Background
The alarm system is a product inseparable from social production and life, usually reminds or warns people to take certain action in the forms of sound, light and the like, and is often applied to the fields of system failure, safety precaution, transportation, medical treatment and rescue, emergency relief, induction detection and the like. Such as a fire alarm system, a gas alarm system, etc. commonly found in life.
Alarm systems typically include a field side and a control side. Sensors in the field side are used to sense the presence of a hazard signal, such as sensing smoke, gas, etc. Upon sensing the presence of a hazard signal, the sensor immediately signals the control side. After receiving the signal, the control side provides electric energy to the warning device at the site side to make the warning device give an alarm in the forms of sound, light and the like. The field side and the control side are typically spaced a distance apart. For example, for a fire alarm system, the control side is typically located in the central control room of the building, while the field side is located in various rooms within the building. The control side and the field side are usually connected by a transmission line such as a cable, and signals and electric power are transmitted therebetween. This transmission line is also called a "fieldbus line".
The field line is used for transmitting signals and electric energy, so that in the non-alarm stage, the control side can continuously monitor whether the field line is open or short-circuited or not, and the alarm system can work normally in the alarm stage. But in addition to open and short circuit faults, the field lines may also be in a "partially open" or "partially short" state.
A partial open circuit refers to a state where the field line resistance is increased but not yet fully open, and a partial short circuit refers to a state where the electrical isolation between two or more field lines is degraded but not yet fully short-circuited. In addition, a full open and a full short can be considered as extreme special cases of a partial open and a partial short. There are many environmental factors as well as human factors that can cause partial open and partial short circuits to occur. For example, in a high humidity environment, contacts at the nodes where the field lines are connected to the alarm system are susceptible to corrosion, increasing the node resistance, resulting in a partially open circuit condition. For example, in drilling construction in a building, the structure of the line of the present invention is easily damaged to be in a virtual lap joint state, resulting in a partially open or partially short circuit state.
Such a "partially open" or "partially short" condition can have a significant effect on the operation of the presence line, and in particular the presence line providing power to the alarm device, and thus can cause the alarm system to malfunction. The warning device, such as a speaker, can be started only with a certain amount of electric energy, and if a partial open circuit occurs in a circuit of the warning system, a large voltage is consumed at the position of the partial open circuit, so that the speaker cannot obtain a sufficient voltage, and cannot be normally started when warning is needed. If there is a partial short circuit in the alarm system, the speaker will not be able to obtain enough current, and the alarm will fail. Therefore, it is necessary to detect the occurrence of a fault before a complete short circuit or a complete open circuit, i.e., at the stage of a partial open circuit or a partial short circuit, so as to avoid the occurrence of the alarm failure.
Currently, alarm systems typically employ End of Line (EOL) modules to detect the occurrence of partial open and partial short faults. FIG. 1 shows the basic structure of a fire alarm system with an EOL module consisting of a resistor connected to the alarm system circuitry through pins T1 and T2. The fire alarm system includes a control side C and a field side F. As shown in fig. 1, the EOL module is connected in parallel with the speakers h, i, j and in series with resistors R2 and R3, and after series is provided with a voltage V2. At this time, the current in the EOL module flows from T2 to T1, and the speakers h, i, j are in the non-operating state due to the opposite polarity of the voltage V2, and do not consume current. The control port MON _ CTRL of switch SW1 is used to control the voltage applied across the EOL module by controlling switch SW 1. When SW1 is turned on, the voltage across the EOL module is V2, and when SW1 is turned off, the voltage across the EOL module is V2-VREF 1.
The alarm system circuit of fig. 1 is in monitor modeAt this time, the control side C monitors whether or not a partial open or a partial short fault has occurred by monitoring the magnitude of the field side F resistance. When partially shorted, the resistance on the field side decreases, and when partially open, the resistance on the field side increases. Specifically, as shown in fig. 1, the control side measures the resistance R on the field side by measuring the voltages VREF1 and VREF2 across the extraction resistor R2FThe conversion relation is RF=[(V2-VREF1)/(VREF1-VREF2)]*R2。
When a fire alarm is sensed by a sensor (not shown in fig. 1), a signal is sent to the control port DIR _ CTRL of the double-pole double-throw switch N1 on the control side C, so that the double-pole double-throw switch N1 is switched. The circuit of fig. 1 is now changed to the configuration shown in fig. 2, when the fire alarm system is in alarm mode, the EOL module and the speakers h, i, j are supplied with voltage from V1, the current in the EOL flows in the direction from T1 to T2, and the speaker sounds an alarm.
