lm7812 voltage regulator ic ship

Procedure

We all very well know regarding the building procedures a DC power supply circuit using a transformer, a bridge rectifier and a filter capacitor.

It just requires connecting four diodes in a bridge configuration and connect it to the secondary of the transformer, the capacitor goes to the output of the bridge terminals.
The output produced across the capacitor is approximately equal to the rated voltage of the transformer, rather a few volts higher than the transformer spec.
However the voltage obtained from the above simple configuration is never regulated and stabilized, meaning the output from it will never be constant and will vary with the varying input mains voltage levels, which we know is never constant.

Varying Voltage

A varying voltage can cause drastic consequences to a sensitive electronic circuit, for example a TTL, LS and HC series of ICs cannot tolerate more than 5 volts and can get immediately damaged.
A CMOS IC cannot stand more than 16 to 18 volts.
A relay if operated at voltages more than its rating can become hot and waste electricity unneces

The specifications of the 78XX series IC are understandable with the following points:

Output voltage tolerances are around 2% at Tj
= 25 C and 4%
Line regulation is around 0.01% of VOUT/V of VIN at 1A load
Internal circuitry is thermal and overload protected
Internal short-circuit current limit protections are also include
Output transistor safe area protection is also one of the features of these ICs