There are very few individuals who could watch the classic sci-fi flick Alien or its action-packed sequel Aliens and not want to slot a motion tracker into their personal toolkit. While Ash's explanation that the device works based on "micro changes in air density" is met with disbelief from Ripley, maker Bence Lukács has an alternative method in mind for his build: passive infra-red and ultrasonic sensors, all linked up to an Arduino Mega microcontroller.
As detailed in his latest Instructable, the project is surprisingly simple: three HC-SR501 passive infra-red motion sensors are used to detect movement within three scanner segments, much like the film version, while an HC-SR04 ultrasonic sensor provides distance information. Readings from these sensors are fed to the Arduino Mega, which in turn generates a convincing display on a low-cost liquid-crystal display module - albeit one capable of tracking only a single target at a time, suited more to the tense first film than its hectic sequel.
The electronics are only part of Bence's build, however. Determined to make something portable and as close to the film props as possible without spending a huge amount of money, Bence cleverly turned to plastic junction boxes and spray paint. With an old PCV tube covered with the grip from a bicycle handlebar, the portable device is finished - and the effect undeniably impressive for all its simplicity.
This is my first Arduino-based Instructable, I hope you will like it. :) I'm a big fan of the first Alien movie and the "old-sci-fi" gadgets, so I decided to make a fully operational portable motion-tracker. In this tutorial I will show you every step how I made it so you can make your own one.