$3 AliExpress 100-240V emergency light (with schematic)

So cheap, but yet actually quite an interesting and functional design.

This is an emergency light designed to be connected to the mains supply, and light automatically when the power fails. The design is all on a single sided circuit board, and actually quite clever. Especially the way they've integrated the control and charging circuitry in amongst the grid of parallel LEDs.

The unit uses a lithium cell, and the most interesting discrete component charging circuitry I've seen, that still manages to cap the charge voltage at 4.17V with just a transistor, resistor and zener diode.

This is another design that suggests that the person who designed it knew their stuff and probably had fun cramming it all onto a cheap single sided PCB.

If you live in a 230V country, then changing the red 680nF dropper capacitor to a lower value will take some of the stress off the main zener diode, and give even lower power consumption.

Here's a listing link for those who were requesting it:-
https://www.aliexpress.com/item/10050...

The current draw at 4.2V, 3.6V and 3V are as follows:-
4.2V = HI-170mA LO-106mA
3.6V = HI-120mA LO-73mA
3.0V = HI-84mA LO-51mA

The capacity of the lithium cell tested as 400mAh.



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