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Picture of Tip31 + LEDs glowing tube
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A very cool glowing tube that will beat to your music. A simple build with a very cool end product. The second photo is a simplified mini version of this project. Use it as a reference or ignore it completely. It sure helped me with this build.

Step 1: Components

Picture of Components
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************PARTS**************
1     tip31 transistor
10  3mm blue LEDs
1    3.5mm audio jack
1    9 volt battery
1    9 volt power jack
2 lead wire
Plexiglas
************TOOLS*************
soldering iron
wire strippers
hot glue gun
600 sand paper
 
This is really cool! say if i wanted to make one with more LED's would i have to increase the voltage? or is current more the issue? bear in mind i'm thinking 30+ LED's

i know this is 2 years too late but it might help someone else. It depends on whether you are running them in parallel or series. if parallel, as long as your source voltage is higher than your forward voltage, you're fine. Most 5mm LEDs run on around 3.6 v at 30mA and a standard phone charger puts out up to 5v at 1000mA, so you could run about 30 LEDs with a standard phone charger, you could use more LEDs if you limit the current to say 25 or 20 mA using a higher ohm resistor.

(input voltage - LED fwd voltage) / LED operating current = resistor value

(input voltage - LED fwd voltage) * LED operating current = resistor power rating