EGS002 board and display for building a pure sine wave inverter

This review will be very short, partly because there’s not much to review here, and partly because the project this board is intended for is still in development. Still, I hope you’ll find it useful.

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I needed this board for one of my projects. I ordered it on April 18 and received it on May 6, which I think is pretty quick. I chose it based simply on the price and the large number of orders. By the way, there’s a catch: if you order the board and display as a set, the price is $5.39 + $1.14 shipping, for a total of $6.53. But if you order the board and display separately, even in the same order, it works out cheaper: $4.84 + $0.74 = $5.58. Yes, strange math...

The boards arrived in a regular envelope, packed in antistatic bags.


The display is tiny. I knew that from the start, but it might come as a surprise to some people, and it may not work for others at all. Even if it does suit your needs, though, it’s not much use; I’ll explain why at the end of the review.


I have no complaints about the display’s appearance; it’s neatly made. The package included a cable for connecting it and a pin header to solder onto the board. We can throw the header straight in the trash: its plating is awful. I should have soldered on my own header from the start.


The board looks just as neat. I won’t go into detail about the components used; it’s all visible anyway.


The board shown in the module’s datasheet looks a little different, but that’s an older version. The real difference is the type of capacitors used: the one I received has two electrolytic capacitors and a ceramic one, while the datasheet shows tantalum capacitors.

I haven’t compared the circuit, but it looks similar to the one in the datasheet. In any case, boards are usually based on the reference design in the datasheet, with minor cosmetic changes.


As luck would have it, I had another board from this series at home, bought as part of an inverter that I’ll tell you about another time.
This one also has a few minor differences: the board I received is at the bottom, and the one from the inverter is at the top.


The visible differences are the types of two capacitors. The one from the inverter uses ceramic capacitors throughout, while the board under review has two electrolytic capacitors.
The new board also has a much later PCB design date.


The dimensions match those given in the datasheet exactly.


I won’t write about the inverter just yet, but it’s already come in handy: it’s much easier to test the board when you don’t have to build a whole supporting circuit for it. Just plug it into the connector and test it :)
By the way, they behave a little differently. This shows up in how they respond to an error when there’s no voltage at the output, though maybe I just imagined it...


I installed the new board and switched it on. Everything seems to work: it regulates the output voltage and generates a sine wave. You can tell the latter even without an oscilloscope.


Let’s get back to the display.
The instructions describe two display options: a 12832 graphical display and a dedicated display, which is the one I bought. To be honest, I was more interested in the graphical one, preferably a large one, but it turns out they’re quite rare and noticeably more expensive. Maybe someone can share a link to a reasonably large 12832 display that’s compatible with this board? As I understand it, it needs to have a serial input.


Connecting it is very simple: the pinouts on the board and display are in the same order, so at first I tested it by simply plugging it into the sine-wave board and tilting it slightly to get a good connection.
This is where I should mention the old board. I’ve seen complaints in reviews of other listings (and, I think, this one too) that the display doesn’t work. Well, it works with the board in this review, but not with the inverter’s original board. Why? Maybe the signal isn’t getting through, or the display output is disabled by default (there are options for that). I’ll have to look into it.


For a more convenient connection, though, it’s obviously easier to solder on the pin header. It seems to be intended to stick up, but the board in my future device is low-profile, so I installed the header facing down.


1. I power up the inverter. It starts, and the output parameters appear on the display. It all looks pretty good, although the text is small. By the way, one reason I wanted the 12832 was that it only has English labels.
2. But wait, why does it show 219 when the output is 230...
3. I raise the output voltage.
4. And the display still says 219. I think I saw it briefly show 220, but I can't say for sure.


And then I realize why this display is completely pointless. Maybe I'm wrong, of course—correct me if I am—but let's try to figure it out.

The board has an external shunt for measuring current and a voltage divider for measuring voltage. So far, so logical.
But wait, the board itself stabilizes the voltage by adjusting the divider. In other words, I can set whatever voltage I want, and the board will adjust the output so that the voltage at the divider input stays fixed. So the output voltage indicator is basically just a number display. It might show the voltage dropping when the board can no longer maintain it, but during normal operation it will show 220 V even if you set the output to the current standard of 230...

Pretty much the same goes for current. The board determines the output current from the voltage across the shunt, whose rating is specified in the datasheet.
But wait, this shunt is in the current-sensing circuit for protection. What if I want a less powerful or more powerful inverter? To make sure the protection works correctly, I recalculate the shunt value—but then the output current readings will change proportionally too....

Frequency. This one makes no sense at all. Why display it if it's fixed? We're generating it ourselves. And if the crystal oscillator glitches and the output is, say, 40 Hz, even if we measure it, we're using that same crystal oscillator, so the display will still show a steady 50 Hz, right?

Temperature. Probably the only thing here that can be displayed more or less accurately. But is the display only there to show the temperature?


The display has a backlight, which is off by default. To turn it on, solder a jumper on the sine board between pins 5 and 6.
I just put a 300 Ω resistor between those pins, and that's more than enough. You could even use a higher value, since the backlight is quite bright. There's definitely no need to connect it directly.

By the way, there's no need to run the backlight power wire from the sine board. You can easily get power from the connector on the display itself.



Well, that's about it—a quick overview.
To sum up just as briefly, I think this is the cheapest board around, but it does its job for the money. The display works, but in my opinion it's useful in maybe 5% of cases—for example, if there's a hole in your enclosure that you need to cover with something.
I have three more of these boards on the way, but this time I ordered them without the display, and I don't regret it at all...

That's all for today. Thanks for reading :)