EP1622106A1 - Hazard warning device, especially for a fire or intrusion signalling system - Google Patents

Abstract

A fire or break in alarm has a series circuit with semiconductor switch (T1), inductance (L1) and high power LED (D1) (Light Emitting Diode)with diode (D4) parallel to the inductance applying the alarm supply voltage to the series circuit terminals, and a signal processor that generates a control signal in the alarm state that causes the switch in the ON state to pass and block a series of short pulses.

Description

The invention relates to a hazard detector, in particular fire or intrusion detector, which receives its supply voltage via a at least two-core cable from a central office or from a built-in battery and at least one sensitive to a physical size sensor and a signal processing circuit which u.a. in the alarm state of the detector, sends a corresponding data telegram to the control center.

Typical hazard detectors are ceiling-mounted fire detectors, intrusion detectors, especially motion detectors, and manually-triggered wall-mounted hazard detectors, especially fire detectors and panic buttons. The detectors communicate either via a cable with at least two wires or wirelessly with a control panel. Line-bound detectors draw their supply voltage via the line from the control center. Wireless detectors usually draw their supply voltage from a built-in battery. In both cases, only a limited amount of electrical power is available for the detector electronics. In the case of conducted detectors, the available electrical power per detector is limited by the fact that a large number of detectors, often more than 100 detectors, are supplied by the control center via a common line, which can accordingly be several hundred meters long. For battery-powered detectors, the power is limited in the interest of a long battery life.

The invention has the object of providing a hazard detector of the type specified in the introduction despite the limited available electrical power with the To provide additional function of a bright optical hazard warning signal that can be safely perceived even in an acute danger situation, eg in smoky rooms or in other stressful situations such as after a burglary.

This object is achieved by a detector with the features specified in claim 1.

This solution has the particular advantage that can be omitted in a so-called object area often additionally mounted or mounted alarm lights or optical escape route markings equipped with such detectors alarm system. The saving of material and installation time is considerable. In addition, existing alarm systems can be retrofitted to detectors according to the invention without the basic installation, ie in particular the wiring of the detectors and / or the central power supply, must be changed or renewed.

The invention makes it possible to equip the detectors with LEDs high Lichtabstrahlleistung that were previously unusable due to their high power requirements of up to 1 A and more in conventional flashing mode for lack of sufficient electrical power of the detector, especially in conventional LED flashers of the vast majority of Supply power is converted because of compared to the supply voltage low forward voltage of the LED in a series resistor into heat. Compared to a conventional flashing circuit for an LED of the same light emission power, the proposed circuit requires only about 10 to 20% of electrical power.

The control signal can be generated as a composite control signal from the message-own signal processing circuit become. The pulse duration of the short pulses is selected so that the semiconductor switch switches to the blocking state as soon as the current through the current slew rate when the semiconductor switch is turned on inductively limiting the inductance and the LED has reached a value defined by the characteristic values of the latter. Subsequently, the freewheeling diode ensures that the current continues to flow through the LED until the energy stored in the inductance is consumed. In this way, during the "ON" time, a rapid succession of flashes of light is produced, but the human eye, due to its inertia, perceives it as a single blink of light, followed by the "OFF" time of the slow blinking beat. The sum of "ON" time and "OFF" time is therefore equal to the period of the flashing frequency, which is usually between 0.5 Hz and 3 Hz.

The flashing clock can, as usual, a frequency in the range of 1 Hz and an "ON" time in the range of 30 ms have (claim 2).

Within the sequence of short pulses, the pulse duration between 5 microseconds and 50 microseconds and the pulse / pause ratio between about 1: 4 and about 1:10 are (claim 3). The pulses, depending on the value of the inductance, may be in accordance with the substantially linear increase and the exponential decay of the current through the LED with a pulse period of e.g. 200 μs consecutive, with the maximum of the light intensity lasts only about 20 μs. During the "ON" time of e.g. 30 ms, the LED emits about 150 individual flashes. This is followed by a pause of 970 ms at a flashing frequency of 1 Hz.

