EP0079010B1 - Smoke detector - Google Patents

Smoke detector Download PDF

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Publication number
EP0079010B1
EP0079010B1 EP82110013A EP82110013A EP0079010B1 EP 0079010 B1 EP0079010 B1 EP 0079010B1 EP 82110013 A EP82110013 A EP 82110013A EP 82110013 A EP82110013 A EP 82110013A EP 0079010 B1 EP0079010 B1 EP 0079010B1
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EP
European Patent Office
Prior art keywords
radiation
smoke detector
radiation source
detector according
threshold value
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP82110013A
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German (de)
French (fr)
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EP0079010A1 (en
Inventor
Jürg Dr. sc. nat. Muggli
Heinz Dipl.-Ing.ETH Güttinger
Zoltan Dipl.-Ing. Horvath
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Cerberus AG
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Cerberus AG
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Priority to AT82110013T priority Critical patent/ATE20398T1/en
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    • 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
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/04—Monitoring of the detection circuits
    • G08B29/043—Monitoring of the detection circuits of fire detection circuits
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
    • G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G08B17/113—Constructional details
    • 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 invention relates to a smoke detector of the type defined in the preamble of claim 1.
  • a smoke detector is known from Japanese published patent application No. 54-85786.
  • a smoke detector is known from WO-PA 80/1326 and EP-PA-14779, in which a radiation source is controlled by a pulse generator and emits short-lasting radiation pulses.
  • the receiver picks up the radiation that is scattered by smoke in the scattering volume, but also radiation that is reflected by the walls.
  • To compensate for aging and the temperature response of the transmitter and receiver e.g. in US Pat. No. 4,180,742
  • this is not sufficient to compensate for all possible changes due to contamination.
  • the main radiation receiver is positioned centrally symmetrically at the top, the reference receiver somewhat laterally at the top in the direct radiation path of the source. With this type of positioning, dust is only deposited on the radiation source. Condensation from gases, on the other hand, will equally prove the main recipient and reference recipient.
  • the regulation of the light output of the transmitter by measuring the signal of the reference cell therefore results in a scatter signal generated by the smoke on the main receiving cell, which is independent of the contamination of the detector.
  • the electronic circuit essentially consists of an oscillator for the power supply to the radiation source regulated by the reference cell, an amplifier and a threshold value detector with differential properties. If the output pulse changes very slowly, as can be generated by contamination, the threshold value is shifted with the level of the output pulse. If the output pulse increases rapidly, as is produced by smoke produced by fire, the threshold value changes only insignificantly, and the flip-flop is triggered when a certain reception height is reached. The threshold detector with differential properties is thus able to correct the slow changes in the output pulse.
  • the combination of this threshold value detector with the radiation pulse controlled by the reference cell results in a smoke detector which does not change its sensitivity to smoke even when heavily soiled. In addition, the aging of the radiation source and the temperature dependence are corrected.
  • the regulation of the radiation source can also be used as follows to trigger an interference signal:
  • the smoke detector retains an unchanged sensitivity to smoke. As soon as this circuit reaches the limits of the possibility of regulation, this can be detected and an interference signal can be triggered.
  • Such a detector thus triggers an interference signal as long as it still has hardly any change in smoke sensitivity, but would soon become insensitive to further contamination or aging of the radiation source.
  • Fig. 1 the structure of a smoke detector according to the invention is shown in section.
  • the radiation source 1 emits radiation in a conical shape into the enclosed space of the detector.
  • a central aperture 50 keeps direct radiation away from the radiation receiver 16.
  • the reference cell 12 is positioned in the radiation cone. This arrangement ensures that radiation receiver 16 and reference cell 12 become equally dirty. In particular, dust deposits mainly on the radiation source 1 and thus influences the reference and scattered light signals equally.
  • a radiation transmitter S In the circuit of an embodiment of the smoke detector according to the invention shown in FIG. 2, a radiation transmitter S, a radiation detector A, a correlator C, a threshold value detector N, an integrator t, an alarm flip-flop K and lie between two lines L and L 2 carrying direct voltage a monitoring circuit with flip-flop U.
  • the radiation transmitter S consists of an oscillator that conducts a current of approximately one ampere through the radiation source 1 at a time interval of approximately two seconds.
  • the radiation source 1 consists of a light or IR radiation emitting diode.
  • the oscillator consists of the power transistor 2 with associated limiting resistor 3, from the drive circuit consisting of transistor 4 with associated limiting resistor 5, and from the feedback element consisting of resistor 7 and capacitor 6.
  • the large capacitor 10 supplies the current pulse for the radiation source 1; it is charged via resistor 11.
  • the current pulse is triggered when the resistors 8 and 9 at the base of the transistor 4 supply the voltage which makes it conductive.
  • the current through the light-emitting diode is regulated via the reference cell (phototransistor 12) with measuring resistor 13 and feedback resistor 14. As soon as the voltage across the resistor 13 is high enough, the transistor 15 becomes somewhat conductive and thus reduces the base current of the power transistor 2.
  • a photo cell can also be used instead of a photo transistor.
  • the radiation detector A consists of the radiation receiver 16 designed as a photocell and the two-stage amplifier consisting of the transistors 17 and 18, the collector resistors 22 and 23, the emitter resistor 20 with a parallel capacitor 21 for higher pulse amplification and the feedback resistor 19. Via resistor 24 and capacitor 25 the blocking pulse is generated from the oscillator. A negative blocking pulse thus appears at the collector of transistor 18 above the coupling capacitor 26, to which the amplified output pulse is added in the positive direction.
  • a phototransistor can also be used as the radiation receiver 16: this would simultaneously replace the transistor 17.
  • a self-conducting P-channel junction field-effect transistor 27 is used as the correlator C, the gate of which is normally low, which makes it conductive and thus any possible interference pulse is short-circuited.
  • the gate is high only during the pulse and the JFET 27 blocks and thus allows the output pulse and blocking pulse to pass.
  • the threshold detector N consists of the self-conducting N-channel junction field-effect transistor 28 and the holding stage with capacitor 29 and the high-resistance resistor 30. With each pulse, the FET 28 is made conductive by the negative blocking pulse. This generates a reset pulse via transistor 31 with base resistor 32. At the same time, the capacitor 29 is charged via the forward diode gate-source of the FET 28. As long as the pulse height remains unchanged, the capacitor 29 remains essentially at the same potential.
  • the integration stage I consists of a counter 33 (eg 4024), which receives counting pulses from the oscillator with each radiation pulse. As long as reset pulses are generated, it is also reset to 0 for each pulse. If there are no reset pulses, the output Q " goes high after 2 n - 1 pulses.
  • a counter 33 eg 4024
  • the flip-flop K consists of the thyristor 34, which is driven by the output Q of the counter.
  • the Zener diode 35 generates a voltage (e.g. 6 V) to distinguish the alarm condition from the fault condition.
  • the monitoring circuit U consists of the voltage divider with resistors 37 and 38 and the thyristor 36.
  • the resistor 3 measures the current through the radiation source 1. As soon as this becomes too high as a result of contamination or aging of the radiation source 1, the thyristor 36 is activated and a malfunction is thus indicated .
  • the circuit shown is only an example. Parts can also be omitted, e.g. Monitoring circuit U or the correlator C.
  • the various elements can also be designed differently, e.g. the threshold value detector can also be differentiated digitally using a counter and a digital / analog converter, as is shown in FIG. 3.
  • the pulse signal is added to the voltage at the voltage divider formed from the resistors 40 and 41 and fed to the negative input of the comparators 45 and 46. These receive voltages on their positive input, which are generated by resistors 42, 43 and 44.
  • the count pulse which is inverted with the element 49, generates a state of the counter 47 which is 1 higher or lower (for example 14516).
  • the state of the counter 47 generates the DC input voltage via the resistors 41 and 40 via the parallel digital / analog converter 48. This circuit ensures that in the idle state the pulse voltage at the negative input oscillates just around the voltage at the positive input of the comparator 46.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Business, Economics & Management (AREA)
  • Computer Security & Cryptography (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Emergency Management (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Vehicle Body Suspensions (AREA)
  • Gyroscopes (AREA)

