EP3455837A1

EP3455837A1 - Fire detector having a photodiode for sensing ambient light to accelerate the emission of a likely fire alarm on the basis thereof

Info

Publication number: EP3455837A1
Application number: EP17720811.3A
Authority: EP
Inventors: Martin Fischer; Thomas Rohrer
Original assignee: Siemens Schweiz AG
Current assignee: Siemens Schweiz AG
Priority date: 2016-05-13
Filing date: 2017-05-03
Publication date: 2019-03-20
Anticipated expiration: 2037-05-03
Also published as: CN109155097B; EP3455837B1; CN109155097A; US20190180590A1; WO2017194367A1; US10467874B2

Abstract

A fire detector having a photodiode for sensing ambient light to accelerate the emission of a potential fire alarm on the basis thereof. The invention relates to a fire detector (1), having a fire sensor (5), a control unit (4) and a photodiode (6) for sensing ambient light in a spectrally limited range from 400 nm to 1150 nm. The control unit is designed to analyse a sensor signal (BS) received from the fire sensor for at least one characteristic fire variable, to evaluate said signal, and to emit a fire alarm (AL) if a fire is detected. In addition, the control unit is designed to analyse a photo signal (PD) received from the photodiode for the presence of flicker frequencies characteristic of open fire and, on the basis thereof, to accelerate the emission of a possible fire alarm by increasing a sampling rate for sensing the sensor signal from the fire sensor, by reducing a filter time (T Filter), in particular a time constant, of an evaluation filter (41) for the fire analysis and/or by reducing an alarm threshold (LEV). The fire detector can be an open scattered-light smoke detector, a closed scattered-light smoke detector or a thermal detector.

Description

description

Fire detector with a photodiode to detect ambient light to speed up the output of a possible fire alarm.

The invention relates to a fire detector, in particular an open and closed Streuf smoke smoke detector and a thermal detector. Such detectors have a fire sensor, e.g. a light emitter and light receiver in a scattered light arrangement with an outside of the scattered light smoke detector outdoors scattered light center. The fire sensor may also be an optical measuring chamber arranged in a detector housing and shielded from ambient light and permeable to smoke to be detected. Furthermore, the fire sensor may have one or more temperature sensors. Such a temperature sensor may e.g. a temperature dependent resistor (thermistor), e.g. a so-called NTC or PTC, or a non-contact temperature sensor with a thermopile or microbolometer.

Furthermore, the fire detector comprises a control unit, preferably a microcontroller. The control unit is set up to analyze a sensor signal received from the fire sensor for at least one characteristic fire parameter, to evaluate it and to output a fire alarm in the event of a detected fire.

A characteristic fire parameter is e.g. in the case of a scattered light smoke detector, exceeding a minimum scattered light level, which correlates with a smoke particle concentration. Alternatively or additionally, an impermissibly high level rise of the scattered light may be a characteristic fire parameter. In the case of a thermal detector, a characteristic fire parameter is e.g. exceeding a minimum temperature in the (immediate) environment of the fire detector, e.g. of at least 60 ° C, 65 °, 70 ° C or 75 ° C. Alternatively or additionally, an impermissibly high temperature rise may also be a characteristic fire parameter, such as e.g. of at least 5 ° C per minute or at least 10 ° C per minute. Open scattered light smoke detectors are e.g. from EP 2093734 A1 and EP 1039426 A2.

Flame detectors are also known from the prior art, for example from DE 10 201 1 083 455 A1 or from EP 2 251 846 A1. Such flame detectors are specially designed to detect open fire as well as issue an alarm in less than a second. They usually comprise two or more pyrosensors as radiation sensors. Such sensors are tuned for the detection of characteristic flicker frequencies of open fire, that is to say of flames and blazing embers, in the infrared range and possibly in the visible and ultraviolet range. The flicker frequencies are typically in a range of 2 Hz to 20 Hz. From EP 1039426 A2, a smartphone with a fire detection application is known, which has suitable program steps for analyzing video image data captured by an internal camera with respect to at least one information characteristic for fire and, if present, outputting an alarm via an output unit. This smartphone is also adapted to analyze the received video signal for the presence of flicker frequencies characteristic of open fire, and to switch from a first low frame rate to a second high frame rate for a significant deviation in two consecutive video frames.

The infrared pyrosensors are typically sensitive to infrared radiation in the wavelength range from 4.0 to 4.8 μιη. This specific radiation is produced by the combustion of carbon and hydrocarbons. Another pyrosensor is sensitive to characteristic emissions of metal fires in the UV range. For outdoor use, flame detectors can also have a radiation sensor that is sensitive to infrared radiation in the wavelength range from 5.1 to 6.0 μιη. This radiation is primarily spurious radiation, e.g. infrared radiation from hot bodies or sunlight. On the basis of all sensor signals, a more reliable evaluation is possible, i. whether it is open fire or not.

On this basis, it is an object of the present invention to provide a fire detector that alerts faster and in particular reliable with little technical overhead.

The object is achieved with the objects of the main claim. Advantageous embodiments of the present invention are indicated in the dependent claims.

According to the invention, the fire detector comprises a photodiode for detecting ambient light in a spectrally limited range from 400 nm to 1 150 nm, i. Ambient light in the optically visible region as well as in the adjacent near UV and infrared range. The control unit is further configured to analyze a photosignal received from the photodiode for the presence of flicker frequencies characteristic of open fire and, depending thereon, to output a possible fire alarm by increasing a sampling rate for detecting the sensor signal from the fire sensor To reduce the filter time of a rating filter for the fire analysis and / or by speeding down an alarm threshold. The filter time is in particular a time constant or an integration time. The core of the invention is therefore the use of a low-cost photodiode as "miniature

Flame detector ", but its qualitative significance is sufficient and it justifies to accelerate the output of a fire alarm in the event of detected Flackerfrequenzen as an indication of the presence of a fire. It is thus advantageous an accelerated, ie a faster output of a fire alarm possible, since in this case can be assumed with a higher probability of a fire. This is the case when the characteristic flicker frequencies are detected for a minimum time, such as 2, 5 or 10 seconds. However, this does not mean that an alarm will be issued after this minimum time. Because this is the quality of

To consider the photodiode signal as much too moderate compared to the sensor signals of spectrally narrow pyrosensors in conjunction with a complex, powerful signal processing. Rather, faster processing of the fire sensor signal, e.g. the scattered light signal, which is omitted because of the otherwise associated loss of false alarm security. In other words, the fire sensor responds more sensitively and faster upon detection of characteristic flicker frequencies, but this is advantageously tolerated because of the high probability of occurrence of a subsequent increase in the amount of flare as a result of a fire. If an "expected" level rise does not occur in the exemplary case of the open scattered light arrangement as a fire sensor, then no fire alarming takes place Fire sensor signal detected faster and thus a fire alarm can be output faster.

By reducing the filter time, the weighting filter responds less slowly. Since the probability of an occurring fire event in detecting the Flackerfrequenzen is assumed to be high or higher than usual, a fire alarm can advantageously be spent faster in favor of safety. The evaluation filter is the input side, the detected, preferably digitized sensor signal supplied from the fire sensor. It is preferably a digital filter, which is realized as a software program and is executed by the microcontroller as a control unit. The digital filter is preferably a low-pass filter or a so-called drag filter. In this case, a certain averaging of the detected sensor signal values takes place so that a fire alarm is not output directly when a fire is detected. Rather, it waits to see whether this event is not sporadic but several times in succession, in order to avoid issuing a false alarm. By lowering the alarm threshold, the fire detector is, so to speak, switched to more sensitive and less robust. As a result, the alarm threshold is advantageously reached faster and consequently the fire alarm is issued faster.

Preferably, the higher the level of the detected flicker frequencies, the faster the output of a possible fire alarm is accelerated. For example, the acceleration can be proportional, progressive or degressive, depending on the flicker frequency level. It can alternatively or additionally take place only after exceeding a minimum detection level. The photodiode is preferably a silicon photodiode and in particular a silicon PIN photodiode. It can be preceded by a daylight blocking filter, which allows only light in a range of 700 nm to 1 150 nm, in particular from 730 nm to 1 100 nm, pass. The additional expense for the integration of such a photodiode in a fire detector is thus very low in terms of circuit technology and cost.

