You don't have to spend a fortune on security -- DIY smart home security is affordable and effective with Aqara devices and other integrations. Aqara Door and Window ...

This compact and affordable door sensor mechanism uses a Hall-effect sensor fixed at the corner of the door frame and a standard bar magnet fixed on the door panel close to the Hall-effect sensor.

This circuit uses a thin piezoelectric sensor to sense the vibrations generated by knocking on a surface; eg, a door or table. Basically, it amplifies and processes the signal from the sensor and ...