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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #11  
Old 09-17-2013, 07:37 AM
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Let's get the basics down. Any part which is heated by a current will get hotter until the radiated heat comes into equilibrium with the generated heat. If it was perfectly insulated, the temperature would theoretically rise toward infinity. In practical terms, if you make a nice wad of fiberglass insulation for the part to be contained, you can get most anything to smoke or burst into flames.

So, how much heat does a 1 watt part make? One watt second per second. How hot will it get? It depends entirely on what it is surrounded with.

Metalmann gave us a clue about how hot an LED would get when surrounded by air. That is a good starting point. You just have to decide what to surround the LED with to get the temperature where you want it.
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Old 09-19-2013, 10:06 PM
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#12 is correct. Take my custom troublelight as an example. The LED's are mounted to a steel pipe, which conducts heat fairly well. But with LED's, the heat sinks out the back, so the inside of the pipe warms up. That air in there just gets hotter and hotter. If you dont drill a couple holes in the bottom and top (convection cooling) the whole light will get too hot to touch after an hour or so, and the LEDs burn out eventually.

If you drill just two 1/4" holes in the bottom, and two in the top, its more then enough to keep the whole light cool. I mean it still gets warm, but you can put your cheek next to the top holes and feel the heat pouring out. It works incredibly well.
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  #13  
Old 01-05-2014, 11:59 PM
snav snav is offline
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Quote:
Originally Posted by BobW55 View Post
Just how much heat do these new super bright LEDs produce?

For example:
If I took a 1 watt white one, drove it at max output, just how hot would it get?
Could I hold it in my fingers, or would I still need a hefty heat sink for it.

Bob
I used resistors to simulate the 8w of heat wasted by the 10w lamp in pic and found that a 25mm x 25mm x 25mm ASIC black anodized five fin heatsink rose to just under 200deg and 265deg at 11.9w, so for your application I would think any TO220 heatsink would work. The trick is to get good contact without shorting the leads.
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  #14  
Old 01-06-2014, 12:24 AM
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There are three types of high power (>1W) /high brightness (gallium nitride) LEDs. The original type are. Made on sapphire substrate and are medium temperature. The newer, low cost LEDs made by Samsung and other companies associated with silicon semiconductors use, naturally, silicon as the substrate. These are generally more thermally sensitive. The newest type and used only by Soraa, use gallium nitride as the substrate. This so called GaN-on-GaN technology has no thermo expansion xoefficient mismatch and allows very high temp operation. Now, the funny part is, there is no general definition of low, medium and high temp because it really depends on the lifetime you define for the product. The new GaN on GaN operate near 200C at the die.

Also, ther is no such thing as a white LED, they are Violet to UV and phosphors are used to generate a range of colors to make white. This is the Soraa PR. They are really impressive bulbs. About $80 each last year - target market was retail displays (everything from jewelry and clothing shops to grocery store freezer displays.



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Old 01-06-2014, 12:42 AM
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$80.00??



Why not get 100 Watts for under $10.00?:


http://www.ebay.com/itm/390738631437...84.m1423.l2649
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  #16  
Old 01-06-2014, 12:52 AM
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Prices appear to have fallen to $35 range. Includes entire bulb (Power supply, heat sink, diffuser with high-efficiency organic phosphors on the diffuser (not on the LED), ...).

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