I recently received an external USB battery as a promotional gift (see image below). While I always thought of these as a superfluous gimmick, I realized that these devices could be quite useful as mobile power source for various projects. After all, dealing with lithium ion batteries in your own projects can be dangerous and you need additional circuitry to ensure charging and voltage conversion.
External USB batteries can be charged with a normal micro-b USB charger and are supposed to output stabilized 5V at above 1A. And they come fully integrated at a price point where it is difficult to get even the battery alone. See Aliexpress for example and many others. Since there is little reason to trust hardware at this price point, I decided to tear the device down to see whether all the necessary parts are there.
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I previously reported on reverse engineering a candle flicker LED. My approach was to extract the “flicker” pattern from the input current variation and to deduce the algorithm from statistical analysis.
Reverse engineering the controller chip
Of course there is another, more involved, approach. And that is to reverse engineer the circuit directly from the die. Andrew Zonenberg from Siliconpr0n decapsulated and imaged the controller chip from one of my LEDs. You can find his report here.
He managed to obtain very high-resolution optical microscopy images of the top-level metal. It turns out that the controller chip is manufactured in a relatively coarse CMOS process with one metal layer and 1-2 µm resolution. This is 1980ies technology. But of course, that is all that is needed for a circuit as simple as a flicker-LED.
Continue reading “Follow up on Candle Flicker LEDs”
There is a new addition to the popular WS2812 family of RGB LEDs with integrated controller: A 8mm through hole version. Right now they seem to be in pilot production stage. The only place that has them is Soldering Sunday where they are called PixelBits. My understanding is that they will also be available at the usual sources later this year. I got a couple of them to test for compatibility with my light_ws2812 library.
What’s pretty cool about these LEDs is that they are diffuse – no more blinding unidirectional light. This might be very useful for indicator lights. Furthermore, you can easily wire them freeform without a pcb. I see a lot of RGB LED cubes coming up…
Continue reading “New member of the WS2812 family”