Abstract

A smoke detector is disclosed having a radiation source operated in a pulsed mode. Externally of a direct radiation region of the radiation source there is arranged a radiation receiver which, in the presence of smoke or other particles emanating from a combustion process and located in the radiation region, is impinged by scattered radiation and delivers an output signal to an evaluation circuit. The evaluation circuit contains switching elements which, when the number of source output signals or pulses exceeds a predetermined threshold value for the number of source output pulses, delivers an alarm signal. Near to the radiation receiver there is arranged a reference cell in the direct radiation beam of the radiation source, this reference cell controlling the emission of radiation by the radiation source. Further, there is provided circuitry which, in the presence of a slow change in the amplitude of the receiver output pulse, adjusts an amplitude threshold value set for the amplitude of the receiver output pulse at a rate corresponding to a time-constant of more than one minute. Consequently, there is obtained an output signal of the radiation receiver which is dependent upon the smoke density and which is independent of the contamination or soiling of the smoke detector.

Description

Die Erfindung geht aus von einem Rauchdetektor der im Oberbegriff des Patentanspruchs 1 definierten Gattung. Ein solcher Rauchdetektor ist aus der japanischen veröffentlichten Patentanmeldung Nr. 54-85786 bekannt.The invention relates to a smoke detector of the type defined in the preamble of claim 1. Such a smoke detector is known from Japanese published patent application No. 54-85786.

