INDUCTIVE LOOP PRESENCE DETECTOR
First Claim
1. An inductive loop presence detector powered by a line voltage, comprising:
- a control unit that receives operating power from the line voltage;
one or more sensing loops connected to the control unit, wherein the control unit powers the sensing loops and detects the presence or lack of presence of an object within the sensing loops based upon a sensed signal from the sensing loops; and
a backup power supply connected to the control unit to supply a backup voltage to the control unit upon interruption of the line voltage.
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Abstract
An inductive loop presence detector for sensing objects, such as rail cars, containing one or more sensing loops. The inductive loop presence detector includes a backup power supply that is connected to a control unit of the detector to power the control unit during an interruption in the line voltage. The backup power supply includes batteries or capacitors that power the control unit when the line voltage is interrupted. The control unit of the inductive loop presence detector operates in a lower power mode when the control unit is supplied with power from the backup power supply. The control unit operates to auto-tune and supply power to the sensing loops to operate at the most desirable frequency based upon the inductance of the sensing loops.
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Citations
19 Claims
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1. An inductive loop presence detector powered by a line voltage, comprising:
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a control unit that receives operating power from the line voltage; one or more sensing loops connected to the control unit, wherein the control unit powers the sensing loops and detects the presence or lack of presence of an object within the sensing loops based upon a sensed signal from the sensing loops; and a backup power supply connected to the control unit to supply a backup voltage to the control unit upon interruption of the line voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of operating an inductive loop presence detector having one or more sensing loops, the method comprising the steps of:
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generating a signal from the control unit to the sensing units; detecting a frequency of a sensed signal from the sensing loops when no object is positioned within the sensing loops; storing the sensed frequency as a reference frequency in a memory of the control unit; continuously monitoring the frequency of the sensed signal; comparing the frequency of the sensed signal to the reference frequency; and generating a signal to indicate the presence of an object when the difference between the frequency of the sensed signal and the reference frequency exceeds a threshold value. - View Dependent Claims (11, 12)
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13. A method of operating an inductive loop presence detector having one or more sensing loops and powered by a line voltage, the method comprising the steps of:
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generating a signal from the control unit to the sensing loops; detecting a reference frequency of a sensed signal from the sensing loops when no object is present; generating an indicator signal when the frequency of the sensed signal changes relative to the reference frequency to indicate the presence of an object within the sensing loops; monitoring for a loss of the line voltage; and operating the control unit in a low power mode upon loss of the line voltage. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification