Analyzing a Copper String Light with unusual Phosphor Converted LEDs

After being amazed about finding a really clever implementation of powerline controlled LEDs in a low cost RGB “copper string light”, I bought a few other products in hope to find more LEDs with integrated ICs. At less than $4.00 including shipping, this was by far the cheapest LED string I bought. This one did not have any ICs inside, but I was still surprised about finding rather unusual phosphor converted LED technology in it.

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Controlling RGB LEDs With Only the Powerlines: Anatomy of a Christmas Light String

The RGB curtain predictably turns into a mess of wires when not used according to instructions.

As should be obvious from this blog, I am somewhat drawn to clever and minimalistic implementations of consumer electronics. Sometimes quite a bit of ingeniosity is going into making something “cheap”. The festive season is a boon to that, as we are bestowed with the latest innovation in animated RGB Christmas lights. I was obviously intrigued, when I learned from a comment on GitHub about a new type of RGB light chain that was controlled using only the power lines. I managed to score a similar product to analyze it.

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Ultra Low Power LED Flasher using the Padauk PFS154

Flashing a LED is certainly among the first set of problems any burgeoning electronics specialist is tackling, may it be by using an ancient NE555 or, more recently, a microcontroller to control the LED. As it turns out, we can turn any trivial problem into a harder one by changing its constraints.

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Power Analysis: Probing WS2812 RGB LEDs

Power analysis is a technique to probe the inner workings of an integrated circuit by measuring changes in the supply current. Whenever a logic gate switches, it will cause a tiny current spike that can be measured externally. By inspecting the temporal variation, especially in reaction to an external signal, it is often possible to deduce information about the construction of the IC.

A few years ago I used a logic analyzer to investigate the protocol of the, then new, WS2812 RGB LED. So, why not revisit this topic to test my newly acquired deep sampling oscilloscope?

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Building a Chaotic Oscillator from Common Components

Sometimes you find things you have not even been looking for…

A chaotic oscillator is an electronic circuit that can exhibit “chaotic“, nonperiodic behavior. A commonly cited example is Chua’s circuit, but there are many others. I always regarded these as carefully designed, rather academic, examples. So I was a bit surprised to observe apparently chaotic behavior in a completely unrelated experiment.

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A LED-Candle based on the 3 cent MCU

After having reviewed sub $0.10 microcontrollers recently, it’s time for some projects using the Padauk PFS154 and PMS150C. Considering my previous investigation of electronic and non-electronic candles, it appears only natural to chose this as a target for the lowest cost microcontrollers.

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SK9822 – a clone of the APA102?

Two years ago I took a deeper look into the APA102. Although it was more expensive than the common WS2812, and harder to come by, it had some intriguing properties. The main benefits are a timing-insensitive  SPI interface, allowing easy interfacing to standard periphery, and a much higher PWM frequency of >19kHz, making the APA102 almost flicker free.

So much about that. Considering how things with LEDs from China go, it should not take too long for clones to appear? Indeed! Recently, several comments showed up on my blog, reporting about issues with APA102 LEDs they bought. It quickly turned out that these were SK9822, APA102 clones from the same company that already brought the SK6812 to us, a WS2812 clone.

One of these people was Mike. He developed the Weblight, a WebUSB controlled RGB LED. The prototype (shown below, red pcb) worked well, but when he commissioned a small production run (black pcb), the LED started to show odd update behavior. Mike was nice enough to share a couple of boards with me for further investigation.

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DICE10 – electronic dice controlled by two GPIO.

Yay,  another mini-project with the ATtiny10!

dice10

A while ago I devised a scheme to drive an electronic dice with only two IO lines. I finally found the time and motivation to build up a small design using this as an entry for the hackaday 1k compo. Please find project details on the hackaday.io page or the github repository.

dice10_withtext

“Reverse engineering” a real candle

Two years ago, I spent some time analyzing the algorithm used in a candle flicker LED as  commonly found in cheap artificial candles. I reverse engineered the  algorithm from the flickering pattern and recreated the algorithm in software. Turns out this is of interest for many people who are searching for artificial candle algorithms – there is a surge of traffic every year around December. However, I just reverse engineered one of the controller ICs – this does not mean that this is a good approximation of a real candle.

But how to get there? First, we need to understand how a real candle behaves. In a recent comment, Gary made the excellent suggestion to record a real candle on video and analyze the data. I noticed something similar could be done in a very quick-and-dirty way, by connecting a photodiode to a digital storage oscilloscope.

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