Ferner ist aus der WO-PA 80/1326 und der EP-PA-14779 ein Rauchdetektor bekannt, bei welchem eine Strahlungsquelle von einem Impulsgeber angesteuert wird und kurzdauernde Strahlungsimpulse aussendet. Der Empfänger nimmt die Strahlung auf, welche von Rauch im Streuvolumen gestreut, aber auch solche, die von den Wänden reflektiert wird. Zur Kompensation von Alterung und Temperaturgang vom Sender und Empfänger ist (z.B. in US-PS 4'180'742) bereits vorgeschlagen worden, bei einem mit Gleichlicht betriebenen Streulichtmelder mit einer zweiten, identischen Empfangszelle das ausgesandte Licht des Senders zu messen und zu regeln. Dies genügt aber nicht zur Kompensation aller möglichen Veränderungen durch Verschmutzung.Furthermore, a smoke detector is known from WO-PA 80/1326 and EP-PA-14779, in which a radiation source is controlled by a pulse generator and emits short-lasting radiation pulses. The receiver picks up the radiation that is scattered by smoke in the scattering volume, but also radiation that is reflected by the walls. To compensate for aging and the temperature response of the transmitter and receiver (e.g. in US Pat. No. 4,180,742), it has already been proposed to measure and regulate the emitted light of the transmitter in the case of a scattered light detector operated with constant light with a second, identical receiving cell. However, this is not sufficient to compensate for all possible changes due to contamination.

Der Erfindung liegt die Aufgabe zu Grunde, einen Rauchdetektor zu schaffen, dessen Funktionsfähigkeit durch keine Art von Verschmutzung beeinträchtigt wird und dessen Rauchempfindlichkeit über längere Zeiträume stabil bleibt. Eine weitere Aufgabe der Erfindung besteht darin, einen Rauchdetektor zu schaffen, der ein Störsignal abgibt, wenn seine Verschmutzung so weit fortgeschritten ist, dass seine Funktionsfähigkeit beeinträchtigt werden könnte.The invention is based on the object of providing a smoke detector whose functionality is not impaired by any type of contamination and whose sensitivity to smoke remains stable over long periods of time. Another object of the invention is to provide a smoke detector which emits an interference signal when its contamination has progressed to such an extent that its functionality could be impaired.

Diese Aufgabe wird erfindungsgemäss durch die im kennzeichnenden Teil des Patentanspruches 1 definierten Merkmale gelöst.According to the invention, this object is achieved by the features defined in the characterizing part of patent claim 1.

Bevorzugte Ausführungsformen und weitere Ausgestaltungen der Erfindung sind in den abhängigen Ansprüchen definiert.Preferred embodiments and further refinements of the invention are defined in the dependent claims.

Einer vorteihalfe Ausgestaltung des erfindungsgemässen Rauchdetektors ist im Patentanspruch 2 angegeben. Der Hauptstrahlungsempfänger ist zentralsymetrisch oben positioniert, der Referenzempfänger etwas seitlich oben im direkten Strahlungsgang der Quelle. Bei dieser Art der Positionierung wird Staub nur auf der Strahlungsquelle abgelagert. Kondensation aus Gasen hingegen wird gleichmässig Hauptempfänger und Referenzempfänger belegen. Die Regelung der Lichtleistung des Senders durch die Messung des Signals der Referenzzelle ergibt deshalb ein vom Rauch erzeugtes Streusignal auf der Hauptempfangszelle, welches unabhängig von der Verschmutzung des Melders ist.An advantageous embodiment of the smoke detector according to the invention is specified in claim 2. The main radiation receiver is positioned centrally symmetrically at the top, the reference receiver somewhat laterally at the top in the direct radiation path of the source. With this type of positioning, dust is only deposited on the radiation source. Condensation from gases, on the other hand, will equally prove the main recipient and reference recipient. The regulation of the light output of the transmitter by measuring the signal of the reference cell therefore results in a scatter signal generated by the smoke on the main receiving cell, which is independent of the contamination of the detector.

Die elektronische Schaltung gemäss einer weiteren Ausgestaltung besteht im wesentlichen aus einem Oszillator zur durch die Referenzzelle geregelten Stromversorgung der Strahlungsquelle, einem Verstärker und einem Schwellenwertdetektor mit Differentialeigenschaften. Bei sehr langsamer Veränderung des Ausgangsimpulses, wie sie durch Verschmutzung erzeugt werden kann, wird Schwellenwert mit der Höhe des Ausgangsimpulses verschoben. Bei schneller Erhöhung des Ausgangsimpulses, wie es durch Feuer entstandener Rauch erzeugt, verändert sich der Schwellenwert nur unwesentlich, und bei Erreichen einer bestimmten Empfangshöhe wird die Kippstufe ausgelöst. Der Schwellenwertdetektor mit Differentialeigenschaften vermag somit die langsamen Aenderungen des Ausgangsimpulses zu korrigieren. Die Kombination dieses Schwellenwertdetektors mit dem durch die Referenzzelle gesteuerten Strahlungspuls ergibt einen Rauchdetektor, der seine Rauchempfindlichkeit auch bei stärkerer Verschmutzung nicht verändert. Ausserdem werden die Alterung der Strahlungsquelle und die Temperaturabhängigkeit korrigiert.The electronic circuit according to a further embodiment essentially consists of an oscillator for the power supply to the radiation source regulated by the reference cell, an amplifier and a threshold value detector with differential properties. If the output pulse changes very slowly, as can be generated by contamination, the threshold value is shifted with the level of the output pulse. If the output pulse increases rapidly, as is produced by smoke produced by fire, the threshold value changes only insignificantly, and the flip-flop is triggered when a certain reception height is reached. The threshold detector with differential properties is thus able to correct the slow changes in the output pulse. The combination of this threshold value detector with the radiation pulse controlled by the reference cell results in a smoke detector which does not change its sensitivity to smoke even when heavily soiled. In addition, the aging of the radiation source and the temperature dependence are corrected.

