Two years ago I found a wonderful thing on Aliexpress - a battery-powered watch with a screen that glows continuously in the dark. I use a couple of these watches myself and have already donated several of them to good people. Recently I bought another couple of pieces, but they turned out to be slightly different and had to be finalized.
I talked about this watch in detail two years ago: https://ammo1.livejournal.com/929294.html. Their main feature is the automatic backlight that turns on at nightfall. The LEDs are very weak, so the batteries last more than a year.
The clock from the new batch has a problem with the backlight - it was too bright and interfered with sleep. It turned out that the clock is different. On the new ones, all the inscriptions are larger.
Inside, there are also differences - in the old "skeleton" of the watch inside it is screwed to the case with four self-tapping screws, in the new ones it is simply inserted. But the main thing is that the watch boards are different. The new watch board looks like this:
As we managed to find out after studying the board and small experiments, this 430 kiloohm resistor is responsible for the brightness of the backlight in the night mode.
To reduce the brightness of the backlight, you need to replace it with a resistor 10-20 times larger. I put 4.8 MOhm.
Now the brightness of the screen of the clock at night is as it should be - they are clearly distinguishable, but their light does not interfere.
I bought a new watch here (now they cost $ 5.10), and where I bought the old ones, they are no longer there.
P.S. Found the same for $ 3.56 and slightly others for $ 3.04. Both with good free shipping (delivery to Pyaterochka is possible). I ordered it here and there, let's see which version comes.
© 2020, Alexey Nadezhin
The main topic of my blog is technology in human life. I write reviews, share experiences, talk about all sorts of interesting things. My second project - lamptest.ru. I test LED bulbs and help figure out which ones are good and which are not so good.