Sound like potential for a DIY lamp?

I don't have or remember the voltage/current curve for your leds, but as log as the voltages and ma. line up, you should be good to go.
I'm sure you read some of the links, they will give you the calcs to figure everything out.

I hope you don't become a statistic of social Darwinism.

Jahulath said:

It came to too many $$ so I started comparing to pre-made devices like this:
http://www.ebay.com/itm/DC-StepDown-Converter-Constant-Current-LED-Driver-Buck-Voltage-Regulator-Circuit-/261096541994?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item3cca910f2a

It looks like it will do the business, Input is good, efficiency is ~90%, they are adjustable (one size fits all and I can dim!!!) it costs $30 less overall than buying all the components! Any thoughts before I order?

Thanks in advance

Click to expand...

you are on the right way with this drivers.

now to your next problem, the Powersupply
wasn´t it 12V?

the little driver has from specs a Dropout voltage of 2V. which is nor bad.

some calculation:
Vf red Led 8 - 8.5V
with the 2V of the driver we have 10.5V max. thats lower then 12V so it will work

Vf blue led 9.6 - 11V that goes to > 11.6 - 13V ...!!
full power not possible

The White LED ran at a flat 12V

Click to expand...

blackout

Thanks Guod, and thanks Tenthirty! Hows this for a plan, if I run the lower voltage ones on the CC pcb and then (because you have to have some resistance in the circuit) I run the 12v whites from 0.1ohm resistors? I noticed during my somewhat shoddy test of the resistors that the lower one I used didn't get anything like as hot, the power wasted by a 0.1ohm resistor should be so low that it doesn't become too hot - I make it 0.1w per LED so for the total for ~12A (10* whites and 2* higher wattage ones) is only a little more than a 1.2W spread over 2 aluminium housed resistors.
For my test I was wasting ~3.9w in one resistor and ~2.2w in the other and there was a very large difference in temperatures between the two.

Is it possible that "burning" 0.6W in one of these should be ok even though I am not fixing the current with this resistor but instead relying on dividing it neatly whilst hoping that I can stabilize the temps on the LEDs with active cooling?

I think I may be deluding myself - thanks again for your time!

The driver looks good to me (but I don't have experience with these, so I'm just going by what it says).

It says you need a heatsink for anything over 15W. I couldn't see where you'd install this heatsink or what sort to get, so I'd want to get details on that, or plan on running well below 15W.

As for the 12V LEDs, this sounds like something similar to the Cree Easywhites - the chip is essentially four LED dies in series, so they require a higher voltage. There's probably documentation out there on the proper way to drive them, but I suspect they might be designed to be run directly across 12V without drivers or resistors.

Hi, in my test I did run one of the warm whites straight off the 12v supply and i seemed fine, the chips are actually 9 led in a little matrix:

You can clearly see each diode in the group, the 10w ones have 9 and the 20w one has 20.

I have 4 of the CC devices on order, once I get through testing with the CC devices I'll have a much better idea of what to do but I am still pretty hopeful that the white ones will run without - I'll tell you in 2 weeks when they arrive

The heatsink goes onto the regulator chip (FET, PWM, - I dunno) they can be bought with this but I have a bunch of RAM sinks from an old PC that will do the job well enough.