One of the basic building blocks of electronics project is building your own DC power supplies from an AC source of 110 V.A.C or 220 V.A.C.The common DC voltages that are necessary to power up the devices are usually in the range of three V DC to 30 V DC. Usually the fixed types of DC voltages are 5V, 9V, 12V, 15V & 18V DC. With the advancement of know-how, lots of devices are using one.8 V DC these days. S M P S is becoming common these days as the demand for miniaturization due to space constraints increases.
Take note that for linear power supply projects, you need to make use of a step down power transformer to step down the AC voltage from the line voltage of 110 V.A.C or 220 V.A.C before using it to supply to the diode bridge.