JP5017078B2 - Alarm - Google Patents

Description

  The present invention relates to an alarm device that makes a judgment on an alarm signal based on a detected environmental change, and in particular, judges an alarm signal based on the amount of smoke sensed by detecting scattered light from smoke. It is related to the alarm to be performed.

  2. Description of the Related Art Conventionally, an alarm device that issues an alarm when an abnormality in an indoor environment is detected has been widely used in buildings, underground malls, ordinary houses, and the like. As one of such alarm devices, there is a smoke detection type alarm device that measures the amount of smoke generated indoors, detects the occurrence of a fire based on the measured amount of smoke, and makes a judgment on the alarm notification. . In order to measure the amount of smoke to detect the occurrence of a fire, the smoke detection type alarm is a photoelectric smoke detector that measures the amount of smoke in the case with a light emitting circuit and a light receiving circuit provided in the case. Prepare.

  A conventional smoke detection type alarm will be briefly described with reference to the schematic diagram of FIG. As shown in FIG. 9, the smoke sensing alarm device 100 has a smoke sensing housing 101 having an opening through which outside air flows into the front end side of the main body when the opposite side to the installation surface of the main body is the front end. Is provided. Since the light emitting element LD that emits light and the light receiving element PD that receives light are housed in the smoke sensing casing 101, the inside of the smoke sensing casing 101 functions as a smoke sensing space.

  Each of the light emitting element LD and the light receiving element PD is electrically connected to an arithmetic circuit mounted on the circuit board 102 by connecting electrodes to the circuit board 102 built in the main body of the alarm device 100. In addition, a speaker (sound generator) SP that performs a reporting operation based on a signal from an arithmetic circuit mounted on the circuit board 102 is provided further on the front end side than the smoke detection housing 101 in the main body of the alarm device 100. .

  With this configuration, when smoke flows into the smoke sensing housing 101, the light emitting element LD emits light, and thus scattered light due to the smoke in the smoke sensing housing 101 is generated. When the scattered light is received by the light receiving element PD, an electric signal based on the amount of received light is generated, and the amount of light received by the light receiving element PD is detected by an arithmetic circuit provided on the circuit board 102. When the amount of smoke flowing into the smoke sensing housing 101 is measured based on the amount of light received by the light receiving element PD, the speaker SP is turned on when it is determined that the measured amount of smoke is greater than a predetermined threshold. Drive and issue an alarm indicating the occurrence of a fire.

  In many smoke sensing type alarm devices represented by the configuration of FIG. 9, power is supplied by a primary battery, and low power consumption is required in order to extend the battery life. For this reason, the power consumption of the alarm device is reduced by restricting the operation of the light emitting element with relatively large power consumption to suppress the power consumption of the photoelectric smoke detector. The present applicant has proposed a photoelectric smoke detector shown in Patent Document 1 as a photoelectric smoke detector used in an alarm device realizing low power consumption by limiting the operation of the light emitting element.

  In the photoelectric smoke detector of Patent Document 1, the light emitting circuit is intermittently driven, and the scattered light generated by the intermittent light emission is received by the light receiving circuit, thereby detecting the generation of smoke. At this time, if the number of times the output of the light receiving circuit indicating the amount of scattered light is detected to be greater than or equal to the reference level exceeds the predetermined value, a prompt alarm is generated by shortening the drive interval of the light emitting circuit. Give information. As described above, the photoelectric smoke detector of Patent Document 1 realizes low power consumption by increasing the drive interval of the light emitting circuit at any time when smoke is not generated.

Similarly, as a photoelectric smoke detector realizing low power consumption, a photoelectric dust sensor device described in Patent Document 2 has been proposed. In the photoelectric dust sensor device of Patent Document 2, the time for continuously passing a current through the LED as the light emitting element is short when the amount of light received by the photodiode as the light receiving element does not exceed a predetermined value. The power consumption is reduced.
JP-A-5-73785 JP 2005-214835 A

  As described above, in the photoelectric smoke sensor in Patent Document 1 and the photoelectric pride sensor device in Patent Document 2, the power consumption at the time when no smoke is generated is suppressed by adjusting the light emission time of the light emitting element. It is supposed to be. However, when low power consumption is realized by limiting the operation time, the detection timing interval becomes long, so that it is delayed with respect to the actual fire occurrence time.

  In addition, when the light emitting element does not exceed the reference value due to aging deterioration, the operation is always performed, and the accurate smoke detection operation cannot be performed. As a result, it is necessary to reduce the reference value in the normal operation. As a result, the period during which the normal operation is performed is shortened, and the amount of reduction in power consumption is less than the desired value.

