Let Adafruit Teach You How to Use NeoPixel LEDs to Create a Fascinating Drip Effect
This effect was achieved with Adafruit NeoPixel LEDs, and Phillip Burgess has a great tutorial that will show you how to reproduce it.
I normally start my Hackster News articles with a short paragraph containing some background information about the subject that is cleverly designed pique your interest. In this case, however, I don’t think that’s necessary. Just take a gander at the GIF below, and you’ll immediately see how cool this effect is. Unless you look very carefully, it really looks like liquid is dripping off of the dragon skull and then splattering onto the cloth below. In actuality, this effect was achieved entirely with Adafruit NeoPixel LEDs, and Phillip Burgess has a great tutorial that will walk you through how to reproduce it.
As Burgess explains, our brains are less than perfect. Our eyes aren’t video cameras that transmit a perfect recording of the world to our brain; they’re more like lenses that our brain uses to focus on the world. Movies, for example, don’t contain any moving images. They just have lots of still images that our brain translates into movement. That same principle is being used here to make it look like liquid is dribbling off of the dragon skull. If you look closely, you can see that there are NeoPixel LED strands that hang down from the skull. If you look even more closely, you may notice that they don’t touch the fabric, but stop a few inches above it.
That’s why this effect all comes down to timing. The “droplet” forms at the top by increasing the brightness of the first LED in the NeoPixel string. Then it starts sliding down the skull. Once it reaches the edge, the speed dramatically accelerates until the lit pixel reaches an approximation of terminal velocity at the end of the strand. The splatter at the bottom comes from a separate set of NeoPixels, and they’re timed properly to light up with the strands above.
The hardware used to do this is: an Adafruit NeoPXL8 FeatherWing, a Feather M0 Basic Proto board, Mini Button PCB NeoPixels and the new 4 mm-wide NeoPixel strips. If your project is larger, you may be able to use standard NeoPixel strips without ruining the effect. The NeoPXL8 can control up to eight NeoPixel strips, so you can have seven “drips.” The eighth connection is used for the splatter LEDs at the bottom. You can set the LEDs to whatever color you like, so you can represent dripping blood just as well as water or glowing radioactive sludge.