The current does not increase with the number of LEDs in series. That is why it is called a constant current power supply. What changes is the forward voltage so...
If you've got 10 LEDs in series with a 300mA current rating and 2.5 Vf/ LED then you still need to supply 300mA to the LEDs but 10 x 2.5 + X Volt for it to work.
Yes, but in this case we have 2 rows of 8LEDs in series for each color so the current will be the double.
I have a few 10watt of these models, same thing only smaller.
To compare, I used a cree ssc p7 (12watt) the ebay ones use double
the power and give off a lot less light than anything i've seen from
Cree or SSC and even NXP (Phillips)
Because of the high wattage, a switching regulator for power, then use
PWM through an n mosfet, tie the base to gnd with a 10k resistor
and you should be good to go.
with these 10watts i have i'm just going to use power transistors, via pwm
with a 200ohm resistor on base, roughly 20ma per pin vs next to no current
on a mosfet.
I know the ebay LEDs are crap but the can be easily changed for a better ones if required almost without changing too much the main circuit.
About using a mosfet... That was the first idea but the people who commented made me learn about the advantages of using constant current supply and I think it's worth it.
I can see the point about each color drawing 500ma...
16 LED per color so with 48W total (48 LEDs), power for each color is around 16W. Using P = I*E, or I = P/E, I = 16W/32v or 500mA.
Exactly, and the supply's will give up to 700mA so I have to set a new limit.
By the way, I didn't want to multiplex but I will have to because the ethernet shield that I'm going to use will take a couple of precious PWM pins and I won't enough.
I was thinking on using the famous TLC5940 (current sinking) between the arduino and the dim pin of the PT4115 pulling up the line. Will this IC be able to PWM 15 channels without flickering?