The times given are to be understood as examples. However, it has been shown in tests that extending the "on" time beyond about 30 to 50 ms is the subjective one perceived brightness of the flashing signal is no longer increased, so only leads to unnecessary additional consumption of electrical power. Conversely, if the value of 30 ms falls below this value, the subjective brightness impression of the blink decreases. It has also been found that increasing the number of individual flashes within the "on" time no longer increases the subjectively perceived brightness, while conversely a significant reduction in the number of individual flashes is perceived as a decrease in intensity.

At the connection point between the semiconductor switch and the inductor, a switching element may be connected, which holds the semiconductor switch in the off state until the current in the inductor, the LED and the free-wheeling diode comprehensive circuit has decayed (claim 4). In this way, with rapidly successive current pulses through the LED, it is avoided that the LED is overloaded by a too early onset of a new current pulse, that is, a too short pulse pause.

For this purpose, the control signal can switch the semiconductor switch via a control transistor, and the switching element which keeps the semiconductor switch in the off state during the decay of the current in the circuit comprising the inductance, the LED and the free-wheeling diode may consist of a diode which acts as a clamping diode between the Base of the control transistor and the connection point between the semiconductor switch and the inductance is connected (claim 5). In particular, in a self-oscillating embodiment of the stored energy in the inductor is thereby exploited even better.

In a preferred embodiment, a current sensing circuit periodically disables the semiconductor switch during the "ON" period in time with the short pulses as soon as the current passes through the LED has reached a predetermined maximum value and switches after the decay of the current, the semiconductor switch again permeable (claim 6). The current measuring circuit thus determines the pulse duration of the short pulses, which switch the semiconductor switch in rapid succession permeable and lock again, whereby the short flashes of light of the LED are generated. This embodiment has the great advantage that the energy content per single flash is essentially independent of the supply voltage, ie remains constant even with decreasing supply voltage, because the semiconductor switch is not after a fixed pulse duration but upon reaching a predetermined current value, ie at high supply voltage earlier, at low supply voltage later, is switched to the blocking state. In particular, when many such detectors are connected in parallel to a common line and form a reporting line, this independence from the supply voltage is a significant advantage, because while the supply voltage at the beginning of the reporting line may be 42 V, for example, at the end of the line, ie last detector, drop to eg 8 V, depending on the operating conditions of the detectors in front of it.

The current measuring circuit can be realized very simply by a current measuring resistor in series with the LED and a comparator, at the first input of which a reference voltage is applied and at the second input of which the current measuring resistor tapped, current-proportional voltage is applied and whose output signal produces the sequence of short pulses representing the Switch semiconductor switch (claim 7).

In a further development of this embodiment, the signal processing circuit need only supply the flashing clock, which is used as the operating voltage of the comparator (claim 8), so that the latter operates only during the "ON" time.

The output of the comparator can be connected via a positive feedback resistor with its first input to produce a switching hysteresis (claim 9), so that the comparator switches the semiconductor switch again permeable only when the current has largely decayed by the LED. The circuit thus operates self-oscillating with respect to the sequence of short pulses.

Instead, as noted above, the already existing signal processing circuitry, which typically includes an application programmable microprocessor, may also provide a composite control signal of a sequence of short pulses during the "on" time of a slow blinking clock. In this embodiment, the current measuring circuit is unnecessary. If the advantage of the aforementioned embodiment, in which the subjective brightness of the flash is independent of the supply voltage, is to be retained, the signal processing circuit must be designed so that it varies the pulse duration of the short pulses as a function of the supply voltage.

To improve the efficiency of the semiconductor switch may consist of at least two parallel and driven in parallel bipolar switching transistors (claim 10), because two switching transistors require less control power because of their higher current amplification at lower currents together and have a lower saturation voltage than a single bipolar transistor, the same power switches.

