Apparatus and method for providing an output signal indicative of a speed of rotation and a direction of rotation of a ferromagnetic object
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.
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:
a plurality of pulses, each one of the plurality of pulses having a leading edge with a transition direction indicative of the direction of rotation.
2. The rotation detector of claim 1 , wherein a frequency of the plurality of pulses is indicative of the speed of rotation of the ferromagnetic object.
3. The rotation detector of claim 1 , wherein ones of the plurality of pulses have time durations in a range of about five to five hundred milliseconds.
4. The rotation detector of claim 1 , wherein the plurality of pulses comprise current pulses.
5. The rotation detector of claim 1 , wherein the plurality of pulses comprise voltage pulses.
6. 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.
7. 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.
8. 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:
a plurality of pulses, each one of the plurality of pulses having a leading edge with a transition direction indicative of the direction of rotation.
9. The method of claim 8 , wherein a frequency of the plurality of pulses is indicative of the speed of rotation of the ferromagnetic object.
10. The method of claim 8 , wherein the plurality of pulses comprise current pulses.
11. The method of claim 8 , wherein the plurality of pulses comprise voltage pulses.
12. The method of claim 8 , wherein at least one Hall effect element is used to generate the first signal.
13. The method of claim 8 , wherein at least one magnetic field sensing element is used to generate the first signal.
14. 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 element.
15. The method of claim 8 , 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.
16. The method of claim 8 , wherein a first magnetic field sensing element and a second magnetic field sensing element are used to generate the first signal, the second magnetic field sensing element disposed a distance away from the first magnetic field sensing element.