Because the loudspeaker is connected with the EOL module in parallel during alarming, the resistance value of a resistor in the EOL module is required to be very high (generally not less than 1k omega) so as to avoid shunting the loudspeaker and prevent the phenomenon that the loudspeaker cannot be started due to insufficient current. But for a high value resistor, the tolerance of the resistance value is large. For example, for a 1k Ω resistor, the tolerance of the resistance value is usually within ± 1%, i.e., ± 10 Ω. Therefore, if the variation in resistance due to partial open and short circuits is small, it is easily "drowned" within the tolerance of the resistance of the resistors in the EOL module, resulting in failure to detect partial open and short faults. Therefore, it is difficult to accurately detect the occurrence of the partial open and partial short faults using the resistor having an excessively high resistance value as the EOL module, and the partial open and partial short faults are often detected after having been deteriorated to some extent. In addition, since the resistance tolerance of the high resistance resistor is large, if it is used as an EOL module, it needs to be calibrated before installation. Even after calibration, the resistance value drift caused by temperature drift and the like is large, and the requirement of accurate detection cannot be met.
Disclosure of Invention
The invention aims to provide an EOL module for an alarm system, which can accurately detect partial open circuit or partial short circuit faults when the faults just start to occur.
The invention provides a line end module for an alarm system, comprising: a first terminal end and a second terminal end; a switch unit and a resistor connected in series between the first and second terminal ends; a voltage polarity sensing circuit coupled between the first and second wire ends for sensing the polarity of the voltage between the first and second wire ends and controlling the switching unit to be on when the sensed polarity indicates that the alarm system is in the monitoring mode and to be off when the sensed polarity indicates that the alarm system is in the alarm mode.
The resistance of the resistors in such EOL modules may be set smaller. Therefore, the tiny resistance value fluctuation caused by the initial occurrence period of the partial open circuit and the partial short circuit can be detected, and the tiny resistance value fluctuation cannot be submerged in the resistance value fluctuation range of the resistor, so that the field line can be detected more accurately, and the field line can be detected accurately when the partial open circuit or the partial short circuit fault just starts to occur.
According to the end of line module provided by the invention, the voltage polarity sensing circuit comprises a first switching device and a control unit, and the switching unit comprises a second switching device, wherein the first switching device and the second switching device are switched under the control of the control unit in a linkage manner.
According to the line end module provided by the invention, the control unit in the voltage polarity sensing circuit determines the sensed voltage polarity according to the current direction flowing through the control unit.
According to the line end module provided by the invention, the voltage polarity sensing circuit further comprises a first unidirectional conductive element and a second unidirectional conductive element, wherein the first switching device can enable one of the first and second unidirectional conductive elements and the control unit to be connected in series between the first and second line ends, and the directions of the first and second unidirectional conductive elements are opposite. According to the line end module provided by the invention, any one of the first one-way conduction element and the second one-way conduction element is a diode.
According to the line end module provided by the invention, a first charge storage device connected with the first switching device in parallel is arranged between the first unidirectional conducting element and the control unit, and a second charge storage device connected with the first switching device in parallel is arranged between the second unidirectional conducting element and the control unit. According to the line end module provided by the invention, any one of the first charge storage device and the second charge storage device is a capacitor.
According to the line end module provided by the invention, the first switching device, the second switching device and the control unit are realized by latching relays. According to the line end module provided by the invention, the latching relay is an electromagnetic latching relay, and the control unit is an excitation coil.
According to the end of line module provided by the invention, the latching relay is a double-pole double-throw relay. According to the invention, the line end module is provided, wherein the threshold voltage of the operation of the exciting coil of the latching relay is lower than the operation voltage between the first terminal and the second terminal of the alarm system in the alarm mode. According to the invention, the line end module is provided, wherein the monitoring voltage of the alarm system in the monitoring mode is lower than the threshold voltage of the excitation coil of the latching relay.
