Multipurpose power supply

As the name suggests this power supply can be used for multiple purpose i.e. it can be used to give power supply to circuit as well as to charge the batteries. It is also known as multiple power supply because it can provide different powers to different circuits at same time i.e. 5v ,8v,12v etc..

Circuit diagram for Power supply

Components used to make power supply

1.      Transformer

2.      Diodes

3.      Capacitors

4.      Regulators

5.      Connectors

6.       LEDs

7.      DPDT switch

Transformer

In this circuit we use center tapped step-down transformer of value 12-0-12 and 500 mA. But to charge batteries you have to use transformer of value 15-0-15 and 1 A. transformer is used to step down the electricity from 220 v AC to 12-15 V AC. Note down that transformer do not change AC to DC ,many students have the doubt that the output of a transformer is DC.

Primary coils of transformer are connected to 220 v AC while secondary coils of a transformer are given to the bridge rectifier.

How to find the primary and secondary coils of a transformer

Bridge rectifier

Bridge rectifier is used to convert AC supply to DC output. It consists of 4 diodes connected in a manner that it gives us DC output.

Regulators

Regulators are the electronic component which regulates the output of a rectifier.i.e regulator regulates the power supply and give us constant output. In this power supply we used three regulators 7812, 7809, 7805 which gives us voltage of 12, 9 and 5 v respectively. Regulator have three legs 1^st one is connected to input i.e. 12-15 v.2^nd one i.e. middle is connected to ground and last one is connected to output. So in this way we get a constant dc power. Here we connect all the regulators in parallel because if any of the regulator get damaged our whole ckt do not break.

Capacitors

In this circuit we use mainly 4 electrolytic  capacitors  1^st one after bridge rectifier,2^nd ,3^rd and 4^{th after} regulators .working of the 4 capacitors is the same i.e. to clip the irregularities in the output. Capacitor which is placed after rectifier has value 450 uf .we can also use 1000uf. While the capacitors after regulators are of 100 uf.

Connectors

Connectors are used to take the output from the regulators. Here basically we use 2 bit connectors.

LEDs

Leds are basically used to indicate that if there is current flowing or not or in other words is ckt working or not.

DPDT switch

DPDT switch is generally used to on or of the ckt.