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Here this circuit diagram is for +12V regulated (fixed voltage) DC power supply. These power supply circuit diagram is ideal for an average current requirement of  1Amp. This  circuit is based on IC LM7812. It is a 3-terminal (+ve) voltage regulator IC. It has short circuit  protection , thermal overload protection.  LM7812 IC is from LM78XX series. The LM78XX series IC is  positive voltage regulator IC for different voltage requirements, for example LM7805 IC is made for 5 volt fixed output voltage . There is LM79XX IC series for negative voltage . Circuit diagram of 12V fixed voltage power supply   A transformer(Tx=Primary 230 Volt, Secondary 12 Volt , 1Amp step down transformer) is used to covert 230V to 12V from mains. Here used a bridge rectifier made by four  1N4007 or 1N4003 diode to convert AC to DC . The filtering capacitor 1000uF,25V is used to reduce the ripple and  get a smooth DC voltage. This circuit is very easy to build. For good p...

Maybe you do not believe , because so long radios sold in the form usiong DC power as the driving component work. But I took to fiddling with radio without making a circuit of electrical current/voltage source which is rather strange. Radio Works well if no one put the components in accordance with its placement or its symbol. Therefore , we must consider the placement and and examined before starting step in assembling this very simple circuit. Description : R1=2K2 C1=Varco (variable capacitors ) 0-250 pF C2=100pF D1=Crystal Diode OA72 A = Receiver Antenna 10-20 meters along L1=Spool of wire antenna using nikelin / copper 0.25mm and 12.5mm koker and as 30 rolls wrapped arround to ferit. The circuit above is only useful as a radio receiver only. Can be called a crystal radio. The diode will process the sound waves through the antenna, then stored to capacitors.