Heatsinks for LEDs

Hello,
I’m planning to make some stairs lights that will be incorporated in wall (off course they will be controlled by arduino:)). I’ve found 1W LEDs sold very cheaply on ebay, that look like these:

The same seller sells heatsinks:

And my question is do those LEDs really need such big heatsinks to function properly…? In my situation I think they will be on for max 5-10 minutes at one time, so maybe I shouldn’t bother myself with additional equipment? :cold_sweat:

do those LEDs really need such big heatsinks to function properly.

I have no idea because you haven't said what you are going to run them at and you have not given a link to the data sheet. I suspect you don't have the data sheet yourself, so we are both guessing.

Grumpy_Mike:

do those LEDs really need such big heatsinks to function properly.

I have no idea because you haven't said what you are going to run them at and you have not given a link to the data sheet. I suspect you don't have the data sheet yourself, so we are both guessing.

Yes, you are right, but I don't think those LEDs differ very much... As far as I saw on ebay, all of them use 3.4-3.7V and 300-350mA.

Those type of LED packages do require heatsinking. Now if that heatsink you show is larger then needed, could be but what do you propose to use instead? Some 1 watt LED packages include a built in metal heat sink on there back surface, but yours only have a flat metal surface designed to mount up against a heat sink surface. Calculating heatsink size involves a lot of variables and usually requires a datasheet to obtain some of the needed information. If you can't do the proper calculations then it's better to error on larger then smaller.

However seeing that you are getting them cheap you can afford to experiment with one to see how long it takes to burn out without any heat sink, and then test another using a small heat sink and see how long that one last before burning out, etc, etc. Hopefully you find the right size heatsink to use before you run out of LEDs. ;)

In my situation I think they will be on for max 5-10 minutes

That is plenty long enough for them to self destruct.

You will be generating 1W of heat, you have to get that heat away using heat sink. Whether it needs to be that big you can't tell without knowing the thermal resistance between the chip and the case. Once you know that you can calculate how hot you can let the case get, then if you know how hot you will be running it at you can calculate how low the thermal resistance of the heat sink has to be. Heat sinks when yo buy them are classed by their thermal resistance. See:- http://www.thebox.myzen.co.uk/Tutorial/Power.html

And my question is do those LEDs really need such big heatsinks to function properly...?

Maybe the guy on ebay is really selling heatsinks, not LEDs. Kind of like the guy who was stealing wheelbarrows*.

Don

  • google for: joke "stealing wheelbarrows"