If you were tasked with the job of building a silhouette scanning device, you might start out with an array of phototransistors or sensors and a light source, and might even consider a mechanical apparatus to move your sensors across an object as needed. This DIY scanner by hacker “MarcioT,” however, turns things on its head using a single light sensor that can scan an object with the help of a 32x32 LED matrix.
Per the video of this project in action below, what’s going on might not be immediately evident. If you watch closely though, you’ll notice lights scanning from the bottom of the matrix to the top. In this near-instant flash of light, each pixel in the matrix turns on and off, and light levels are compared via an analog input. For increased accuracy, each pixel flashes multiple times, and the analog readings summed by the setup’s Arduino Uno controller. If the difference exceeds a certain threshold, that means there’s an object between that point on the matrix and the sensor.
With all these values recorded, the matrix then turns from part of a sensor setup into an actual display, lighting up the pixels not obscured by anything on top of it. It’s a really ingenious and simple concept that perhaps we’ll see in more projects down the road.