LED help

mrgk

Hi All.

Im looking for some info on some leds what i need is cree XR-E Q5 essentially!!!

i need them in cool white(10000 K) and some blue and royal blue.

I need advice on where to get them, where to get the heat sinks, fans and how to hook em up. I have very lil experience with led and electronic in general, so I need major helo. would you please help me with this.
Regards

Bruthal

Not sure where to get any of the parts except do the usual google search.

Them cree led`s have a forward voltage of 3.7volts whch gives a current flow of 1000miliamps or 1 amp. So this means you can connect up to 3.7 volts direct to it.

If you connected 12 volts to it, you would need a resistor of value as follows

12v supply - forward voltage 3.7v = 8.3v

To get the resistor its now volts/current which is 8.3v/1 amp = 8.3 ohms so a 10 ohm resistor would do.

Because its 1 amp peak current for that LED, the resistor will work out at the supply voltage minus the 3.7v forward voltage of the LED. Because V/I in this case is dividing by 1.

2 10 ohm resistors in parallel will give you 5 ohms, 3 in parallel will give you 3.3 ohms suitable for a 6v supply.

mrgk

robbie7730 wrote: »

Not sure where to get any of the parts except do the usual google search.

Them cree led`s have a forward voltage of 3.7volts whch gives a current flow of 1000miliamps or 1 amp. So this means you can connect up to 3.7 volts direct to it.

If you connected 12 volts to it, you would need a resistor of value as follows

12v supply - forward voltage 3.7v = 8.3v

To get the resistor its now volts/current which is 8.3v/1 amp = 8.3 ohms so a 10 ohm resistor would do.

Because its 1 amp peak current for that LED, the resistor will work out at the supply voltage minus the 3.7v forward voltage of the LED. Because V/I in this case is dividing by 1.

2 10 ohm resistors in parallel will give you 5 ohms, 3 in parallel will give you 3.3 ohms suitable for a 6v supply.

Heya
Have you done this before yourself? and have you any experience regarding this type of leds??? have you any experience on hooking this up to a aluminium heat sink? and if you do where do you get the heat sinks?

Bruthal

mrgk wrote: »

Heya
Have you done this before yourself? and have you any experience regarding this type of leds??? have you any experience on hooking this up to a aluminium heat sink? and if you do where do you get the heat sinks?

No experience with the cree leds except for one in a flashlight i have. I have made up a few 555 timer circuits to run flashing standard LED`s or the same 555 timer chips as LED dimmers with pwm switching etc alright, for various things.

The cree leds are soldered to a circuit board and the circuit board dissipates heat, but further aluminium heat sinks can be attached with thermal paste if required, which probably would be if your driving it at its full capacity.

Here is that one you listed, on a site which might be of some help.

DublinDilbert

For any of these power LEDs your going to need good heat sinking. Using the figures above there's 3.7w of power going in. Assume say 50% they are 50% efficient, this means about 2w will go into the heat sink from each led.

If you just buy the leds you'll need an aluminium clad pcb made up to suit them. you might be able to but LEDs pre mounted on Alu PCBs but these might not work space wise...

Bruthal

What are you using the LED`s for OP?