Electronic vehicle theft detection system employing a magnetic field sensor
First Claim
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1. An electronic theft detection system for a vehicle comprising:
- a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing first electrical sensor signals representing a fixed direction of the vehicle in relation to the earth'"'"'s magnetic field when parked;
a processing circuit coupled to said sensor for processing signals from said sensor, said processing circuit responsive to said first sensor signals for calculating and storing fixed direction information representing the heading of the vehicle when parked, said processing circuit comparing said fixed direction information with signals from said sensor representing current heading information for the vehicle and generating an alarm output signal indicating the vehicle has moved from a parked position and the current heading and said fixed direction information differ by a predetermined amount.
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Abstract
An electronic vehicle theft detection system employing a magnetic field sensor for mounting within a vehicle to provide signal information representing the earth'"'"'s magnetic field. The sensor is coupled to an electrical processing circuit for sampling the data provided by the sensor and for generating a theft alarm signal when the heading of the vehicle has changed due to unauthorized movement of the vehicle.
89 Citations
27 Claims
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1. An electronic theft detection system for a vehicle comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing first electrical sensor signals representing a fixed direction of the vehicle in relation to the earth'"'"'s magnetic field when parked; a processing circuit coupled to said sensor for processing signals from said sensor, said processing circuit responsive to said first sensor signals for calculating and storing fixed direction information representing the heading of the vehicle when parked, said processing circuit comparing said fixed direction information with signals from said sensor representing current heading information for the vehicle and generating an alarm output signal indicating the vehicle has moved from a parked position and the current heading and said fixed direction information differ by a predetermined amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An electronic theft detection system for a vehicle comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical sensor signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field when parked; a processing circuit coupled to said sensor for processing said sensor signals, said processing circuit responsive to said sensor signals for calculating and storing information representing a heading of the vehicle when parked, said processing circuit comparing such stored information with current heading information and generating an alarm output signal indicating movement of the vehicle when a predetermined relationship exists between the current heading and said stored heading information; and a timer circuit coupled to said processing circuit for supplying an interrupt signal applied to said processing circuit for causing said processing circuit to exit a low-power mode of operation and to enter an active mode of operation. - View Dependent Claims (12, 13, 14)
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15. An electronic theft detection system for a vehicle comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing signals representing a direction of the vehicle in relation to the earth'"'"'s magnetic field; and a processing circuit coupled to said sensor for processing said sensor signals, said processing circuit responsive to said sensor signals for calculating and storing a current heading of the vehicle and the current field strength of the magnetic field detected by said sensor, said processing circuit comparing the current heading with at least one stored heading value and the current field strength with at least one stored field strength value, said processing circuit generating an output signal indicating unauthorized movement of the vehicle when the comparison indicates a predetermined difference in said stored and current sensor signals, wherein said predetermined difference represents a difference in heading which is at least four times greater than the average difference in field strength. - View Dependent Claims (16, 17, 18)
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19. An electronic theft detection system for a vehicle comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical sensor signals representing a direction of the vehicle in relation to the earth'"'"'s magnetic field; and a processing circuit coupled to said sensor for processing said sensor signals, said processing circuit responsive to said sensor signals for calculating and storing a current heading of the vehicle and the current field strength of the magnetic field within the vehicle, said processing circuit calculating an averaged heading and field strength, said processing circuit calculating an averaged difference between said current heading and said averaged heading and an averaged difference between said current field strength and said averaged field strength, said processing circuit generating an alarm output signal indicating theft of the vehicle when said averaged difference in heading exceeds said averaged difference in field strength by a predetermined amount sufficient to indicate unauthorized movement of the vehicle. - View Dependent Claims (20, 21, 22, 23, 24)
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25. An electronic theft detection system for a vehicle comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical sensor signals representing a direction of the vehicle in relation to the earth'"'"'s magnetic field; and a processing circuit coupled to said sensor for processing said sensor signals, said processing circuit responsive to said sensor signals for calculating and storing a current heading of the vehicle and the current field strength of the magnetic field within the vehicle, said processing circuit calculating an averaged heading and field strength, said processing circuit calculating an averaged difference between said current heading and said averaged heading and an averaged difference between said current field strength and said averaged field strength, said processing circuit generating an alarm output signal indicating theft of the vehicle when said averaged difference in heading exceeds said averaged difference in field strength by a predetermined amount, wherein said predetermined amount comprises an averaged difference in heading which is at least four times greater than the averaged difference in field strength.
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26. An electronic theft detection and compass system for a vehicle comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical sensor signals representing a direction of the vehicle in relation to the earth'"'"'s magnetic field; a processing circuit coupled to said sensor for processing said sensor signals; a display circuit coupled to said processing circuit; said processing circuit responsive to said sensor signals for calculating and storing a current heading of the vehicle and for generating a display output signal to said display circuit for displaying the heading of the vehicle when in operation, said processing circuit comparing the current heading of the vehicle with at least one stored heading value and generating a theft alarm output signal indicating theft of the vehicle when a predetermined relationship exists between the current heading and said at least one stored heading value when the vehicle is parked; and a timer circuit coupled to said processing circuit for supplying an interrupt signal applied to said processing circuit for causing said processing circuit to exit a low-power mode of operation and to enter an active mode of operation. - View Dependent Claims (27)
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Specification