LM7805 is a 5 volt fixed voltage regulator IC but it can also be used to make a adjustable power supply circuit. The schematic diagram shown below is a 5V to 12V adjustable power supply using 7805 IC. The voltage between 5 to 12 volt can be ajusted with 550 ohms potentiometer.
Use a 9 volt 2 amp transformer. The IC become hot during operation due to which a suitable heatsink is required.