Hello Arduino Fans
I wanted to double check to see what step down buck converter that I need to buy in order to bring down an 18V DC battery source down to 12V DC required by at 10W 12V DC cob led.
Would the following do the job?
Or perhaps this instead?
I Think this is a good match. Please confirm
Good Match ?
Looking forward to your comments
The 10watt COB LED needs a constant CURRENT driver, not a constant VOLTAGE supply.
So the first two links are not ok.
The third one is all you need.
Solder wires to the PWM input of that PT4115 chip and big capacitor negative/ground, and you can dim the LED with an Arduino PWM pin.
Leo..
Cool. 
Thanks for that. On a side note can I power a 12V Cob led directly with a 12V battery or do I also need a LED driver as well?
First of all, there are no 12volt LEDs.
LEDs sold as "12volt" could have a simple series resistor included to limit current (e.g. LED strips).
A simple resistor can't keep LED current (brightness) constant if supply voltage and/or LED temperature varies.
Post a link to that "12volt/10watt COB LED".
10watt COBs are usually made with three strings of three 1watt LEDs.
Those LEDs (if white) have a Vf (working voltage) of about 3.3volt each.
So Vf of a 10watt COB is about 10volt (when warm/hot).
LED drivers, like the one you posted, need about 2volt overhead to work (minimum).
So a 12volt supply should just be enough.
But, the LED driver you linked to is designed to replace AC powered halogen lights with LED lights.
It has a bridge rectifier (four diodes) included, that drop (loose) another volt.
If you want to power the LED driver from 12volt, then you should bypass that bridge,
by connecting the 12volt supply directly to the big electrolytic cap.
Wise to also do that if you power the module from ~18volt (an old 19volt laptop suplly is perfect).
Leo..
This is the led in question
Yes, exactly as I posted.
Three LEDs in series, three strings, 9*1watt COB.
Leo..
Great! Thanks again for the tips. For future reference, can you recommend a LED driver for a 10W cob? One not designed for AC?
Most bare LED driver boards on ebay have that bridge rectifier.
Shouldn't be a problem to solder wires to the cap though.
This board doesn't have the bridge, but it's wrongly advertised as 3watt.
700mA is 2watt per LED in a string.
So 6watt into a 3-string COB (the one you have).
Leo..