Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/16—Actuation by interference with mechanical vibrations in air or other fluid
  • G08B13/1654—Actuation by interference with mechanical vibrations in air or other fluid using passive vibration detection systems
  • G08B13/1681—Actuation by interference with mechanical vibrations in air or other fluid using passive vibration detection systems using infrasonic detecting means, e.g. a microphone operating below the audible frequency range
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
  • G08B29/18—Prevention or correction of operating errors
  • G08B29/20—Calibration, including self-calibrating arrangements
  • G08B29/24—Self-calibration, e.g. compensating for environmental drift or ageing of components

Definitions

• the present invention relates to alarm devices capable of detecting the differences in sound pressure consecutive to the inadvertent opening or the breaking of a door or a window and relates in particular to a very low self-regulating alarm device. energy consumption.
• the output signal from a microphone is first amplified, then, in general, compared to a fixed reference voltage in a comparator whose output can have two states possible depending on the relative value of the signal from the microphone and the reference voltage.
• a comparator whose output can have two states possible depending on the relative value of the signal from the microphone and the reference voltage.
• These devices set off the alarm under the effect of an aperiodic compression wave, while they are insensitive to a periodic signal such as an audible sound, the monitoring taking place in particular on the shape and amplitude of the signals. captured.
• the adjustment of the sensitivity threshold must be carried out manually, case by case.
• the sensitivity threshold of these detectors should be set at a relatively high value, so that they do not take into account these random and fugitive atmospheric disturbances, but inevitable since they are conditioned by the presence of strong wind. Such an adjustment is made to the detriment of the effectiveness of the detector in calm weather.
• a differential acoustic pressure detector has a sensitivity threshold permanently adjusted to its optimal value by the microphone output signal which is a function of atmospheric disturbances picked up at the microphone input.
• the object of the invention is to provide self-regulating alarm devices exhibiting insignificant operating differences from one device to another, in particular because part of the functions of the device is performed by a microprocessor.
• Another object of the invention is to provide an alarm device of the above type having very low energy consumption thanks to the use of a microprocessor.
• the invention relates to an alarm device comprising a sound pressure sensor supplying an analog signal on the one hand to a first amplifier means and on the other hand to a second amplifier means, a first comparator whose input + is connected to the output of the second amplifying means and the output of which provides an alarm signal to alarm means in the event of a break-in or attempted break-in.
• This device includes self-regulation means mainly consisting of an analog-digital converter whose input is connected to the output of the first amplifier means to output a digital signal as a function of atmospheric disturbance and a microprocessor programmed to supply, in response to the detection of the digital signal supplied by the converter, a digital signal at the input of the comparator, the pulses of which have a variable width which increases as a function of the duration and the extent of the atmospheric disturbance so as to increase automatically the triggering threshold of the alarm device and therefore decrease its sensitivity when the acoustic sensor detects an atmospheric disturbance such as Fri.
• self-regulation means mainly consisting of an analog-digital converter whose input is connected to the output of the first amplifier means to output a digital signal as a function of atmospheric disturbance and a microprocessor programmed to supply, in response to the detection of the digital signal supplied by the converter, a digital signal at the input of the comparator, the pulses of which have a variable width which increases as a function of the duration and the extent of the atmospheric disturbance so as to increase automatically
• FIG. 1 is a block diagram of an alarm device according to the invention. invention
• Figure 2 is a diagram showing the signals observed at different points of the device when it is at rest, when it reacts to an atmospheric disturbance and when it is in the presence of a break-in.
• the signals received by an acoustic sensor 10 are transmitted on the one hand to the input + of a constant gain amplifier means 12 and on the other hand to the input + an adjustable gain amplifier means 14 via a resistor 16 connected to a voltage of 0.8 volts.
• the amplifier means 12 is mainly composed of an operational amplifier 13 comprising between its input - and its output a resistor (of a value of 3M ⁇ ) and a capacitor (of a value of InF) serving as feedback to limit the gain.
• the input - is connected to ground via an electrolytic capacitor preventing amplification of the quiescent voltage.
• the amplifier means 14 is mainly composed of an operational amplifier 15 comprising between its input - and its output a resistor (with a value of 4.7M ⁇ ) and a capacitor (with a value of InF) serving as a counter reaction to limit gain.
• the input - is connected to ground via an electrolytic capacitor 20 preventing the amplification of the quiescent voltage and a potentiometer 22 from 210 to 10,000 whose adjustment is made according to the room in which the alarm device is installed, the necessary gain of the amplifying means being all the lower as said room is acoustically sealed.
• the output of the amplifier means 12 is connected to the input + of a comparator 24 which has the function of transforming the analog signal supplied by the amplifier means 12 into a binary signal whose width is a function of the importance of the disturbance and which is transmitted to the microprocessor 26 in order to self-regulate the alarm device.