Es hat sich als vorteilhaft erwiesen, in der vorerwähnten Schaltung Mittel vorzusehen, durch welche ein Sperrpuls erzeugt wird (beispielsweise durch einen elektrischen Puls eines Oszillators), sowie Mittel, durch welche die Differenz dieses Sperrpulses und des Ausgangsimpulses des Strahlungsempfängers gebildet wird, welche dann als Rückstellsignal einer Zähleinrichtung zugeführt wird, wobei die Zähleinrichtung bei Ausbleiben des Rückstellsignals weitergeschaltet wird und bei Erreichen eines vorbestimmten Zählerstandes ein Alarmsignal auslöst. Eine derart verbesserte Schaltung ist besonders unempfindlich gegen elektrische Störungen, insbesondere hochfrequente elektrische Störungen, da diese höchstens ein zusätzliches Rückstellsignal für die Zähleinrichtung erzeugen können, wodurch der Rauchdetektor gegen die Auslösung von Fehlalarmen sicherer wird.It has proven to be advantageous to provide means in the aforementioned circuit by means of which a blocking pulse is generated (for example by an electrical pulse from an oscillator), and means by which the difference between this blocking pulse and the output pulse of the radiation receiver is formed, which then Reset signal is fed to a counting device, the counting device being switched on if the reset signal fails to appear and triggering an alarm signal when a predetermined counter reading is reached. Such an improved circuit is particularly insensitive to electrical interference, in particular high-frequency electrical interference, since these can at most generate an additional reset signal for the counting device, as a result of which the smoke detector is safer against the triggering of false alarms.

Ausserdem kann die Regelung der Strahlungsquelle auch folgendermassen zur Auslösung eines Störsignals verwendet werden: Solange die Strahlungsquelle durch die Referenzzelle voll nachgeregelt werden kann, behält der Rauchdetektor eine unveränderte Rauchempfindlichkeit. Sobald dieser Schaltkreis an die Grenzen der Regelungsmöglichkeit kommt, kann dies detektiert werden, und ein Störsignal kann ausgelöst werden. Ein solcher Detektor löst also ein Störsignal aus, solange er zwar noch eine kaum veränderte Rauchempfindlichkeit besitzt, aber durch weitere Verschmutzung oder Alterung der Strahlungsquelle bald unempfindlich werden würde.In addition, the regulation of the radiation source can also be used as follows to trigger an interference signal: As long as the radiation source can be fully readjusted by the reference cell, the smoke detector retains an unchanged sensitivity to smoke. As soon as this circuit reaches the limits of the possibility of regulation, this can be detected and an interference signal can be triggered. Such a detector thus triggers an interference signal as long as it still has hardly any change in smoke sensitivity, but would soon become insensitive to further contamination or aging of the radiation source.

Eine Ausführungsform des erfindungsgemässen Rauchdetektors wird im folgenden anhand der Figuren näher erläutert.

  • Fig. 1 zeigt einen Rauchdetektor mit Referenzzelle.
  • Fig. 2 stellt die Schaltung eines bevorzugten Ausführungsbeispieles dar.
  • Fig. 3 stellt eine weitere Schaltung mit digitaler Nachführung dar.
An embodiment of the smoke detector according to the invention is explained in more detail below with reference to the figures.
  • Fig. 1 shows a smoke detector with a reference cell.
  • Fig. 2 shows the circuit of a preferred embodiment.
  • Fig. 3 shows another circuit with digital tracking.

In Fig. 1 ist im Schnitt der Aufbau eines erfindungsgemässen Rauchdetektors dargestellt. Die Strahlungsquelle 1 sendet hohlkegelförmig Strahlung in den umschlossenen Raum des Detektors aus. Eine Zentralblende 50 hält direkte Strahlung vom Strahlungsempfänger 16 fern. Hingegen ist die Referenzzelle 12 im Strahlungskegel positioniert. Durch diese Anordnung wird erreicht, dass Strahlungsempfänger 16 und Referenzzelle 12 gleich stark verschmutzen. Insbesondere lagert sich Staub hauptsächlich auf der Strahlungsquelle 1 ab und beeinflusst damit Referenz- und Streulichtsignal gleichermassen.In Fig. 1, the structure of a smoke detector according to the invention is shown in section. The radiation source 1 emits radiation in a conical shape into the enclosed space of the detector. A central aperture 50 keeps direct radiation away from the radiation receiver 16. In contrast, the reference cell 12 is positioned in the radiation cone. This arrangement ensures that radiation receiver 16 and reference cell 12 become equally dirty. In particular, dust deposits mainly on the radiation source 1 and thus influences the reference and scattered light signals equally.