The invention also provides a control method for the alarm system, wherein one or more warning devices are connected in parallel on two lines led out from the control side of the alarm system, and the far ends of the two lines are connected with a line tail end module, the control method comprises the following steps: when the alarm system is in an alarm mode, applying a first voltage to the line to drive the alarm device to act, and simultaneously disconnecting the line end module from the line; applying a second voltage to the line while the alarm system is in a monitoring mode to cause the end of line module to couple into a monitoring loop that includes the line; applying a third voltage to the line to detect if a fault has occurred on the line after the alarm system is in a monitoring mode and the end of line module has been coupled into the monitoring loop; the polarity of the first voltage is opposite to that of the second voltage and the third voltage, and the third voltage is lower than the second voltage.
According to the control method provided by the present invention, further comprising a step of initializing the line end module, the initializing step comprising: applying the first voltage to the line to initialize the end of line module to its disconnection from the line; applying a third voltage, lower than the first voltage, to the end of line module to monitor whether a first fault occurs in a line connected to the alarm system. Wherein the first fault includes a partial short circuit and a connection error.
According to the control method provided by the present invention, the initialization step further includes: applying the second voltage to the line such that the end of line module is coupled into a monitoring loop including the line; applying the third voltage lower than the second voltage to the line to detect whether a second fault occurs in the line of the alarm system. Wherein preferably said second fault comprises a partial open circuit.
According to the control method provided by the present invention, the initialization step further includes: measuring a resistance value of the line connected to a control side of the alarm system in a case where the third voltage is applied to the line; and recording the measured resistance value as a detection baseline for judging partial open circuit and partial short circuit.
The present invention also provides a controller for an alarm system, wherein one or more warning devices are connected in parallel to two lines led out from the controller of the alarm system, and a line end module is connected to distal ends of the two lines, the controller comprising: the alarm unit is used for applying a first voltage to the line to drive the warning device to act and simultaneously disconnecting the line end module from the line when the alarm system is in an alarm mode; a monitoring mode switching unit for applying a second voltage to the line when the alarm system is in a monitoring mode so that the end of line module is coupled into a monitoring loop including the line; a monitoring unit that applies a third voltage to the line to detect whether a fault has occurred on the line after the alarm system is in a monitoring mode and the end of line module has been coupled into the monitoring loop; the polarity of the first voltage is opposite to that of the second voltage and the third voltage, and the third voltage is lower than the second voltage.
According to the controller provided by the invention, the controller further comprises an initialization unit which comprises: a reset subunit for applying the first voltage to the line to initialize the end of line module to be disconnected from the line; a detection subunit for applying the third voltage to the end-of-line module to monitor whether a first fault occurs in a line connected to the alarm system.
According to the controller provided by the present invention, wherein the initialization unit further includes: a switching subunit for applying the second voltage to the line such that the end of line module is coupled into a monitoring loop including the line; the detection subunit applies the third voltage to the line to detect whether a second fault occurs in the line of the alarm system.
According to the controller provided by the present invention, wherein the initialization unit further includes: a measuring subunit for measuring a resistance value of the line connected to a control side of the alarm system in a case where the third voltage is applied to the line; and the recording subunit is used for recording the measured resistance value as a detection baseline for judging partial open circuit and partial short circuit.
According to the controller provided by the invention, the first fault comprises a partial short circuit and a connection error, or the second fault comprises a partial open circuit.
The EOL module for the alarm system can be accurately detected when a partial open circuit or a partial short circuit fault just starts to occur, and calibration before installation is not needed.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings.
According to one embodiment of the invention, an EOL module for an alarm system is provided, the basic circuit structure of which is shown in fig. 3. The pins T1 and T2 are used for being connected to an alarm system circuit, so that the EOL module is connected with an alarm device such as a loudspeaker in parallel. A switch unit S11 and a resistor R1 are connected in series between the pins T1 and T2. The EOL module further has a voltage polarity sensing circuit P for sensing the polarity of the voltage between the pins T1 and T2 and controlling the switching unit S11 to be turned on and off according to the sensed polarity.
When the alarm system is in the monitoring mode, the voltage V of the T2 pinT2Voltage V higher than pin T1T1The voltage polarity sensing circuit P turns on the switching unit S11, connects the resistor R1 to the present field line for measurement of the resistance of the present field line, thereby determining whether a partial open and partial short fault has occurred. When the alarm system is in the alarm mode, VT2Below VT1At this time, the voltage polarity sensing circuit P turns off the switching unit S11 to disconnect the resistor R1 from the present field line.
