Patent US2526225A successfully refreshed from Google Patents.
US3685013A
Expired / Lapsed
US
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Self-adjusting vehicle detector system
Assignee: PRECISION WINDING CO Inc
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Filing: 1970-08-14
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Granted: 1972-08-15
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Expires: 1990-08-14
Abstract
Abstract In this vehicle detector system a fixed frequency oscillatory signal produced by a voltage controlled, fixed frequency oscillatory signal source is passed to an untuned circuit including an inductive loop. A vehicle moving over the inductive loop will vary the inductance and the loading of the loop, and thus will vary the voltage amplitude of the oscillatory signal, which is rectified and amplified, and passed to an amplitude comparator circuit by means of which the amplitude of the rectified oscillatory signal is compared with the amplitude of a fixed voltage reference signal. The output of the comparator circuit is passed to a sample and hold circuit which provides the voltage feedback signal by which the voltage amplitude of the output of the oscillatory signal source is controlled. The sample and hold circuit also provides the input signal to the output relay driver amplifier. The sample and hold circuit produces output relay actuating signals in response to the rapid change of comparator output signals produced by the moving of a vehicle into position over the inductive pickup loop, but does not produce output relay actuating signals in response to slowly occurring events, such as the drifting of the parameters of the pickup loop due to moisture, changes in temperature, etc.
Inventors
- 👤 Joseph L Brickner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 06:19
CPC Classifications
G; G08; G08G; G08G1/00; G08G1/01; G08G1/042
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
163 words
A vehicle detector system, comprising: an inductive loop positioned adjacent a vehicular traffic path; signal source means for providing a first oscillatory signal the amplitude and frequency of which are substantially independent of the movement of vehicles on said vehicular traffic path past said inductive loop and are substantially independent of the electrical parameters of said inductive loop, the amplitude of said first oscillatory signal being controlled by an electrical feedback signal; vehicle responsive means including said inductive loop for receiving said first oscillatory signal and producing a second oscillatory signal the amplitude of which relative to the amplitude of said first oscillatory signal varies when a vehicle moves past said inductive loop on said vehicular traffic path, said inductive loop being non-resonant with any other part of said vehicle responsive means at the frequency of said first oscillatory signal; and feedback means responsive to said second oscillatory signal and coupled to said signal source means for supplying said electrical feedback signal thereto.
Claim 2
Dependent Claim
163 words
A vehicle detector system, comprising: an inductive loop positioned adjacent a vehicular traffic path; signal source means for providing a first oscillatory signal the amplitude and frequency of which are substantially independent of the movement of vehicles on said vehicular traffic path past said inductive loop and are substantially independent of the electrical parameters of said inductive loop, the amplitude of said first oscillatory signal being controlled by an electrical feedback signal; vehicle responsive means including said inductive loop for receiving said first oscillatory signal and producing a second oscillatory signal the amplitude of which relative to the amplitude of said first oscillatory signal varies when a vehicle moves past said inductive loop on said vehicular traffic path, said inductive loop being non-resonant with any other part of said vehicle responsive means at the frequency of said first oscillatory signal; and feedback means responsive to said second oscillatory signal and coupled to said signal source means for supplying said electrical feedback signal thereto.
Claim 3
Dependent Claim
71 words
A vehicle detector system as claimed in claim 1 in which said vehicle responsive means comprises an impedance matching transformer across the secondary winding of which said inductive loop is connected, and a capacitor connected across the secondary winding of said impedance matching transformer, the capacitance of said capacitor being such that it does not resonate with the inductance of said pickup loop at the frequency of said first oscillatory signal.
Claim 4
Dependent Claim
45 words
A vehicle detector system as claimed in claim 1 in which said vehicle responsive means comprises a solid state constant current driver circuit including a transistor having an impedance in its emitter circuit, and the terminals of said inductive loop are connected across said impedance.
Claim 5
Dependent Claim
52 words
A vehicle detector system as claimed in claim 1 in which said feedback means includes a MOSFET connected in circuit as a source-follower and a resistance-capacitance network supplying a control signal to the gate electrode of said MOSFET, and said electrical feedback signal is derived from the output of said MOSFET source-follower.