As a freewheeling diode is particularly suitable because of their low forward voltage a Schottky diode (claim 11).

To avoid repercussions of the short, high current pulses on the supply or line voltage and loads of the feeders, ie the reporting line, by strong r Peak currents is expedient the semiconductor switch, a storage capacitor is connected upstream, which is connected via a series resistor to the supply voltage terminal. (Claim 12).

The slow flashing and, in the case of a composite control signal, even the sequence of short pulses corresponding to a series of individual flashes can be derived with little effort from the internal working clock of the usual microprocessor of the signal processing circuit.

Fig. 1

eine Prinzipschaltbild

Fig. 2

ein Spannungs-/Zeitdiagramm des Steuersignals in Fig. 1 und

Fig. 3

ein Schaltbild einer beispielhaften Ausführungsform.

The invention will be explained below with reference to the drawing. It shows:

Fig. 1

a schematic diagram

Fig. 2

a voltage / time diagram of the control signal in Fig. 1 and

Fig. 3

a circuit diagram of an exemplary embodiment.

The circuit of FIG. 1 is intended for installation in a hazard detector of any kind, known and therefore not shown, which contains in its housing a sensor signal processing and communication circuit comprising a microprocessor. At the terminals 1 and 2 of the circuit is the DC supply voltage or line voltage of the detector. This can vary between 42V and 8V. In series with a switching transistor Q1 are an inductance L1 and a bright, eg red LED D1, which is installed in a suitable orientation of its main beam axis in the detector or possibly in its base. Parallel to the series connection of L1 and D1 is a freewheeling diode D4. At a terminal 3 of the circuit is applied to a control signal whose time-dependent History is shown in more detail in Fig. 2, upper diagram. The control signal is supplied via a voltage divider R21, R22 to the base of a control transistor Q3. The base of Q3 is connected to the collector of Q1 via a clamp diode D2. In the emitter branch of Q3 is a current limiting resistor R23. The collector of Q3 is connected to the base of Q1. A resistor R24 between the base and the emitter of Q1 keeps it locked in the de-energized state of Q3. Between the terminals 1 and 2, a sieve member of a low-resistance series resistor and a storage capacitor, analog R1, C1 in Fig. 3, are.

According to the upper diagram in FIG. 2, the control signal at terminal 3 in FIG. 1 consists of a rapid series of rectangular pulses within a slow basic clock T1 corresponding to the desired flashing rate of the warning light of eg 1 Hz. Each basic clock comprises a (short) "ON" Time T2 of eg 30 ms and a (long) "OFF" time T3 of accordingly 970 ms. The rapid succession of rectangular pulses in the "ON" time T2 has a period t1 of about 200 μ s, a pulse duration of t2, for example 20 microseconds and accordingly, a pulse interval t3 of 180 μ s. A control signal with this illustrated curve can be generated with one of the usual and well-known timing generator circuits, which are therefore not described. In particular, if the detector supply voltage is not subject to very large fluctuations, the control signal can be generated with the course shown by appropriate wiring and programming of the message's own microprocessor.

With the rising edge of each pulse of the control signal, Q1 turns on, so that the supply voltage (minus the saturation voltage of Q1) is applied to L1, D1. Through L1 and D1 flows a current I, which rises approximately linearly up to the falling edge of the pulse. The pulse duration t2 is therefore dimensioned as a function of the characteristic values of L1 and D1 so that the falling edge of the pulse switches the switching transistor Q1 into the blocking state when the current through D1 has reached the permissible maximum value. As a result of the freewheeling diode D4, the current in the circuit consisting of L1, D1 and D4 decays exponentially. The pulse pause t3 is so dimensioned that the current has decayed to about zero before the rising edge of the next pulse switches the switching transistor Q1 again permeable. This is shown in the lower diagram in FIG. 2. Should the current not have decayed sufficiently at the end of t3, the clamping diode D2 holds the base of the control transistor Q3 at a negative potential close to that of the terminal 2, so that the control transistor Q3 is not already with the rising edge of the next pulse but only after the decay of the current in the circuit L1, D1, D4 can switch permeable.

