A magnetic field sensor arrangement includes a magnetic field sensor element configured to provide a sensor output signal responsive to a magnetic field, wherein the sensor output signal is representative of a magnetic field amplitude; a processing module configured to provide a processed sensor output signal representative of the sensor output signal; a switching level calculation module configured to calculate a switching level, (1) during a power up mode, based on a default switching level, and (2) during a running mode, based on the processed sensor output signal; a comparator module configured to compare the processed sensor output signal with the switching level, and to provide a comparator output signal based on the comparison; and a storage module configured to store the default switching level, provide the default switching level during the power up mode, and update the default switching level during the running mode.

To provide a magnetic sensor circuit which does not output spike-like voltage errors to a signal processing circuit. A magnetic sensor circuit is provided which is configured so as to output an output signal to a signal processing circuit through a plurality of hall elements driven by a first switch circuit and a second switch circuit controlled by a second control circuit and in which the first switch circuit controls timings at which spikes occur in the output signal of each of the hall elements in such a manner that the timings are not the same, and the second switch circuit selects and outputs an output signal having a period of a timing free of the occurrence of a spike.

A magnetic field sensor apparatus includes a sensor signal generator generating a sensor signal responsive to a magnetic field. A switching level provider provides during a power up mode a switching level based on a most recently updated valid one of a first and a second value of a default switching level. If an update triggering condition occurs, the not most recently updated one of the first and second values of the default switching level is updated and the most recently updated one of the first and second values of the default switching level is maintained unchanged until a next update triggering condition occurs, so that the first and second values of the default switching level are updated alternately on consecutive triggering conditions.

There is provided a method of arranging a security alarm system on a window/door and framing. The system includes an object and a sensor which is capable of detecting the object within a predetermined range. The method includes positioning a first of the sensor and object on a first of the window/door and framing. The method includes opening the window/door to a threshold distance which facilitates ventilation and inhibits an intruder from passing through the window/door. The method includes positioning a second of the sensor and object along a second of the window/door and framing such that the sensor is able to detect the object as the window/door is opened up to but not past the threshold distance.

There is also provided in combination, a window/door, framing extending about the window/door and a security alarm system coupled to the window/door and framing in the manner described above.

There is provided a method of installing a magnetic proximity sensor including positioning the magnetic field sensor in a desired location and positioning a magnet in a desired location relative to the magnetic field sensor, with an indicator of the sensor continuing to be turned on during the predetermined period of time when the magnetic field generated by the magnet is sensed by the magnetic field sensor, and being turned off during the predetermined period of time when the magnetic field generated by the magnet is not sensed by the magnetic field sensor. The indicator light thus assists in determining proper relative positioning of the magnet and the magnetic field sensor. If after the predetermined period of time more time is needed to install the magnetic proximity sensor, the method includes initiates another predetermined period of time by removing and replacing a lid of the magnetic proximity sensor.

Various implementations include earbud cases with a Hall effect sensor configured to aid in detecting whether the case is open or closed. Certain additional implementations include a holder for a Hall effect sensor in an earbud case. In some particular aspects, a case for a set of earbuds includes: a top section including a set of magnets; and a base section movably coupled with the top section, the base section having: an upper compartment including a set of slots for holding the earbuds; and a lower compartment, having: a printed circuit board (PCB); a holder coupled with the PCB; and a Hall effect sensor coupled with holder, wherein the holder separates the Hall effect sensor from the PCB.

A mechanical rodent trap has a jaw mounted to a base, with a trigger therebetween which is activated by the incidence of a rodent. An acceleration sensor is mounted in a case in the base in a sensor module that logs and transmit a signal indicating activation of the trap. Alternatively a magnet holder secures a magnet to the trigger, and a Hall effect sensor is used in the sensor module. The sensor modules are sealed within a compartment formed with the base beneath the trigger and closed by a cover.

A system and method that can automatically select a frequency of a magnetic field in a magnetic tracking system. A magnetic tracking system emits an alternating magnetic field using a set of three frequencies. In the present approach, a transmitter is capable of generating multiple sets of three frequencies. A processor selects a first set of frequencies to use and causes the receiver to measure the amplitude of the magnetic field at those frequencies. In one embodiment, the frequency set having the lowest energy is selected. The processor then compares an estimated jitter at those frequencies to the actual jitter experienced using the frequencies. If the actual jitter exceeds the estimated jitter by a predetermined amount, the processor switches to a different set of frequencies and causes the receiver to measure the magnetic field at the new set of frequencies. The process may repeat using the additional sets of frequencies.

There is provided a method of arranging a security alarm system on a window/door and framing. The system includes an object and a sensor which is capable of detecting the object within a predetermined range. The method includes positioning a first of the sensor and object on a first of the window/door and framing. The method includes opening the window/door to a threshold distance which facilitates ventilation and inhibits an intruder from passing through the window/door. The method includes positioning a second of the sensor and object along a second of the window/door and framing such that the sensor is able to detect the object as the window/door is opened up to but not past the threshold distance. There is also provided in combination, a window/door, framing extending about the window/door and a security alarm system coupled to the window/door and framing in the manner described above.

A magnetic proximity sensor assembly 10. The magnetic proximity sensor assembly 10 comprises a switch assembly 12 received in a blind bore 14 of a body tube 16. The switch assembly 12 comprises a magnetic assembly 18 moveable in the blind bore 14. The switch assembly 12 comprises an operator 42 which extends from the magnetic assembly 18 and serves as a drive for a moving contact 44 positioned between a first contact 46 and a second contact 48. The magnetic assembly 18 comprises a primary magnet 20 and a biasing magnet 22. The switch assembly 12 comprises a center magnet 26 interposed between the primary magnet 20 and the biasing magnet 22. The blind bore 14 has a uniform bore diameter. The magnetic proximity sensor assembly 10 comprises a sleeve 28 in the blind bore 14 contacting the closed end 30 of the blind bore 14. The switch assembly 12 is seated on the sleeve 28 such that the primary magnet 20 of the magnetic assembly 18 is surrounded by the sleeve 28.