Varible Voltage regulator is a circuit that serves to supply a component or electronic equipment. It is similiar to the power supply, but on Variable Voltage regulator has an adjustable output. And adjusted by potentiometer not rotary switch. Voltage input about 1 Volt to 35 Volt Maximum. This is use 5A transformer but if you have a 3A transformer its can be use.
Schematic below :
|To adjust the voltage use potentiometer on R2 .|