Novice needs help

[wicked demon]

Hi. I have never really wired anything and a friend showed me some questionable stuff, and I have concerns.
I am making LED strips in parallel. example;
-
90 bulbs -30 rows of 3 x 3.5v+100ohm resistor
12v 1.5a dc power supply
-
How do I figure out how much light I am producing?
-
Is it ok to use any DC converter as long as I use a calculator and the appropriat resister?
-
If a spec says to use an 82ohm can a 100 be used?
-
What limits the number of lights you can put in parallel?

 

[nein166]

Hi. I have never really wired anything and a friend showed me some questionable stuff, and I have concerns.
I am making LED strips in parallel. example;
-
90 bulbs -30 rows of 3 x 3.5v+100ohm resistor
12v 1.5a dc power supply
I think your going to use 5mm LEDs with the legs right, looks like it will work
Your setting up a 3 Series x 30 Parallel array
+ ___________________
....|.......|........................|
..Res..Res...................Res
....|.......|........................|
..Led...Led...................Led
....|.......|......~repeat~.....|
..Led...Led ....~27x~.... Led
....|........|.......................|
..Led...Led...................Led
- _I____I______________I

How do I figure out how much light I am producing?
How much current are the LEDs seeing? I figure with the 100ohm resistor on each series of 3 the leds will see 15ma each
-
Is it ok to use any DC converter as long as I use a calculator and the appropriat resister?
Well best to use a switching converter not a transformer coil
-
If a spec says to use an 82ohm can a 100 be used?
Sure but you'll get less current at the LED since the resistor consumes more
A lower resistor would let more current thru but might overdrive your 5mm and burn them out
-
What limits the number of lights you can put in parallel?
The amount of current your power supply can deliver
Your setup shouldn't use more than 0.6A

This site may help if you haven't found it already
http://ledcalc.com/