This is very useful when you are beginner in electronics technology.
I'm going to make an 12V adjustable voltage.You can adjust the output voltage by the potentiometer.
Minimum of 0.01mV.
Maximum of around 12V.
You will need:
*1 pc transformer 12V output with a current ranging from 100mA-2A
*8 pcs 1N4001 diodes
*2 pcs 1000uf capacitors,rated with 25V
*4 pcs 100nf capacitors,you can also used 0.1uf capacitors,rated with 16V
*2 pcs 1uf capacitors,rated with 16V
*2 pcs 470 ohm resistors,1/4 watt
*2 pcs LM7812 regulator or AN7812(the same output voltage with the LM7812)
*2 pcs LED 5mm(3V)any color you want
*2 pcs 50k potentiometer
*1 pc rocker switch
*hook up wires or jumper wires
*Illustration board to make base of your project
*Printed Circuit Board
All these materials needed are available in electronics store or you can see in a radios,amplifier,etc....
Put the transformer inside the case.
Tap the fuse and switch to the transformer.