Maker Billy O'Sullivan has built a Python-based Raspberry Pi Zero-powered replica of the motion tracker from the game Alien: Isolation, using a convincing 3D-printed housing to hold an array of ultrasonic distance sensors.
"It's a 3D-printed chassis using Prusament Mystic Green filament [which] kind of gives it a nice uh nice kind of a green color change look," O'Sullivan explains of the build. "It's got a Raspberry Pi for the brain, it's got three of these HC-SR04 sensors to do the distance measuring, it's got a a buzzer here that beeps every time that this little line comes up and down the screen to scan."
Film aficionados will recognize the core concept of the motion tracker — which, despite the reassurances of android Ash, does not appear to operate on the basis of micro-changes in air density — as having been introduced in Ridley Scott's 1979 horror classic Alien and refined in James Cameron's 1986 sequel Aliens as a standard tool of the Colonial Marines.
O'Sullivan's inspiration, however, comes directly from Creative Assembly's 2014 survival horror game Alien: Isolation, in which Ellen Ripley's daughter is given the mission of investigating the space station Sevastopol and its xenomorph inhabitant — using the motion tracker as a key tool for avoiding the alien and the gruesome death an encounter with it would bring.
The physical incarnation of the in-game item uses a Raspberry Pi Zero single-board computer running a custom Python program to reproduce the in-game scanner's user interface onto a 4" square-format display. A buzzer provides sound effects to match, while the actual motion data comes from a trio of HC-SR04 ultrasonic distance sensors. Power is provided from an internal battery pack, chargeable via USB Type-C.
"It's got two modes of operation," O'Sullivan explains. "It's got a demo mode […] that's simulating activity, that doesn't use the sensors to get distances or anything like that — it just uses numbers I put into the code. It's also got a live mode [which] does make use of these sensors. The live mode will detect an object that's in front of you and these sensors will give a distance to them which is translated onto this radar screen."
A demonstration video with a tour of the build is available on O'Sullivan's YouTube channel Shed Tech, with source code and a build guide published to GitHub under the reciprocal GNU General Public License 2. The STL files for 3D-printing the chassis, meanwhile, have been uploaded to Printables under the Creative Commons Attribution Non-Commercial Share Alike 4.0 International license.