LCD display 1602 or

A while ago, I posted a review of a USB-to-RS232 TTL converter. In the review, I mentioned that the package contained more than just the converter. But I was busy with work and couldn't post a review of the other item in the package right away, so I'm filling that gap now.

First, I should mention that, as I wrote in my previous review, the seller not only raised the price of the item but also started charging for shipping to Ukraine. As a result, buying from this particular seller is no longer appealing at all.

This type of display is probably one of the most popular and is used in many hobby projects and other designs. The datasheet for this display model is here. This display is compatible with the HD44780, so it can be used in devices that work with this controller.

It arrived in a regular envelope. When I picked it up at the post office, I thought it must have been crushed ages ago, but I was wrong.


Inside, it was packed in a regular zip-lock bag. Still, even if it had been crushed, I would have found a use for it anyway.


From the front, it's just a display. I doubt anyone will see anything new here.


On the back are two chip-on-board ICs and a few resistors. The backlight resistor is already on the board, by the way, so you can simply apply 5 V to the backlight pins.


I don't know why I bought it. Maybe I'm becoming a shopaholic—I just saw the low price and bought it.
The display doesn't support Cyrillic, though sometimes that isn't a dealbreaker, at least for me. I like the backlight: at a current draw of 20 mA, it shines about twice as brightly as the displays I bought quite a while ago for various projects. Those needed 200 mA, a tenfold difference. The backlight is designed so that the LED on the right shines very brightly sideways, though, so you'll need to cover it with something or paint over it. The older displays don't have this issue, but I still don't want to go back to them.
Still, it may not be a problem if the enclosure is closed.


The digits are clear, with no complaints; the contrast was also easy to adjust.

The idea for this review came about spontaneously, when several things came together at once.
— The display itself had just arrived.
— I saw a review here of a device for identifying semiconductor pinouts.
— The paper for printing circuit boards had arrived, and I needed something to test it on.


The instrument's circuit differs slightly from the basic circuit, but the differences are minor. For example, the 35 V converter is turned off by applying 5 V to the control input of the MC34063 converter IC. Contrast is adjusted with a single resistor rather than two, connected between the adjustment input and circuit ground. A TL431B with 0.5% accuracy is used as the voltage reference. The power-control circuit has also been modified slightly.

The components were selected for this circuit (though, to be more precise, I drew the circuit from the PCB layout); some were bought, and some were salvaged from other devices.
I made the PCB while reviewing the paper, but had to set it aside because it had an error: the display contacts were shifted by 2 mm. I could have soldered it using component lead offcuts and bent them into place, but decided to make a new board instead. Building the instrument from the existing circuit would be no problem, but debugging it in that configuration would be inconvenient. I'll probably give the leftover board to someone.
The photo shows both PCB versions: the defective one is at the bottom, and the corrected one is at the top.


The assembled and tested board worked without any problems; all I had to do was calibrate it and adjust the display contrast resistor. The battery in the photo is from an old GPS navigator. It no longer works properly in that device, but it's found a great new home here.


The jumpers are on the back of the board—a trade-off for using a single-sided board.


Assembled, it looks quite compact.


And it actually works, too.


Measuring a transistor's parameters




And the first capacitor I could find.


Downloads
Schematic, board layout (all components are labeled), firmware (English) and configuration bits, Ponyprog with AtMega328 support, and instructions in Russian. Download
Also included: WinAVR for compiling your own settings, the source files I used to compile the firmware, and compilation instructions. — Download.
Datasheets for the components used — Download.

I plan to make or find an enclosure and choose a small, high-capacity battery that will fit between the board and the display.

All in all, I tried to gather as much information as possible in one place to make it easy to build this device yourself. I really hope I succeeded.

Summary.
What can I say? It's a display, and it works fine. The backlight is bright and energy-efficient, the characters are clear, and the price is reasonable (definitely cheaper than buying one locally, at least). There's no Cyrillic, but nobody promised there would be—and I don't always need it anyway, at least not personally.
I'll have to order a couple more to keep as spares. It's a shame the seller raised the price and started charging for shipping here; I'll have to find another one now.