Thanks for the answer sir! My group mate had already went to an electronic technician. The technician used a bridge rectifier 1N4001, Hr1061, 220 micro farad 1000 micro farad capacitors, 6 zener diodes of 3.3, 4.3 for 4.5, 6, 7.5, 8.7 for 9 and 12. volts and voltage selector. Our input voltage is 12 voltage from ac transformer.