DIY Inverter with ATmega328P

Building a DIY inverter using an ATmega328P microcontroller is an exciting project that introduces you to the fundamentals of power electronics and embedded systems. This article walks you through the step-by-step process of constructing an inverter capable of converting 12V DC to 220V AC with a 50Hz output frequency.

Components Required

Circuit Diagram

Circuit Explanation

1. PWM Generation:

   • The ATmega328P microcontroller generates opposite polarity PWM signals on pins PD3 and PD5.

   • These signals ensure that one MOSFET is ON while the other is OFF.

2. BJT Switching:

   • The PWM signals from PD3 and PD5 pass through 1kΩ resistors to the bases of BC547 transistors.

   • The collectors of the BJTs are connected to the gates of the IRFZ44N MOSFETs.

   • 10kΩ resistors pull the collectors to +12V for proper switching operation.

3. MOSFET Control:

   • The MOSFETs’ drain terminals are connected to the primary winding of the transformer.

   • The center-tap of the primary winding is connected to the +12V DC source.

   • The source terminals of both MOSFETs are tied to ground, with 1N4001 diodes across their drain and source terminals for protection.

4. Transformer and Output:

   • The 3P2S transformer steps up the voltage by a factor of 19, producing a high AC voltage (~220V) at the secondary.

   • A 47nF capacitor across the secondary terminals smoothens the PWM output into a sine-like AC waveform.

5. Voltage Regulation:

   • The LM7805 regulates the 12V input down to 5V for powering the ATmega328P.

   • Decoupling capacitors (0.22µF and 0.1µF) stabilize the input and output of the LM7805.

How the Code Works

// Define the output pins
int pwm_top = 3;
int pwm_bottom = 5;

void setup() {
  pinMode(pwm_top, OUTPUT);
  pinMode(pwm_bottom, OUTPUT);

  digitalWrite(pwm_top, LOW);
  digitalWrite(pwm_bottom, LOW);
}

void loop() {
  // Alternate the signals
  digitalWrite(pwm_top, LOW);
  digitalWrite(pwm_bottom, HIGH);
  delay(8); // Approximately 62.5Hz frequency

  digitalWrite(pwm_top, HIGH);
  digitalWrite(pwm_bottom, LOW);
  delay(8);
}

Explanation:

• Pin Definitions:

  • Pins 3 and 5 are designated as outputs to control the PWM signals for the top and bottom MOSFETs.

• Setup Function:

  • Initializes both pins as LOW to ensure safe startup.

• Loop Function:

  • Alternates the signals on the two pins every 8ms, producing a 50Hz square wave.

Applications of DIY Inverter

This DIY inverter can be used in various scenarios, such as:

1. Home Electricity Backup:

   • Use the inverter as a backup power source during outages to power low-wattage appliances like lights and fans.

2. Solar Energy Systems:

   • Integrate the inverter with a solar panel system to convert DC power from batteries to usable AC power.

   • Learn more about the transformer’s role in such systems at What Kind of Transformer is Used in Inverters.

3. Portable Equipment:

   • Power small tools, routers, or other electronics in remote locations.

4. Learning Platform:

   • Build the inverter to understand the principles of PWM, transformers, and power electronics. Additional details can be explored in How to Build an Inverter with Arduino.

Safety Notes

• Always handle high voltages with caution.

• Ensure proper insulation and avoid touching exposed wires.

• Test the circuit with low-power loads before connecting sensitive or high-power devices.

Conclusion

Building a DIY inverter with the ATmega328P microcontroller is a rewarding project that combines programming and electronics skills. With this guide, you’ll have a working inverter capable of powering AC loads like light bulbs or small appliances. Explore more about inverter designs at Building a 12V DC to 220V AC Inverter or How to Make an Inverter Using a 555 Timer.