Power supply device in fire alarm systems

Abstract: In a fire alarm system, control means (PSW1, PSW2) are provided which permit power supply to certain power consuming parts during predetermined operating times only, e.g. of the reference voltage supply to the comparators (CM) of fire detectors during the detecting time only, or power supply to switch means (DIP) to set their self-address in the terminals only at the time of switching of the power supply or of resetting.

Description: The present invention concerns a power supply device in a fire alarm system employing a polling system having terminals and/or repeaters connected to a control panel by supply lines and to which fire detectors and/or controlled apparatus to detect an abnormality such as a fire or an improper operation status of controlled apparatus are connected. Examples of controlled apparatus are a fire door, a smoke damper, or the like. Known fire alarm systems maintain their functions for several hours even in the case of power failure, and sound emergency bells for a predetermined length of time if a fire should break out even during the time of power failure. For this purpose, the control panels are equipped with emergency power supplies, e.g. with rechargeable batteries. But, the comparators in such fire alarm systems consume comparatively much electricity. Among others, the current consumption at the reference voltage supply source which supplies the reference voltage needed for the judgement or check whether or not an abnormality such as a fire has occured or a controlled apparatus such as a fire door is in the properly controlled state is so large that the power consumption of the fire alarm system as a whole is increased considerably. Further, the longer the power supply/signal lines in the system are extended, the greater the influence of power consumption becomes. Moreover, in a fire alarm system employing the polling system, each of the terminals such as a fire detector or a repeater is equipped with a dip-switch, which is used for setting a predetermined value indication the self-address and/or the kind of the terminal. When a repeater is called from the control panel, the address transmitted by the control panel is checked with the self-address, and if they match, the repeater performs the operation in accordance with the control command from the control panel. In such a system, a current flows through the dip-switch circuit at all times, enabling the address from the control panel to be checked with the self-address, and/or kind of the terminal to be discriminated. The circuit for checking the self-addresses and/or discriminating the kind of the terminal consumes much electricity, and consequently, the fire alarm system as a whole is also consuming much electricity. Document GB-A-2149547 discloses a polling type surveillance control apparatus where upon coincidence of an address signal and of a self-address of a detector a multivibrator is triggered to provide power for a predetermined time to the detector. Document US-A-4030095 discloses an alarm system where the sensing circuits are energized sequentially from a pulse source means and generate an alarm indication only during the time of its energizing pulse. It is an object of the present invention to eliminate the above-mentioned drawbacks of prior art fire alarm systems and to provide a fire alarm system in which not only the electricity consumed by the detectors is lessened, but the power consumption of the fire alarm system as a whole can be reduced. Also, it is an object of the present invention to reduce the power consumption in the circuit which checks the address from the control panel with the self-address and/or the circuit which discriminates the kind of the terminal, during polling. A further object is to improve the signal processing speed and to shorten the polling time. The invention by which these objects are achieved is characterized in that the terminals and/or repeaters are equipped with comparators receiving at their inputs a signal from the detectors and/or controlled apparatus and a reference voltage to detect an abnormality and to transmit an information to the contral panel, and with a power supply control means which permits application of the reference voltage to the comparators or a voltage to further predetermined parts of the terminals or repeaters only during their operating times. In a further improvement, in a fire alarm system having switch means to set their self-addresses and/ or kinds in the terminals and with control means to read the self-addresses from the switch means and to write them in a RAM, a power supply control means is provided which supplies power to the said switch means at the initial time only, i.e. at the time of switching on of the the power supply and/or of resetting. The invention is described in more detail with reference to preferred embodiments illustrated in the attached figures. Fig. 1 is a block diagram of a fire alarm system, Fig. 2 is a circuit diagram showing principal parts of a fire alarm system, Fig. 3 is a circuit diagram of a fire alarm system of the polling type, and Fig. 4 is a flowchart showing the operation of the above