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I am building a small LED lamp from a jar(about 100ml), so all components should fit in it. I decided to use a LED drive/Joule Thief, that I found at online Chinese store.
Datasheets (all I can find is in Chinese language): https://pdf1.alldatasheet.com/datasheet-pdf/view/1133536/SHININGIC/YX8122.html
https://datasheetspdf.com/pdf/785935/ETC/YX8122/1
I also found similar question: LEDs driver circuit

The circuit is very simple, but I still failing to make it work. I have a white 5mm LED(3.3V, 20mA), 3v button battery and 47uH inductor, but the LED won't light up. I don't know what I'm doing wrong, if I increase inductor to 1mH the LED is glowing, but not at the full power. I tried to connect red LED (1.8v, 20mA), but it glows even weaker. I don't want to change battery type as it perfectly fits in the jar and I can't use two batteries, for the same reason, they won't fit.

In summary, the goal is to make white led glow as long as possible using 3v button battery. Is it possible to make it by using yx8122 led drive? If no, then what the purpose of this IC?

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  • \$\begingroup\$ The YX8122 can boost the voltage, but it can't do anything about the current. Button cells aren't made to deliver the current it takes to light an LED. \$\endgroup\$ – JRE Jan 16 at 23:04
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A dim LED can be powered from a button battery cell for a short time. I have some cheap solar garden lights that use a 1.2V AAA Ni-MH battery that is charged by a 30mA/2V solar panel all day. Its QX5252 IC is similar to yours but has an English datasheet and it lights a single LED or a colors changing IC brightly all night. My AAA battery is MUCH larger than your button battery and it is charged all day every day.

Some LED novelties use three 1.5V button batteries in series and a resistor to limit the LED current. They light for a few hours.

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This is a boost converter, so 3 volts into 3 volts is not enough. You can get 6, 9, or 12 volt LEDs from Digikey, who has the best search. Digikey includes Lumens-per-Watt, which is a measure of how efficient the LED is. I usually stay with CREE, which is a good name. If you order the single LED, you can first try 2, 3, and 4 LEDs in series to find out which works best -- one combo will be the most efficient. The best LEDs can be expensive (the 12 volt CREE are around $4 each for qty 1), and if so, you will really want a quality LED driver -- you never get more than you pay for, and an expensive LED deserves the protection of a professional supported chip having a good datasheet, and hopefully some example circuits and an application note or two. The datasheet of a good LED driver will come with guidance on how to use it. Good luck!

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