Preferably, the photodiode is followed by a transimpedance amplifier or a transimpedance converter, which converts the photocurrent generated by the photodiode into a measuring voltage proportional thereto. The photocurrent is in turn proportional to the received luminous flux. As a result, optical disturbances such as the flickering of fluorescent tubes or incident sunlight can be advantageously reduced. Such a photodiode, e.g. from OSRAM (type BPW 34 FAS), i. Compared to a pyrosensor particularly inexpensive available.

The control unit is preferably set up to suppress or prevent the output of a possible fire alarm solely on the basis of detected characteristic flicker frequencies in the received photo signal. In other words, the presence of a characteristic fire parameter in the sensor signal received by the fire sensor must have been detected at least by the control unit. This prevents the output of a possible false alarm, should the expected fire event subsequently not be detected by the actual fire sensor. This is e.g. the case when flickering candlelight is detected by the photodiode as an open fire, but this does not significantly increase the stray light level in the vicinity of the fire detector in the optical measuring chamber of the fire detector or this leads to any significant increase in temperature in the vicinity of the fire detector.

According to one embodiment, the fire detector is an open scattered light smoke detector. The latter has a housing, a circuit carrier and a light emitter and a light receiver. The light emitter and the light receiver are arranged in the housing. Furthermore, the light emitter and the light receiver are arranged in a scattered light arrangement with a light scattering center outside the scattered light smoke detector, in particular outdoors. The scattered light arrangement forms the fire sensor with the light transmitter and the light receiver. The control unit is set up to analyze a scattered light signal received from the fire sensor, which forms the sensor signal, at an inadmissibly high signal level as a fire parameter and / or at an impermissibly high slew rate of the sensor signal as a further fire parameter. Preferably, the light emitter and the light receiver are arranged on the circuit carrier. The latter is preferably accommodated in the housing of the scattered light smoke detector.

According to a particularly advantageous embodiment, the light receiver for the optical scattered light detection and the photodiode for detecting ambient light are realized as a common photodiode. The particular advantage is the use of a single photodiode both for scattered light detection and for flame detection. This simplifies the structure of the fire detector according to the invention. He is also cheaper to produce.

In particular, the control unit is set up to analyze the scattered light / photo signal received by the common photodiode in time-separated phases. For this purpose, the control unit is adapted to the received scatter light / photo signal in a respective first phase to an inadmissibly high signal level and / or an inadmissibly high

Rate of sleeper to analyze. It is also set up to analyze the received scattered light / photosignal in a respective second phase for the presence of characteristic flicker frequencies. The two temporal phases do not overlap. They are preferably repeated alternately periodically. It is also possible for several first phases or several second phases to follow one another. This e.g. when a large increase in the scattered light signal has been detected or when a flicker frequency has been detected.

In the respective first phase of the light transmitter, it is repeated, in particular periodically, with a pulsed signal sequence for emitting corresponding light pulses. The period of the pulsed signal sequence is preferably in the range of 1 to 10 seconds. In other words, a pulsed signal sequence is transmitted every 1 to 10 seconds. The pulsed signal sequence is preferably a rectangular clock signal, which drives the light transmitter, for example, via a switch in the same clock, so that a sequence of periodic light pulses is generated in the light transmitter. In addition, such a pulsed signal sequence has a number of pulses, preferably in the range of 32 to 1000 pulses. The duration of such a signal sequence itself is in the range of 0.25 to 2 milliseconds. Thus, the ratio of the signal sequence period to the duration of a signal sequence itself is in the range of two to three orders of magnitude above. The duration of a single pulse itself is typically in the range of 0.25 to 2 microseconds. By limiting the signal of the light receiver by means of a first filter, which is preferably tuned to the same clock signal frequency of the pulsed signal sequence, light signals with other frequencies are effectively suppressed. In other words, only pulsed scattered light from detected particles, such as smoke particles, is taken into account in the detection by way of signal technology. In practice, this is a bandpass filter or high-pass filter, which suppresses at least the frequency components in the photodiode or scattered light signal below the clock signal frequency. The filter frequency of the high pass filter and the lower filter frequency of the bandpass filter is in the range of 250 kHz to 2 MHz on the assumption that the pulse duration of a single pulse is in the range of 0.25 to 2 microseconds and that the clock or light signal is rectangular. The filtered photodiode or scattered light signal is then fed to an A / D converter, which converts this signal into corresponding digital values for further fire analysis. In the respective second phase, the light transmitter is dark-controlled. The second phase can thus also be referred to as dark phase, in which the light emitter does not emit light. In this phase, the frequency components in the photodiode signal of the light receiver are signal limited by means of a second filter, wherein the second filter is a low-pass filter. The corner frequency of the low-pass filter is dimensioned such that the flicker frequencies to be detected in the respective second phase in the range from 2 to 20 Hz can pass the low-pass filter. The cut-off frequency, ie the filter frequency of the low-pass filter, is preferably set to a frequency in the range of 20 Hz to 40 Hz, but at least to a frequency of at least 20 Hz. When setting, for example, to a value of 40 Hz, optical light signals are, for example, from light - Tube lights or computer monitors effectively suppressed. The photodiode signal filtered in this way is then fed to a further A / D converter, which converts this signal into corresponding digital values for the further flicker frequency analysis.

According to an advantageous embodiment, the control unit is set up to determine a first DC component from the received scattered light / photosignal, and also adapted to subtract this first DC component from the received scattered light / photosignal to obtain a substantially DC-free scattered light / photosignal ,

As a result, the remaining higher-frequency component in the scattered light / photo signal is shifted into the working range for signal processing in the sense of an offset. A possible oversteer this is thus advantageously avoided. The signal processing can e.g. a transimpedance amplifier, bandpass or low pass filter or an A / D converter. In the simplest case, the scatter light / photo signal is fed to a low-pass filter whose cutoff frequency is in a range of 1 to 2000 Hz, preferably in the range of 20 to 150 Hz.

In particular, the control unit is set up to compare the determined first DC component with a predetermined overmodulation value and to output a fault message if the determined first DC component exceeds the overmodulation value for a predetermined minimum time.

In this case the photodiode is exposed to such a high brightness that it overdrives. Reliable optical smoke detection is no longer possible under these circumstances. By issuing a fault message, a user can then be made aware of the remedy.

The override value can be related, for example, to the illuminance of the photodiode to which the photodiode or the common photodiode is exposed. The predetermined overmodulation value is preferably more than 100,000 lux. The value of 100,000 lux corresponds to a bright sunny day, whereby the fire detector or the photodiode is then exposed to direct sunlight on such a bright sunny day. The predetermined minimum time for the output of the fault message is preferably in the range of 10 seconds to 10 minutes. According to a further embodiment, and independently of the invention made, the control unit is set up to monitor the scattered light / photosignal emitted by the (common) photodiode for a minimum brightness value being undershot and to lower an alarm threshold for the output of a possible fire alarm , For this purpose, the control unit is set up to determine a second DC component from the received scattered light / photosignal. This represents a long-term average brightness value. It is also set up to monitor this second DC component to below the minimum brightness value as well as dependent on the alarm threshold for the output of a possible fire alarm to reduce. Because of the more sensitive setting of the fire alarm is then in the dark, such as at night, an advantageously faster alerting possible. This is because with lower brightness, such as Lux values of less than 1 lux, fewer disturbances from the detector environment can be expected as during the day. Such optical disturbances are, for example, the flickering of fluorescent tubes or incident sunlight on the fire detector. According to a further embodiment, the fire detector is a (exclusive) scattered light smoke detector, which has a arranged in a detector housing, shielded from ambient light and permeable to smoke to be detected optical measuring chamber as a fire sensor. The control unit is adapted to analyze a received from the optical measuring chamber scattered light signal, which forms the sensor signal to an inadmissibly high signal level as fire characteristic and / or an inadmissibly high rate of increase of the sensor signal as a further fire characteristic back and in the case of a detected fire a fire alarm issue.

According to another embodiment, the fire detector has at least one temperature sensor, in particular a thermistor, for detecting an ambient temperature in the immediate area around the fire detector. The control unit is set up to take into account the detected ambient temperature in the fire analysis. Such a thermistor is e.g. a so-called NTC or PTC. The temperature sensor may also be a non-contact temperature sensor with a thermopile or a microbolometer. By taking into account the ambient temperature, a fire can be detected even more reliably in the sense of a multi-criteria fire detector. This is e.g. for a smoke-free fire, such as e.g. at a

Alcohol fire. In this case, a fire is detected only by the strong increase in the ambient temperature, while the scattered light level increases only slightly.