In the EOL module provided in the present invention, the switch unit S11 is controlled by the voltage polarity sensing circuit P. When the alarm system is in the alarm mode, the voltage polarity sensing circuit P disconnects the resistor R1 from the alarm system circuit. Therefore, the resistor R1 does not shunt the alarm device (e.g., speaker, etc.), so the resistance of the resistor R1 in the EOL module of the present invention can be set smaller than the single resistor EOL module of the background art. Therefore, the slight fluctuation of the resistance value caused in the early stage of the occurrence of the partial open circuit and the partial short circuit can be detected without being submerged in the fluctuation range of the resistance value of the resistor R1. Therefore, the EOL provided by the invention can realize more accurate detection of field lines, and can accurately detect partial open circuit or partial short circuit faults when the faults just start to occur.
According to yet another embodiment of the present invention, an EOL module for an alarm system is provided, the basic circuit structure of which is shown in fig. 4. The pins T1 and T2 are used for being connected to an alarm system circuit, so that the EOL module is connected with an alarm device such as a loudspeaker in parallel. The EOL module provided in this embodiment employs a double-pole double-throw electromagnetic latching relay K11. As shown in fig. 4, the latch relay K11 includes field coil pins 1, 8, and further includes first and second sets of switch pins 2, 3, 4, 5, 6, 7. Wherein a first set of switch pins 2, 3, 4 together form a first switching means, wherein pin 3 is switchable between pins 2 and 4. Wherein the second set of switch pins 5, 6, 7 together form a second switching means, wherein pin 6 is switchable between pins 5 and 7, and the switching of pin 3 and pin 6 is ganged. To more clearly illustrate the topology of the overall circuit, the various pins of the latching relay K11 are divided into three parts in fig. 4. The latching relay K11 has a first position and a second position. In the first position (monitoring mode), pins 6 and 7 are in communication and pins 3 and 2 are in communication (i.e., the positions shown in fig. 4). In the second position (alarm mode), pins 6 and 5 are in communication and pins 3 and 4 are in communication.
Depending on the nature of the latching relay, when latching relay K11 is in the first position as shown in FIG. 4, if voltage V is applied to field coil pin 1k1Higher than the voltage V applied to pin 8k8And V isk1-Vk8Greater than a certain motion threshold Vth(9V in this embodiment) the latching relay K11 will switch from the first position to the second position. If Vk1-Vk8Below the action threshold VthThe latching relay K11 will maintain the current first position. Correspondingly, when latch relay K11 is in the second position, voltage V is applied to field coil pin 8k8Higher than the voltage V applied to pin 1k1And V isk8-Vk1Greater than a certain motion threshold Vth(9V in this embodiment), the latching relay K11 will switch from the second position to the first position. If Vk8-Vk1Below the action threshold VthThe latching relay K11 will maintain the current second position.
In the EOL module in this embodiment, one set of switch pins 5, 6, 7 in the latch relay K11 is made to control when the resistor R11 is switched into the T1-T2 loop. The exciter coil pins 1, 8 and the other set of switch pins 2, 3, 4 are made part of a voltage polarity sensing circuit P. Therefore, the double-pole double-throw latch relay K11 is utilized to have the linked pin switching and latching property, and the position switching of the latch relay is controlled by controlling the polarity and the magnitude of the voltage on the exciting coil pin, so that the resistor R11 can be disconnected from the alarm system circuit when the alarm system is in the alarm mode. Meanwhile, since the diode V13 is in the reverse state, the voltage polarity sensing circuit P does not consume current in the alarm mode, and the exciting coil no longer bears a high voltage.
FIG. 4 shows the circuit configuration of the EOL module when the latch relay K11 is in the first position (i.e., R11 is connected to the T1-T2 terminals in the monitor mode). The Transient Voltage Suppressor (TVS) V16 is connected between the pins T1 and T2 and is used for protecting an EOL module from line-to-line surge impact. Reverse series zener diodes V14 and V15 are connected in parallel across the excitation coil pins 1, 8 of the latch relay K11 for protecting the excitation coil of the latch relay K11 from overvoltage. When pins 2 and 3 of the latch relay K11 are connected, the diode V12 and the exciting coil of the latch relay K11 are connected in series between pins T1 and T2. When the pins 4 and 3 of the latch relay K11 are connected, the diode V13 and the exciting coil of the latch relay K11 are connected in series between the pins T1 and T2. The diode V12 and the diode V13 are connected in opposite directions in the circuit. The resistor R11 is connected in series with a set of switch pins 5, 6, 7 of the latch relay K11 between the pins T1, T2.