The LED D1 emits about 100 to 200 individual flashes during each "on" time T2 of eg 20 to 40 ms of the slow flashing rate. However, the sum of these individual flashes looks like a single blink to the human eye. When using an LED with a permissible peak current of about 450 mA, and an inductance of 1 mH at a low as possible ohmic resistance of, for example 1 Ω (by which the values of the fast pulse sequence mentioned are compatible), found this (apparent) flashing signal for the Subjectively the human eye subjectively the same intensity and thus the same warning function as a continuous blinking signal with the slow flashing.

The high efficiency and accordingly the low power consumption of this circuit is further based on the fact that the power loss of the circuit because of the low on resistances of Q1, D1 and D4 and the low ohmic resistance of L1 very small and the Consumption of control power is low, unlike circuits in which the LED is operated via a series resistor, which converts most of the electrical power to dissipated heat.

Fig. 3 shows the complete circuit diagram of an improved embodiment of the circuit. About the terminal 1 and a filter element consisting of a low resistance R1 and a storage capacitor C1, the line voltage is applied to the emitters of two parallel switching transistors T1, T2 with common emitter / base resistor R2. The terminal 3 is connected to a port of a microprocessor which supplies a clock signal with the slow flashing rate of about 1 Hz and an "ON" time of about 30 ms an operational amplifier OP1 as its operating voltage of 3.3 V, for example. Whose first, non-inverting input is connected to the tap of a voltage divider R3, R4 between the operating voltage of the OP1 and the reference potential and via a positive feedback resistor R5 to the output of OP1. The output signal of OP1 is supplied via R6 to the base of a transistor T3, which plays the role of the control transistor Q3 in FIG. In its emitter branch is accordingly a current limiting resistor R7, while its collector is connected to the bases of the two parallel switching transistors T1 and T2, which play the role of the switching transistor Q1 in Fig. 1. In their common collector branch is accordingly the series connection of the inductor L1 and the LED D1, the cathode but not deviating from Fig. 1 is not directly connected via a very low-impedance current measuring resistor R8 to the reference potential and to the second, inverting input of the OP1. Parallel to the series circuit of L1, D1 and R8 is the free-wheeling diode D4, here in the form of a Schottky diode with a correspondingly low forward voltage of about 0.4 V. Between the base of T3 and the collectors of T1, T2 is analogous to Fig. 1, the clamping diode D2.

When terminal 3 is supplied with the slow clock signal which provides the operating voltage for OP1 in the "ON" time, its inverting input is at the reference potential of zero volts of terminal 2, and the non-inverting input through R3 is at a positive voltage such that the output of OP1 provides a signal close to the operating or clocked voltage that turns T3 transparent across R6, which in turn causes T1 and T2 to pass. Corresponding to the voltage divider ratio of R4 to (R5 approximately parallel R3), a reference voltage of approximately 100 mV is established at the non-inverting input of OP1. Simultaneously, the current in the series circuit L1, D1, R8 begins to increase linearly until the voltage drop across R8 reaches a positive value equal to or slightly greater than the reference voltage at the noninverting input of OP1. As a result, the output signal of OP1 tilts to zero volts, thereby blocking T3, and thus also T1 and T2. At the same time, the reference voltage at the non-inverting input of OP1 changes to the much smaller value corresponding to the now-divisional ratio of R3 to (R5 parallel to R4), i. to about 10 mV. As a result of this hysteresis OP1 generates the next pulse only when the current through R8 has decayed so far that the voltage at the inverting input of OP1 has become smaller than this low reference value at the noninverting input. However, the diode D2 blocks T3 until also D4 blocks, i. until the energy stored in L1 is (almost) completely consumed.