According to another embodiment, the fire detector is an (exclusive) thermal detector with a temperature sensor as a fire sensor. The control unit is set up to receive a temperature signal received as a sensor signal by the temperature sensor at an impermissibly high ambient temperature as a fire parameter and / or at an impermissibly high temperature. increase in temperature as an additional fire parameter and issue a fire alarm in the event of a detected fire. As described above, such a temperature sensor may be a temperature-dependent resistor (thermistor), such as an NTC or PTC.

According to a particular embodiment, the temperature sensor is a non-contact temperature sensor which comprises a heat radiation sensor sensitive to thermal radiation in the infrared range. The latter is for example a thermopile or a microbolometer. In particular, the heat radiation sensor is not imaging. In other words, it has a single pixel. Furthermore, the fire detector comprises a detector housing with a

Detector hood, wherein the heat radiation sensor is then arranged in the detector housing and is aligned to the mathematical derivation of the ambient temperature optically on the inside of the detector hood. The detector hood is formed in the region of the inside so thermally conductive to an opposite region of the outside of the detector hood that the adjusts itself on the inside housing temperature of the ambient temperature at the opposite region of the detector hood follows, especially within a few seconds, such. 5 seconds. The temperature sensor installed in the detector housing makes the fire detector less susceptible to contamination. In addition, no circuitry and assembly consuming installation of the thermistor in the housing is required.

According to another embodiment of the closed-loop light smoke detector and of the thermal detector and independently of the invention made, the control unit is designed to monitor the photosignal output by the photodiode for a value below a minimum brightness value and to set an alarming threshold for the output of a possible fire alarm to speed up the issue of a possible fire alarm. Because of the more sensitive setting of the fire detector, in the dark, e.g. at night, advantageously a faster alerting possible. This is possible because, with lower brightness, e.g. at lux values of less than 1 lux, with less interference from the

Detector environment is expected as daytime. Such disturbances are e.g. the lighting of candles, spreading smoke when cooking and frying, or lighting a fireplace.

According to another embodiment, the considered fire alarms are wired or wirelessly connected to a higher-level control center. The control unit is set up to output the undershooting and undershooting of the minimum brightness level as a day / night identifier to the control center. As a result, higher-order control by the central unit may be effected e.g. the downturn of blinds or the reduction of heating power in the building are caused.

The invention and advantageous embodiments of the present invention will be explained using the example of the following figures. Showing: a spectral characteristic of a silicon photodiode with and without upstream daylight filter, an example of a photodiode received photosignal with characteristic Flackerfrequenzen for open fire, the corresponding to the photosignal according to FIG 2 frequency spectrum, for example, an open scattered light detector with a lying outside the detector scattered light center Smoke detection and with a photodiode for detecting ambient light for detection of open fire according to the invention, a first embodiment of the fire detector according to the invention with a common photodiode for smoke detection and for the ambient light, a functional block diagram of a detector control unit with an evaluation filter with adjustable time constant to to accelerate the issue of a possible fire alarm according to the invention. a second functional block diagram of a detector control unit with input-side detection and evaluation of a scattered light / photo signal from a common photodiode and with a Nachterkennung according to the invention, a third functional block diagram of a control unit as an exemplary embodiment of the inventive offset compensation of the photodiode, an exemplary Stray light smoke detector of closed design as a fire detector with an optical measuring chamber and with a photodiode for ambient light for

9 in a plan view along the line of sight IX, an embodiment of the fire detector according to the invention with a common optical waveguide for ambient light detection by means of the photodiode and as an indicator in the sense of operational readiness, the example according to FIG. 1 in a plan view along the viewing direction XI, a functional block diagram of a detector control unit with an adjustable time constant weighting filter to accelerate the output of a possible fire alarm according to the invention, an exemplary thermal detector with a temperature sensor and with an ambient light photodiode for detecting open fire according to the invention in a sectional view, The example of FIG 14 in a plan view and in XIG view there, a first embodiment of the invention fire detector with a non-contact temperature sensor having a heat radiation in the infrared sensitive thermopile as a heat radiation sensor, a second embodiment of the invention fire detector with a common light guide for ambient light detection by means of Photodiode and as an indicator in the sense of a ready-to-operate display, a functional block diagram of a detector control unit with an evaluation filter with setting lable time constant to speed up the issue of a possible fire alarm according to the invention. a second functional block diagram of a detector control unit with a temperature sensor with thermopile according to the invention, and a third functional block diagram of a detector control unit in addition to alternately driving an indicator light emitting diode and for detecting the ambient light by means of the indicator light emitting diode LED, switched in a mode as a photodiode according to the invention.

1 shows a spectral characteristic of a silicon PIN photodiode with and without upstream daylight filter. The maximum, normalized to 100% spectral sensitivity S _Re i is at a light wavelength λ of about 900 nm, ie in the near infrared range. The solid curve shows the spectral sensitivity S _Re i of a silicon PIN photodiode with upstream daylight filter. In this case, light having a wavelength λ of less than 730 nm is suppressed. By contrast, the dashed branch of the characteristic curve shows the spectral sensitivity S _Re i of the silicon PIN photodiode without a daylight filter.

FIG. 2 shows an example of a photo signal PD having characteristic flicker frequencies for open fire, measured in millivolts, received by a photodiode 6. It will be the at the Photodiode 6 generated photovoltage measured as a photo signal PD. The measurement took place over a period of 4 seconds and shows cyclic voltage spikes in the range of 20 to 30 mV, which correlate with the flickering of the flames of open fire.

FIG. 3 shows the frequency spectrum associated with the photo signal PD according to FIG. A denotes the spectral amplitude, measured in dB and plotted against the frequency f in Hertz. Considering only the frequency range of at least 2 Hz, which is decisive for the flickering, one recognizes the reciprocal decrease of the amplitude for increasing frequencies above 2 Hz. The spectrum shown is typical and significant for open flickering fire.

FIG. 4 shows, by way of example, an open scattered light detector 1 with a scattered light center SZ outside the detector 1 for smoke detection and with a photodiode 6 for detecting ambient light for detecting an open fire according to the invention.

In the present example, the detector 1 has a housing 2, which is composed of a base body 21 and a detector hood 22. With the base body 21, the detector 1 can then preferably be releasably attached to a detector base mounted on a ceiling. Both housing parts 21, 22 are usually made of a light-tight plastic housing. In or on the housing 2, a circuit substrate 3 is received, on which a light emitter S in the form of a light emitting diode, a light receiver E in the form of a photosensor and a microcontroller 4 are applied as a control unit. The photosensor E is preferably a photodiode. Light transmitter S and light receiver E are thus arranged on the one hand in the housing 2. On the other hand, they are also arranged in a scattered light arrangement SA with a scattered light center SZ outside the scattered light smoke detector 1 in the open air. In this case, the scattered light arrangement SA together with the light transmitter S and the light receiver E forms the actual fire sensor.

For smoke detection outdoors, two openings in the detector hood 22 are present. Through the first opening passes from the light emitter S emitted light beam to the outside. Conversely, the scattered light from the smoke particles to be detected passes through the second aperture to the light receiver E in the housing 2. In the present example, the two apertures not further indicated are passed through a transparent cover, such as a cover. made of plastic, finished.

The control unit 4 shown is now set up to analyze a scattered light signal received from the fire sensor to an inadmissibly high signal level as a fire parameter. Alternatively or additionally, it may be configured to analyze the scattered light signal for an impermissibly high slew rate as a further fire parameter. In the event of a detected fire, a fire alarm AL can be output by means of the control unit 4. The scattered light smoke detector 1 has a photodiode 6 for detecting ambient light. In the present example, the photodiode 6 is arranged on the circuit carrier 3 and aligned such that it "looks through" to the outside through a further opening in the detector hood 22. Preferably, the further opening is located at a central location of the detector hood 22, so that a symmetrical all-round view The central main axis of the detector 1 is designated by Z. Such detectors 1 typically have a rotationally symmetrical design, wherein FOV denotes the optical detection range of the photodiode 6. Furthermore, the further opening is provided by a further transparent one Cover AB completed to prevent the ingress of dirt into the

To prevent housing interior. The covers AB may already be provided with or have a daylight filter. In the example of the present FIG 4 also the central cover AB is formed as an optical lens L. This allows an extended optical all-round view.