When the alarm system is in the monitoring mode, VT2Higher than VT1. The field coil pins 1 and 8 of latch relay K11 are non-conductive due to the reversal of diode V12. Between switch pins 6 and 7And is turned on to connect the resistor R11 between the terminals T1 and T2, thereby achieving monitoring of the line condition. Meanwhile, since the diode V12 is in the reverse state, the voltage polarity sensing circuit P does not consume current in the monitoring mode.
When the alarm system needs to send out an alarm signal, VT2Below VT1，VT1-VT2Greater than VK1-VK8At this time, the diode V12 is turned on, and the voltage difference between the field coil pins 1 and 8 of the latch relay K11 is made larger than the operation threshold VthThereby causing latch relay K11 to switch from the first position to the second position as shown in fig. 5. At this time, the switch pin 6 of the latch relay is communicated with the switch pin 5, and the switch pin 3 is communicated with the switch pin 4. At this point, the field coil pins 1 and 8 of latch relay K11 are no longer subjected to high voltage due to the reversal of diode V13. An open circuit is established between switch pins 6 and 7 and the open circuit position is latched thereby disconnecting resistor R11 from the alarm system circuit.
In the EOL module of this embodiment, a capacitor C11 is connected in parallel between switch pins 2 and 3 of the latch relay K11, and a capacitor C12 is connected in parallel between switch pins 3 and 4. The capacitors C11 and C12 function to maintain the continuity of the current in the excitation coil of the latch relay K11 during the switching of the latch relay K11 between the first position and the second position. For example, at the moment pin 3 is disconnected from pin 2 and switched to pin 4, if capacitor C11 is not present, the current in the field coil of latch relay K11 is suddenly interrupted, and at this time, the field coil may not yet generate enough force to complete the switching from pin 3 to pin 4, and at this time, pin 3 is again connected to pin 2, and finally pin 3 oscillates between pins 2 and 4. In this embodiment, a capacitor C11 is connected in parallel between the switch pins 2 and 3 to solve this problem. At the instant pin 3 is disconnected from pin 2, capacitor C11 is charged, thereby maintaining the continuity of the current in the field coil of latch relay K11 and creating a continuous and sufficient force to complete the switch from pin 3 to pin 4. Similarly, having capacitor C12 connected in parallel between switch pins 4 and 3 prevents pin 3 from oscillating between pins 2 and 4 when latching relay K11 switches from the second position to the first position.
In this embodiment, R11 is 68 Ω, for example, and the exciting coil resistance of the latch relay is 1.44k Ω, for example. R13 is, for example, a current limiting resistor of 390 Ω. The resistance values of these resistors are not restrictive, and those skilled in the art can make various changes according to actual needs.
In the EOL module provided in this embodiment, diodes (V12, V13), a resistor R13, a capacitor (C11, C12), an excitation coil in the latch relay K11, and a first switching device (including switch pins 2, 3, 4) are used to form a voltage polarity sensing circuit, and a second switching device (including switch pins 5, 6, 7) for controlling the latch relay K11, so that the resistor R11 is disconnected from or connected to the alarm system circuit. When the alarm system is in the alarm mode, the voltage polarity sensing circuit may disconnect the resistor R11 from the alarm system circuitry. Therefore, the resistor R11 does not shunt the alarm device (e.g., speaker, etc.), so the resistance of the resistor R11 in the EOL module of the present embodiment can be set smaller than that of the related art single-resistor EOL module. Therefore, the slight fluctuation of the resistance value caused by the initial occurrence of the partial open circuit and the partial short circuit can be detected without being submerged in the tolerance range of the resistance value of the resistor R11.
In addition, the voltage polarity sensing circuit in this embodiment is not turned on in the monitoring mode and the alarm mode, and does not consume electric energy, so that the accuracy of field line resistance measurement is not affected in the detection mode, and the activation of an alarm device (such as a speaker) is not affected in the alarm mode.
According to another embodiment of the present invention, there is also provided an initialization method of the EOL module, and fig. 6 shows a timing chart of the initialization method. The initialization method provided by the embodiment comprises the following steps:
1) initialization of the latch relay K11 (S1).