embodiments of fire alarm systems. In the figures, the following references are used: RE control panel T1 - TN repeaters PSW1 - PSW2 power supply control means CM comparator TVG reference voltage supply source DE fire detector DIP dip-switch RAM1 - RAM2 random access memories ROM1 read-only memory IF1 - IF6 interfaces MPU microprocessor unit In the embodiment of a fire alarm system shown in Fig. 1, plural repeaters T1 - TN as terminals are connected to a control panel RE, for example, by a pair of power supply/signal lines L, and plural fire detectors DE are connected to the repeater T1. While in Fig. 1 the repeater T1 alone is shown in detail, the other repeaters T2 - TN are the same as repeater T1. The repeater T1 is equipped with a microprocessor MPU, a ROM1 containing programs related to the flowchart shown in Fig. 3, a RAM1 used as work area, a RAM2 storing the self-address of the repeater T1, a comparator CM for fire signal discrimination to detect an abnormality such as fire, a reference voltage supply source TVG supplying a reference voltage to the comparator CM, and a power supply control means PSW1 controlling the reference voltage supply to the comparator CM. The repeater T1 is further equipped with a dip-switch DIP as switch means to set the self-address of the repeater T1, a power supply means PSW2 to supply power to the dip-switch only at the initial time, a transmission unit TX equipped with a parallel/serial converter and a transmission circuit, and a receiver unit RX equipped with a receiving circuit and a serial/parallel conversion circuit. Fig. 2 and 3 are circuit diagrams which concretely show principal parts of the above embodiment. In Fig. 2 a signal from the fire detector DE is transmitted to the (-)input terminal of the comparator CM via a resistor R2, and a reference voltage from the reference voltage supply source TVG is supplied to the (+)input terminal of the comparator CM. The reference supply source TVG generates the reference voltage by dividing the power supply voltage by means of resistors R3 and R4, and a transistor TR is connected between the power supply and the reference voltage supply source TVG. The power supply control means PSW1 comprises the transistor TR and an inverter I which reverses the signal from IF2. The IF2 circuit generates a high output during the anormality (such as fire) detecting time only. Upon generation of the high output by the IF2, the inverter I outputs a low signal which causes the transistor TR to switch on. The reference voltage supply source TVG is an example of means to supply a reference voltage to the comparator which detects an abnormality such as fire. The power supply control means PSW1 is an example of means which allows the reference voltage supply to the comparator during the abnormality (such as fire) detecting time only. In Fig. 3 each point between each contact of the dip-switch DIP and each resistor is connected with the input terminal of the IF3, and a transistor TR2 is connected between each of the above contacts and the earth. The power supply means PSW2 is equipped with said transistor TR2 and an amplifier AMP, and is connected with the output of the IF4. The power supply means PSW2 is an example of means to supply power to the dip-switch DIP at the initial time, i.e. at the time of the switching on of the power supply or the resetting. The IF3 is an example of control means to read the self-address from the dip-switch DIP at the initial time and to write it in the RAM. The operation of the above embodiments is described hereinafter with reference to the flowchart shown in Fig. 4. When the power is applied from the control panel RE, or a reset command is received for fire resetting operation or the power supply is temporarily interrupted, the initial processing such as clearing the RAM1 and the RAM2 and setting the initial value is performed (S1). After setting the ON signal on the IF4 (S2), the self-address of the repeater T1 is read from the dip-switch DIP (S3). This self-address has previously been set at the time of mounting the dip-switch DIP. As the ON signal is set on the IF4, the ON signal is applied to the base of the transistor TR2 through the amplifier AMP. With the transistor TR2 switched on, the power supply is applied to the dip-switch DIP, and a signal corresponding to the content (self-address) set on the dip-switch DIP is transmitted to the IF3, through which the data which has been read is written in the RAM2. Upon completion of the reading of the self-address (S4), the OFF signal is set on the IF4 (S5). Then, the transistor TR2 is switched off, and no current flows therefrom to the dip-switch DIP. Therefore, no useless current flows to the dip-switch DIP after the OFF signal has been set on the IF4. In other words, a current flows to the dip-switch only at the initial time, and therefore there is no waste of power. When polling is performed from the control panel RE, and the polling address and the self-address stored in the RAM2 have matched (S6), the ON signal is set on the IF2 (S7). Then, a result of comparision by the comparator CM, for example the presence or absence of a fire signal is held in the IF1 (S8). By using the