  In view of such a problem, the present invention proposes an alarm device that can be in a standby mode at all times when no smoke is generated and can reduce power consumption by reducing the amount of current to the light emitting element. With the goal.

  In order to achieve the above object, an alarm device of the present invention receives a light emitting element that irradiates light to a smoke monitoring space and scattered light caused by smoke that has entered the smoke monitoring space based on light from the light emitting element. Then, a light receiving element that outputs a smoke detection signal that is an electric signal based on the received light amount, and a signal value of the smoke detection signal from the light receiving element are compared with a first threshold value, and are larger than the first threshold value. And a signal processing unit that issues a fire alarm when the alarm is activated, and includes a current adjustment unit that switches an amount of current supplied to the light emitting element, and the signal processing unit is in a standby mode. The current adjustment unit sets the amount of current supplied to the light emitting element to the first amount of current, and compares the second threshold value smaller than the first threshold value with the signal value of the smoke detection signal, Signal value of the smoke detection signal When it is determined that the current value is larger than the second threshold value, the mode is changed to a sensing mode, and the current amount supplied to the light emitting element by the current adjustment unit is switched to a second current amount larger than the first current amount. The reference value to be compared with the smoke detection signal is switched to the first threshold value, and the signal value of the electric signal from the light receiving element is compared with the first threshold value. It is characterized by performing the notification.

In this configuration, the ratio (Ib / Ia) of the second current amount (Ib) to the first current amount (Ia) is α, and the signal value of the smoke detection signal when no smoke is V0. When the relationship between the first threshold value (Vth1) and the second threshold value (Vth2) satisfies the following expression (1), the transition from the standby mode to the sensing mode is performed smoothly. be able to.
α × (Vth2−V0) <Vth1−V0 (1)

  In such an alarm device, the signal processing unit further adds a third threshold value smaller than the first threshold value to a reference value in the detection mode, compares the smoke detection signal, and compares the signal value of the smoke detection signal. When the value becomes smaller than the third threshold value, the mode is shifted to the standby mode, and the current amount supplied to the light emitting element by the current adjustment unit is switched to the first current amount and compared with the smoke detection signal. The threshold value may be switched to the second threshold value.

In this configuration, the ratio (Ib / Ia) of the second current amount (Ib) to the first current amount (Ia) is α, and the signal value of the smoke detection signal when no smoke is V0. When the relationship between the second threshold value (Vth3) and the third threshold value (Vth3) satisfies the following expression (2), hysteresis is given to the transition from the sensing mode to the standby mode. Therefore, it is possible to smoothly return to the standby mode at the time of erroneous detection.
Vth3−V0 <α × (Vth2−V0) (2)

The signal processing unit further includes a timer unit for measuring time, and the signal processing unit has a signal value of the smoke detection signal before the time measured by the timer unit exceeds a predetermined time after shifting to the detection mode. When the number of times that the first threshold is exceeded is not equal to or greater than a predetermined number , the mode is shifted to the standby mode, and the amount of current supplied to the light emitting element by the current adjustment unit is switched to the first amount of current The reference value to be compared with the smoke detection signal may be switched to the second threshold value.

  With this configuration, when shifting to the sensing mode due to erroneous detection, it is possible to return to the standby mode after elapse of a predetermined time, so that power consumption during erroneous detection can be suppressed, and the device The SN ratio (Signal to Noise ratio) of the main body can be improved.

  Further, in any one of the above alarm devices, when the light emission amount of the light emitting element is lowered to a predetermined level, the current adjusting unit increases the first and second current amounts supplied to the light emitting element. It is good.

  With such a configuration, the first and second current amounts to the light emitting element can be increased based on a decrease in the light emission amount of the light emitting element due to aging and the environment. Sensitivity degradation in sensing can be prevented.

  According to the present invention, the power consumption of the alarm device at any time can be suppressed by supplying the first current amount having a small current amount to the light emitting element in the standby mode in which no smoke is generated. Therefore, unlike the conventional case, the power consumption can be reduced without changing the operation timing of the light emitting element at any time, and therefore the delay time sensed with respect to the actual smoke generation time can be shortened.

<Basic configuration>
The basic configuration of the alarm device of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the internal configuration of the alarm device of the present invention. In the following description, as an alarm device, an alarm device having the mechanism shown in FIG. 9 shown in [Background Art] will be described as an example, but an alarm device having a photoelectric smoke detector will be described. Not only, but also an air conditioner such as a photoelectric dust sensor device as shown in Patent Document 2 or an air cleaner or an air conditioner provided with the photoelectric dust sensor device may be used.

