LED lights have become cheaper and cheaper in the last years. But they are still a bit more expensive than Halogen lamps. To save money, some people might have a look at Chinese shopping sites. I wanted to know what you get if you pay less than 5$ for an LED lamp.
My delivery arrived like this:
Yes, it fell apart already during shipping. It consists of some PCBs with LEDs soldered together by hand and a cheap plastic cap. You don’t really want to use something like this on mains voltages – right?
However, this gives us the chance to look what’s inside of this thing.
Ok, this is really the simplest circuit you can think of. You see a suppressor capacitor (the red one), a bridge rectifier (the small black part with the 4 pins), a small 4.7uF electrolytic capacitor and a few resistors.
The two 51Ohm resistors are connected in parallel and they limit the current flowing through the LEDs.
Better designs use switching mode power supplies with a fixed current output. However, you won’t get this if you buy the cheapest stuff on the internet.
Especially the fact that this ding falls apart on the slightest touch and every part of the circuit runs at mains voltages makes them extremely dangerous. After the the rectification you can expect almost 300V DC on the board. This is even more dangerous than 230V AC.
Do not use something like this!