According to the invention, the control unit 4 is now adapted to analyze a photosignal received by the photodiode 6 for the presence of open flame characteristic flicker frequencies and, depending thereon, to accelerate the output of a possible fire alarm. It is also set up to monitor the photosignal for an undershooting and undershooting of a minimum brightness level and to output it as a day / night identifier T / N, symbolized by a sun and moon symbol, such as, for example, T / N. to a higher-level headquarters. 5 shows a first embodiment of the fire detector 1 according to the invention with a common photodiode 6 '. It is designed for both smoke detection and ambient light detection.

6 shows a functional block diagram of a detector control unit 4 with a weighting filter 41 with adjustable time constant T _F _in order to accelerate the output of a possible fire alarm according to the invention.

The illustrated functional blocks 40-44 are preferably implemented as software, i. as program routines executed by a processor-based control unit, e.g. by a microcontroller. The program routines are loaded in a memory of the microcontroller 4. The memory is preferably a nonvolatile electronic memory such as e.g. a Flash-Speid rather. In addition, the microcontroller 4 may have specific functional blocks which are already integrated as hardware functional units in the microcontroller 4, e.g. Analog-to-digital converters 51, 52, signal processors, digital input / output units and bus interfaces.

In the example, the microcontroller 4 comprises two analog-to-digital converters 51, 52. The first A / D converter 51 is provided for digitizing a filtered scattered light signal BS ', which indirectly from the light receiver E of the stray light assembly SA comes. The second A / D converter 52 is provided for digitizing a photo signal PD output from the photodiode 6.

To carry out the open scattered light smoke detection, the light transmitter S, ie the light emitting diode, is driven by a frequency generator 46 periodically with a pulsed signal sequence in the range of 0.25 to 2 MHz. The light-emitting diode S in turn emits corresponding light pulses into the scattered light center SZ. The frequency generator 46 is controlled on the input side via a logic block 40 of the control unit 4 via a clock signal f _clock , wherein the frequency generator 46 outputs a pulsed signal sequence per clock with a predetermined number of pulses, such as in the range of 32 to 1000 pulses. The clock signal f _clock output from the logic block 40 has a frequency in the range of 0.1 to 1 Hz.

The photodiode E provided for scattered light detection is followed by a transimpedance amplifier 62, which converts the photocurrent generated by the photodiode E into a suitable measuring voltage for signal processing. This amplified scattered light signal BS is finally fed to a bandpass filter 56, which is realized as a digital filter. This bandpass filter 56 can pass only the high-frequency signal components in the unfiltered scattered light signal BS, which coincide approximately with the high-frequency pulsed signal sequence. As a result, low-frequency optical interference signals are effectively suppressed.

The clock signal f _clock is also supplied to the first A / D converter 51, which then converts the currently applied filtered scattered light signal BS 'into a digital value. The digitized scattered light signal BS 'is then fed to a (digital) weighting filter 41 along the optical path. The weighting filter 41 is preferably a digital low-pass filter which performs some signal smoothing or averaging. However, this filtering causes a delayed filter response at the output of the weighting filter 41 analogous to a filter time constant in a low-pass filter. The unspecified output signal of the evaluation filter 41 is subsequently supplied to a comparator 44, which compares this with an alarm threshold LEV, which corresponds to a minimum smoke concentration value for the fire alarm. If the filter output signal exceeds this comparison value LEV, the output of a fire alarm AL, such as, for example, to a higher-level fire alarm control panel takes place.

According to the invention, the microcontroller 4 is also set up to receive the photosignal PD received by the photodiode 6 for the presence of open-fire characteristic

Analyze flicker frequencies and, depending on this, speed up the issue of a possible fire alarm. The spectral signal analysis can e.g. by means of a digital

Fourier transform or be performed by means of a wavelet analysis. Technically, this is done on the one hand by the function block flicker frequency detector 42. In the case of detected flickering fire these outputs a flicker indicator F to a logic block 40, then the sampling rate and the clock frequency of the clock signal increases f _clock of the A / D converter 51 for digitizing the filtered scattered light signal BS 'and / or the filter time constant T _{FMter of} the _{weighting filter} 41 is lowered. The flicker indicator F can be, for example, a binary value, such as 0 or 1, or a digital value, for example in the value range from 0 to 9. For the binary case, the value 0 can be, for example, the absence of flicker frequencies and the value 1 corresponding to Represent presence. In the digital case, for example, the value 0 can represent the absence of flicker frequencies. For example, values 1 through 9 may indicate the presence of flicker frequencies, with high numbers indicating high flicker frequency levels and low numbers indicating flicker frequency levels. By increasing the sampling rate, the digitized filtered scattered light signal BS 'arrives faster at the evaluation filter 41 for further processing. On the other hand, speaking the weighting filter 41 by reducing the filter time constant T _fo t _e r faster so that an actual increase in the filtered scattered light signal BS 'also leads to a faster fire alarm AL. Increasing the sampling rate and / or decreasing the filter time constant T _fl | _ter , for example, for the digital case of the flicker indicator F as a function of its value range.

Alternatively or additionally, the logic block 40 may be programmed to lower the alarm threshold LEV in response to the flicker indicator F, as shown in FIG. 10%, 20%, 30% or 50%. As a result, an accelerated output of a fire alarm takes place for the case of fire occurring with an increased probability due to the detected flicker frequency.

7 shows a second functional block diagram of a detector control unit 4 with input-side detection and evaluation of a scattered light / photosignal BS from a common photodiode 6 'and with a night detection according to the invention.

The control unit 4 is set up to analyze the scattered light / photosignal BS, PD received by the common photodiode 6 'in time-separated phases.

In a respective first phase, to which the clock signal f _{clock is} assigned, the control unit 4 analyzes the signal level of the filtered scattered light / photosignal BS ', whether this is unduly high. Alternatively or additionally, it analyzes whether this signal level rises inadmissibly fast.

In addition, the control unit 4 is configured to analyze the received scattered light / photosignal BS, PD in a respective second phase, which is associated with the second clock signal f _clock 2, for the presence of characteristic flicker frequencies. The received scattered light / photosignal BS, PD first passes through a low-pass filter 57 in order in particular to suppress the high-frequency signal components which originate indirectly from the clock generator 46. The signal at the output of the low-pass filter 57 is fed to an A / D converter 52, which converts this signal into corresponding digital values for the following flicker frequency detector 42. The latter, as already described in the example of FIG. 6, performs a spectral signal analysis with regard to the occurrence of flicker frequencies characteristic of open fire.

The phase-offset control of the two A / D converter 51, 52 is required only in the context of fire analysis. Depending on the microcontroller used as a control unit 4, both A / D converter 51, 52 are also controlled simultaneously, which can be advantageous for the power consumption according to the respective concept.

Compared to the previous embodiment according to FIG. 6, the control unit 4 additionally comprises a night detection function block 43 in order to reduce an alarm threshold LEV for the output of a possible fire alarm AL according to the invention in dependence on the determined brightness in the surroundings of the fire detector.

In the example of the present FIG. 7, the control unit 4 determines a second DC component H / D from the received scattered light / photosignal BS, PD, which represents a long-time-average brightness value. It monitors this second DC component H / D down to a minimum brightness value and then sets depending on the alarm threshold LEV for the output of a possible fire alarm AL down.

The night detection block 43 has a digital low-pass filter with a corner frequency in the range from 0 to 0.1 for the determination of the second DC component H / D. On the input side, the night detection block 43 is supplied with the scattered light / photosignal already prefiltered by the low-pass filter 57 and digitized by the A / D converter 52. The second DC component H / D can represent a binary brightness value for light or dark. Preferably, it represents a digital value, e.g. a lux value, with a graded value range.

The logic block 40 is now programmed so that the alarm threshold LEV is lowered, in particular, when the second DC component H / D falls below a minimum brightness value, such as e.g. a value of 1 lux. This exemplary value corresponds to a dark to very dim environment. In such an environment, fewer optical disturbances from the detector environment can be expected than during the day. By assuming lesser disturbances from the detector environment, the alarm threshold LEV can be lowered. Due to the more sensitive setting, an accelerated emission of a fire alarm takes place, since the reduced alarm threshold LEV is now more quickly exceeded by the output signal of the weighting filter 41.