Therefore, the circuit does not need its own clock generator for generating the fast clock with the short period t1, but is self-oscillating.

With the selected values, namely a line voltage of 42 V, an inductance of L1 of 1 mH at a resistance of 1.12 Ω and 0.22 Ω for R8, the current through L1, D1, R8 after t2 equals about 17 μs through R8 and the reference voltage at the noninverting input of OP1 set maximum value of 450 mA, in which T1 and T2 are switched to the blocking state.

Claims (12)

Hazard detector, in particular fire or burglar alarm, which receives its supply voltage via a at least two-wire line from a central office or from a built-in battery and at least one sensitive to a physical size sensor and a signal processing circuit includes, inter alia, in the alarm state of the detector a corresponding data telegram to the Central sends, characterized in that the detector comprises a series circuit of a semiconductor switch (Q1), an inductance (L1) and a high-brightness LED (D1), that parallel to the inductance (L1) and the LED (D1) a freewheeling diode (D4 ) is that at the terminals of the series circuit, the supply voltage of the detector is applied, and that the signal processing circuit in the alarm state of the detector generates a control signal, the semiconductor switch during a slow flash clock corresponding "ON" time in a sequence of short pulses transmissive switches and locks , Hazard detector according to claim 1, characterized in that the flash clock has a frequency in the range of 0.5 to 3 Hz and an "ON" time in the range of 30 ms. Hazard detector according to claim 1 or 2, characterized in that within the sequence of short pulses, the pulse duration between 5 microseconds and 50 microseconds and the pulse / pause ratio between about 1: 4 and about 1:10 are. Hazard detector according to one of claims 1 to 3, characterized characterized in that connected to the connection point between the semiconductor switch (Q1; T1, T2) and the inductor (L1) is a switching element (D2) which holds the semiconductor switch (Q1; T1, T2) in the off state until the current in the one of the semiconductor switches (Q1; Inductance (L1), the LED (D1) and the freewheeling diode (D4) comprising circuit has decayed. A danger detector according to claim 4, characterized in that the control signal switches the semiconductor switch (Q1; T1, T2) via a control transistor (Q3; T3) and that the switching element which switches the semiconductor switch during the decay of the current in which the inductance, the LED and the freewheeling diode comprising circuit in the off state, consisting of a diode (D2), which is connected as a clamping diode between the base of the control transistor (Q3, T3) and the connection point between the semiconductor switch (Q1, T1, T2) and the inductance (L1) , Hazard detector according to one of Claims 1 to 5, characterized in that a current measuring circuit (OP1, R8) respectively blocks the semiconducting switch (T1, T2) which is permeable, as soon as the current through the LED (D1) has reached a predetermined maximum value. Hazard detector according to claim 6, characterized in that the current measuring circuit comprises a measuring resistor (R8) in series with the LED (D1) and a comparator (OP1) that at the first input of the comparator, a reference voltage and at the second input to the measuring resistor (R8) tapped, current-proportional voltage is applied, and that the output signal of the comparator provides the sequence of short pulses that switch the semiconductor switch (T1, T2). Hazard detector according to claim 6 or 7, characterized in that the signal processing circuit supplies as a control signal only the flash cycle and this is applied to the operating voltage terminal of the comparator (OP1). Hazard detector according to claim 7 or 8, characterized in that the output of the comparator (OP1) via a positive feedback resistor (R5) is connected to the first input. Hazard detector according to one of claims 1 to 9, characterized in that the semiconductor switch consists of at least two parallel and parallel controlled switching transistors (T1, T2). Hazard detector according to one of claims 1 to 10, characterized in that the freewheeling diode is a Schottky diode (D4). Hazard detector according to one of claims 1 to 11, characterized in that the semiconductor switch, a storage capacitor (C1) is connected upstream, which is connected via a series resistor (R1) to the supply voltage terminal (1).

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