Cree High Power Led Recessed Light to Go in Self Made!

There are already many solutions to replace recessed halogen lamps, but so far nothing from the stool has torn me. Often only inferior offered LEDs to completely inflated prices, which can emit very little light and only very partially replace the traditional halogen lamp in the installed state. In this blog post, I will now present my personal installation solution with 10 each other hanging lamps installation. Of all until we get a concept, what should the lamp and what we create value. In other words: What our lamp better to can, as what is on the market.

What Do Able the Lamp?

For one, the lamp of amount of emitted light a conventional 35W halogen lamp must be equal. To do this, we set views times on a Lumentabelle, which should be easy to find on the Internet. To the example this here, I regularly use.

Here now is an entry of a 35 W halogen lamp approx. 400 lumen. Target is also to come as close as possible to an efficiency of 100 lumen/W. Also the LED lamp must fit in a normal installation version (mounting diameter: 75 mm) that I have already the versions available, I need only a solution, as I that integrate LED into this version.

Selection of LED, As Well As the Driver

According to, as it is many LEDs on the market, I looked at all data sheets for the CREE LEDs me well-known dealers at one. Manufacturer CREE currently has the best selection of LEDs, as well as all data sheets, which I need for my choice in my opinion.
After a slightly longer search I decided for the CREE XML T3. The voltage of the LED is approx. 3,1V in this case.

Now we have to find yet a suitable driver for the LED. In my case I’m looking for a driver that can provide 10 of this led with 1,4A. By Daisy, this should pose no problem. (More precisely explained in How to fix LEDs?) The requirements for the driver are at least 3,1V as well as 1,4A constant current.
Again, this was a search started. After a perceived half eternity I am struck however. Max 36V 1,4A constant current. Sounds not bad, is purchased.

Intermediate status:
LED is chosen, driver for the LED is ordered lamp holder available.

Cooling of the LED

As mentioned in one of my first blog posts for the FAQ section, it is absolutely necessary to cool. It is not enough so, simply choose an LED, to buy the driver to connect to and that’s it. The cooling system and the choice of the heat sink is here decisive for the success or failure of the project. Granted, cause less suitable cooling systems also a temporary success. The chip temperature of the LED but climbs over its critical value of approx. 120 ° (90° of the heat sink are about), it’s only a matter of time until the spirit gives up and becomes blind.

Now back to the construction of the LED. Normally, the used version for halogen lamps is designed. To be more accurate for halogen lamps with a diameter of 50 mm. Looking for a heat sink, which has exactly 50mm diameter and that enough cools for approximately 4W of power LED is so.
To be honest I don’t know.

If you have no idea, just shut. […] Would I do the blog entry was already over. So if you have no idea, you must get that idea. It was so on the test.

Selection of the Heat Sink

So I found a little at Amazon and found three lamps. (The first, the second and the third)

But since I need just the heat sink, I took it completely apart and set the rest aside. The 3 different heat sink were equipped with ever a CREE LED and connected. After approx. 1 hour continuous operation was respectively the temperature measured and selected the best heat sink:

The picture above shows the measurement. To see the display, 65.3 ° C are continuous operation after approx. 1 h. The temperature sensor the LED is centered on the star heat sink and so measures the temperature directly at the LED.
65° was however still slightly too high to me, therefore I brought just a small heat sink on the back to make a small additional cooling effect. However, I didn’t make another measurement. (should I do maybe to test the effect.)

Assembling the LED


Everything perfectly! Except that the driver instead of 1,4A makes constant only 1,3A everything in the best order was. A measurement on the 235V page made me somewhat puzzled. 235V input at fairly constant 172mA AC makes 40,42W together. On the low voltage side, however, the following measurements: 1,30A 30,7V (makes 39,91W). The efficiency of the driver is almost 99% therefore approximately 98.7% (rounded up). Man now believes the data sheet by CREE and it now comes my values measured on an overall efficiency of about 95 lumens per watt.

Built the whole way, as follows: