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Topic: Power Leds 101 for begineers (Read 683 times) previous topic - next topic

buton

So i just  to confirm i am understanding all the theory behind leds or power leds, to start a simple project.

So i have this led  http://www.digikey.com/product-detail/en/XMLEZW-00-0000-0B00U440H/XMLEZW-00-0000-0B00U440H-ND/2681802

http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXML_EZW.pdf

Max Current 2A
Forward Voltage 6V

So from what i am reading

I will need a power supply bigger than the Forward Voltage of 6 V right?
so if i keep my voltage around 7 to 8 V it will be good. will it be better with 12 V?

if i use a second led in series my power supply has to be bigger than 12 V right because the voltage drop acrross each led will be 6V so 6 times 2 is 12 V..?


to prevent my  led from dimming i need to use a current driver(controller).  Rated for the current i want to operate my led, for example http://www.cui.com/Product/Resource/DigiKeyPDF/VLD25-SMT.pdf

it is rated for 700 ma so that will do the job right?

is there anything else i am missing?
visit www.diveduino.com

fungus


Sounds correct to me...


so if i keep my voltage around 7 to 8 V it will be good. will it be better with 12 V?


7-8V is better because the controller won't have to work so hard (it won't get as hot).
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Grumpy_Mike

Quote
is there anything else i am missing?

I think you have it covers. The only thing is that you might look at is the heat the led and controller will generate. This might require heat sinks.

fungus


it is rated for 700 ma so that will do the job right?


700mA will be with a heatsink. Read the datasheet carefully to see how it needs to be mounted on the PCB.

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Headroom

Most high power LEDs are first reflow soldered to a mcpcb ( metal core printed circuit board ). That mcpcb while itself being a form of a heat sink, is usually too small to dissipate the heat of a 700mA LED. Thus, that mcpcb with the LED then is mounted to a bigger heat sink either with thermal epoxy, thermal tape or thermal paste and screws.

Reflow soldering this LED " in the raw" to an mcpcb takes some form of equipment that most beginners don't have on hand, or experience with.

If you are interested in that specific LED, perhaps look for a supplier that has this mounted already on a mcpcb.

Here for example:
http://www.ledsupply.com/creexml.php
http://trippylighting.com

http://ledshield.wordpress.com/

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