How To Build An Inverter
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In this article, i will show you how to build a home made 12 V / 220 V (2000 W) Inverter completely professional capable of giving in output more than 1.500 Watts. I wanted to make something very nice so i decided that the construction will look very commercial and has the shape of a central unit of a computer.
1. What is An Inverter?
A 12V/220V inverter is a device that converts 12 volts of direct current (DC) from a battery, such as those used in cars or solar power systems, into 220 volts of alternating current (AC), which is the standard voltage for household appliances in many countries.
This conversion allows users to power a wide range of devices, from lights and fans to sensitive electronics, using a portable or off-grid power source. Inverters can produce different waveforms, including pure sine wave outputs, which provide clean and stable power ideal for delicate equipment, and modified sine wave outputs, suitable for less sensitive devices.
Widely utilized in applications such as backup power systems, RVs, and boats, 12V/220V inverters enhance the versatility of energy use, enabling access to AC power wherever needed.
2. Brief Explanation
The homemade inverter project consists of two main parts: the logic section and the power section. The logic part features a PIC18F2550 microcontroller, which, while not strictly necessary, enhances system control and safety. This microcontroller monitors battery levels, shutting off the relay to disconnect the circuit if the voltage exceeds or drops below safe limits. Additionally, it provides automatic shutdown in the event of a short circuit, ensuring the inverter operates safely.
The power section is built around 12 IRF1405 MOSFETs, allowing for an impressive output capability of 1000W, assuming a quality battery and transformer are used. The PCB routing is designed symmetrically to address the imperfections in the MOSFET’s RDSON, minimizing parasitic effects and electromagnetic interference. This careful layout ensures even current sharing across the MOSFET gates, improving efficiency and performance.
To further enhance functionality, I opted to create two separate boards—one for the logic and one for the power—significantly reducing interference and optimizing overall circuit performance. The inverter uses a robust output transformer and is currently powered by a 12V 7Ah battery, suitable for testing purposes. Although I have plans to incorporate a more powerful battery later, the current setup is adequate for initial evaluations.
Moreover, I integrated a charging circuit that the microcontroller will manage to control the charging process and disconnect the relay when the battery is fully charged. While I have yet to connect the charger, this feature will be implemented in future iterations, adding even more functionality to the inverter system.
3. Schematic Of The Command Circuit
Here are the diagrams for the logic part of the inverter, which should be quite clear for understanding the design.
The power supply for the logic section is managed using an LM317 voltage regulator, providing a stable 5 volts. In practice, the setup delivers approximately 4.9 volts due to component tolerances. The output voltage from the LM317 is determined by resistors R1LM and R2LM, using the standard formula Vout=1.25×(1+R2LMR1LM)V_{out} = 1.25 \times (1 + \frac{R2LM}{R1LM}). A capacitor bank surrounds the regulator to stabilize the voltage and mitigate any unwanted fluctuations.
At the heart of the logic part is the PIC18F2550 microcontroller, which controls all signals. Initially, I had planned to use an AVR ATmega16 with Microchip Studio, but since the unit I had was non-functional, I switched to the MikroC environment with the PIC18F2550. The code will be made available later as I update it.
The logic section includes several LEDs for operational status indicators:
- Flashing Green LED: Indicates startup.
- Solid Green LED: Signifies normal operation (battery and charger functioning).
- Flashing Red LED: Alerts to output voltage anomalies.
- Solid Red LED: Indicates a discharged battery.
Resistors R3 and R4 are utilized to measure the battery voltage via the ADC of the PIC. While diode D2 is included in the diagram, it is not essential for the circuit’s operation.
Additionally, there’s a terminal block for connecting a 2×16 LCD for display purposes, along with a three-output terminal block for a potentiometer to adjust the screen contrast. A push button is provided to reset the system in case of a fault, and a buzzer, controlled by a transistor, adds a melodic sound for notifications. This thoughtful design enhances user interaction and ensures the inverter operates reliably.
4. Schematic Of The Power Circuit
The second diagram focuses on the production of 220V AC and begins with a switch that activates the circuit, initially engaging an open contact relay. A CD4047 timer IC generates the necessary pulse signals, with outputs 10 and 11 providing square wave signals that are inverted relative to each other. These outputs drive the MOSFETs, allowing for efficient switching and control of the power flow to the transformer.
The transformer is connected to the 12V battery, with its respective drain points linked to the two stages of the MOSFETs. This configuration allows for effective conversion of the DC input to the desired AC output.
For charging, the circuit includes a diode bridge followed by a charge regulation setup, which provides approximately 4A of current for a voltage range between 12.4V and 15V. The diode bridge must be rated to handle at least 4A at 35V to ensure reliable performance. The 2N3055 transistor within this circuit should be mounted on a heatsink to manage heat dissipation effectively, preventing overheating during operation.
To protect the circuit from excessive current, the base current of transistor Q17 is limited, ensuring that it operates within safe parameters. The detection of the charger connection is managed by the Signal_Charge, which uses a voltage divider bridge. The resulting analog voltage is interpreted by the PIC as a logic level, activating an interrupt. This mechanism halts the circuit, allowing the microcontroller to take control of the charging process, thereby enhancing the safety and efficiency of the inverter system.
This careful design ensures that the inverter operates reliably, effectively manages power conversion, and integrates a robust charging solution.
