Hall-effect switches are commonly used in transition detection applications, as shown in Figure 4-1. The opening and closing of a car door most resembles the hinge motion, where the magnet swings toward or away from the sensor.

Figure 4-1 Examples of Transition Detection Design Implementations

The magnetic implementation of this function involves embedding the magnet in the door such that the magnet moves in a hinge type motion as the door opens and closes. A Hall-effect switch installed in the door frame opposite the magnet and detects the presence or absence of the magnetic field. Omnipolar switches like the TMAG5131-Q1 can trigger for either North or South magnetic fields as shown in Figure 4-2, whereas unipolar switches can only trigger for one polarity.

Figure 4-2 Omnipolar Hall-Effect Switch Operation

The main objective is to design the system such that the spatial coordinates of the transition region fall within the spatial coordinates associated with the B_OP maximum and B_RP minimum specifications.

Important variables to consider when implementing transition detection include magnet size and type, Hall-effect switch selection, and the placement of the magnet and the switch. Magnetic simulation tools like TI Magnetic Sense Simulator (TIMSS) help determine these variables and facilitate rapid design iteration.