IFF system keeps you from shooting your friends

IMU

An IFF system – Identification of Friend or Foe – are used by military aircraft in battle situations to determine if another aircraft is being piloted by a fellow aviator or an enemy. For the boots on the ground, friendly fire is generally regarded as a very bad thing, so a few students in [Bruce Land]‘s ECE 4760 class at Cornell decided to make a wearable version of an IFF for their final project.

[Wen Hao Lui] and [Aadeetya Shreedhar] broke their project down into two parts: an initiator unit and a receiver unit. The initiator unit sends an encryption key to the receiver unit which, in turn, replies back to say, ‘don’t shoot.’ [Wen] and [Aadeetya] needed to choose between using RF or laser-based communications for the initiator, but the difficulty in acquiring or building a radio antenna with the requisite directionality made a laser the obvious choice.

The receiver unit has eight phototransistors attached to a vest and will reply to the initiator unit via a Wi.232 radio module when the laser illuminates the phototransistors. In the event of an enemy acquiring one of these vests, the project includes a pulse detection circuit that will erase the encryption keys when the wearer’s pulse drops to zero. A bit morbid, but the video after the break sure makes it look cool.

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Almost building an engine from hardware store parts

engine

You can build a surprising amount of stuff from parts you can pick up at a hardware store. Sometimes, though, getting a project built from sections of pipe is very, very difficult. That’s the case with [Lou]‘s hardware store engine: despite an inordinate amount of cleverness, he just can’t seem to get an engine made from pipe fitting to work and is now asking for some ideas from other ingenious makers.

The engine uses regular oxygen and propane tanks you can pick up at Home Depot with torch heads soldered onto half inch pipe. The fuel and oxygen are mixed in a T fitting until a grill igniter sets the gas mixture ablaze pushing a cylinder down the length of a copper pipe. The cylinder is attached to an aluminum flywheel that also controls the opening and closing of the oxygen and propane valves as well as switching the grill igniter on and off.

Right now, [Lou] can get the engine running, but only for one stroke of the cylinder. He’s having a bit of a problem turning this into a working motor. If you’ve got any idea on how to make [Lou]‘s engine work, drop a line in the comments. We’ll throw our two cents in and say he needs a valve on the exhaust, but other suggestions are always welcome.

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