A little about why an inverter with a pure sine wave is important for an ordinary household consumer. Without going into the jungle of electrical engineering, purely at the household level, many electrical appliances will work only if the output signal is a pure sine wave, other devices will work on a square wave, but with a significant loss of power and with a potential risk of failure. Risk devices include refrigerators, pumps, washing machines, heating boilers, etc.
The shape of the output signal does not really matter for most modern TVs, LED lamps, devices that have their own power supplies, such as a laptop.
Accordingly, the price of an inverter (or uninterruptible power supply) with a pure sine wave is significantly higher.
In this article, a DIY craftsman will tell us how to make an inexpensive pure sine wave inverter from 12V to 220V (DC-AC) from scratch. The project is based on an inexpensive EGS002 SPWM driver board module. The inverter board can handle up to 1 kW (depending on the size of the transformer). About $ 30 was spent on the creation of this project.
Tools and materials: – EGS002 SPWM inverter driver module;
– MOS- transistors IRF3205 or IRLB4132 – 16 pcs;
– Transformer 12 V – 220 V (500 W/1000 W);
– Transistor insulation kit – 16 pcs.; – TIP31C NPN transistor; – L7805 voltage stabilizer; – 1N4007 diode (8 pcs.); – NTC thermistor 10 kOhm; – Multi-turn trimmer 10 kOhm; – 10 Ohm resistor (4 pcs.); – Resistor 2.2 kOhm; – Resistor 10 kOhm (4 pcs.); – Resistor 100 kOhm (2 pcs.); – Capacitor 470 nF 25v;
– Capacitor 2.2 uF 350 V;
– Capacitor 2.2 μF 25V;
– Capacitor 10 μF 25 V;
– Capacitor 100 μF 25 V;
– Developing solution (sodium hydroxide); < br> – Etchant (Iron Chloride);
– Hacksaw for metal;
-Soldering accessories; -Plastic box;
Step one: about the project
Some general information about the project.
Power plants use generators that generate a pure sinusoidal signal. All of our AC units were originally designed to work with this waveform.
Sine wave inverters were extremely expensive a few years ago ($ 200-1000), and as a result, square wave and modified square wave became common and affordable options.
Square wave inverters are less efficient and can damage sensitive devices.
Since rectangular inverters are cheap, they create unpleasant humming sounds in motors, transformers, etc. Therefore, the master decided to make an inverter with a pure sine wave.
The transformer can be replaced to work with 110V/220V/230V outputs.
The device has an output voltage feedback (constant AC output voltage)
Undistorted pure sine wave output (with load)
Selectable output frequency (60Hz/50Hz)
Modular design with the ability to replace components
The project consists of two parts. First, we analyze the first, part, and as the second comes out, it will be presented to the readers. In the second part, the master plans to improve the design.
The next single coil inductor design is expected to have a smaller form factor, higher conversion efficiency and lower standby power consumption. Components will be replaced with SMD components. More improvements will be made.
Be especially careful with this design as it produces “high voltage-high current” output. The board was designed for a 1 kW transformer. Due to its lack, I was only able to purchase an extra 500W 12V – 220V UPS transformer. As far as I know, I was only able to achieve 400W with minimal sine wave distortion. The second part of the video tutorial will show you how to troubleshoot and connect to a larger transformer. Part 3 will show you how to design an inverter for a specific user using the EGS002 module, and part 4 will show you how to create the best 48V inverter for my autonomous solar panel.
Step two: about the EGS002 board
The EGS002 is a $ 3 one-stop solution for building pure sine wave inverters. It is possible to build from it inverter units of low power and high power. Right out of the box, this isn't an inverter yet. To turn it into a functional inverter, you need a harness.
Good high-power commercial pure sine wave inverters are very expensive. and their prices range from $ 120 to $ 400. With EGS002, you can design all kinds of inverters with input voltage, output voltage and power rating of your choice. The total cost of the project is about $ 20, which is ten times less.
Now let's look at what is on the EGS002 board.
SOIC EG8010 microcontroller – EGS002 uses EG8010 ASIC microcontroller chip to output SPWM logic signals to drive H-Bridge inverters. The IC is also equipped with I/O specially designed for closed loop voltage control, trip current control, temperature control, and fan drive output. Unlike the Arduino based inverter project, the chip is preprogrammed and ready to use.
