Circuit Of adapter 12 V
This is of a dual regulated that provides +12V and -12V from the AC mains. A regulator like this is a very essential tool on the work bench of an electronic hobbyist.
Transformer T1 steps down the AC mains voltage and diodes D1, D2, D3 and D4 does the job of rectification. Capacitors C1 and C2 does of filtering.C3, C4, C7and C8 are decoupling capacitors. IC 7812 and 7912 are used for the purpose of voltage regulation in which the former is a positive 12V regulator and later is a negative 12V regulator. The output of 7812 will be +12V and that of 7912 will be -12V.
Circuit Of adapter 12 V
Use Transformer 15-0-15 V, 1A secondary step-down transformer. Capacitor C1,C2,C5 and C6 must be rated 50V or more.