data held in the IF1, the OFF signal is set on the IF2 (S9). In other words, the IF2 outputs a high signal only when polling is performed from the control panel RE. Therefore, only at this time the transistor TR switches on, and the power supply control means PSW1 becomes conductive, allowing a current to flow to the reference voltage supply source TVG and the reference voltage to be applied to the (+)input terminal of the comparator CM. Upon completion of reading the data from the comparator CM, the transistor TR switches off, interrupting the current flow to the reference voltage supply source TVG. Therefore, no power is wasted at the reference voltage supply source TVG. In case a "fire" decision has been made on the basis of the output signal from the comparator (S10), a fire signal is set on the IF5 (S11), and fire information is transmitted to the control panel RE (S12). In the above embodiment, the comparator CM, the power supply control means PSW1, the power supply means PSW2, and the elements IF1, IF2, and IF3 may be replaced by a microcomputer. Also, a timer means may be installed as the power supply control means PSW1 so that the reference voltage can be supplied to the comparator CM based on the output of the timer means, i.e. while the timer means is generating an output. Further, the power supply means may be located at the position marked "a" in Fig. 3, namely between the resistor connected in series with the dip-switch DIP and the power supply. While the above described embodiment illustrates a case with a supervisory repeater to which fire detectors are connected, the same applies to cases where the terminal is a repeater to which controlled apparatus such as fire doors and/or smoke dampers are connected and which is equipped with a comparator to detect an operating signal (operating status) of the controlled apparatus, or the terminal is an abnormality detector such as a fire detector equipped with a comparator to judge whether the fire phenomenon has exceeded a certain predetermined level or not. The same applies also to the case with switch means provided on the terminal to set kinds of supervisory or control repeaters, analog or ON/OFF type fire detectors. The present invention has the effect to reduce the power consumption at the reference voltage supply source which supplies a reference voltage to the comparator of a fire detector. Furthermore, it has the effect to reduce the power consumption in the circuit which checks the address from the control panel with the self-address and/or sets and discriminates the kind of the repeater. Further, it has the effect to improve the signal processing speed and to shorten, in the case of a polling system, the polling time because the reading of the address and kind from the switch means are performed only at the initial time, i.e. at the time of switching on of the power supply and of resetting, and the operations are carried out with memories of the RAM thereafter.

Claims: A power supply device in a fire alarm system employing a polling system having terminals (T1 - TN) and/or repeaters connected to a control panel (RE) by supply lines (L) and to which fire detectors (DE) and/or controlled apparatus to detect an abnormality such as fire or an improper operation status of a controlled apparatus are connected, characterized in that the terminals and/or repeaters (T1 - TN) are equipped with comparators (CM) receiving at their inputs a signal from the detectors (DE) and/or controlled apparatus and a reference voltage (TVG) to detect an abnormality and to transmit an information to the control panel (RE), and with a power supply control means (PSW1, PSW2) which permits application of the reference voltage to the comparators (CM) or voltage to further predetermined parts (TVG, DIP) of the terminals or repeaters (T1 - TN) only during their operating times. A device according to claim 1, characterized in that the terminals (T1 - TN) and/or repeaters comprise switch means (DIP) to set their self-addresses and/or kinds of the terminal, and power supply control means (PSW2) designed to supply power to said switch means (DIP) only during the initial time of switching on of the power supply and/or of a resetting. A device according to claim 2, characterized in that the power supply control means (PSW2) is designed to supply power to control means (IF3) to read the self-addresses from the switch means (DIP) and to store them in a RAM during said initial time only. A device according to one of claims 1 - 3, characterized in that the power supply control means (PSW1) is designed to permit the reference voltage supply to the comparators (CM) when the terminals and/or repeaters (T1 - TN) are called up from the control panel (RE). A device according to one of claims 1 - 3, characterized in that the power supply control means (PSW1) is equipped with timer means to permit the reference voltage supply to the comparators (CM) in dependance of the output of said timer means.

Inventors: SHUTOKU RJUJI, TAKAHASHI KAORU, TSUMUJI AKIO, SHUTOKU, RJUJI, TAKAHASHI, KAORU, TSUMUJI, AKIO
Applicants: NOHMI BOSAI LTD, NOHMI BOSAI LTD.
Application year: 1990
Main classification: G08B17
IPC codes: G08B17