The initial position of latch relay K11 prior to its installation may be unknown due to shipping, external vibration, etc. After installation of the EOL module, the position of the latch relay K11 needs to be initialized. Specifically, a relatively large voltage, for example, 28V (as shown in FIG. 6), with a polarity of V, is applied between the pins T1 and T2 of the EOL moduleT1Higher than VT2. In this way, the latch relay K11 can be initialized to the second position regardless of whether its initial position is the first position (for monitor mode) or the second position (for alarm mode). This step is for example about 5 milliseconds in duration.
2) Detection of partial short circuit and connection error (S2).
A lower voltage, e.g., 5V, is applied between pins T1 and T2 of the EOL module for 1 second (as shown in FIG. 6) with a voltage polarity of VT1Below VT2，VT2-VT1=5V (less than action threshold V)th= 9V), the latch relay K11 remains in the second position. At this time, R11 is turned off, and only the diode V13 and the exciting coil of the latch relay K11 are connected in series to the alarm system circuit. Since the resistance of the live line is much smaller than the resistance of the excitation coil, the resistance of the live side detected by the control terminal should be approximately equal to the resistance of the excitation coil of latching relay K11 (e.g., 1.44K Ω in the present embodiment), otherwise a partial short-circuit fault or connection error in the live line would be indicated. If the partial short-circuit fault or the connection error occurs, an error is reported, and if the partial short-circuit fault or the connection error does not occur, the next step is carried out.
3) The position of the latch relay K11 is switched to the first position (S3).
A voltage of, for example, 12V is applied between pins T1 and T2 of the EOL module for 5 milliseconds (as shown in FIG. 6), with a voltage polarity of VT1Below VT2，VT2-VT1=12V (greater than action threshold V)th= 9V), the position of the latch relay K11 is switched to the first position. At this time, the monitoring mode is switched, and only the resistor R11 is connected to the circuit of the alarm system T1-T2.
4) Detection of a partial open circuit (S4).
A voltage of 5V is applied between the T1 and T2 pins of the EOL module for 1 second (as shown in FIG. 6), with a voltage polarity of VT1Below VT2，VT2-VT1=5V (less than operation threshold Vth = 9V). The control end judges whether a partial open fault occurs on the field side by measuring the resistance of the current field line. If the partial open circuit fault occurs, an error is reported, and if the partial open circuit fault does not occur, the next step is carried out.
5) A detected baseline of the field line resistance is recorded (S5).
A voltage of 5V is applied between the T1 and T2 pins of the EOL module for 1 second (as shown in FIG. 6), with a voltage polarity of VT1Below VT2，VT2-VT1=5V (less than action threshold V)th= 9V). In step 2) partial short circuits and connection errors have been excluded and in step 4) partial open circuits have been excluded. Therefore, the field line at this time can be considered to be in a normal state. In step 5), the control side records the resistance value when the present line is in a normal state as a detection baseline for subsequently judging whether the current line is partially open or partially short.
6) Measurement of the line resistance value and failure judgment (S6).
A voltage of 5V is applied between the T1 and T2 pins of the EOL module for 1 second (as shown in FIG. 6), with a voltage polarity of VT1Below VT2，VT2-VT1=5V (less than action threshold V)th= 9V). The control side detects the resistance value of the existing field line and judges whether partial short circuit and partial open circuit faults occur in the existing field line according to the detection base line obtained in the step 5). If the resistance value of the detected field line is lower than the detection baseline by a certain threshold value, reporting partial short-circuit fault, and if the resistance value of the detected field line is higher than the detection baseline by a certain threshold valueIs reported, a partial open fault is reported.
In practical applications, the steps of detecting the line resistance value and determining a fault (S6) may be performed intermittently in order to save electric power. As shown in fig. 6, after detecting the field resistance value for a certain period of time, a standby time S0 may be set, and the steps of detecting the field line resistance value and determining the fault (S6) are repeated. The process (S3) of step 3) may also be performed once before repeating the detection of the live line resistance value and the failure determination (S6) step, ensuring that the latch relay K11 is in the first position.
When a fire alarm occurs, the alarm system will be in alarm mode, where 28V will be applied across pins T1 and T2 (shown as A in FIG. 6, indicating an alarm mode time period), with voltage polarity VT1Higher than VT2，VT1-VT2=28V (greater than action threshold V)th= 9V). At this point, latch relay K11 will be switched to the second position, disconnecting R11 from the alarm system circuitry to avoid shunting the speaker. After the switching is completed, since the diode V13 is in the reverse state, the voltage polarity sensing circuit P does not consume current, and the exciting coil is no longer subjected to a high voltage. In the period A, the voltage between the pins T1 and T2 can be continuous or pulse, which respectively corresponds to the condition that the loudspeaker continuously sounds and intermittently sounds.
