0603 LEDs wiring help...

[thearkman2009]

I just got 100 of the little babies, and I have already done the WIFI and MS LED swap.  They work perfectly there.

Now I want to do the sound reactive mod, but have 17 LEDs (18 after I get my clear analog stick in) to put in all the buttons, but there is a problem.

I used several online LED calculator sites, and I get different responses from each one.  SUPPOSEDLY, you cant hook up 17 LEDs in series.  (yeah right)

Volts = 3.0 - 3.2
20 mAh each
MCD = 70

There should be no reason why I cant hook them up in series, or at LEAST 7 of them in series and the rest in parallel.

Sickmods calc says that 7 in series is a no-go, and parallel uses 15 ohm, 1/2 watt (just one)

LED calculator says that 7 in series is a no-go, and parallel uses a 91 ohm resistor after EACH LED.

What the  !  Come on, someone explain this to me.  My math says that its QUITE possible to do at least 20 in series if you wanted to.  Why can nobody get their story straight.

Also, would I have to use 1 LM386 for the speaker mod in the UMD door, and a 2n2222 NPN for the sound reactive for the LEDs?  (would prefer it that way if it works well)

Try to be as noob-friendly as possible, in case any noobs come looking for answers.   

[jakxxx]

I think there is an error in your series calculations.  For resistance you have to  subtract the voltage requirement for EACH LED in the series.  So considering there are only 3.6V and 5V available to you as sources inside the PSP, the maximuim you could use is 1 LED.  R = (Vs - Vl) / Il

Vs = 5v or 3.6v (supply voltage)
Vl = 3v * n (n being the number of LED in series)
Il = 20mA (current required by leds)

R = (5 - (3*2)) /.020
R = -50 ohms
you can't have a minus rating in ohms

This link is very useful for LED info:
http://www.kpsec.freeuk.com/components/led.htm

They recommend never connecting LEDs in parallel with one resistor if they are of different types.  They recommend using a resistor on each leg of the parallel circuit for each LED.

After reading many many post regarding this I think it is coming back to me.  I took electrical engineering in university in the early 90s.  I hope this helps.  Moderators plz correct me if I an wrong. 

[thearkman2009]

No, its not you.  I think I am slipping.  It was late 90s when I was in school, and have not really needed that knowledge since then.  I am used to working with 12 and 24 volt sources, so I bet I used either 12 or24 instead of 5 for the source.  lol  Dont know how I could let that skip past me.  I know I stay up too late, but damn!  lol