Music box power issue

Other Hardware Motors, Mechanics, Power and CNC
1

Hello,

So i'm trying to this http://hacknmod.com/hack/led-light-box-thumps-to-your-music/
and i've got an issue with powering the LED's.
It asks for a 12v battary for 4 leds that are in a series.
If i'm gonna put them into a series, where would i get a little 12v battery?
it also appears that i do not need any resistors so that makes me question if this guide is legit or if itll damage my things.
I've already got the tip31 and the leds, as well as the plug although i'm gonna get a hole instead.
so!

1)where would i get a 12v battery? (like the size of a 9v?)
2) is this guide legit?
3) will i have to go paralell, if so i should need resistors(right?)

2

  1. A 12v battery the size of a 9v 'transistor' battery would have very little capacity. Energizer makes an A23 battery used for things like garage door remotes. They also make the A27 of similar size. To get something small you could stack up four Lithium coin sells.

  2. Looks like it would probably work for a while. It would probably work better if you calculated a current limiting resistor instead of just using LED's in series.

  3. You should use a current limiting resistor in either case. If you switch to parallel you need a resistor per LED. It would also allow for a lower voltage power source like a 3v Lithium coin cell.

3

Oh really?
Could you explain how that would work?
How could i get it down to that little of a voltage powering 4 battaries in a paralell?