how you can take a computer u hv old (power supply unit) and turn it into a power supply that will power your Arduino and give you all the amperage you need as well as your standard 3.3 volts, 5 volts, and 12 volts for any accessories/electronics used on your breadboard And arduino power ,led 5v,12v power, fan cooling
1.Computer Power Supply Unit
2.Soldering Iron + Solder
4.dc adapter power jack 2.1mm
The diagram at right shows the main output connector of the power supply when viewed from the end. The colors represent the different colored wires going into it. Common colors represent common functions, ie all red wires are +5 volts, all black wires are common and so on. The connections most useful to us as haunters are the +5V (red wires) , +12V (yellow wire) and the Common or ground (black wires). Both 5 and 12 volt lines normally deliver ample current for our needs.
Of the other voltages available, the +3.3V connection delivers ample current, it’s just not a very useful voltage. The +5VSB (5 volts, always on), -12V and -5V are normally very low current lines and are of little use to us.
The green wire, pin 14, is the on/off switching line. To turn the power supply on, the green line needs to be shorted to a Common line. An easy way to do this is to insert a jumper between pin 14 and pin 13
Most power supplies require a load across one or more of the outputs to operate. The link I give above shows how to add a resistor across the 5 volt side of the supply to act as a load.
For more detail: Power Supply unit for arduino power and breadboard