8 shows a third functional block diagram of a control unit 4 as an exemplary embodiment of the inventive offset compensation for the photodiode 6 '. For offset compensation, ie for compensation of the DC component of the scattered light / photosignal BS, PD, this is supplied by way of example to a non-inverting input of an operational amplifier 63. At the same time, the output of the operational amplifier 63 is fed back to the non-inverting input via a feedback resistor (not further described). The present circuit arrangement thus represents schematically a transimpedance converter known per se, which converts the photocurrent generated by the photodiode 6 'into a proportional photovoltage at the output of the operational amplifier 63. The offset compensation advantageously prevents overmodulation of the transimpedance amplifier.

The circuit arrangement in FIG. 8 shows in detail a control circuit for the offset compensation according to the invention. In this case, the control loop comprises the operational amplifier 63 as a comparison element, a downstream low-pass filter 57 with an exemplary corner frequency of 20 Hz, a following A / D converter 52, a controller implemented by the logic block 40, the input side to the output of the A / D Converter 52 is connected, a controller subsequent to the digital / analog converter 58 and the D / A converter 58 following, not further designated voltage-controlled current source. The latter acts as feedback of the control loop to the inverting input of the transimpedance converter or operational amplifier 63.

In the regulated state, a substantially DC-free scattered light / photosignal AC is present at the output of the operational amplifier 63. On the one hand, this signal AC is fed to a bandpass filter 56, which is tuned to the carrier or clock frequency of the frequency generator 46. The thus filtered scattered light / photosignal BS 'is then, as described above, output to an A / D converter 51, which supplies the corresponding digitized values to a downstream weighting filter 41 for fire analysis.

On the other hand, according to the invention, the substantially DC-free stray light / photo signal AC is fed to a low-pass filter 57 with an exemplary corner frequency of 20 Hz. The signal applied to the filter output forms the control deviation RA of the control loop. This is fed to the A / D converter 52, which converts the signal of the control deviation RA into corresponding digital values of the control deviation RA '. A subsequent controller realized in software in the logic block 40 determines a first DC component OFFSET for the offset compensation of the received scattered light / photosignal BS, PD as a function of the magnitude of the system deviation RA '. This first DC component OFFSET converts a downstream D / A converter 58 into a DC voltage, by means of which a following voltage-controlled current source is triggered. The latter causes, via the inverting input of the operational amplifier 63, that this first DC component OFFSET is subtracted from the received scattered light / photosignal BS, PD, in order finally to produce the substantially DC-free scattered light / photosignal AC. The control loop is now closed. Furthermore, as already described, the output signal of the A / D converter 52 is again supplied to a flicker frequency block 42 for detecting flicker frequencies characteristic of open-fire.

In the present example, the logic block 40 is also set up or programmed to compare the determined first DC offset OFFSET with a predetermined override value and to output a fault message ST if the determined first DC offset element OFFSET exceeds the overmodulation value for a predetermined minimum time.

FIG. 9 shows an exemplary scattered light smoke detector 1 of a closed type as a fire detector with an optical measuring chamber 10 and with a photodiode 6 for ambient light for detecting an open fire according to the invention in a sectional illustration.

In the present example, the detector 1 has a housing 2, which is composed of a base body 21 and a detector hood 22. With the base body 21, the detector 1 can then preferably be detachably attached to a detector base 1 1 mounted on a ceiling. Both housing parts 21, 22 are usually made of a light-tight plastic housing. In the interior of the detector 1, a circuit substrate 3 is added. On this, in addition to a microcontroller 4 as a control unit and a transmitter S, typically an LED, and a receiver E, typically a photodiode, arranged as parts of a stray light assembly SA. SZ designates the scattered light center SZ or measurement volume for optical smoke detection formed by the scattered light arrangement SA. The scattered light arrangement SA is surrounded by a labyrinth and together with it forms the optical measuring chamber 10. The latter thus forms a fire sensor 10. With OF an exemplary circumferential smoke inlet opening and with N an insect protection is designated. In the area of the smoke inlet opening OF two opposing thermistors 5 are present for detecting the ambient temperature as an additional fire characteristic. Within the detector hood 22, a photodiode 6 is arranged, which is opposite to a recess AN on the outside of the detector hood 22. Through this recess AN, the photodiode 6 can "see through" into the surroundings around the detector 1. FOV denotes the associated optical detection area of the photodiode 6. Open fire in this detection area FOV, symbolized by a flame symbol, is then optical through the photodiode 6 In the present example, the recess AN in the detector hood 22 is provided with a transparent cover AB for protection against contamination The cover AB is preferably made of a translucent plastic It may be provided with a daylight filter In addition, a day / night identifier T / N can be output, where Z denotes the geometric central main axis of the detector 1. FIG. 10 shows the example according to FIG. 9 in a plan view along the registered viewing direction X. According to the invention, the control unit 4 is now set up to analyze and depend on a photosignal received by the photodiode 6 for the presence of flank frequencies characteristic of open flame of accelerating the issue of a possible fire alarm. In addition, it is also already set up to monitor the photosignal on an undershooting of a minimum brightness level and output as a day / night identifier T / N, symbolized by a sun and moon symbol. The latter can be output to a higher-level control center in order, for example, to switch blinds on or off or, for example, to switch light on and off. FIG. 11 shows an embodiment of the fire detector 1 according to the invention with a common light guide 7 for detecting the ambient light by means of the photodiode 6 and as an indicator in the sense of a ready-to-operate display. The photodiode 6 shown is preferably a silicon photodiode and in particular a silicon PIN photodiode.

In contrast to the previous embodiment, the photodiode 6 is now arranged on the circuit carrier 3 for the ambient light detection. It is preferably applied adjacent to a likewise arranged on the circuit substrate 3 indicator light emitting diode LED.

The light guide 7 is such that it faces a first end of both the indicator LED LED and the photodiode 6. The second end of the optical waveguide 7 preferably protrudes through a central recess in the detector hood 22. As a result, ambient light can be detected through the optical waveguide 7 by means of the photodiode 6. Independently of this, light of the indicator light-emitting diode LED can be coupled out through the light guide 7 at the second end of the light guide 7 in the opposite way. The indicator LED LED is cycled, e.g. every 30 seconds, to send an optically visible pulse to the ready display of the fire detector 1 driven. In particular, the second end of the light guide 7 is formed as an optical lens L. As a result, ambient light can be detected from a larger optical detection range FOV. In addition, the ready display of the fire detector 1 can be seen in a larger solid angle range. The light guide 7 is preferably made in one piece and made of a transparent plastic.

FIG 12 shows the example according to FIG 11 in a plan view along the registered in Figure 1 1 viewing XII. In this illustration, in particular the central arrangement of the second end of the light guide 7 can be seen.

FIG. 13 shows a functional block diagram of a detector control unit 4 with a weighting filter 41 with adjustable time constant T _F _in order to accelerate the output of a possible fire alarm according to the invention. The illustrated functional blocks 40-44 are preferably implemented as software, i. E. as program routines executed by a processor-based control unit, such as a microcontroller. The program routines are loaded in a memory of the microcontroller 4. The memory is preferably a nonvolatile electronic memory, such as a flash memory. The microcontroller 4 may moreover have specific functional blocks which are already integrated as hardware functional units in the microcontroller 4, such as analog-to-digital converters 51-53, signal processors, digital input / output units and bus interfaces.

In the upper left part of FIG. 13, a stray light arrangement SA can be seen as part of the optical measuring chamber or of the fire sensor. The scattered light arrangement SA has a transmitter S and receiver E. Both are aligned to a common scattered light center SZ as a measuring volume and spectrally matched. The transmitter S is in particular a light emitting diode. The receiver E is a photosensor and preferably a photodiode. The light-emitting diode is designed in particular for emitting monochromatic infrared light, preferably in the range from 860 to 940 nm ± 40 nm, and / or from monochromatic ultraviolet light, preferably in the range from 390 to 460 nm ± 40 nm. Stray light which originates from particles to be detected, such as smoke particles in the scattered light center SZ, is then detectable by the receiver E. The scattered light level or the amplitude of the scattered light signal BS, is a measure of the concentration of the detected particles. Preferably, the scattered light signal BS is previously amplified by means of an amplifier 62, in particular by means of a transimpedance amplifier. For repeatedly pulsed activation of the light-emitting diode S, the logic block 40 of the control unit 4 outputs a pulsed clock signal f _clock . This is amplified by a further amplifier 61 and supplied to the light-emitting diode S. Typically, the clock signal f _{clock is} cyclic. It preferably has a pulse width in the range of 50 to 500 is and a clock frequency in the range of 0, 1 to 2 Hz. For synchronous detection of the scattered light, this clock signal f _{clock is} fed to an associated analog-to-digital converter 51.

