How to Build a 12 DC Volt Into a 220 AC Inverter

Two power transistors drive the inverter circuit.

Power inverters convert direct current (or DC) electrical energy into alternating current (or AC) electrical energy. Power inverters can be useful when an electrical device must be used, but no wall outlet is available.

In the United States, many power inverters change 12-volt DC power into 110-volt AC power. In other parts of the world, most electrical devices require 220-volts AC. With the proper use of transistors, transformers, and oscillator circuits, it is possible to invert power to either AC voltage from a 12-volt DC source.

Things You'll Need

• Two bipolar junction TIP32 (PNP) transistors
• Two 820-ohm carbon film resistors
• Two 82-ohm carbon film resistors
• One 0.47 microfarad electrolytic (polarized) capacitor
• One 24-volt center-tapped transformer
• One 12-volt DC power supply
• One 2:1 power transformer
• Two ring terminals
• Electrical pliers
• Electric wire
• Soldering iron
• Electronic (rosin core) solder

Instructions

1. Cut ten lengths of wire, and strip 1/2-inch of insulation from the ends of each wire. Attach one end of the first wire to one of the end terminals on the center tapped side of the 24-volt transformer, and solder the connection. Attach one end of the second wire to the remaining end terminal on the center tapped side of the transformer, and solder the wire to the terminal. Attach one end of the third wire to the center tap, and solder the wire to the terminal.

2. Using electrical pliers, twist together the negative (marked) lead of the capacitor, the collector lead from the first transistor, one of the leads from the first 820-ohm resistor, and the free end of the first wire. Solder this connection. Twist together the positive (unmarked) lead of the capacitor jointly with the collector terminal lead of the second transistor, one of the leads from the second 820-ohm resistor, and the free end of the second wire. Solder this connection.

3. Twist together one end of the fourth wire jointly with one of the leads from the first 82-ohm resistor, the emitter leads from both transistors, and one of the leads from the second 82-ohm resistor. Solder this connection. Twist together one end of the fifth wire to the free lead of the first 820-ohm resistor, and solder the joint.

4. Twist together the free end of the fifth wire jointly with the base lead on the second transistor, and with the free lead of the first 82-ohm resistor. Solder this joint. Twist together one end of the sixth wire with the second 820-ohm resistor, and solder the joint. Twist together the free end of the sixth wire jointly with the Base lead on the first transistor, and with the free lead of the second 82-ohm resistor. Solder this joint as well.

5. 

   Two transformers are needed to step up the voltage to 220 VAC.

   Attach one end of the seventh wire to one of the terminals on the side of the 2:1 transformer that has fewer coil turns, and solder the wire to the terminal. Attach the other end of the seventh wire to one of the free terminals on the 24-volt transformer, and solder the connection. Attach one end of the eighth wire to the remaining terminal on the side of the 2:1 transformer with fewer turns, and solder the connection. Attach the free end of the eighth wire to the free terminal on the 24-volt transformer, and solder this connection.

6. Attach one end of the ninth wire to one of the terminals on the side of the 2:1 transformer that has more coil turns, and solder the wire to the terminal. Slip a ring terminal over the free end of the ninth wire, and solder the terminal to the wire. Attach one end of the tenth wire to the transformer terminal on the side with more coil turns, and solder the wire to the terminal. Slip the remaining ring terminal over the free end of the tenth wire, and solder the wire to the terminal.

7. 

   If a 12V battery is not readily available, two 6V batteries wired in series can be used as the DC power supply.

   Connect the free end of the fourth wire to the positive terminal on the 12-volt power supply. Connect the free end of the third wire to the negative terminal on the power supply.

References

• Electronic Devices; Thomas Floyd; 1996
• Principles of Electric Circuits; Thomas Floyd; 1997
• Electronic Circuits Archive: 12 to 120 Volt Inverter Circuit

Resources

• Read this Article in Spanish
• Radio Shack: 24V Transformer
• Triad Magnetics: Power Transformers