- Design Center
- About Allegro
Seatbelt buckles commonly use a vane interrupt style of sensing to determine when a buckle is latched. It includes a magnet and a unipolar, Hall-effect switch inside the buckle holder. When in the latched position, the ferrous material of the buckle itself interrupts the path of the magnetic field to the sensing element, thereby switching the device on, and informing the airbag system that the buckle is engaged (latched).
It is also common for seat belt buckle systems to utilize two-wire, unipolar, Hall-effect sensor ICs, because they require one less wire for operation and they provide inherent diagnostics (output current will be in one of two narrow ranges, any other value indicates conditions that may be a short, open or other type of fault).