In the present example, the microcontroller 4 comprises by way of example three analog-to-digital converters 51-53. The first A / D converter 51 serves to digitize the scattered light signal BS from the fire sensor, i. here from the optical measuring chamber. The second A / D converter 52 is provided for digitizing a photo signal PD provided by a photodiode 6 for encircling

Ambient light is provided in the (immediate) environment of the detector 1. Preferably, the photosignal PD is previously by means of an amplifier 61, typically by means of a

Amplified transimpedance amplifier. The third A / D converter 53 is provided for digitizing a temperature signal TS, which is output by an NTC as a temperature sensor 5 for detecting the ambient temperature UT in the (immediate) environment of the detector 1. The digitized scattered light signal is then fed to a (digital) weighting filter 41 along the optical path. The weighting filter 41 is preferably a digital low-pass filter which performs some signal smoothing or averaging. However, this filtering causes a delayed filter response at the output of the weighting filter 41 analogous to a filter time constant in a low-pass filter. The unspecified output signal of the weighting filter 41 is subsequently fed to a comparator 44, which compares this with an alarm threshold LEV, such as with a minimum concentration value for the alarm. If the filter output signal exceeds this comparison value LEV, the output of a fire alarm AL, such as, for example, to a higher-level fire alarm control panel takes place. According to the invention, the microcontroller 4 is also set up to analyze the photosignal PD received by the photodiode 6 for the presence of flicker frequencies characteristic of open fire and, depending on this, to accelerate the output of a possible fire alarm. The spectral signal analysis can eg by means of a digital

Fourier transform or be performed by means of a wavelet analysis. Technically, this is done on the one hand by the function block flicker frequency detector 42. In the case of detected flickering fire, it outputs a flicker indicator F to a logic block 40, which then increases the sampling rate of the A / D converter 51 for the digitization of the scattered light signal BS and / or the filter time constant T _Fi | _ter decreased. The flicker indicator F can be, for example, a binary value, such as 0 or 1, or a digital value, for example in the value range from 0 to 9. For the binary case, the value 0 can be, for example, the absence of flicker frequencies and the value 1 corresponding to Represent presence. In the digital case, for example, the value 0 can represent the absence of flicker frequencies. For example, values 1 through 9 may indicate the presence of flicker frequencies, with high numbers indicating high flicker frequency levels and low numbers indicating flicker frequency levels. By increasing the clock frequency or the sampling rate f _clock , the digitized scattered light signal BS is faster at the evaluation filter 41 for further processing. On the other hand, the weighting filter 41 speaks by decreasing the filter time constant T _fl | _ter to faster so that an actual increase in the scattered light level BS also leads to a faster fire alarm AL. The increase of the sampling rate f _clock and / or the reduction of the filter time constant T _fl | _ter , for example, for the digital case of the flicker indicator F as a function of its value range.

Alternatively or additionally, the logic block 40 may also be programmed to lower the alarm threshold LEV when a light / dark indicator H / D provided by the functional block 43 of the microcontroller 4 falls below a minimum brightness level. Such a value is for example 0, 1 lux, 1 lux or 5 lux. These exemplary values correspond to a dark to very dim environment. For example, the value for the alarm threshold LEV can be reduced by 10%, 20, 30% or 50%. As described above, in such an environment, fewer disturbances from the detector environment can be expected, such as during the day, such as with the increase of smoke particles by the lighting of candles, by propagating smoke during cooking and roasting, or by the lighting of a fireplace and the like , As a result of the assumption of lesser disturbances from the detector environment, the alarm threshold LEV can therefore also be lowered. The more sensitive setting accelerates the emission of a fire alarm by faster exceeding the lowered alarm threshold LEV by the output of the weighting filter 41. The day / night detection is performed by a low-pass filtering of the photosignal PD with a time constant of less than 1 Hz, in particular less than 0, 1 Hz. In the example of FIG 13, the control unit 4 with a thermistor 5 (NTC) for detection of the

Ambient temperature UT in the immediate area connected to the fire detector. The control unit 4 is configured according to the invention to take into account the detected ambient temperature UT in the fire analysis. As a result, a fire can be detected even more reliably in the sense of a multi-criteria fire detector. In the present example, the temperature signal TS output by the thermistor 5 is converted by the third A / D converter 53 into digital temperature values T, which are then taken into account by the logic block 40 of the control unit 4 during the fire analysis.

FIG. 14 shows an exemplary thermal detector 1 with a temperature sensor 5 and with a photodiode 6 for detecting ambient light for detecting an open fire according to the invention in a sectional view.

In the present example, the detector 1 has a housing 2, which is composed of a base body 21 and a detector hood 22. With the base body 21, the detector 1 can then preferably be releasably attached to a detector base mounted on a ceiling. Both housing parts 21, 22 are usually made of a light-tight plastic housing. In the detector hood 22, a central opening is provided, in which a thermistor 5 is mounted as a temperature sensor protected against possible mechanical effects. Due to the central arrangement, a direction-independent detection of the ambient temperature UT in the immediate vicinity of the detector 1 is possible (see also FIG. 15). In the interior IR of the detector 1, a circuit substrate 3 is further accommodated, on which in addition to a Mikrocontrol- ler 4 as a control unit and the photodiode 6 is arranged. Opposite the photodiode 6 there is a recess AN in the detector hood 22, through which the photodiode 6 can "see through" into the surroundings around the detector 1. FOV denotes the associated optical detection range of the photodiode 6. Open flame in this detection range FOV, symbolized by a flame symbol, can then be optically detected by the photodiode 6. In the present example, the recess AN is provided in the detector hood 22 with a transparent cover AB to protect against contamination.The cover AB is preferably made of a translucent plastic already with a daylight film be provided ter or have such. In the case of a detected fire, a fire alarm AL and a day / night identifier T / N, symbolized by an arrow, can be output.

FIG. 15 shows the example according to FIG. 14 in a plan view along the viewing direction shown in FIG. Z denotes the geometric central main axis of the detector 1. According to the invention, the control unit 4 is now adapted to analyze a photosignal received by the photodiode 6 for the presence of flicker frequencies characteristic of open fire and, depending on this, to accelerate the output of a possible fire alarm. It is also set up to monitor the photosignal for an undershooting and undershooting of a minimum brightness level and to output it as a day / night identifier T / N, symbolized by a sun and moon symbol, such as, for example, T / N. to a higher-level headquarters.

16 shows a first embodiment of the fire detector 1 according to the invention with a non-contact temperature sensor 5 having a heat radiation W sensitive in the infrared range thermopile 50 as a heat radiation sensor.

In contrast to the previous embodiment, the thermopile 50 is arranged in the detector housing 2 on the circuit substrate 3 and aligned to detect the ambient temperature UT visually on the inside of the detector hood 22 IS. The optically detected surface on the inside IS of the detector hood 22 is designated as the measuring surface M in FIG. In particular, the thermopile 50 is again arranged centrally in the detector housing 2, in order to enable a direction-independent detection of the ambient temperature UT in the immediate vicinity of the detector 1. In this case, the detector hood 22 in the central region 23 of the inner side IS is formed such thermally conductive to an opposite region of the outside of the detector hood 22, that the housing temperature T on the inner side IS the ambient temperature UT at the opposite region of the detector hood 22 follows. In the simplest case, the wall thickness in the central area 23 can be reduced, as e.g. to half a millimeter. Alternatively, this central region 23 may be thermally insulated from the rest of the surrounding detector hood 22. In most cases, no change in the wall thickness of the detector hood 22 will be required.

