Electronic compass for automotive vehicles

• US 4,402,142 A
• Filed: 05/07/1981
• Issued: 09/06/1983
• Est. Priority Date: 09/04/1980
• Status: Expired due to Term

• Current Assignee: Robert C. Dinsmore
• Original Assignee: Robert C. Dinsmore
• Inventors: Dinsmore, Robert C.
• Primary Examiner(s): Martin, Jr., William D.
• Application Number:
  US06/261,524
• Time in Patent Office: 852 Days
• Field of Search: 33/361, 33/355 R, 33/357, 33/362, 33/363 R, 33/363 Q, 33/348
• US Class Current: 33/348
• CPC Class Codes: G01C 17/26 using electric pick-offs for transmission to final indicator, e.g. photocell

Abstract

An electronic compass for vehicles such as automobiles comprising a float mechanism including a permanent magnet for following the earth'"'"'s magnetic field and four Hall effect sensors for detecting magnet orientation at points corresponding to the cardinal compass points. The Hall effect sensors are connected to triggering circuits having overlapping thresholds so that two circumferentially adjacent sensors and sensor trigger circuits cooperate to indicate not only the corresponding cardinal compass points but also the secondary compass point intermediate the cardinal points. The sensor trigger circuitry is connected to a two-character multiple-segment display for indicating vehicle orientation at either one of the four cardinal compass points or one of the four secondary compass points intermediate successive cardinal points. Circuitry for compensating for variations in the earth'"'"'s magnetic field caused by the vehicle comprises a pair of electromagnetic coils having perpendicular axes which perpendicularly intersect the axis of float rotation and variable resistors coupled to the coils for varying the magnetic compensation field generated by each coil independently of the other.

Claims

1. A compass for vehicles such as automobiles and the like comprising first means adapted for fixed disposition with respect to said vehicle and second means adapted for movement with respect to said first means for following the earth'"'"'s magnetic field, sensing means responsive to relative positions of said first and second means for indicating orientation of said vehicle with respect to the earth'"'"'s magnetic field, and means responsive to said sensing means for displaying said orientation including two-character display means for displaying said orientation as one of the characters "N", "E", "S" and "W" indicative of the cardinal compass points and as two-character combinations of said characters indicative of secondary compass points intermediate successive ones of said cardinal compass points,

said two character display means comprising a multiple-aperture light pipe in which the first display character is a multiple-segment character defined by six linear segment apertures disposed in a first rectangular pattern having two segment apertures on each side and one segment aperture on each end, a seventh segment aperture extending across said first rectangular pattern between said two segment apertures on each side of said first rectangular pattern, and eighth and ninth segment apertures extending diagonally across said first rectangular pattern, and the second character is a multiple-segment character defined by six linear segment apertures disposed in a second rectangular pattern laterally adjacent to said first rectangular pattern and having two segment apertures on each side and one segment aperture on each end, a seventh segment aperture extending across said second rectangular pattern between said two segment apertures on each side of said second rectangular pattern, eighth and ninth segment apertures extending in an inverted V-shaped pattern between lower corners of said second rectangular pattern,

said first through said seventh segments of said first display character being identical to said first through said seventh segments of said second display character,

said two character display means further comprising eighteen individually selectable light emitting means disposed one in association with each said aperture for selectively and alternately indicating at said first display character the letters "N" and "S" and for selectively and alternately indicating at said second display character the letters "E" and "W".

2. The compass set forth in claim 1 wherein said second means comprises a permanent magnet adapted to rotate about an axis which is fixed with respect to said vehicle as a function of the earth'"'"'s magnetic field,

wherein said first means comprises four discrete magnetic field sensor elements disposed at quadrature orientations about said axis, and

wherein said sensing means includes four amplifier means each individually responsive to an associated said sensor element for providing an output signal indicative of a cardinal compass point over a preselected angular range about said axis, with said angular ranges of said amplifier means associated with adjacent sensor elements overlapping so as to provide indications of secondary compass points intermediate said cardinal compass points within said overlap.

3. The compass set forth in claim 2 wherein said magnetic sensor elements comprise Hall effect sensors.

4. The compass set forth in claim 1 further comprising means for compensating for variations in the earth'"'"'s magnetic field caused by said vehicle comprising first and second electromagnetic coil means having axes perpendicular to each other and perpendicularly intersecting the axis of rotation of said second means, and means for separately adjusting the magnetic field generated by each said coil means.

5. The compass set forth in claim 4 wherein said means for separately adjusting said fields comprises four variable resistance means having end terminals connected across a source of electric power and variable resistance terminals, means connecting each said coils across a corresponding pair of said variable resistance terminals, and means for conjointly adjusting resistance at each said pair of variable resistance terminals independently of the other said pair.

6. In a compass for vehicles such as automobiles and the like, and including first means adapted for fixed disposition with respect to a said vehicle, second means including permanent magnet means mounted for rotational movement about an axis with respect to said first means as a function of the earth'"'"'s magnetic field and means for indicating orientation of said vehicle with respect to the earth'"'"'s magnetic field as a function of position of said second means with respect to said first means, means for compensating for variations in the earth'"'"'s magnetic field upon said second means caused by said vehicle comprising first and second electromagnetic coil means mounted in fixed position with respect to said first means on axes which are perpendicular to each other and which perpendicularly intersect said axis, and means for separately adjusting current flow through each said coil means so as to adjust the effective magnetic field generated by each said coil means.

7. The compass set forth in claim 6 wherein said means for separately adjusting said fields comprises four variable resistance means having end terminals connected across a source of electric power and variable resistance terminals, means connecting each said coils across a corresponding pair of said variable resistance terminals, and means for conjointly adjusting resistance at each said pair of variable resistance terminals independently of the other said pair.