SECURITY DEVICE WITH BIDIRECTIONAL COMMUNICATION

Abstract: A security device with bidirectional communication capability comprising logic control means which are adapted to control at least one LED for indicating the operating status of a peripheral unit in which the security device is accommodated. The device comprises at least one resistor which is connected in parallel to the at least one LED, for converting into voltage light energy received from the at least one LED, the LED being connected to means for evaluating the voltage generated thereby, the means being in turn connected to the logic control means.

Description: SECURITY DEVICE WITH BIDIRECTIONAL COMMUNICATION TECHNICAL FIELD The present invention relates to a security device with bidirectional communication. More particularly, the invention relates to a security device capable of communicating both with a control unit and directly with a user. BACKGROUND ART It is known that most currently commercially available security systems generally have the following operating criterion. A control unit manages peripheral units (usually sensors or actuators) by means of a two-wire line or by means of radio systems. More recent security systems in fact allow to address (via hardware or software) the peripheral units. In this case, the control unit determines whether, according to the control program, the environmental parameters detected by the sensors correspond or not to an alarm condition and the control unit therefore activates, if appropriate, the corresponding alarm procedures, such as visual or acoustic signals or the like. Usually, communication between the control units and the peripheral units is entrusted to proprietary protocols which are compatible with the power supply requirements, if any, of the sensors and most of all with the requirements of sturdiness and immunity to noise which are typical of a security system. Clearly, the possibility of communication between the control unit and the peripheral units allows higher flexibility and maintenance capability of the security system and ultimately gives an added value to the system as a whole. However, communication between the control unit and the peripheral units is entrusted exclusively to a two-wire line, as mentioned, such as for example a bus, or to radio systems. In practice, the only option is to act from the control unit toward the peripheral units and it is not possible to act directly on said peripheral units, thus bypassing the control unit. DISCLOSURE OF THE INVENTION The aim of the present invention is to provide a security device with bidirectional communication capability which allows users to act directly on the peripheral units in addition to acting on them from the control unit. Within this aim, an object of the present invention is to provide a security device with bidirectional communication capability which allows to use the normal visual indication device of a peripheral unit for interacting with said peripheral unit. Another object of the present invention is to provide a security device with bidirectional communication capability which allows to interact with a peripheral unit directly at the site where said peripheral unit is installed. Another object of the present invention is to provide a security device with bidirectional communication capability which is highly reliable, relatively simple to manufacture and at competitive costs. This aim and these and other objects which will become better apparent hereinafter are achieved by a security device with bidirectional communication capability, comprising logic control means which are adapted to control at least one LED for indicating the operating status of a peripheral unit in which said security device is accommodated, characterized in that it comprises at least one resistor which is connected in parallel to said at least one LED, for converting into voltage light energy received from said at least one LED, said LED being connected to means for evaluating said voltage generated thereby, said means being in turn connected to said logic control means. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the invention will become better apparent from the description of preferred but not exclusive embodiments of the device according to the present invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a circuit diagram of the security device according to the present invention; Figure 2 is a block diagram of the interaction between a peripheral unit which accommodates the security device according to the present invention and an external unit; Figure 3 is a block diagram of a second embodiment of the interaction between a peripheral unit in which the device according to the invention is incorporated and an external unit. WAYS OF CARRYING OUT THE INVENTION With reference to the figures, and initially with reference to Figure 1, the security device according to the present invention, generally designated by the reference numeral 10, comprises logic control means 12 which are connected to memory means 13 and to management means 14 which are adapted to manage the operation of at least one LED. The logic control means 12 are connected to a power buffer 15, which is adapted to drive at least one LED 16 which provides an indication of the operating status of the peripheral unit in which the security device is accommodated. The peripheral unit can be for example a sensor or an actuator. A resistor 17 is interposed between the output of the power buffer 15 and the LED 16 and allows to reduce the current in output from the power buffer 15 for supplying power to the LED 16. The particularity of the invention is that the LED 16 is used not only as a device for signaling the operating status of the peripheral unit but also in reverse, as explained in detail hereinafter. The LED is in fact usually a device designed to convert