Wire-based safety device for the detection of the theft of an object to be protected and operating method

• US 20030122672A1
• Filed: 11/13/2002
• Published: 07/03/2003
• Est. Priority Date: 11/13/2001
• Status: Active Grant

• Current Assignee: Saaa - Systemes D'Automatismes D'Alarmes Automatiques
• Original Assignee: Saaa - Systemes D'Automatismes D'Alarmes Automatiques
• Inventors: Billiard, Jean-Pierre
• Granted Patent: US 6,842,114 B2
• Time in Patent Office: Days
• US Class Current: 340/568.2
• CPC Class Codes: G08B 13/1454 Circuit arrangements thereof

Abstract

The invention concerns an electronic wire-based safety device for the detection of a theft of an object to be protected, the device comprising at least one detector (1) connected by a wire-based electric link (2) to a signalling unit (3), the detector being arranged in relation with an object to be protected, the detector exhibiting at least a first electrical status in relation with the object and a second status when the object is detached from the detector, the unit comprising at least one threshold voltage comparator with inputs/outputs whereof one input is connected to the detector by the link and whereof at least one output indicates by signals at least the presence or the absence of the object in relation to the status of the detector. According to the invention, the link comprises two wires whereof a first is connected to a common point and the second is connected via at least one first resistor (R3) to a voltage generator with respect to the common point, the second wire being connected to the input of the comparator, and the comparator comprises an analogue digital voltage converter (4) for digital measurements of the voltage and a central processing unit controlled by an operating programme. An implementation method completes the invention. The detectors can be active or passive.

Claims

1. A wire-based safety electronic device for the detection of the theft of an object to be protected, the device comprising at least one detector (1) connected by a wire-based electric link (2) to a signalling unit (3),

the detector, having at least one electrical status, being arranged in relation with an object to be protected,

the link transmitting the electrical status to the unit in the form of a voltage determined on the link,

the unit comprising at least a threshold voltage comparator with inputs/outputs whereof at least one input is connected to the detector by the link and whereof at least one output indicates by signals at least the presence or the absence of the object in relation to the electrical status of the detector,

the link comprising two wires whereof a first is connected to a common point and the second is connected via at least one first resistor (R3) to a voltage generator with respect to the common point, the second wire being connected to the input of the comparator,

the comparator comprising an analogue digital voltage converter (4) for digital measurements of the voltage and a digital calculation central unit controlled by an operating programme enabling the generation of signals in relation to the digital comparison between the measurement and digital reference thresholds,

characterised in that the detector comprises a sensor and shows at least a first electrical status when the sensor is in relation with the object and a second electrical status when the object is detached from the sensor, and it comprises means to further generate a status linked with the absence or the presence of the detector on the link, a resistor being arranged between both wires of the link in the detector, in parallel with the sensor.

2. A device according to claim 1, characterised in that the digital reference thresholds are proportional to the voltage of the voltage generator.

3. A device according to claim 1 or 2 characterised in that the digital reference thresholds are proportional to a mobile average calculated on a determined number of digital measurements of the voltage of the link.

4. A device according to claim 1, 2 or 3, characterised in that the voltage generator is a fixed voltage regulator.

5. A device according to claim 1, 2 or 3, characterised in that the voltage generator is a variable voltage regulator controlled by the calculation central unit, and preferably, a analogue digital converter.

6. A device according to any of the previous claims, characterised in that the detector is passive and that the electrical statuses are created by variation of the resistor of the detector, the detector comprising a second resistor in series with the sensor which is a switch in mechanical association with the object, the assembly being connected between both wires of the link.

7. A device according to any of the claims 1 to 5, characterised in that the detector is passive and that the electrical statuses are created by variation of the resistor of the detector, the sensor being a connector of both wires of the link intended to be connected to a socket of the object to be protected, the socket of the object exhibiting a load resistance.

8. A device according to any of the claims 1 to 5, characterised in that the detector is passive and the electrical statuses are created by an active electronic circuit contained in the object to be protected, said electronic active circuit being connected to a socket of the object to be protected and the sensor is a connector of both wires of the link and intended to be connected to the socket of the object to be protected.

9. A device according to any of the claims 1 to 5, characterised in that the detector is active and the electrical statuses are created by an active electronic circuit, the sensor being a Hall effect circuit in relation with a static magnetic field generator fixed to the object to be protected.

10. A device according to any of the claims 1 to 5, characterised in that the detector is active and the electrical statuses are created by an active electronic circuit, the sensor being a sensor for measuring physical parameters such as, notably, force, displacement, tilt, capacity, said parameter measuring sensor being fixed to the object to be protected and that can be associated with a microcontroller in the detector.

11. A device according to any of the claims 1 to 5, characterised in that the detector is active and comprises at least one sensor which is a communicating electronic chip with power supply and with at least transmission of binary data on a two-wire-based link.

12. A device according to the claim 10 or 11, characterised in that the electric power supply of the detector active is ensured by both-wire-based link.

13. A device according to the claim 10 or 11 characterised in that the electric power supply of the detector active is ensured by an additional wire in the wire-based link with recall of said power supply by a common wire.

14. A device according to any of the claims 10 to 13, characterised in that in the case of an active detector, the resistor in parallel of the sensor is omitted, the load brought by the sensor causing a measurable voltage drop enabling the generation of the status linked with the absence or the presence of the detector on the link.

15. An operating method of a theft detection device comprising at least one detector connected by a wire-based electrical link to a signalling unit, characterised in that the device is according to any of the previous claims and that one converts the voltage of the link into digital value and that one performs a comparison of said value with at least one digital reference threshold in order to produce signals in relation to the status of the detector, one of the statuses being linked with the absence or the presence of the detector on the link, a resistor having been arranged between both wires of the link in the detector, in parallel of the sensor.

16. A method according to claim 15, characterised in that during an initialisation or addition/withdrawal phase of detector, one determines detection windows delineated by digital reference thresholds for the statuses transmitted by a link of a detector.

17. A method according to claim 15 or 16, characterised in that one determines the digital reference thresholds for a link and a given detector on the basis of a mobile average of measurements performed on said link and said detector for a given status.

18. A method according to claim 15, 16 or 17, characterised in that one further determines the type of each detector of a given link during the first installation of the link and/or of each addition or withdrawal of detectors or when resetting.

19. A method according to any of the claims 15 to 18, characterised in that one follows up the consumer'"'"'s interest in the product.