You need to be careful with the forward voltage specification. The datasheet hasJohn,
The OP posted a link to the site where he purchased the LED's on page 2:
http://www.componentsuperstore.com/...entifier=HPWTMD00F4000LUMILEDSLIGHTING6901870
P/N: HPWT-MD00-F4000
70mA @ 2.6V
I have similar LED's from the same mfg.; but mine are red-orange instead of red, and different lens. That's why I suggested he check to see what his Vdrop was @ 70mA; my actual reading is 2.66v not 2.6 as per the datasheet.
Having a separate NUD4001 for each group of four is very good idea. You do not needThe idea I have is to supply each string of four LED's with a separate NUD4001 IC; that would put each of them operating at < 15% of their maximum rating; quite a safety factor. Although a single NUD4001 could power multiple strings, if an LED failed in either shorted, or even worse, open mode, it would result in the remaining LED's operating outside of their specs.
Especially if your PCB software is scriptable ;-)But for power dissipation, it would be best to use a printed circuit board.
They're really not hard to make - do you have a laser printer?
Do you have PWM current source that you were thinking of using?so what the heck am I supposed to do? This is all just confusing me now. I figured it what be a matter of wiring the leds together, to a pwm, and with designated resistors. I never expected that I'd have this much to think through. It's just confusing me and frustrating me now. I need a clear way to do this. I know you guys are giving me the best ideas to making this work but I'm just not smart enough with this stuff to follow. I don't want to make you guys spell out everything but I need a clear cut idea. NUD4001 for every string? Do I need a pwm along with the NUD4001's? Resistors needed in between serires? What's going on?
I am going to let you tell meI just wanted to post something else. A guy just posted on my other forum that he was using 1 27ohm resistor for every 5 leds. He said it dissipated about 115mW and he didn't feel any heat from the leds. Now does that math seem correct?
The Vf of your LEDs is apx 2.6V. 5 * 26 = 13V. This is above the 12V of yourIf I were to do 5leds per string would that be better? There would be one string of 4 leds on the outer tails tho, since it only has 24 leds but the inner tails would be perfectly space with 6 sets of 5 leds. Thoughts? Math? Is that a better way to go to spread the voltage drop?
If you did a PCB layout it would probably take you about 2-3 hours to assembly.(should take we at least two weeks to wire them all)