electric energy into light energy, with a photoelectric effect, in order to provide in this case an indication of the operating status of the peripheral unit. In the device according to the invention, the LED also acts as a photodiode, i.e., it performs the opposite conversion, from light energy to electric energy. It is in fact known that a p-n junction, if crossed by a current, can emit photons whose energy is linked to the type of doping of the junction. Likewise, if a p-n junction is illuminated by photons of the appropriate energy, hole-electron pairs are produced which, by flowing through the junction, generate a current which is proportional to the intensity of the incident light. Obviously, the efficiency of quantum conversion, i.e., the amount of current that can be generated in relation to a given incident light energy, is very low for an LED, since the LED is an optoelectronic device designed and optimized for the opposite conversion, i.e., from electric energy to light energy. However, the photocurrent that is obtained from the LED if it is illuminated appropriately with a light source tuned to the same wavelength as the LED is capable of providing a signal whose amplitude is sufficient to allow processing by an amplifier-comparator block. Therefore, by modulating the signal of the illuminating source with a train of pulses, it is possible to reconstruct said signal at the output of the signal processing system. In this manner, an additional semiduplex communication channel is available which, in addition to the conventional two-wire line that connects the peripheral unit to a control unit, allows communication with said control unit. In practice, the security device 10 according to the invention therefore comprises an additional resistor 18 which is connected in parallel to the LED 16 so as to convert into voltage the current generated when the LED 16 acts as a receiver. The number of resistors 18 is of course equal to the number of LEDs 16 provided in output to the peripheral unit that accommodates the security device 10. Switching means 19 are further provided in order to connect the voltage signal produced by the LED 16 when it is lit to comparator means 20 which are adapted to compare said voltage signal with a comparison voltage 21, so as to generate a signal 22 which represents the difference between the voltage detected by the LED 16 and the reference voltage 21 sent by the logic control means 12. The amplifier-comparator 20 further allows to amplify said voltage difference signal. The switching means 19 are therefore normally operatively open when the LED 16 acts as an optoelectronic device for indicating the operating status of the peripheral unit, i.e., when it provides an external indication of the operation of said peripheral unit. Vice versa, when the LED 16 acts as a receiving element the switching means 19 are closed, activating the path that connects the LED 16 to the amplifier-comparator means 20, shifting the power buffer 15 to a high- impedance state. Substantially, a second communication channel, this time of the optical type, is created alongside the normal two-wire or radio communication channel that connects the peripheral unit to the control unit (which is not shown in the figures). Figure 2 is a schematic view of a peripheral unit 30 which internally accommodates the security device 10 according to the present invention. The reference numeral 16 designates, in this case, again the LED for external indication of the operating status of said peripheral unit. In order to illuminate the LED 16 from outside and thus make it act as a receiving element, a first embodiment provides for an external unit 31 which is appropriately provided with an optical input and output device. In the first embodiment shown in Figure 2, the optical input and output device comprises at least one ultrabright LED 32 which is arranged to the side of a photodiode or phototransistor 33 so that the LED 32 is capable of illuminating the LED 16 of the peripheral unit 30 and thus make it act as a receiving element. At the same time, the photodiode 33 of the external unit 31 allows to receive light information from the LED 16 of the peripheral unit 30. The external unit 31 is appropriately interfaced mechanically with the peripheral unit 30 so as to keep the optical input and output device 32, 33 at a short distance from the LED 16. In a second embodiment, shown in Figure 3, the peripheral unit 30 is again interfaced with the external unit 31, but in this case the optical input- output device is constituted by at least one optical fiber 34. This last solution allows the operator to program, test and obtain data from peripheral units even if they are located in difficult and awkward positions, without having to remove the peripheral unit from its support. In practice it has been observed that the security device according to the invention allows to obtain an additional bidirectional communication channel which is added alongside the normal communication channel provided between a peripheral unit and a control unit meant to control the operation of said peripheral unit. Moreover, the "optical" channel thus created allows the operator to act directly on the peripheral units in the operating environment, i.e., at the installation site, with consequent advantages in terms of operation and maintenance. Moreover, the security device according to the invention can be easily integrated in a control unit of a commercially known type with a minimal increase in its dimensions. The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may further be replaced with other technically equivalent elements. In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art. The disclosures in Italian Patent application No. PD2000A000084, from which this application claims priority, are incorporated herein by reference.

