I've been looking around a little bit to try and figure out what lumen output I should really aim for, and I'm thinking I should shoot for a lot lower than I was originally thinking. I might still need to use LEDs that need heat dissipation, but I probably wouldn't need as much power as I originally thought.

Are "discrete" LEDs just LEDs that don't need cooling? I've been looking into those too, and I think building a PCB board with those would be way easier, as many are through-hole mount. It's just difficult to tell how bright they really are as they're rated in millicandela, and I'm also unsure what viewing angle to pick. I'm thinking somewhere between 30 and 60 degrees.

 

[Audioguru]

It is illegal to modify lighting on motor vehicles in Canada to prevent do-it-yourselfers from getting the brightness, viewing angle and color wrong. I hope that you will never be driving in front of me at night, or on a corner when I drive past.

 

[Derek R]

It is illegal to modify lighting on motor vehicles in Canada to prevent do-it-yourselfers from getting the brightness, viewing angle and color wrong. I hope that you will never be driving in front of me at night, or on a corner when I drive past.

So in Canada you have to keep the stock bulbs and everything? you're not even allowed to put say a putco LED bulb in the socket/housing in your vehicle?

Why would you hope I'll never be driving near you, rather than just hoping I'll get it right, or helping me get it right.....

 

[duke37]

There are european standards for vehicle lighting. Many years ago Ford had poor lights which caused accidents, they had to change.

If the standard lights are changed by a bodger, then the insurance will be invalid and a prison sentance is a possibility.
Even changing the type of tyre (tire) can invalidate the insurance.

Road safety is paramount.

 

[Derek R]

Allow me to explain so that I don't have any more people telling me that I'm endangering myself.

This was the light when I first got my bike (license plate is photoshopped):


As you can see, the light is broken, and there are no turn signals. The light has integrated turn signals. This is legal in the USA (where I live).

Here is the light I replaced it with:



As you can see, new light, no longer damaged. This one has integrated turn signals as well, but still there are no separate turn signals like the stock setup.

Still legal. The light is not OEM, and it is LED, but it's about the same brightness as the OEM incandescent light housing.

Now, I have purchased the OEM turn signal housings, and DOT approved clear turn signal covers (instead of amber). I have these OEM turn signals set up using Putco LED bulbs to act as both brake lights and turn signals. However, these Putco LED bulbs show up inside of these OEM turn signal housings as a single, excruciatingly bright point. If I am sitting at a stop light with a car directly behind me and my hand or foot on the brake, it is going to be uncomfortably bright for the person in that car. This is why I am interested in mounting LEDs on a flat circuit board and mounting it inside of the turn signal housing. This way I could spread the light out over a larger area and end up with lights that are just as bright, but in a way that is not as concentrated to one single point.