The current ambient temperature UT or the housing temperature T following this is calculated from the heat radiation value detected by the heat radiation sensor 50 according to the pyrometric measurement principle. In this case, the emissivity for the heat radiation W of the measuring surface M is included in the calculation. This value can be determined metrologically and is typically in the range of 0.75 to 0.9. In this case, the blacker the measuring surface, the greater the emissivity. An emissivity of 1.0 corresponds to the theoretically maximum achievable value for a black emitter. The computational determination can be carried out by a microcontroller integrated in the thermopile 50, which output side outputs the currently determined temperature value and thus represents a non-contact temperature sensor. Alternatively, the thermopile 50 can only output a current heat radiation value, which is then detected by the microcontroller 4 of the fire engine 1 and further processed for calculating the current temperature value. For this purpose, the associated emissivity is preferably stored in the microcontroller 4.

FIG. 17 shows a second embodiment of the fire detector 1 according to the invention with a common light guide 7 for detecting the ambient light by means of the photodiode 6 and as an indicator in the sense of a ready-to-operate display. For this purpose, an indicator light-emitting diode LED is arranged adjacent to the photodiode 6 on the circuit carrier 6. The light guide 7 is such that it faces a first end of both the indicator light emitting diode LED and the photodiode 6. The second end of the light guide 7 preferably protrudes through a central recess in the detector hood 22. Thereby

Ambient light through the light guide 7 by means of the photodiode 6 detectable. Irrespective of this, light of the indicator light-emitting diode LED can be coupled out in the opposite direction through the light guide 7 at the second end of the light guide 7. The indicator LED LED is typically cycled to emit an optically visible pulse, such as e.g. every 30 seconds, activated for ready display of the fire detector 1. In particular, the second end of the light guide 7 is formed as an optical lens L. As a result, ambient light can be detected from a larger optical detection range FOV. In addition, the operational indication of the

Detect fire detector 1 in a larger solid angle range. The light guide 7 is preferably made in one piece and made of a transparent plastic. The photodiode 6 shown is preferably a silicon photodiode and in particular a silicon PIN photodiode.

Alternatively, it is possible to dispense with such a photodiode produced especially for light detection. In this case, the optical fiber 7 is located with its first end only of the indicator light emitting diode LED. The light extraction of the LED light is again at the second end of the light guide 7 in the vicinity of the fire detector. 1

According to the invention, the indicator LED is now provided for ambient light detection, since in principle any light emitting diode is also suitable for the detection of ambient light, albeit with significantly lower efficiency. In this case, the indicator LED LED is alternately switched to a light generation operation mode and a photodiode operation mode (see the explanations below in FIG. 20).

In contrast to FIG. 14 and FIG. 16, the fire detector 1 has, for example, two opposing temperature sensors 5 for detecting the ambient temperature UT. FIG. 18 shows a functional block diagram of a detector control unit 4 with an evaluation filter 41 with adjustable filter time in order to accelerate the output of a possible fire alarm.

The illustrated functional blocks 40-44 are preferably implemented as software, i. as program routines executed by a processor-based control unit, e.g. by a microcontroller. The program routines are loaded in a memory of the microcontroller 4. The memory is preferably a nonvolatile electronic memory such as e.g. a flash memory. In addition, the microcontroller 4 may have specific functional blocks which are already integrated as hardware functional units in the microcontroller 4, e.g. Analog-to-digital converters 51, 52, signal processors, digital input / output units and bus interfaces. By way of example, in the present example, the microcontroller 4 comprises two analog-to-digital converters 51, 52 in order to obtain a current temperature signal BS from the fire sensor 5, i. Here from an NTC, as well as a photosignal PD from a photodiode 6 to digitize. The digitized temperature signal is then fed to a (digital) weighting filter 41 along the thermal path. The weighting filter 41 is preferably a digital low-pass filter, which performs a certain signal smoothing or averaging. However, this filtering causes a delayed filter response at the output of the weighting filter 41 analogous to a filter time constant in a low-pass filter. The unspecified output signal of the weighting filter 41 is subsequently fed to a comparator 44, which compares it with an alarm threshold LEV, such as e.g. with a temperature value of 65 °. If the filter output signal exceeds this comparison value LEV, the output of a fire alarm AL, e.g. to a higher-level fire alarm system.

According to the invention, the microcontroller 4 is also set up to analyze the photosignal PD received by the photodiode 6 for the presence of flicker frequencies characteristic of open fire and, depending on this, to accelerate the output of a possible fire alarm. The spectral signal analysis can e.g. by means of a digital

Fourier transform or be performed by means of a wavelet analysis. Technically, this is done on the one hand by the function block flicker frequency detector 42. In the case of detected flickering fire these outputs a flicker indicator F to a logic block 40, which then increases the sampling rate f _clock of the A / D converter 51 for digitizing the temperature signal BS and / or the filter time constant T _Fi | _te humiliated. The flicker indicator F can be, for example, a binary value, such as 0 or 1, or a digital value, such as in the value range of

0 to 9. For the binary case, the value 0 can, for example, represent the absence of flicker frequencies and the value 1 corresponding to the presence. In the digital case, for example, the value 0 may represent the absence of flicker frequencies. For example, values 1 through 9 may indicate the presence of flicker frequencies, with high numbers indicating high flicker frequency levels and low numbers indicating flicker frequency levels. By increasing the sampling rate f _T akt, the digitized temperature signal BS is applied more quickly to the evaluation filter 41 for further processing. On the other hand, the weighting filter 41 speaks by reducing the filter time. constant _tension _ter faster, so that an actual increase in the temperature signal BS also leads to a faster fire alarm AL. Increasing the sampling rate f _clock and / or decreasing the filter time constant T _fi | _ter , for example, for the digital case of the flicker indicator F as a function of its value range. Alternatively or additionally, the logic block 40 may be programmed to lower the alarm threshold LEV, such as from 65 ° to 60 °. As a result, an accelerated output of a fire alarm takes place for the case of fire occurring with increased probability due to the detected flicker frequency.

Alternatively or additionally, the logic block 40 can also be programmed to lower the alarm threshold LEV, in particular when a light / dark indicator H / D provided by the functional block 43 of the microcontroller 4 falls below a minimum brightness value, such as e.g. a value of 1 lux. This exemplary value corresponds to a dark to very dim environment. In such an environment, fewer thermal disturbances from the detector environment can be expected, such as during the daytime, e.g. with the temperature fluctuations described above. By assuming lesser disturbances from the detector environment, the alarm threshold LEV can be lowered. Due to the more sensitive setting, an accelerated emission of a fire alarm takes place, since the reduced alarm threshold LEV is now more quickly exceeded by the output signal of the weighting filter 41. The day / night detection is carried out by a low-pass filtering of the photosignal PD with a time constant of less than 1 Hz, in particular less than 0, 1 Hz.

19 shows a second functional block diagram of a detector control unit 4 with a temperature sensor 5 with thermopile 50 according to the invention.

In contrast to the previous embodiment, the current ambient temperature UT or the following housing temperature T is determined with a temperature calculation block 54 of the microcontroller 4. In the latter case, a digitized thermal signal WS is supplied by means of an A / D converter 51 from a thermopile 50 as an example of a thermal radiation sensor. In the computational determination, the emissivity for the heat radiation W in the infrared region of the measurement surface M is included in the calculation.

FIG. 20 shows a third functional block diagram of a detector control unit 4 in addition to the alternating activation of an indicator light-emitting diode LED and for detecting the ambient light by means of the indicator light-emitting diode LED, switched in an operating mode as a photodiode 5 according to the invention.

In comparison to the previous FIG. 18, the logic block 40 alternately activates a switching unit 55 via a switching signal US, so that in a first phase the indicator LED LED can be driven with a current signal IND from a pulse generating unit 45 for momentary lighting, such as every 30 seconds. In a second phase of the logic block 40 controls the switching unit 55 so that the low photo signal PD from the indicator LED LED is supplied to an amplifier 60. This in turn is followed by an A / D converter 52 for digitizing the photo signal PD. The amplifier 60 is preferably a transimpedance amplifier.