• the value of the time delay can be fixed at ls so that if the signal received on line 30 lasts less than this time delay, the microprocessor 26 takes no action.
• the output of the amplifier means 14 is connected to the input + of a comparator 34 which transforms the analog signal supplied by the amplifier means 14 into a binary signal which is transmitted to the microprocessor 26 in order to inform it of an opening untimely door or break-in.
• the microprocessor 26 transmits a signal to the alarm means 28 which is preferably a radio transmitter transmitting the alarm signal to the alarm center.
• the microprocessor 26 is programmed to transmit a signal on its output 32 when it detects a digital signal of value 1 on its input 30 coming from the comparator 24.
• This signal is formed by pulses of width variable depending on the number and width of the pulses with a value of 1 detected on input 30. Indeed, assuming a sampling of a frequency of 150Hz of this input, an input bit of a frequency of 15Hz will therefore be sampled about 5 times if the received signal is a perfect sinusoid.
• the width of the pulse transmitted on line 32 will be increased. In the same way, this width is reduced each time the microprocessor detects the value 0 of the signal on line 30. It can therefore be seen that the stronger the wind, the wider the pulses transmitted to the output of comparator 24 and the more pulse delivered on line 32 will also be wide. A modulation by pulse width is thus obtained.
• the pulse transmitted on line 32 more or less charges the capacitor 38 (of value l ⁇ F) through the resistor 36 (of value 4.7 M ⁇ ) and supplies a voltage whose value depends on the width of the pulse supplied on line 32.
• the wider this pulse the higher the voltage provided on the input - of the comparator 34 is high and less is the sensitivity of the comparator 34 to react to the signal received from the sensor 10 to trigger the alarm 28.
• the duration during which the microprocessor 26 reacts to the presence atmospheric disturbance by transmitting increasingly large pulses to the integrator 36-38 can be limited to a maximum value such as 10 or 20s.
• an auto-calibration of the device takes place at the end of the initialization phase, after power-up, and consists for the microprocessor in finding the width of the signal 32 which allows optimal sensitivity. By proceeding by successive adjustments to signal 32, it searches for the sensitivity threshold causing an untimely triggering materialized by a permanent signal 32. However, periodic readjustments are necessary due to possible thermal variations. The microprocessor does this in two ways. In the absence of an incident, it recalculates the optimal width of the signal 32 (for example every hour). In the event of an incident detected, it checks that it is not a trigger untimely by testing the sensitivity threshold before validating the incident.
• FIG. 2 makes it possible to illustrate the value of the signals Si at the output of the amplifier means 12, S 2 at the output of the comparator 24, S 3 at the output of the comparator 34, S 4 on the output line 32 , S 5 at the input of the comparator 34 and S 6 at the output of the microprocessor 26 towards the alarm 28, when 1) the device is at rest, 2) in the presence of an atmospheric disturbance and 3) in the presence of a break-in.
• the signal Si supplied by the amplifier means 12 has a constant value (0.8 volts) and the comparators 24 and 34 provide each an almost zero signal S 2 or S 3 .
• the signal S 4 supplied by the microprocessor on line 32 is a regular signal which makes it possible to obtain a signal S5 on the input - of the comparator equal to approximately 1 volt.
• the signal S 3 being reduced to 0, it is the same for the alarm signal Se.
• the signal Si supplied at the output of the amplifier means 12 becomes approximately sinusoidal and the signal S 2 supplied to the microprocessor is formed by pulses of variable width depending on the extent of the disturbance.
• the signal S 3 is still almost zero because the sensitivity threshold has been increased. Indeed, the existence of pulses S 2 leads to the generation by the microprocessor of pulses S whose width depends on the width and the number of pulses S 2 , which results in a signal S 5 of higher voltage (2 volts in this case) at the input - of comparator 34. As before, the signal S 3 being reduced to 0, it is the same for the alarm signal S 6 .
• this width is between a minimum width and a maximum width, it is a shock (against a window for example) or an attempted break-in, while the break-in will not be proven that if this width is greater than the maximum width.
• the comparator 24 could be replaced by an analog-to-digital converter making it possible to provide bit configurations associated with the signature of possible atmospheric disturbances, said configurations being analyzed and recognized by the microprocessor 26 before the latter transmits a signal S 4 on its output 32 which is a function of the detected disturbance.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Burglar Alarm Systems (AREA)
• Fire Alarms (AREA)
• Emergency Alarm Devices (AREA)
• Alarm Systems (AREA)
• Fire-Detection Mechanisms (AREA)

Applications Claiming Priority (3)

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• 2000
  • 2000-05-18 FR FR0006360A patent/FR2809215B1/fr not_active Expired - Fee Related
• 2001
  • 2001-05-18 CA CA002407117A patent/CA2407117A1/fr not_active Abandoned
  • 2001-05-18 DE DE60105289T patent/DE60105289T2/de not_active Expired - Fee Related
  • 2001-05-18 WO PCT/FR2001/001541 patent/WO2001088870A1/fr active IP Right Grant
  • 2001-05-18 ES ES01936588T patent/ES2228868T3/es not_active Expired - Lifetime
  • 2001-05-18 AT AT01936588T patent/ATE275279T1/de not_active IP Right Cessation
  • 2001-05-18 EP EP01936588A patent/EP1287508B1/de not_active Expired - Lifetime
  • 2001-05-18 AU AU2001262464A patent/AU2001262464A1/en not_active Abandoned
  • 2001-05-18 PT PT01936588T patent/PT1287508E/pt unknown

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