12V regulated power supply circuit diagram

A 12V regulated power supply is a simple yet highly practical circuit used in various electronics projects. One of the most popular ways to achieve this is by using the 7812 voltage regulator, part of the 78xx series of fixed-voltage regulators. In this post, we will guide you through the process of designing and understanding a 12V regulated power supply circuit using a 7812 IC.

What is a 7812 Voltage Regulator?

The 7812 is a 12V fixed-voltage regulator from the 78xx family, which can provide a constant 12V output regardless of variations in input voltage or load conditions. It has three pins: input, ground, and output.

  • Input (Pin 1): Accepts an unregulated input voltage.
  • Ground (Pin 2): Common reference for input and output.
  • Output (Pin 3): Provides a regulated 12V output.

The 7812 IC can handle an input voltage between 14.5V to 35V and provides up to 1.5A of output current with proper heat sinking.

Circuit Diagram of 12V Regulated Power Supply Using 7812

Below is a simple step-by-step guide to building a regulated 12V power supply using the 7812 voltage regulator:

Components Required:

  • 7812 Voltage Regulator IC
  • Step-down transformer (230V AC to 15V AC)
  • Bridge rectifier (four diodes or a full-wave bridge rectifier module)
  • Capacitors: 1000µF, 0.1µF, and 0.33µF
  • Resistors (optional for load regulation, but not mandatory)
  • Heat sink for the 7812 (optional but recommended)
  • Wires and soldering tools

Step 1: Step-Down Transformer

To power the 7812, you need to step down the high AC voltage from the mains (230V or 110V) to a lower AC voltage. A transformer is used for this. For a 12V regulator, we typically use a 15V AC step-down transformer. This ensures that after rectification and filtering, we have enough voltage for regulation.

Step 2: Bridge Rectifier

The output from the transformer is an alternating current (AC) voltage, which needs to be converted into direct current (DC) using a bridge rectifier. A bridge rectifier consists of four diodes arranged in such a way that it allows only the positive half of the AC cycle to pass through. You can also use a pre-built bridge rectifier module for ease.

Step 3: Smoothing Capacitor

After rectification, the output will be pulsating DC, which needs to be smoothed out. To smooth this ripple, use a large electrolytic capacitor (e.g., 1000µF). This capacitor will store charge and release it when the voltage dips, thus reducing ripple and providing a more stable DC output.

Step 4: 7812 Voltage Regulator

Now, the smoothed DC output is fed into the input pin of the 7812 voltage regulator. The regulator will output a steady 12V on the output pin, regardless of minor fluctuations in the input voltage. Ensure you connect the pins correctly:

  • Pin 1 (Input): Connect to the rectified and filtered DC voltage (approx. 15-25V DC).
  • Pin 2 (Ground): Connect to the ground line.
  • Pin 3 (Output): This is where you get the regulated 12V DC output.

Additional Capacitors:

  • Use a 0.33µF capacitor between the input and ground to stabilize input voltage.
  • Use a 0.1µF capacitor between the output and ground to reduce high-frequency noise.

These capacitors help improve stability, particularly in cases of noise or fast-switching transients in the input power.

Step 5: Heat Sink (Optional but Recommended)

If your circuit will draw significant current (close to the 1.5A limit), the 7812 voltage regulator can get hot. To prevent overheating and ensure proper functioning, attach a heat sink to the regulator. This helps dissipate heat efficiently.

Final Circuit Diagram

Here’s a basic diagram for the 12V regulated power supply circuit using a 7812 voltage regulator:

How the Circuit Works:

  1. AC to DC Conversion: The transformer steps down the 230V AC to 15V AC, which is then rectified to DC by the bridge rectifier.
  2. Smoothing: The large electrolytic capacitor smooths out the rectified DC to reduce ripple.
  3. Voltage Regulation: The 7812 IC regulates the smoothed DC voltage to a constant 12V DC.
  4. Final Output: The final output is a stable 12V DC, suitable for powering various electronic devices.

Conclusion:

Building a 12V regulated power supply using a 7812 voltage regulator is a great project for both beginners and experienced electronics hobbyists. It provides a clean, stable voltage ideal for powering circuits like microcontrollers, sensors, and other electronics. The use of simple components like a transformer, bridge rectifier, capacitors, and the 7812 IC makes this circuit both reliable and affordable. Be sure to include a heat sink if your load draws significant current to ensure long-term stability.

Applications of a 12V Regulated Power Supply:

  • Powering microcontrollers (e.g., Arduino, Raspberry Pi)
  • Supplying voltage to sensors and relays
  • Small DC motors and LEDs
  • Audio systems
  • Any project requiring a stable 12V DC supply

Feel free to leave any comments or questions below, and happy building!

Location: Ramala, Uttar Pradesh 250623, India

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