Claims: CLAIMS 1. A security device with bidirectional communication capability, comprising logic control means which are adapted to control at least one LED for indicating the operating status of a peripheral unit in which said security device is accommodated, characterized in that it comprises at least one resistor which is connected in parallel to said at least one LED, for converting into voltage light energy received from said at least one LED, said LED being connected to means for evaluating said voltage generated thereby, said means being in turn connected to said logic control means. 2. The device according to claim 1, characterized in that said means for evaluating said voltage generated by said at least one LED comprise amplifier and comparator means adapted to compare said voltage generated by said LED with the reference voltage generated by said logic control means, in order to obtain a voltage difference signal which is adapted to be sent to said logic control means. 3. The device according to claims 1 and 2, characterized in that said amplifier and comparator means are connected to said at least one LED by virtue of switching means. 4. The device according to one or more of the preceding claims, characterized in that said logic control means drive said at least one LED by means of a power buffer. 5. The device according to one or more of the preceding claims, characterized in that at least one resistor is interposed between said power buffer and said at least one LED and is connected in series to said at least one LED. 6. The device according to one or more of the preceding claims, characterized in that it comprises an external unit which is adapted to interface with said peripheral unit that accommodates said security device, said external unit being provided with an optical input and output device adapted to communicate with said at least one LED. 7. The device according to claim 6, characterized in that said optical input and output device of said external unit comprises at least one ultrabright LED and at least one photodiode or phototransistor. 8. The device according to claim 6, characterized in that said optical input and output device of said external unit comprises at least one optical fiber. 9. The device according to one or more of the preceding claims, characterized in that said logic control means are connected to memory means and to means for managing said at least one LED. 10. An external unit for transmitting an optical signal to an LED of a peripheral unit provided with a security device according to one or more of the preceding claims, characterized in that it comprises an optical input and output device which is adapted to communicate bidirectionally with said at least one LED of said peripheral unit. 11. The external unit according to claim 10, characterized in that said optical input and output device comprises at least one ultrabright LED and at least one photodiode or phototransistor. 12. The external unit according to claim 10, characterized in that said optical input and output device comprises at least one optical fiber. 13. The external unit according to one or more of claims 10 to 12, characterized in that it is interfaced mechanically with said peripheral unit, so as to keep said optical input and output device in a position in which it faces said at least one LED of said peripheral unit. 14. A method for providing an optical communication channel between a peripheral unit and the external control unit, characterized in that it comprises the steps of: using at least one LED of said peripheral unit to receive an optical signal sent by an external unit; converting said optical signal received by said at least one LED into a voltage signal; evaluating said voltage signal by way of logic control means. 15. The method according to claim 14, characterized in that the step of evaluating said voltage signal comprises the amplification and comparison of said voltage signal with a reference voltage sent by said logic control means. 16. The method according to claim 14, characterized in that it comprises the step of connecting said at least one LED with means for evaluating said voltage signal by way of switching means.

Inventors: ZAMBON CRISTIANO, ZAMBON, CRISTIANO
Applicants: SYSTEM SENSOR DIVISION OF PITT, ZAMBON CRISTIANO, SYSTEM SENSOR DIVISION OF PITTWAY CORPORATION, ZAMBON, CRISTIANO
Application year: 2001
Main classification: G08B5
IPC codes: G08B5