  The alarm device shown in FIG. 1 includes, as circuits mounted on a circuit board 102, an LED drive circuit 1 that supplies current to a light emitting diode (LED) that is a light emitting element, and a photodiode PD that is a light receiving element. A current-voltage conversion circuit 2 that converts the current signal photoelectrically converted into a voltage signal, an amplification circuit 3 that amplifies the voltage signal output from the current-voltage conversion circuit 2 and outputs it as a smoke detection signal, Based on the smoke detection signal, the signal processing circuit 4 that measures the amount of smoke inside the smoke detection housing 101 serving as a smoke monitoring space, and whether or not the speaker (sound generator) SP can be driven based on the measurement result of the signal processing circuit 4 And a current adjustment circuit 6 that adjusts the amount of current supplied from the LED drive circuit 1 based on the measurement result of the signal processing circuit 4.

  As described in [Background Art], the alarm device configured in this way is similarly configured to emit scattered light based on the light emission of the light emitting diode LD provided in the smoke sensing housing 101. Light is received by a photodiode PD provided in the body 101. At this time, since the LED driving circuit 1 supplies current to the light emitting diode LD only during the period t every period T, the light emitting diode LD emits light during the period t every period T. In the photodiode PD, when the light emitting diode LD emits light, a current signal based on a current value corresponding to the amount of received light is generated by a photoelectric conversion operation and supplied to the current-voltage conversion circuit 2.

  The current signal from the photodiode PD is converted into a voltage signal by the current-voltage conversion circuit 2 and then amplified to a signal value that can be calculated by the amplification circuit 3 and output to the signal processing circuit 4 as a smoke detection signal. . Then, the signal processing circuit 4 determines, based on the signal value of the smoke detection signal, whether to operate in a standby mode in which power consumption is suppressed or a detection mode that determines whether an alarm can be issued.

  In the standby mode corresponding to the always small amount of smoke flowing into the smoke sensing casing 101, the current adjustment circuit 6 supplies the light amount to the light emitting diode LD from the LED drive circuit 1 with a small value. The current amount Ia is set. In other words, the standby mode is a low power consumption mode in which the light emission amount of the light emitting diode LD is reduced. Since the light emission amount of the light emitting diode LD is reduced, the signal value of the smoke detection signal output to the signal processing circuit 4 is also reduced as the light reception amount in the photodiode PD is also reduced. That is, the sensitivity of the smoke detector including the light emitting diode LD and the photodiode PD is lowered to perform coarse smoke detection operation.

  Further, in this standby mode, the signal processing circuit 4 compares the signal value of the smoke detection signal with the threshold value Vth2 in order to determine whether or not to shift to the detection mode. When it is confirmed that the signal value of the smoke detection signal output from the amplifier circuit 3 is larger than the threshold value Vth2, the notification determination / control circuit 5 determines whether the speaker SP can issue the alarm. Transition to sensing mode. On the other hand, when the signal value of the smoke detection signal output from the amplifier circuit 3 is equal to or lower than the threshold value Vth2, the operation in the standby mode is continued without performing the transition to the detection mode.

  In the sensing mode shifted from the standby mode, the current adjustment circuit 6 supplies the second amount of current supplied from the LED drive circuit 1 to the light emitting diode LD by α times the first current value Ia (α> 1). The current amount Ib is set. Therefore, since the light emission amount of the light emitting diode LD increases, the signal value of the smoke detection signal output to the signal processing circuit 4 also increases as the light reception amount of the photodiode PD increases. That is, the smoke detector including the light emitting diode LD and the photodiode PD is increased in sensitivity to perform a high-definition smoke detection operation.

In this sensing mode, a threshold value Vth1 for performing fire detection is set, and the signal processing circuit 4 compares the signal value of the smoke sensing signal with the threshold value Vth1. When the signal value of the smoke detection signal when no smoke is in the standby mode is V0, the relationship between the threshold value Vth1 and the threshold value Vth2 in the standby mode satisfies the following expression (3).
α × (Vth2−V0) <Vth1−V0 (3)

  When it is confirmed that the signal value of the smoke detection signal output from the amplifier circuit 3 is larger than the threshold value Vth1, a smoke detection signal indicating that the amount of smoke is large is output to the alarm determination / control circuit 5. To do. The alarm determination / control circuit 5 determines whether or not a fire has occurred based on the frequency of occurrence of the smoke detection signal output from the signal processing circuit 4. If the frequency of occurrence of the smoke detection signal is high, the speaker SP A warning signal for driving is output. Therefore, the speaker SP is driven by the alarm signal and issues a fire alarm.