High and Low side MOSFET/IGBT driver – The board also contains two IR2110S MOSFET drivers to drive the N-channel H-bridge MOSFET for SPWM and polarity switching to transformer or inductor.
OP-AMP for current measurement – there is an OP-AMP LM393 on the board to amplify the voltage from the shunt resistor. The boosted voltage is returned to the analog input of the EG8010 as the IC uses it for overcurrent protection.
LCD Output – The EG8010 microcontroller has already been preprogrammed to work with its own LCD. You can add a dollar to the EGS002 for $ 3 to get an optional LCD screen. Displays output voltage, current, temperature and frequency mode.
Single LED error indicator – there is one red LED on the board, which will blink a certain number of times, indicating errors for troubleshooting.
You can familiarize yourself with the documentation for the EGS002 board and similar EG8010 by downloading the pdf below.
EG8010 IC Datasheet.pdfEGS002 SPWM Driver Board Datasheet.pdf
Step three: setting up EGS002 (selectable 60Hz and 50Hz)
There are soldering pads on the back of the board in the upper left part for adjusting certain parameters of the board. See the table at the end of the step or read the quick start guide to set the desired parameters.
Setting the AC frequency.
Depending on the country or continent you live in, the AC frequency of the unit will vary. For example: in the Philippines and America it is 60 Hz, in India, China and Europe (and in Russia) it is 50 Hz. By default, the board is set to 50Hz.
To set to 60Hz, solder jumper JP1 and remove JP5.
If you have EGS002 + LCD combo kit, you can turn off the LED backlight of the LCD screen to save power. You can also solder the switch to JP9 to be able to turn it on and off at any time. It is enabled by default.
Turn on LCD backlight – jumper JP9.
Soft start mode.
Soft start mode is a useful feature to prevent a surge in power consumption after connecting a DC power source to the inverter while the load is connected. In soft start mode, the voltage will slowly increase to the output voltage you set for 3 seconds (ex: 0-220V in 3 seconds). It also prevents sparks when connecting the inverter to the battery. If you are planning to build a UPS circuit, you will have to turn it off.
To enable soft start mode, install jumper JP2 and remove JP6.
Deadtime is the time in seconds during which MOSFETs- transistors must turn off before switching phases. This is to prevent cross-conduction (fast short-circuiting) through the half-bridge MOSFET (a pair of vertical MOSFETs) during high-speed switching of the H-bridge setup. There are four modes. The default is 300 ns, which is the most suitable for most tasks.
To change the settings to custom:
300 ns – jumper JP7 and JP8.
500 ns – jumper JP3 and JP8.
1.0us – jumper JP4 and JP7.
1.5 μs – jumper JP3 and JP4
Step four: circuits < br>The left side of the circuit refers to what is on the EGS002 board, and the right side refers to the circuit that will need to be wired to build a fully functional inverter.
The master has linked the drain pins of the MOSFET, the 12V cooling fan, and the 12V pin of the EGS002 board as Vcc (input power supply). Note that the 12-volt pin of the EGS002 is what provides the IR2110S driver outputs for MOSFET gates. This means that the maximum input voltage for the inverter is limited by the maximum gate voltage of the MOSFET (typically 20V) and the maximum input voltage of the regulator to 5V (35V for the 7805). Going forward, he is planning another manual on inverter systems with higher input voltages (24V/48V/72V).
He also connected four MOSFETs in parallel for each of the 4 MOSFETs used in the H-bridge assembly, for a total of 16 MOSFETs. This was done to reduce the on-state resistance of the system for the installation of more powerful transformers (+1 kW @ 12V). You can leave some MOSFET slots empty for 4/8/12 MOSFETs.
Step Five: PCB Design
You can make your own homemade PCB or choose a professional PCB manufacturer on our website.
For this project, the master decided to make a homemade double-sided PCB. Instead of transferring toner, he used a method of making a photosensitive circuit board similar to that used by factories. The method is convenient for inkjet printing, in contrast to the technology of transferring toner.
Download files for printing or self-production of boards can be found below. The gerber files have also been included in the zip archive. You can order PCBs on PCBway without downloading gerber by simply clicking on the top two links below.
