Circuit Variable Supply78XX
This variable power supply is using 7805, 7809, 7812 or 7815
voltage regulators, where the last 2 digits represents the maximum output voltage of the IC.
This
circuit offers excellent ripple rejection, eliminates mains hum, and has a design using a pi filtered C-L-C.
The transformer has a 240V primary and has a secondary rated 24V at 2A. The bridge rectifier contains 4 diodes, their current rating needs to be high with respect to the transformers output current; if not the current may damage the diodes. C1 is the mainfiltering capacitor, the supply is further smoothed by the combination of L1 and C3. C2 and C4 are decoupling capacitors; their action further reduce ripple factor.