Bei der in Fig. 2 dargestellten Schaltung einer Ausführungsform des erfindungsgemässen Rauchdetektors liegen zwischen zwei Gleichspannung führenden Leitungen L, und L2 ein Strahlungssender S, ein Strahlungsaufnehmer A, ein Korrelator C, ein Schwellenwertdetektor N, ein Integrator t, eine Alarm-Kippstufe K und eine Ueberwachungsschaltung mit Kippstufe U.In the circuit of an embodiment of the smoke detector according to the invention shown in FIG. 2, a radiation transmitter S, a radiation detector A, a correlator C, a threshold value detector N, an integrator t, an alarm flip-flop K and lie between two lines L and L 2 carrying direct voltage a monitoring circuit with flip-flop U.

Der Strahlungssender S besteht aus einem Oszillator, der in einem Zeitabstand von etwa zwei Sekunden einen Strom von zirka einem Ampere etwa 100 µs durch die Strahlungsquelle 1 leitet. Die Strahlungsquelle 1 besteht aus einer Licht oder IR-Strahlung emittierenden Diode. Der Oszillator besteht aus dem Leistungstransistor 2 mit zugehörigem Begrenzungswiderstand 3, aus der aus Transistor 4 mit zugehörigem Begrenzungswiderstand 5 bestehenden Ansteuerschaltung, sowie aus dem aus Widerstand 7 und Kondensator 6 bestehenden Rückkopplungsglied. Der grosse Kondensator 10 liefert den Strompuls für die Strahlungsquelle 1; er wird über den Widerstand 11 aufgeladen. Der Strompuls wird ausgelöst, wenn die Widerstände 8 und 9 an der Basis des Transistors 4 die Spannung liefern, welche diesen leitend macht.The radiation transmitter S consists of an oscillator that conducts a current of approximately one ampere through the radiation source 1 at a time interval of approximately two seconds. The radiation source 1 consists of a light or IR radiation emitting diode. The oscillator consists of the power transistor 2 with associated limiting resistor 3, from the drive circuit consisting of transistor 4 with associated limiting resistor 5, and from the feedback element consisting of resistor 7 and capacitor 6. The large capacitor 10 supplies the current pulse for the radiation source 1; it is charged via resistor 11. The current pulse is triggered when the resistors 8 and 9 at the base of the transistor 4 supply the voltage which makes it conductive.

Der Strom durch die Leuchtdiode (Strahlungsquelle 1) wird über die Referenzzelle (Fototransistor 12) mit Messwiderstand 13 und Rückkopplungswiderstand 14 geregelt. Sobald die Spannung am Widerstand 13 hoch genung ist, wird der Transistor 15 etwas leitend und reduziert damit den Basisstrom des Leistungstransistors 2. Statt eines Fototransistors kann natürlich auch eine Fotozelle verwendet werden.The current through the light-emitting diode (radiation source 1) is regulated via the reference cell (phototransistor 12) with measuring resistor 13 and feedback resistor 14. As soon as the voltage across the resistor 13 is high enough, the transistor 15 becomes somewhat conductive and thus reduces the base current of the power transistor 2. Of course, a photo cell can also be used instead of a photo transistor.

Der Strahlungsaufnehmer A besteht aus dem als Fotozelle ausgebildeten Strahlungsempfänger 16 und dem zweistufigen Verstärker, bestehend aus den Transistoren 17 und 18, den Kollektorwiderständen 22 und 23, dem Emitterwiderstand 20 mit parallelem Kondensator 21 zur höheren Pulsverstärkung und dem Rückkopplungswiderstand 19. Ueber Widerstand 24 und Kondensator 25 wird aus dem Oszillator der Sperrpuls erzeugt. Am Kollektor von Transistor 18 erscheint über dem Kopplungskondensator 26 somit ein negativer Sperrpuls, wozu in positiver Richtung der verstärkte Ausgangsimpuls dazugezählt wird. Statt einer Fotozelle kann als Strahlungsempfänger 16 auch ein Fototransistor verwendet werden: dieser würde gleichzeitig den Transistor 17 ersetzen.The radiation detector A consists of the radiation receiver 16 designed as a photocell and the two-stage amplifier consisting of the transistors 17 and 18, the collector resistors 22 and 23, the emitter resistor 20 with a parallel capacitor 21 for higher pulse amplification and the feedback resistor 19. Via resistor 24 and capacitor 25 the blocking pulse is generated from the oscillator. A negative blocking pulse thus appears at the collector of transistor 18 above the coupling capacitor 26, to which the amplified output pulse is added in the positive direction. Instead of a photocell, a phototransistor can also be used as the radiation receiver 16: this would simultaneously replace the transistor 17.

Als Korrelator C wird ein selbstleitender P-Kanal-Sperrschicht-Feldeffekttransistor 27 verwendet, dessen Gate normalerweise tief liegt, wodurch er leitend ist und damit jeder mögliche Störpuls kurzgeschlossen wird. Nur während des Pulses liegt das Gate hoch und der JFET 27 sperrt und lässt damit den Ausgangsimpuls und Sperrpuls durch.A self-conducting P-channel junction field-effect transistor 27 is used as the correlator C, the gate of which is normally low, which makes it conductive and thus any possible interference pulse is short-circuited. The gate is high only during the pulse and the JFET 27 blocks and thus allows the output pulse and blocking pulse to pass.

