So I'm going to ask my girlfriend to prom and I'm currently in a digital engineering class in high school and I thought to myself hey what if I made a little board with some LEDs that lit up and said "Prom?". I have ordered some Chanzon 5mm 3v and 20ma LED diodes from Amazon, I'm not entirely sure how many LEDs I will need just yet but, I know I will be using more than 60 but no more than 100, I came into this thinking I would be able to just run them all in a series and it would light up. I have now gotten deeper into this project and I am in need of some help, if you can offer any help it would all be greatly appreciated, thank you
No, you won't be able to wire them all in series, but how you wire them depends a lot on what power source you intend to use. Do you want this to be portable, i.e. battery operated? How long do you intend to let it run? I image a fairly short time?
You could drive them directly without resistors as Matt suggested, but I would be careful about that - you might not get consistent intensity from them, and on the other hand you might also overdrive them, especially if you have them all in parallel at 3V.
You can minimize the number of resistors though with longer chains. Maybe a couple of 9V in series would work. Wire about 4-5 per chain plus a resistor in series. Assuming 3V each with 5 in series, you would have 15V. For nominal 9V batteries you would have about 18V, so 3V to drop 20mA. 150 Ohm resistor. You may not need 20mA though, so you could try resistors like 180, 220, or 330 Ohm. Having more in series should help keep them more consistent in intensity because the forward drops will average out somewhat in each chain. You can experiment along these lines to see what works best for you. And good luck!