A lockbox opens when a magnet is moved across its surface in a programmed pattern, with no visible keyhole or keypad. An 8-by-8 array of 64 magnetic sensors tracks the motion; when the gesture matches the stored pattern, a servo releases the latch.
Creator Stephen Cass found that the sensor area was only about three centimeters square, making it difficult to trace the gesture reliably. He decorated the box with a Celtic knot pattern and used part of it as a disguised positioning guide.
To hide the lock, he made a secret magnetic gesture and then hid the gesture's guide inside decorative knotwork. Opening a box becomes a tiny puzzle.
Auto Perfume Sprayer is a work-in-progress device intended to check a person's odor as they return home. A smell sensor feeds readings to a microcontroller; when the result is classified as 'BAD,' a servo presses a perfume bottle to spray automatically.
Makers BULAT IARKIEV and Yadanar Htay describe the project on ProtoPedia as a way to respond to odors that people may not notice themselves, such as after exercise. The project is currently marked as in development.
Come home and the doorway silently judges your smell, then responds with perfume. That's a rather opinionated welcome.
Guy Dupont made Clock That Is Wrong, a digital clock that deliberately shows an incorrect time when its person sensor detects a face. The maker has shared the parts, wiring and CircuitPython code for the project.
The moment you try to use this clock, it refuses to tell you the time.
A door sensor uses crushed garlic peel and plastic to generate an electrical signal as the door opens. When the layers touch and separate, static electricity is produced. A two-sided garlic-peel version generated about 400 volts at very low current.
Researchers Deepak Bharti and Manas Tiwari at Malaviya National Institute of Technology Jaipur demonstrated a home-security system that alerts a smartphone when the door opens, detecting openings with 92% accuracy across 50 tests. The sensing element needs no external power, although the microcontroller transmitting the alert used a power bank.
A home-security sensor relies on the peel of a garlic clove. Kitchen scraps have found a new job guarding the door.
Older CH-53 helicopters use an unusual system to warn crews about cracks in their rotor blades while airborne. Each blade is pressurized with nitrogen; if a crack causes pressure to drop, a mechanical indicator exposes a small amount of strontium-90.
A detector on the helicopter can sense that radiation, providing a warning without putting fragile electronics or complicated wiring on a spinning rotor. Hackaday revisited this decades-old solution.
Sending a sensor signal from a spinning rotor was difficult, so the solution became: expose a radioactive source and detect that instead. The engineering constraint is ordinary; the answer escalates spectacularly.
To hide the lock, he made a secret magnetic gesture and then hid the gesture's guide inside decorative knotwork. Opening a box becomes a tiny puzzle.