Der Schwellwertdetektor N besteht aus dem selbstleitenden N-Kanal-Sperrschicht-Feldeffekttransistor 28 und der Haltestufe mit Kondensator 29 und dem hochohmigen Widerstand 30. Bei jedem Impuls wird durch den negativen Sperrpuls der FET 28 leitend gemacht. Dies erzeugt über Transistor 31 mit Basiswiderstand 32 einen Rückstellpuls. Gleichzeitig wird über die Vorwärtsdiode Gate-Source des FET 28 der Kondensator 29 aufgeladen. Solange die Pulshöhe unverändert bleibt, bleibt der Kondensator 29 im wesentlichen auf dem gleichen Potential.The threshold detector N consists of the self-conducting N-channel junction field-effect transistor 28 and the holding stage with capacitor 29 and the high-resistance resistor 30. With each pulse, the FET 28 is made conductive by the negative blocking pulse. This generates a reset pulse via transistor 31 with base resistor 32. At the same time, the capacitor 29 is charged via the forward diode gate-source of the FET 28. As long as the pulse height remains unchanged, the capacitor 29 remains essentially at the same potential.

Ueber den Widerstand 30 entlädt er sich ganz wenig und wird beim nächsten Puls wieder auf das vorhergehende Potential aufgeladen. Bei sehr langsamen Aenderungen der Pulshöhe folgt das Potential des Kondensators 29 entsprechend. Falls Rauch in den Detektor eindringt, wird der Puls am Gate des FET 28 betragsmässig kleiner. Falls er klein genug wird, wird der FET während des Pulses nicht mehr leitend, wodurch kein Rückstellimpuls mehr erzeugt wird.It discharges very little via resistor 30 and is recharged to the previous potential at the next pulse. If the pulse height changes very slowly, the potential of the capacitor 29 follows accordingly. If smoke penetrates the detector, the pulse at the gate of the FET 28 becomes smaller in amount. If it becomes small enough, the FET will no longer conduct during the pulse, as a result of which no reset pulse will be generated.

Die Integrationsstufe I besteht aus einem Zähler 33 (z.B. 4024), welcher Zählimpulse vom Oszillator bei jedem Strahlungsimpuls erhält. Solange Rückstellimpulse erzeugt werden, wird er aber bei jedem Puls auch wieder auf 0 zurückgestellt. Bei Ausbleiben der Rückstellimpulse geht nach 2n-1Pulsen der Ausgang Q" hoch.The integration stage I consists of a counter 33 (eg 4024), which receives counting pulses from the oscillator with each radiation pulse. As long as reset pulses are generated, it is also reset to 0 for each pulse. If there are no reset pulses, the output Q " goes high after 2 n - 1 pulses.

Die Kippstufe K besteht aus dem Thyristor 34, der vom Ausgang Q des Zählers angesteuert wird. Die Zenerdiode 35 erzeugt eine Spannung (z.B. 6 V), um den Alarmzustand vom Störzustand zu unterscheiden.The flip-flop K consists of the thyristor 34, which is driven by the output Q of the counter. The Zener diode 35 generates a voltage (e.g. 6 V) to distinguish the alarm condition from the fault condition.

Die Ueberwachungsschaltung U besteht aus dem Spannungsteiler mit Widerständen 37 und 38 und dem Thyristor 36. Der Widerstand 3 misst den Strom durch die Strahlungsquelle 1. Sobald dieser infolge Verschmutzung oder Alterung der Strahlungsquelle 1 zu hoch wird, wird der Thyristor 36 angesteuert und damit Störung angezeigt.The monitoring circuit U consists of the voltage divider with resistors 37 and 38 and the thyristor 36. The resistor 3 measures the current through the radiation source 1. As soon as this becomes too high as a result of contamination or aging of the radiation source 1, the thyristor 36 is activated and a malfunction is thus indicated .

Die angegebene Schaltung ist nur ein Beispiel. Es lassen sich auch Teile weglassen, wie z.B. Ueberwachungschaltung U oder der Korrelator C. Die verschiedenen Elemente lassen sich auch anders ausbilden, z.B. kann die Differenzierung des Schwellenwertdetektors auch digital mit einem Zähler und einem Digital/Analog-Wandler erfolgen, wie dies in Fig. 3 dargestellt wird.The circuit shown is only an example. Parts can also be omitted, e.g. Monitoring circuit U or the correlator C. The various elements can also be designed differently, e.g. the threshold value detector can also be differentiated digitally using a counter and a digital / analog converter, as is shown in FIG. 3.

