Remote indicating solid state compass

• US 4,163,326 A
• Filed: 06/10/1977
• Issued: 08/07/1979
• Est. Priority Date: 03/18/1974
• Status: Expired due to Term

• Current Assignee: Robert A. Edwards
• Original Assignee: Robert A. Edwards
• Inventors: Edwards, Robert A.
• Primary Examiner(s): Martin, Jr., William D.
• Application Number:
  US05/805,401
• Time in Patent Office: 788 Days
• Field of Search: 33/361, 33/355 R, 33/357, 33/358, 33/363, 324/251, 324/249
• US Class Current: 33/361
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01C 17/36 Repeaters for remote indication of readings of a master compass

Abstract

A solid state compass system for use with automobiles or the like. The system consists of a dashboard mounted readout unit which receives signals provided thereto from a remotely located solid state magnetic bearing sensor, the latter being responsive to the earth'"'"'s magnetic field. The solid state magnetic bearing sensor described herein, includes a pair of Hall effect semiconductors and ancillary electronic circuits. Two ancillary circuit types are described. One circuit is designed to output digital codes indicative of magnetic heading; the other circuit is designed to output two currents which are indicative of sine and cosine components of magnetic heading. The circuit designed to output digital codes includes sinusoidal waveform generators, a binary counter, a differential comparator amplifier and digital latch and decoding circuits. The circuit designed to output currents indicative of sine and cosine components of magnetic heading are comprised of a pair of linear differential buffer amplifiers. The dashboard mounted readout unit designed to accept digital codes may be defined by a plurality of discrete indicators, such as light emitting diodes, or segmented alpha indicators or so forth may be employed. The dashboard mounted readout unit designed to accept two currents which are indicative of sine and cosine components of magnetic heading may be characterized as a pointer which is pivoted about an axle by the influence of the magnetic field induced by a surrounding stator whose windings receive the aforementioned two currents. The solid state sensor unit is preferably located at a point on the vehicle distant from large bodies of iron or steel and where the earth'"'"'s field is strong relative to fields associated with permanently magnetized auto parts.

Claims

1. A remote indicating solid state compass which produces a discrete display of heading referenced to compass points for use in automobiles or the like including in combination, a digital counting means comprising counter and free running oscillator for continuously outputting digital code signals, sine and cosine voltage synthesizer circuit means for converting said digital code signals to sine and cosine voltage waveforms, magnetic heading sensing means including two Hall effect generators mounted in vertical planes at right angles to one another, one generator receiving said sine voltage across its current input terminals, the other generator receiving said cosine voltage across its current input terminals and with the two generators'"'"' Hall voltage output terminals connected in series for outputting a Hall effect generator difference voltage whose phase with respect to the applied sine voltage is proportional to heading, amplifier means for receiving said difference voltage and for producing therefrom an amplifier output signal which switches from one to the other of two levels when the polarity of said difference voltage reverses, logic D type latch circuit means receiving digital code data input from said digital counting means and clock input from said amplifier means for storing the digital code present when the clock input transitions positively, decoding means for converting codes stored in said D latches to code signals for controlling display means, display means comprising light emitting elements which indicate automobile heading relative to points of the compass.

2. A system in accordance with claim 1, wherein said decoding means comprises gates for converting codes stored in said latches to codes for driving segmented displays and wherein said display means comprises segmented alpha indicators which display combinations of letters N, E, S, W indicative of automobile heading in terms of compass points.

3. A system in accordance with claim 1, wherein said decoding means comprises gates for converting codes stored in said latches to codes for driving single and pairs of a group of illuminatable indicators and wherein said display means comprises said group of illuminatable indicators located adjacent to cardinal map letters N, E, S, W and whereby said map letters adjoining said illuminated indicators indicate automobile heading in terms of compass points.