Inverter main board Filter connection board
File package: schematic, printed circuit board and documentation files to download in zip archive
PDF – files:
Filter backplane (bottom layer) .PDF Inverter main board (bottom layer) .PDF Inverter main board (top layer).
Step six: making the board
Next, the master starts making the boards. Instead of transferring toner, he used a method of making a photosensitive circuit board similar to that used by factories. It is convenient for inkjet printing as opposed to toner transfer technology.
Then removes the light-shielding film from the printed circuit board. If you are not using clear film for your PCB routing, you can apply a little baby cream to make the print translucent on the paper, which will allow light to pass through the paper. Then we place the board with the breadboard under a UV lamp for 7 minutes or for 10-15 minutes under a fluorescent lamp.
After the photo-exposure process, immerses the photo-exposed printed circuit board into the developing solution ( supplied with photosensitive PCB packages). The chemical used is alkali or sodium hydroxide mixed with water. Eventually, traces of the mask will appear.
Next, he places the board in an etching solution with ferric chloride.
After etching, rinses the board and removes paint residues.
Step Seven: Installation
Drills holes in the radiator.
One of the limitations of DIY PCBs is the lack of conductive through holes and vias. The wizard designed a PCB to work with through holes. Simply strip the solid wire and solder it to connect the high current lines on each side.
The traces can be tinned with solder to provide more current and prevent oxidation of copper in the future.
Then he mounts the board according to the diagram. As stated in the previous step, home PCBs do not have through holes. Be sure to solder the component legs to the top and bottom copper pads.
Marks and drills holes in radiator.
The master uses MOSFETs- transistors in TO-220 package. The metal tongue of the MOSFET is technically tied to its source. Electrical isolation must be provided to avoid conduction between other sets of MOSFETs.
Add some thermal paste.
Apply an insulating gasket (mica/fiberglass).
Add thermal paste.
Add a plastic sleeve (screw insulation).
Screw the bolts to the radiator.
Also missing on the printed circuit board solder mask. Take some duct tape and insulate the bottom of the heatsink so that it doesn't short-circuit the copper paths on the top layer of the PCB.
The circuit uses a shunt resistor for current sensing and overcurrent protection. Instead of bulky, high power resistors, you can use solid copper wire as a makeshift low profile shunt resistor. The master stripped a copper single-core wire with a diameter of 2 mm, cut it to 60 mm, bent and soldered to the board.
Installs a 3300 uF 25 V capacitor to ground between the heatsinks and a +12 VDC power input to improve stability.
A 10 kΩ NTC sensor must be connected to the pads on the board for temperature control. If you don't plan on using a temperature sensor, just connect a 10K resistor to it. On the other hand, the inverter will still work with or without a 12V cooling fan.
The EGS002 board is sold separately and includes a display and a 7-pin connector. Just connect the LCD pins to the output on the EGS002 LCD. Both the LCD display and the EGS002 board have inscriptions about where to connect it.
Solders the transformer wires to the board and wires to the power input.
A filter capacitor must be added to smooth out the coarse and spiky output from the transformer. According to the datasheet, a simple 2.2 μF + 350 V capacitor (unpolarized) should work. The master made a simple circuit board for him, connecting three screw terminals in parallel to it. A pair of wires goes to the high voltage output of the transformer, another pair goes to the outlet, and a third pair goes back to the feedback input of the main board of the inverter.
This is what the oscillograms look like with and without a capacitor. < br> Step eight: calibrating the output voltage and device testing
Be sure to calibrate the output voltage before using the inverter. The assembled inverter design provides for output voltage feedback control. This means that the user can set a specific output voltage and the inverter will try to maintain that specified output voltage even when the voltage drops when the battery (power supply) starts to discharge. This setting has a limit: if your inverter can no longer maintain the set output voltage, the error LED will flash and the inverter will automatically shut down.
Connect a voltmeter to the AC output.
Set the voltmeter to the AC range.
Turn on the inverter.
Turning the trimmer resistor set the voltage (220 V/230 V).
During testing, the master connected a 3S6P 18650 lithium-ion battery as a power source. For the test, he chose a lithium-ion battery, since each cell can deliver 20 A or just 120 A. As for the output signal, he only managed to get about 400 watts at the output with a pure output waveform. Then the inverter is simply turned off. But, as already mentioned, the master continues to work on improving the device.