Apparatus and method for providing an output signal indicative of a speed of rotation and a direction of rotation of a ferromagnetic object

Patent metadata

Field	Value
Publication number	US-8994369-B2
Application number	US-201314093815-A
Country	US
Kind code	B2
Filing date	Dec 2, 2013
Priority date	Jul 31, 2008
Publication date	Mar 31, 2015
Grant date	Mar 31, 2015

Abstract

An apparatus and a method provide an output signal indicative of a speed of rotation and a direction of rotation of a ferromagnetic object capable of rotating. A variety of signal formats of the output signal are described.

First claim

What is claimed is:

1. A rotation detector, comprising:
a magnetic field sensor for providing an output signal proportional to a magnetic field associated with a ferromagnetic object capable of rotating;
one or more detector circuits coupled to receive the output signal from the magnetic field sensor, each configured to detect a rotation of the ferromagnetic object, the one or more detector circuits configured to generate a respective one or more output signals, each output signal having respective rising and falling edges; and
an output protocol circuit coupled to receive the one or more output signals from the one or more detector circuits and configured to generate an output signal indicative of a speed of rotation of the ferromagnetic object and also indicative of a direction of rotation of the ferromagnetic object, wherein the output signal generated by the output protocol circuit comprises:
instances of a first pulse set when the ferromagnetic object is rotating in a first direction and instances of a second different pulse set when the ferromagnetic object is rotating in a second different direction, wherein each instance of the first pulse set consists of a first quantity of pulses having one or more pulses and each instance of the second pulse set consists of a second different quantity of pulses having one or more pulses.

2. The rotation detector of claim 1 , wherein a frequency of occurrence of the instances of the first pulse set or a frequency of occurrence of the instances of the second pulse set are indicative of the speed of rotation of the ferromagnetic object.

3. The rotation detector of claim 1 , wherein ones of a pulse within the instances of the first pulse set or a pulse within the instances of the second pulse set have time durations in a range of about five to five hundred milliseconds.

4. The rotation detector of claim 1 , wherein a frequency of occurrence of the instances of the first pulse set is about the same as a frequency of occurrence of the instances of the second pulse set when the speed of rotation of the ferromagnetic object is the same when the ferromagnetic object is rotating in the first direction and when the ferromagnetic object is rotating in the second direction.

5. The rotation detector of claim 1 , wherein the one or more pulses of the first pulse set each have the same leading edge transition direction, which is the same as the leading edge transition direction of each of the one or more pulses of the second pulse set.

6. The rotation detector of claim 1 , wherein the one or more pulses of the first pulse set each have the same leading edge transition direction, which is opposite from the leading edge transition direction of each of the one or more pulses of the second pulse set.

7. The rotation detector of claim 1 , wherein the one or more pulses of the first pulse set or the one or more pulses of the second pulse set comprise current pulses.

8. The rotation detector of claim 1 , wherein the one or more pulses of the first pulse set or the one or more pulses of the second pulse set comprise voltage pulses.

9. The rotation detector of claim 1 , wherein the magnetic field sensor comprises:
a first Hall effect element; and
a second Hall effect element disposed a distance away from the first Hall effect element.

10. The rotation detector of claim 1 , wherein the magnetic field sensor comprises at least three magnetic field sensing elements, each magnetic field sensing element spaced apart from an adjacent magnetic field sensing element by a predetermined distance, and wherein a first pair of magnetic field sensing elements selected from among the three magnetic field sensing elements is configured to generate a first differential signal and a second different pair of magnetic field sensing elements selected from among the three magnetic field sensing elements is configured to generate a second differential signal.

11. A method of detecting a rotation of a ferromagnetic object, the method comprising:
generating a first signal proportional to a magnetic field associated with the ferromagnetic object;
detecting a rotation of the ferromagnetic object in response to the first signal;
generating one or more second signals, each having respective rising and falling edges in response to the detecting; and
generating a third signal in response to the one or more second signals, the third signal indicative of a speed of rotation of the ferromagnetic object and also indicative of a direction of rotation of the ferromagnetic object, wherein the third signal comprises:
instances of a first pulse set when the ferromagnetic object is rotating in a first direction and instances of a second different pulse set when the ferromagnetic object is rotating in a second different direction, wherein each instance of the first pulse set consists of a first quantity of pulses having one or more pulses and each instance of the second pulse set consists of a second different quantity of pulses having one or more pulses.

12. The method of claim 11 , wherein a frequency of occurrence of the instances of the first pulse set or a frequency of occurrence of the instances of the second pulse set are indicative of the speed of rotation of the ferromagnetic object.

13. The method of claim 11 , wherein a frequency of occurrence of the instances of the first pulse set is about the same as a frequency of occurrence of the instances of the second pulse set when the speed of rotation of the ferromagnetic object is the same when the ferromagnetic object is rotating in the first direction and when the ferromagnetic object is rotating in the second direction.

14. The method of claim 11 , wherein the first quantity of pulses consists of one pulse and the second quantity of pulses comprises a plurality of pulses.

15. The method of claim 11 , wherein one or more pulses of the first pulse set each have the same leading edge transition direction, which is the same as the leading edge transition direction of the each of the one or more pulses of the second pulse set.

16. The method of claim 11 , wherein the one or more pulses of the first pulse set each have the same leading edge transition direction, which is opposite from the leading edge transition direction of each of the one or more pulses of the second pulse set.

17. The method of claim 11 , wherein the one or more pulses of the first pulse set or one or more pulses of the second pulse set comprise current pulses.

18. The method of claim 11 , wherein the one or more pulses of the first pulse set or the one or more pulses of the second pulse set comprise voltage pulses.

19. The method of claim 11 , wherein at least one Hall effect element is used to generate the first signal.

20. The method of claim 11 , wherein at least one magnetic field sensing element is used to generate the first signal.

21. The rotation detector of claim 1 , wherein the magnetic field sensor comprises:
a first magnetic field sensing element; and
a second magnetic field sensing element disposed a distance away from the first magnetic field sensing.

22. The method of claim 11 , wherein a first Hall effect element and a second Hall effect element are used to generate the first signal, the second Hall effect element disposed a distance away from the first magnetic field sensing element.

23. The method of claim 11 , wherein a first magnetic field sensing element and a second magnetic field sensing element are used to generate the first

Assignees

• Allegro Microsystems Llc

Inventors

• Vig Ravi
• Scheller P Karl
• David Paul A

Classifications

• G01P3/44 Primary

  for measuring angular speed (G01P3/56 takes precedence) · CPC title

• G01P13/045

  with speed indication · CPC title

• G01P3/489 Primary

  Digital circuits therefor · CPC title

• G01P3/488 Primary

  delivered by variable reluctance detectors · CPC title

• G01R33/07

  Hall effect devices · CPC title