When the alarm is released, the steps S2, S3, S4, S5 and S6 (as shown in fig. 6) in the above initialization method are repeated to return the alarm system to the monitoring mode again.
The original detection baseline can still be used, taking into account that during the time the alarm occurs, no significant change in field line resistance occurs. Therefore, after the alarm is released, steps S2, S4, and S5 may be omitted and only S3 and S6 may be performed.
The steps of the operation method provided in the above embodiments are not limited, and those skilled in the art can flexibly combine the above steps according to the actual needs according to the functions of the above steps.
The above-described operation method may be implemented by, for example, a controller or a control platform in the control side C in fig. 1. As shown in fig. 1 and 2, a controller for an alarm system is configured to drive and control one or more alarm devices h, i, j, which are connected in parallel to two lines leading from the controller of the alarm system, and a line end module EOL is connected to distal ends of the two lines. Fig. 7 exemplarily shows a block diagram of a controller for an alarm system according to an embodiment of the present invention.
As shown in fig. 7, the controller includes an alarm unit 710 for applying a first voltage (e.g., + 28V) to the line to actuate the alarm device while disconnecting the EOL from the line when the alarm system is in the alarm mode; a monitoring mode switching unit 720 for applying a second voltage (e.g., -9V) to the line when the alarm system is in a monitoring mode, so that the EOL is coupled into a monitoring loop including the line; a monitoring unit 730, applying a third voltage (e.g., -5V) to the line after the alarm system is in a monitoring mode and EOL has been coupled into the monitoring loop to detect if a fault has occurred on the line; the polarity of the first voltage is opposite to that of the second voltage and the third voltage, and the third voltage is lower than the second voltage.
Preferably, the controller further comprises an initialization unit 740 for implementing the initialization action. Specifically, the initialization unit 740 includes: a reset subunit 741, configured to apply the first voltage to the line so as to initialize EOL to be disconnected from the line; a detection subunit 742 for applying the third voltage to the EOL to monitor whether a first fault occurs in a line connected to the alarm system. The first fault includes a partial short circuit and a connection error.
Preferably, the initialization unit 740 may further include: a switching subunit 743 for applying the second voltage to the line such that EOL is coupled into a monitoring loop including the line; at this time, the detecting subunit 742 applies the third voltage to the line to detect whether a second fault occurs in the line of the alarm system. The second fault comprises a partial open circuit.
Optionally, the initialization unit 740 further includes: a measurement sub-unit 744 for measuring a resistance value of the line connected to a control side of the alarm system in a case where the third voltage is applied to the line; and a recording subunit 745 for recording the measured resistance value as a detection baseline for judging partial open circuit and partial short circuit.
In the above embodiments, the present invention has been described by taking an electromagnetic latch relay as an example. In other embodiments according to the present invention, the present invention may be implemented by using other types of relays having a latch function, and may also be implemented by using other types of switching devices having a latch function.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above description is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations can be made by those skilled in the art without departing from the spirit and principles of the invention.
List of reference numerals
An end of line module EOL; pins T1, T2; a control side C; a field side F;
speakers h, i, j; voltages V1, V2; a double pole double throw switch N1; switches S11, SW 1; a voltage polarity sensing circuit P; resistors R11, R1, R2, R3; latch relay K11 switch pins 2, 3, 4, 5, 6, 7; excitation coil pins 1 and 8; capacitors C11, C12; initialization of latch relay K11S 1; detection of partial short circuit and connection error S2;
switching the position of the latch relay K11 to the first position S3; detection of a partial open circuit S4;
recording a detection baseline of the field line resistance S5; measurement of the line resistance value and failure determination S6;
standby time S0; an alert mode time period A; a control terminal DIR _ CTRL of the double-pole double-throw switch N1;
a control port MON _ CTRL of switch SW 1; voltages VREF1, VREF2 across resistor R2
Controller 700 alarm unit 710; a monitor mode switching unit 720; a monitoring unit 730;
an initialization unit 740; a reset subunit 741; a detection subunit 742; switch subunit 743
A quantum measurement unit 744; a recording subunit 745.