Prescott constructed his Infrared Seeking Sentinel by modifying a Nerf Vulcan EBF-25, the belt-fed, fully automatic dart cannon that mounts onto its own tripod. He added a Devantech TPA81 thermopile array to scan for targets in the room, a stepper motor and drive train to pan the the barrel toward its target, and an electronic trigger that bypasses the manual trigger.
The whole rig is orchestrated by an Atmega168 micro controller, while aluminum sheet metal plates hold all the hardware and lock the tripod's tilt ability. The electronics are powered by a 7.2 amp hour seal rechargeable lead acid battery, so the Sentinel can be deployed almost anywhere--just like with the last Team Fortress 2 update!
While it all makes for an impressive mod, I'm compelled to point out that Prescott didn't think of everything. Next time he should add a speaker and a creepy sing-song robot voice to complete my Portal flashbacks.
