In this project, I will show you a Power supply circuit using a Centre tapped step-down transformer, which gets input from mains AC 220V and output gives DC 12V 500mA. It can be used as a DC source for battery charging modules, Arduino board, LED driver, amplifier, etc.

Let's make it!

## Components List

The following components are required for this project:
• T1: 12-0-12 Volt 500mA Step-down Transformer (1 pcs)
• D1, D2: 1N7004 Diode (2 pcs)
• C1: 2200uF, 25V Capacitor (1 pcs)
• D3: 3mm Red LED (1 pcs)
• R1: 4K7 Resistor (1 pcs)
• Connecting Wire

## DC 12V 500mA Power Supply Circuit Diagram

Schematic of a.c. 220V to d.c. 12V 500mA power supply circuit using 12-0-12 Centre tapped Step-down transformer shown below.

### Circuit Explanation

The working principle of this Power supply circuit is simple. The circuit is also known as Centre-Tap full-Wave Rectifier.

When the circuit gets the power from the mains, the Transformer (T1) step-down the 220V AC to 12-0-12 Volt 500mA AC across a centre tapped secondary winding. Now, this step-down voltage rectify with the two diodes (D1 and D2) and providing full wave rectification DC 12V 500mA DC output voltage. A capacitor (C1) is parallel connected with the output to providing the filtering action. For power ON Indication, a LED (D3) is used with Resistor (R1).

## Demo & Testing

Below, you can see the 12-0-12 Volt 500mA Centre Tapped Step Down Transformer 12V Power Supply in action. Here, I power the circuit from 220V mains. Also, measuring the Output Voltage (V) and Current (A) using a Digital Multimeter.

 Voltage Measuring: The Output voltage is 12V, but without load it gives 14.26V or more.
 Current Measuring: The Output Current is 0.47 Amp shown in DMM, which is 500 mA (approx).