Originally posted by: Calculator83
Ok,, I think this is cool.. So I need to Order THAT driver.
Which LED do I order, they all seem the same to me. K2,, K2 Star,, III,,, VI,
I think I want my Light to be with One white and One blue..
How come the Blue ones have such lower Lumens.??
That driver is 1000 mA, and will drive a regulated 1000 mA through the LEDs connected to it.
There are 2 types of K2 LED. 1500 mA ones and 700 mA ones. If you connect a single 700 mA LED to the that driver, then it will burn out the LED. There are ways around this - e.g. you could connect 2 blue LEDs in
parallel. I know I said LEDs are best not used in parallel, but the luxeons have better quality control and don't vary as much as cheaper LEDs, plus if you connect 2 7000 mA LEDs to a 1000 mA source - you're underpowering them, so you've got a reasonable safety margin, in case one hogs the power.
There are a whole bunch of different types of luxeon LED.
The first distinction is the difference between the emitter LED and the star LEDs. The Star LEDs consist of a emitter soldered onto a metal star shaped heatspreader. The heat spreader also has solder pads where you can attach wires - this is better because you don't have to solder the fragile and heat sensisive LED directly. Don't get the emitters, you need a heatspreader - but the emitter die is only about 2 mm in size which means perfect contact is required. The emitter core has to be soldered to the heatspreader in order to prevent the core from overheating. The stars are ready to go from the factory.
Luxeon I is the original design - 1 W of power, about 15-25x as powerful as a conventional LED.
Luxeon III is a more modern, more powerful version - 3 W of power, about 50-80 x as powerful as a conventional LED.
Luxeon V was a variant of luxeon I - basically 4 luxeon I chips in a single package. Very expensive, but very powerful.
Luxeon K2 is the very latest in LED technology. Available in 2 power levels - roughly equivalent to luxeon III and luxeon V - but these are single core, not quad core like the luxeon V.
There is an important problem with the Luxeon III and V star LEDs. The heatspreader is soldered directly to the LED die. This means that the heatspreader is connected to the LED electrically. You can't put multiple III or V LEDs on the same heatsink, because the power will flow through the heat spreaders and heatsink.
In the Luxeon K2 stars, more modern thermal technology allows the heatspreader to work, while being electrically insulated from the LED. This means there is no problem putting multiple LEDs on a single heatsink.
As to the difference in brightness - it's several factors:
1. There are 2 white LEDs on that page with 2 different power - 700 mA and 1500 mA. Whereas there is only 1 blue (700 mA).
2. The human eye is less sensitive to blue light, so blue LEDs appear dimmer (the 'lumen' takes into account how bright something looks to the human eye).
3. The catalog page I linked have been careless in the specs. Luxeon provide two power specifications - light at 50% electrical power, and light output at 100% electrical power. They've put the 50% rating down for the blue, and 100% for the white.
The way I'd do it, is to use the 1000 mA driver. Then use a SPDT switch to connect the driver either to: 1 White 1500 mA LED, or 2 blue 700 mA LEDs in parallel. All the LEDs can be attached to the same heatsink if you use K2 stars.
One final point. Luxeon LEDs have a very wide beam - they are like flood lights. Normal LEDs have a very narrow beam (spot lights). A lot of this is marketing. Cheap LED makers like to put very high intensity numbers on their spec sheets (mCd). By making the beam narrower, they make the beam more intense (so more mCd) even though the LED is the same. If you want a narrow beam from luxeon LEDs, then you can get add-on lenses that will change the beam shape. There is a wide variety of lenses to suit different purposes.
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