This is a simple approach to obtain a 12V and 5V DC power supply using a single circuit. The circuit uses two ICs 7812(IC1) and 7805 (IC2) for obtaining the required voltages. The AC mains voltage will be stepped down by the transformer T1, rectified by bridge B1 and filtered by capacitor C1 to obtain a steady DC level .The IC1 regulates this voltage to obtain a steady 12V DC. The output of the IC1 will be regulated by the IC2 to obtain a steady 5V DC at its output. In this way both 12V and 5V DC are obtained.
Such a circuit is very useful in cases when we need two DC voltages for the operation of a circuit. By varying the type number of the IC1 and IC2, various combinations of output voltages can be obtained. If 7806 is used for IC2, we will get 6V instead of 5V.Same way if 7809 is used for IC1 we get 9V instead of 12V.
Circuit diagram with Parts list.
- Assemble the circuit on a good quality PCB or common board.
- The transformer T1 can be a 230V primary, 15V secondary, 1A step-down transformer.
- The fuse F1 can be of 1A.
- The switch S1 can be a SPST ON/OFF switch.
- The LED D1 acts as a power ON indicator.
- If 1A bridge B1 is not available, make one using four 1N4007 diodes.
- 78XX series ICs can deliver only up to 1A output current.