A maker has developed an innovative approach to object security by constructing a hidden lock that responds exclusively to a programmable magnetic gesture. This system avoids the vulnerabilities of standard magnetic locks, which can often be defeated by any strong magnet once their location is discovered. Instead, the creator opted for a setup capable of reading a complex, localized motion pattern.
The core of this project relies on a US $100 magnetic imaging tile from SparkFun, featuring an 8-by-8 grid of Hall-effect sensors. This board communicates via an SPI interface with a $32 Teensy 4.1 microcontroller. Because the sensors measure both the magnitude and polarity of magnetic fields very rapidly, the system can accurately trace a magnet moving across a small 3-centimeter square sensing area. To ensure high security against electronic snooping, the entire mechanism could potentially be concealed behind copper sheeting. This sheeting would act as a Faraday cage, blocking RFID signals and electromagnetic fields, rendering the lock invisible to scanners.
For the physical prototype, the builder installed the electronics inside a wooden craft box, utilizing a servo motor for the locking latch. Since the sensor area is remarkably small, they incorporated a Celtic knotwork design on the outside of the box to serve as a camouflaged reference guide for executing the magnetic gesture. While the current prototype works effectively, the creator notes that a completely drained battery would permanently seal the box, suggesting that future iterations might require a hidden inductive charging coil to prevent accidental lockouts.