Ueber den Kopplungskondensator 39 wird das Pulssignal zu der Spannung an dem aus den Widerständen 40 und 41 gebildeten Spannungsteiler addiert und an den negativen Eingang der Komparatoren 45 und 46 geführt. Diese erhalten auf ihren positiven Eingang Spannungen, die durch die Widerstände 42, 43 und 44 erzeugt werden. Am Ende jedes Pulses erzeugt je nach dem Zustand des Komparators 46 der Zählimpuls, welcher mit dem Element 49 invertiert wird, einen um 1 höheren oder tieferen Zustand des Zählers 47 (z.B. 14516). Der Zustand des Zählers 47 erzeugt über den parallelen Digital/Analog-Wandler 48 die Eingangsgleichspannung über die Widerstände 41 und 40. Durch diese Schaltung wird erreicht, dass im Ruhezustand die Pulsspannung am negativen Eingang gerade um die Spannung am positiven Eingang des Komparators 46 pendelt. Bei schneller Verminderung des Betrages des Pulses kann der Zähler 47 diese Spannung nicht nachführen. Sobald der Puls die Spannung am positiven Eingang des Komparators 45 nicht mehr erreicht, wird kein Rückstellimpuls mehr erzeugt und der Zähler 33 wird nicht mehr rückgestellt. Diese Art von Schaltung lässt sich natürlich auch in einer Detektorschaltung ohne Sperrpuls verwenden.Via the coupling capacitor 39, the pulse signal is added to the voltage at the voltage divider formed from the resistors 40 and 41 and fed to the negative input of the comparators 45 and 46. These receive voltages on their positive input, which are generated by resistors 42, 43 and 44. At the end of each pulse, depending on the state of the comparator 46, the count pulse, which is inverted with the element 49, generates a state of the counter 47 which is 1 higher or lower (for example 14516). The state of the counter 47 generates the DC input voltage via the resistors 41 and 40 via the parallel digital / analog converter 48. This circuit ensures that in the idle state the pulse voltage at the negative input oscillates just around the voltage at the positive input of the comparator 46. If the amount of the pulse is reduced rapidly, the counter 47 cannot track this voltage. As soon as the pulse no longer reaches the voltage at the positive input of comparator 45, no reset pulse is generated and counter 33 is no longer reset. This type of circuit can of course also be used in a detector circuit without a blocking pulse.

Claims (15)

1. Smoke detector having a radiation source (1), a radiation receiver (16) arranged externally of the direct radiation region of the radiation source (1), said radiation receiver in the presence of smoke in the radiation region being impinged by scattered radiation and delivering output pulses, a reference cell (12) located in the direct beam of the transmitted radiation emanating from the radiation source (1) and arranged near to the radiation receiver (16), said reference cell controlling the transmission of radiation from the radiation source (1) and an evaluation circuit comprising a radiation acceptor circuit (A) and a threshold value detector (N), which, when the amplitude of the output pulses of the radiation receiver (16) exceeds a predetermined threshold value, deliver a signal to a toggle stage (K) for outputting an alarm signal, characterized in that said radiation source is operated in a pulsed mode and that there are provided in the threshold value detector (N) switching elements (28, 29, 39), which in the presence of a slow change of the amplitude of the output pulses of the reference cell (12), adjust the threshold value to the amplitude of said output pulses so as to have a time-constant greater than one minute.
2. Smoke detector according to patent claim 1, characterized in that the smoke detector comprises a cylindrical housing, which is fastened with its upper surface to the ceiling of the room to be monitored, and further characterized in that the radiation source (1) is positioned at the lower surface of the cylinder in its axis and that the radiation receiver (16) is positioned in the axis of the cylinder above the radiation source (1) and the reference cell (12) outside of the axis of the cylinder above the radiation source (1).
3. Smoke detector according to anyone of the patent claims 1 and 2, characterized in that the reference cell (12) is a phototransistor or a photodiode.
4. Smoke detector according to anyone of the patent claims 1 to 3, characterized in that the smoke detector comprises means which in the presence of each pulse regulates the current of the radiation source (1) such that the reference cell generates a predetermined signal.
5. Smoke detector according to anyone of the patent claims 1 to 3, characterized in that the smoke detector comprises means which regulates during each pulse the current of the radiation source (1) to a predetermined level, said reference cell (12) slowly adjusting said level.
6. Smoke detector according to anyone of the patent claims 1 to 5, characterized in that the smoke detector comprises a capacitor (29) which is charged by a received pulse to a predetermined potential, and further means (28) for maintaining the threshold value, the exceeding of which delivers a signal to a constant voltage to the potential appearing at said capacitor (29).
7. Smoke detector according to anyone of the patent claims 1 to 6, characterized in that means (24, 25) are provided for producing a blocking pulse, that further means (N) are provided for generating a reset signal when the value of the difference of the blocking pulse and received pulse falls below a predetermined value, which reset signal resets an integrator (I) arranged after said means (N).
8. Smoke detector according to patent claim 6, characterized in that said means (28) for the slow adjustment of the threshold value deetection is formed by a depletion layer-field-effect transistor (28) with a holder capacitor (29) provided at the gate of said depletion layer-field-effect transistor (28).
9. Smoke detector according to anyone of the patent claims 1 to 5 and 7, characterized in that said means for the slow adjustment of the threshold value is formed by an up-down counter (47) and a digital-to-analog converter (48).
10. Smoke detector according to patent claim 9, characerized in that a comparator is provided which controls the updown counter (47) for up or down counting and that the digital-to-analog- converter (48) which is controlled by the counter (47) controls a direct-current voltage to which there is added the received pulse.
11. Smoke detector according to anyone of the patent claims 6 to 10, characterized in that a subsequently connected counter (33) is provided which after a predetermined number of smoke receiving pulses above the threshold value controls the toggle stage (K).
12. Smoke detector according to anyone of the patent claims 1 to 11, characterized in that means (U) are provided for measuring the current flowing through the radiation source (1) and delivering a disturbance signal when such current exceeds a predetermined threshold value.
13. Smoke detector according to patent claim I2,characterized in that a thyristor (36) is provided which is triggered in the presence of a disturbance signal.
14. Smoke detector according to patent claim 12, characerized in that an oscillator short- circuiting lines L1 and L2 of said smoke detector for 0,5 to 10 second at a time interval of 20 to 200 seconds.
EP82110013A 1981-11-11 1982-10-29 Smoke detector Expired EP0079010B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82110013T ATE20398T1 (en) 1981-11-11 1982-10-29 SMOKE DETECTOR.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH724881A CH655396B (en) 1981-11-11 1981-11-11
CH7248/81 1981-11-11

