Hi, I am making an LED sign and I think that I have everything worked out but since I have never done anything like this I want to make sure. I don't want to solder in 100+ leds then blow them all as soon as I turn them on. I am using an old laptop charger for power whose output is 19.5 volts, 3.34 Amps. I am going to try to make strings of 5 leds in series with a 100 ohm resistor and put lots of those strings in parallel. I got the resistance with this calculation: R = (V1 - V2) / I V1 = supply voltage V2 = LED voltage I = LED current R = (19.5 - [5 x 3.5]) / 0.02 R = (19.5 - 17.5) / 0.02 R = 2 / 0.02 R = 100 The amount of current that all those leds will need should be 2.12 amps A = 0.02 x 106 A = 2.12 That is what I got so in theory this should work but I would like to make sure it will work before I spend hours making my sign. Thank you all in advance.