5. List Of Components
You need the following components to make the project:
- 1 LCD alphanumeric
- 1 Microcontroller PIC18F4550
- 10 Resistors 1k
- 10 Resistors 10k
- 5 Resistors 2.2k
- 3 Resistors 560k
- 4 Resistors 220 Ohms
- 4 Resistors 390 Ohms
- 10 Capacitors 10 uF 25V
- 5 Capacitors 1000 uF 50 V
- 3 Capactors 100 nF
- 12 MOSFET IRF1405
- 2 Relay 12V Coil
- 1 TIP122
- 1 TIP35
- 3 Diode 1n4007
- 2 Diode zener 15V
- Wires
- A battery of 12V 10AH minimum
- A transformer 12-0-12 / 220 V 10 A or 5A
- 1 Printed circuit board facultative
6. The PIC18F2550
In our inverter project, we utilized the PIC18F2550 microcontroller to effectively manage the system’s operations. This versatile chip provided the necessary processing power to control the inverter’s functions, including generating the sine wave signal for the output. With its built-in USB interface, we were able to easily interface with external devices for monitoring and control.
The PIC18F2550’s high-speed performance ensured that our inverter could respond quickly to changes in load, while its multiple I/O ports allowed us to connect various sensors and components seamlessly. Overall, the PIC18F2550 played a crucial role in enhancing the functionality and reliability of our inverter, making it a vital component in our project.
One of the standout features of the PIC18F2550 is its high-speed performance, capable of executing instructions at a clock speed of up to 48 MHz. This allows for quick processing and responsive control in applications ranging from robotics to automation. Additionally, the microcontroller includes multiple I/O ports, analog-to-digital converters, and various communication interfaces such as SPI and I²C, facilitating seamless integration with sensors and other peripherals.
We chose the PIC18F2550 microcontroller for our inverter project due to its impressive combination of features and capabilities that perfectly suit our needs. Its integrated USB interface simplifies connectivity with external devices, allowing for easy monitoring and control of the inverter system. The microcontroller’s high processing speed and 32 kB of Flash memory enable us to run complex algorithms efficiently, ensuring precise control of the sine wave generation.
Additionally, the PIC18F2550 offers multiple analog-to-digital converters and I/O ports, which facilitate seamless integration with sensors and other components in the inverter circuit. This flexibility allows us to adapt the system for various applications and improve overall performance. By leveraging the capabilities of the PIC18F2550, we can enhance the functionality and reliability of our inverter, making it a key component in achieving our project’s goals.
7. The Microcontroller Code
The microcontroller code is the final and crucial component of the inverter project, serving as the heart of the system. This code is responsible for managing the entire operation of the inverter, including generating the wave signal that controls the switching of the power transistors. It determines how the inverter responds to varying loads, regulates output voltage, and ensures the overall efficiency of power conversion.
In essence, the microcontroller acts as the brain, coordinating the timing and sequence of operations necessary to produce a stable and reliable 220V AC output from the 12V DC input. Its ability to monitor parameters such as voltage and current allows for real-time adjustments, enhancing safety and performance.
If you’re interested in understanding how this code works and how it integrates with the hardware, feel free to reach out through the contact provided, and I’ll be happy to share the details. This knowledge can empower you to customize and optimize your inverter project for specific applications, making the code a vital aspect of your inverter’s functionality.
8. The Battery
The 12V battery serves as the essential power source for our 12V to 220V inverter, providing the necessary direct current (DC) input for the system. This battery, typically a sealed lead-acid or lithium-ion type, is designed to deliver consistent voltage and ample capacity to support the inverter’s operation.
With a capacity of 7Ah, it can efficiently power the inverter during testing, ensuring a reliable output of 220V AC for various applications. The battery’s ability to handle high discharge rates is crucial, as it must support the inverter’s power demands, particularly when driving larger loads.
The battery’s health and charge level are monitored by the microcontroller, which safeguards against over-discharge and helps maintain optimal performance. This setup not only enhances the inverter’s functionality but also ensures a safe and efficient power supply for connected devices.
8. The Transformer
When building a 12V to 220V inverter, the choice of transformer is critical for ensuring efficient power conversion. Here are some key considerations and types of transformers you can use:
1. Step-Up Transformer:
- Function: A step-up transformer is designed to increase voltage from a lower level (12V) to a higher level (220V).
- Specifications: Look for a transformer rated for at least 1000W to match the inverter’s output capacity. It should have a primary winding designed for 12V and a secondary winding for 220V.
2. Transformer Type:
- Toroidal Transformers: These are more efficient due to their compact design and lower electromagnetic interference. They are often lighter and produce less heat, making them a good choice for high-frequency applications.
- E-I Transformers: These traditional transformers are commonly used and can be found in various power ratings. They are robust and easily available but may be bulkier and heavier than toroidal types.
3. Considerations for Selection:
- Power Rating: Ensure the transformer can handle the maximum load you expect the inverter to power. For a 2000W inverter, a transformer rated above 2000W is recommended to ensure reliability.
- Frequency Response: Depending on the inverter design (especially if using PWM), ensure the transformer can handle the frequency of the signals being used, typically around 50-60 Hz for standard AC applications.
- Insulation and Cooling: Transformers with good insulation and heat dissipation capabilities are crucial, especially under continuous load to prevent overheating.
Choosing the right transformer is vital to ensure that the inverter operates efficiently, reliably, and safely, allowing you to effectively convert 12V DC to 220V AC for a variety of applications.
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