Publications (2)

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EP0079010A1 EP0079010A1 (en) 1983-05-18
EP0079010B1 true EP0079010B1 (en) 1986-06-11

Family

ID=4322161

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EP82110013A Expired EP0079010B1 (en) 1981-11-11 1982-10-29 Smoke detector

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US (1) US4555634A (en)
EP (1) EP0079010B1 (en)
JP (1) JPS5888641A (en)
AT (1) ATE20398T1 (en)
AU (1) AU556838B2 (en)
BR (1) BR8206536A (en)
CA (1) CA1208334A (en)
CH (1) CH655396B (en)
DE (1) DE3271683D1 (en)
DK (1) DK502382A (en)
ES (1) ES517587A0 (en)
FI (1) FI823837L (en)
IL (1) IL67158A0 (en)
NO (1) NO156149C (en)
NZ (1) NZ202365A (en)
YU (1) YU252382A (en)
ZA (1) ZA828097B (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59187246A (en) * 1983-04-08 1984-10-24 Nohmi Bosai Kogyo Co Ltd Inspecting apparatus of function of photoelectric smoke sensor
US4823015A (en) * 1985-05-08 1989-04-18 Adt, Inc. Electrical interference free projected beam smoke detector
DE3831654A1 (en) * 1988-09-17 1990-03-22 Hartwig Beyersdorf OPTICAL SMOKE DETECTOR
JPH02112096A (en) * 1988-10-21 1990-04-24 Matsushita Electric Works Ltd Sensor made into ic
GB8913773D0 (en) * 1989-06-15 1989-08-02 Fire Fighting Enterprises Uk L Particle detectors
AU652513B2 (en) * 1992-06-29 1994-08-25 Nohmi Bosai Ltd Smoke detecting apparatus for fire alarm
CH685410A5 (en) * 1993-02-15 1995-06-30 Cerberus Ag Device for functional testing of smoke detectors.
US5929981A (en) * 1996-06-18 1999-07-27 Ohmeda Inc. System for monitoring contamination of optical elements in a Raman gas analyzer
US6503893B2 (en) 1996-12-30 2003-01-07 Bone Care International, Inc. Method of treating hyperproliferative diseases using active vitamin D analogues

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Publication number Priority date Publication date Assignee Title
CH566059A5 (en) * 1972-03-07 1975-08-29 Protecbat La Detection Electro
CH546989A (en) * 1972-12-06 1974-03-15 Cerberus Ag METHOD AND DEVICE FOR FIRE NOTIFICATION.
US4011458A (en) * 1975-10-09 1977-03-08 Pyrotector, Incorporated Photoelectric detector with light source intensity regulation
US4206456A (en) * 1975-06-23 1980-06-03 Chloride Incorporated Smoke detector
US4242673A (en) * 1978-03-13 1980-12-30 American District Telegraph Company Optical particle detector
US4180742A (en) * 1978-03-27 1979-12-25 Chloride Incorporated Detector with supervisory signal from monitor cell
CH638331A5 (en) * 1979-02-22 1983-09-15 Cerberus Ag SMOKE DETECTOR.
DE2907173A1 (en) * 1979-02-23 1980-09-04 Hekatron Gmbh CIRCUIT ARRANGEMENT FOR AN OPTICAL FLUE GAS DETECTOR

Also Published As

Publication number Publication date
FI823837A0 (en) 1982-11-09
ES8401656A1 (en) 1983-12-16
ES517587A0 (en) 1983-12-16
FI823837L (en) 1983-05-12
JPS5888641A (en) 1983-05-26
US4555634A (en) 1985-11-26
DK502382A (en) 1983-05-12
DE3271683D1 (en) 1986-07-17
ATE20398T1 (en) 1986-06-15
AU556838B2 (en) 1986-11-20
AU9017682A (en) 1983-05-19
ZA828097B (en) 1983-09-28
NO823753L (en) 1983-05-13
BR8206536A (en) 1983-09-27
NO156149C (en) 1987-08-05
EP0079010A1 (en) 1983-05-18
YU252382A (en) 1985-10-31
CA1208334A (en) 1986-07-22
NO156149B (en) 1987-04-21
CH655396B (en) 1986-04-15
IL67158A0 (en) 1983-03-31
NZ202365A (en) 1985-09-13

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