LIST OF REFERENCE NUMBERS

1 fire detector, open scattered light smoke detector, closed scattered light smoke detector, thermal detector, heat detector, point detector

2 housings, plastic housing

3 circuit carrier, circuit board

4 control unit, microcontroller

5 temperature sensor, thermistor, NTC, temperature sensor

6 (separate) photodiode, IR photodiode, silicon PIN photodiode

6 'common photodiode, IR photodiode, silicon PIN photodiode

7 light guides

10 fire sensor, optical measuring chamber, labyrinth

1 1 detector base

21 basic body

22 Detector cover, housing cover

23 central housing part

40 function block, logic block

41 Function block, weighting filter

42 function block, flicker frequency detector

43 Function block, night detection block

44 function block, comparator

45 function block, pulse generation unit

46 Function Block, Frequency Generator, RF Burst Generator

47 Function block, brightness compensation

50 thermopiles

51 - 53 A / D converter, analog / digital converter

54 temperature calculation block

55 switching unit, multiplexer

56, 57 frequency filter, digital filter, high pass filter, low pass filter

60 - 63 amplifiers, transimpedance amplifiers

A amplitude, signal amplitude

AB cover, transparent cover, window

AC DC-free scattered light / photosignal

AL fire alarm, alarm message, alarm information

AN recess, recess, opening

BS sensor signal, fire sensor signal, scattered light signal, temperature signal

BS 'filtered scattered light signal

E light receiver, photosensor, photodiode

F flicker indicator ""

28

FZ filter time setting signal, setting signal f frequency

FOV coverage area, field-of-view

f _clock , f _clock2 clock signal, second clock signal

GAIN gain

H / D second DC component, light / dark indicator

L lens, optical lens

LED indicator LED

LEV alert threshold

N net, insect repellent, grid

OF housing opening, smoke inlet opening

PD photosignal, photodiode signal

RA, RA 'deviation

S Light transmitter, optical transmitter unit, LED S _Re i relative spectral sensitivity

SA scattered light arrangement

SZ scattered light center, measuring volume

t time, timeline

T temperature value

TS temperature sensor signal

T / N day / night identifier

T _fi iter filter time, filter time constant

UT ambient temperature

Z major axis, symmetry axis

λ light wavelength

Claims

claims

1. Fire detector, in particular open scattered light smoke detector, with a fire sensor, with a control unit (4) and with a photodiode (6, 6 ') for detecting ambient light in a spectrally limited range of 400 to 1 150 nm, wherein the control unit (4) is configured to analyze a sensor signal received from the fire sensor (BS) for at least one characteristic fire parameter, to evaluate and to output a fire alarm (AL) in the case of a detected fire, and wherein the control unit (4) is additionally configured to receive one of the Photodiode (6, 6 ') received photosignal (PD) to analyze the presence of flicker frequencies characteristic of open fire and depending on the issue of a possible fire alarm (AL) by increasing a sampling rate for the detection of the sensor signal (BS) from the fire sensor (5), by decreasing a filter time (T _F iit _er ), in particular a time constant, of a weighting filter (41) for d speed up the fire analysis and / or by lowering the alarm threshold (LEV).

2. Fire detector according to claim 1, wherein the control unit (4) is adapted to suppress the output of a possible fire alarm (AL) solely on the basis of detected characteristic Flackerfrequenzen in the received photosignal (PD).

3. Fire detector according to claim 1 or 2, wherein the photodiode (6, 6 ') is a silicon photodiode.

4. Fire detector according to one of the preceding claims, wherein the photodiode (6, 6 ') is preceded by a daylight blocking filter, which only light in a range of 700 to 1 150 nm, in particular from 730 to 1 100 nm, happen.

5. Fire detector according to one of the preceding claims, wherein the fire detector is an open scattered light smoke detector, wherein the scattered light smoke detector comprises a housing (2), a circuit carrier (3), a light emitter (S) and a light receiver (E), wherein the light emitter (S ) and the light receiver (E) are arranged in the housing (2), wherein the light emitter (S) and the light receiver (E) are arranged in a scattered light arrangement (SA) with a scattered light center (SZ) lying outside the scattered light smoke detector, wherein the scattered light arrangement ( SA) with the light emitter (S) and the light receiver (E) forms the fire sensor, and wherein the control unit (4) is adapted to a received from the fire sensor scattered light signal as a sensor signal (BS) to an inadmissibly high signal level as fire characteristic and / or an unacceptably high

Rate of increase of the sensor signal (BS) to analyze as a further fire characteristic and output in case of a detected fire a fire alarm (AL).

6. Fire detector according to claim 5, wherein the light receiver (E) for the scattered light detection and the photodiode (6) for the ambient light detection as a common photodiode (6 ') are realized.

7. A fire detector according to claim 6, wherein the control unit (4) is adapted to analyze the scattered light / photosignal (BS, PD) received by the common photodiode (6 ') in time-separated phases, the control unit (4) being arranged for this purpose is to analyze the received scattered light / photosignal (BS, PD) in a respective first phase to an inadmissibly high signal level and / or an impermissibly high slew rate, and adapted to receive the received scattered light / photosignal (BS, PD) in of a respective second phase for the presence of characteristic Flackerfrequenzen out.

8. Fire detector according to one of claims 5 to 7, wherein the control unit (4) is adapted to determine a first DC component (OFFSET) from the received scattered light / photosignal (BS, PD), and also adapted to this first DC component (OFFSET) to subtract from the received scattered light / photosignal (BS, PD) to obtain a substantially equal-share stray light / photosignal (AC).

9. Fire detector according to claim 8, wherein the control unit (4) is adapted to compare the determined first DC component (OFFSET) with a predetermined override value and output a fault message (ST), if the determined first DC component (OFFSET) the override value for a exceeds specified minimum time.

10. Fire detector according to one of claims 5 to 9, wherein the control unit (4) is adapted to determine a second DC component (H / D) from the received scattered light / photosignal (BS, PD), which represents a long-term average brightness value, and wherein the control unit (4) is additionally set up to monitor this second DC component (H / D) to a value below a minimum brightness value as well as to lower an alarm threshold (LEV) for the output of a possible fire alarm (AL).

1 1. A fire detector according to any one of claims 1 to 4, wherein the fire detector is a scattered light smoke detector, which in a detector housing (2) arranged, shielded from ambient light and transparent to be detected smoke optical measuring chamber (10) as a fire sensor, wherein the control unit (4) is set up to analyze a scattered light signal received by the optical measuring chamber (10) as sensor signal (BS) at an inadmissibly high signal level as a fire parameter and / or at an inadmissibly high slew rate of the sensor signal (BS) as a further fire parameter; In the event of a detected fire, issue a fire alarm (AL).

12. Fire detector according to one of claims, wherein the fire detector has a temperature sensor (5), in particular a thermistor, for detecting an ambient temperature (UT) in the immediate area around the fire detector and wherein the control unit (4) is adapted to the detected ambient temperature ( UT) in the fire analysis.

13. Fire detector according to one of claims 1 to 4, wherein the fire detector is an exclusive thermal detector with a temperature sensor (5) as a fire sensor, wherein the control unit (4) is adapted to receive a temperature sensor (5) as a sensor signal (BS) Temperature signal on an impermissible high ambient temperature (UT) as a fire characteristic and / or an inadmissibly high temperature rise to analyze as a further fire characteristic and output in case of a detected fire a fire alarm (AL).

14. Fire detector according to claim 13, wherein the temperature sensor (5) is a non-contact temperature sensor, which comprises a heat radiation (W) sensitive in the infrared range heat radiation sensor, in particular a thermopile or a microbolometer, the fire detector a detector housing (2) with a detector hood (22), wherein the heat radiation sensor (6) arranged in the detector housing (2) and for the mathematical derivative of the ambient temperature (UT) optically on the inside (IS) of the detector hood (22) is aligned, and wherein the detector hood (22) in the area the inner side (IS) is so thermally conductive to an opposite region of the outside of the detector hood (22) is formed, that on the inside (IS) adjusting housing temperature (T) of the ambient temperature (UT) at the opposite region of the detector hood (22) follows.

Fire detector according to one of the preceding claims, wherein the control unit (4) is adapted to lower an alarm threshold (LEV) for the output of a fire alarm (AL) to accelerate the output of a fire alarm (AL), if the presence of for open flame characteristic flicker frequencies has been detected.

16. Fire alarm according to one of claims 1 1 to 15, wherein the control unit (4) is also adapted to monitor the output from the photodiode (6) photosignal (PD) to fall below a minimum brightness value and is adapted to an alarm threshold ( LEV) for the output of a possible fire alarm (AL).

17. A fire detector according to claim 16, wherein the fire detector is wired or wirelessly connected to a parent center and wherein the control unit (4) is adapted to the exceeding and falling below the minimum brightness level as day / night identifier (T / N) to the center issue.