Claim 6
Dependent Claim
163 words
A vehicle detector system, comprising: an inductive loop positioned adjacent a vehicular traffic path; signal source means for providing a first oscillatory signal the amplitude and frequency of which are substantially independent of the movement of vehicles on said vehicular traffic path past said inductive loop and are substantially independent of the electrical parameters of said inductive loop, the operation of said signal source means being controlled by an electrical feedback signal; vehicle responsive means including said inductive loop for receiving said first oscillatory signal and producing a second oscillatory signal the amplitude of which relative to the amplitude of said first oscillatory signal varies when a vehicle moves past said inductive loop on said vehicular traffic path, said inductive loop being non-resonant with any other part of said vehicle responsive means at the frequency of said first oscillatory signal; and feedback means responsive to said second oscillatory signal and coupled to said signal source means for supplying said electrical feedback signal thereto.
Claim 7
Dependent Claim
163 words
A vehicle detector system, comprising: an inductive loop positioned adjacent a vehicular traffic path; signal source means for providing a first oscillatory signal the amplitude and frequency of which are substantially independent of the movement of vehicles on said vehicular traffic path past said inductive loop and are substantially independent of the electrical parameters of said inductive loop, the operation of said signal source means being controlled by an electrical feedback signal; vehicle responsive means including said inductive loop for receiving said first oscillatory signal and producing a second oscillatory signal the amplitude of which relative to the amplitude of said first oscillatory signal varies when a vehicle moves past said inductive loop on said vehicular traffic path, said inductive loop being non-resonant with any other part of said vehicle responsive means at the frequency of said first oscillatory signal; and feedback means responsive to said second oscillatory signal and coupled to said signal source means for supplying said electrical feedback signal thereto.
Claim 8
Dependent Claim
52 words
A vehicle detector system as claimed in claim 5 in which said feedback means includes a MOSFET connected in circuit as a source-follower and a resistance-capacitance network supplying a control signal to the gate electrode of said MOSFET, and said electrical feedback signal is derived from the output of said MOSFET source-follower.
Claim 9
Dependent Claim
63 words
A vehicle detector system as claimed in claim 5 in which said feedback means comprises a MOSFET and a resistance-capacitance network including a capacitor and being capable of maintaining a voltage thereacross for a predetermined interval of time, said resistance-capacitance network being coupled to the gate connection of said MOSFET, and the high input impedance of said MOSFET minimizing leakage from said capacitor.
Claim 10
Dependent Claim
189 words
A vehicle detector system comprising an oscillator for generating an oscillatory signal, said oscillator being controlled by an electrical feedback signal, a constant current driver coupled to said oscillator to receive the oscillatory signal therefrom, an untuned circuit coupled to said constant current driver, said untuned circuit including means for coupling an inductive loop thereto, rectifying means coupled to said untuned circuit for generating a first signal varying in accordance with the amplitude of the oscillatory signal appearing across said untuned circuit, an operational amplifier connected as a summing amplifier for comparing said first signal with a standard voltage to thereby generate a second signal varying in accordance with the amplitude of the oscillatory signal appearing across said untuned circuit, a feedback signal generating circuit including a storage capacitor and a diode-connected transistor coupled between the storage capacitor and said operational amplifier for passing variations of one polarity of said secOnd signal to charge the storage capacitor, said feedback signal generating circuit further including a MOSFET for passing a signal from said storage capacitor to said oscillator for controlling said oscillator, whereby leakage from said storage capacitor is minimized.
Claim 11
Dependent Claim
189 words
A vehicle detector system comprising an oscillator for generating an oscillatory signal, said oscillator being controlled by an electrical feedback signal, a constant current driver coupled to said oscillator to receive the oscillatory signal therefrom, an untuned circuit coupled to said constant current driver, said untuned circuit including means for coupling an inductive loop thereto, rectifying means coupled to said untuned circuit for generating a first signal varying in accordance with the amplitude of the oscillatory signal appearing across said untuned circuit, an operational amplifier connected as a summing amplifier for comparing said first signal with a standard voltage to thereby generate a second signal varying in accordance with the amplitude of the oscillatory signal appearing across said untuned circuit, a feedback signal generating circuit including a storage capacitor and a diode-connected transistor coupled between the storage capacitor and said operational amplifier for passing variations of one polarity of said secOnd signal to charge the storage capacitor, said feedback signal generating circuit further including a MOSFET for passing a signal from said storage capacitor to said oscillator for controlling said oscillator, whereby leakage from said storage capacitor is minimized.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-15 | 1976-02-14 | 1976-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-15 | 1980-02-14 | 1980-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-15 | 1984-02-14 | 1984-08-15 | $7700.00 | Window Closed / Lapsed |