  If the frequency of occurrence of the smoke detection signal is low, an alarm is not issued from the speaker SP, and a transition to the original standby mode is made, thereby entering a low power consumption mode. In addition, when the alarm device that issued the alarm is instructed by an external operation using a button or network communication (not shown), the alarm from the speaker SP is stopped and the standby mode Then, the coarse smoke detection operation is started again.

  In the following embodiments, details will be described with reference to the above-described configuration and operation, and an example of a circuit configuration in each characteristic block. Note that the circuit configuration examples in the following embodiments are merely examples, and other circuit configurations may be used as long as similar operations are performed. Further, it may have a microprocessor and may have a configuration in which a program for performing the same operation for switching between the standby mode and the sensing mode is installed.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing details of the internal configuration of the alarm device in the present embodiment. FIG. 3 is a timing chart for showing the operation state of each part in the alarm device configured as shown in FIG. 2, wherein (a) shows the operation when the alarm is issued, (b) Shows the operation when no alarm is issued.

1. Configuration and Operation of Alarm Device The alarm device in the present embodiment includes each block provided in the alarm device that is the basic configuration of FIG. The block diagram of FIG. 2 shows a detailed configuration example of the LED drive circuit 1, the signal processing circuit 4, the alarm determination / control circuit 5, and the current adjustment circuit 6 in the alarm device. Below, the detailed structure of the LED drive circuit 1, the signal processing circuit 4, the alert determination / control circuit 5, and the current adjustment circuit 6 and the operation | movement based on this structure are demonstrated.

1-1. LED drive circuit The LED drive circuit 1 includes an npn transistor Tr1 whose collector is connected to the cathode of the light emitting diode LD whose power supply voltage is applied to the anode, one end connected to the emitter of the transistor Tr1, and the other end grounded. And a timing control circuit 11 for supplying a drive signal to the base of the transistor Tr1.

  According to the LED drive circuit 1 configured as described above, the transistor Tr1 is turned on by outputting a drive signal that becomes high only for a predetermined time t from the timing control circuit 11 for each period T. As a result, a current flows through the light emitting diode LD for a predetermined time t every period T, and a light emitting operation for smoke detection is performed.

1-2. Signal Processing Circuit The signal processing circuit 4 has a comparator C1 in which the signal value of the smoke detection signal from the amplifier circuit 3 is input to the non-inverting input terminal (+), and an output from the comparator C1 is input to the set terminal (S). RS flip-flop 41, and a 2-input 1-output AND (logical product) gate A1 to which the signal value of the smoke detection signal from the amplifier circuit 3 and the output from the output terminal (Q) of the RS flip-flop 41 are input. , The comparator C2 in which the output from the AND gate A1 is input to the non-inverting input terminal (+), the comparator C3 in which the output from the AND gate A1 is input to the inverting input terminal (−), the RS flip-flop 41 and the comparator And a 2-input 1-output AND gate A2 to which the outputs of C3 are input.

The output from the AND gate A2 is input to the reset terminal (R) of the RS flip-flop 41, and the inverting input terminal (−) of each of the comparators C1 and C2 has a voltage Vth2 that is the second threshold value, the first A voltage Vth1 that is a threshold value is applied, and a voltage Vth3 that is a third threshold value is applied to the non-inverting input terminal (+) of the comparator C3. The relationship between the first to third threshold values Vth1 to Vth3 satisfies the following expression (4) when the signal value of the smoke detection signal when no smoke is in the standby mode is V0.
Vth3-V0 <α × (Vth2-V0) <Vth1-V0 (4)

  Outputs from the comparators C2 and C3 are supplied to the alarm determination / control circuit 5, and outputs from the comparator C1 and the AND gate A2 are supplied to the current adjustment circuit 6. The AND gate A1 operates as a gate circuit that determines whether or not the smoke detection signal from the amplifier circuit 3 input to one input terminal can be output to the comparators C2 and C3. That is, whether or not to output the smoke detection signal from the amplifier circuit 3 is determined based on the output from the RS flip-flop 41 input to the other input terminal.

  Furthermore, the RS flip-flop 41 operates at the rising edge when the input to the set terminal or the reset terminal changes from low to high, and the output from the output terminal is switched. That is, in the RS flip-flop 41, when the input to the set terminal rises high, the output from the output terminal switches to high, while when the input to the reset terminal rises high, the output from the output terminal Switch to low.

  According to the signal processing circuit 4 configured as described above, when the signal value of the smoke detection signal from the amplifier circuit 3 becomes larger than the second threshold value Vth2 in the initial state where the output from the RS flip-flop 41 is low, the comparator The output from C1 switches to high. Thereby, since the input to the set terminal of the RS flip-flop 41 is switched to high, the output from the RS flip-flop 41 is switched from low to high. Further, a high output from the comparator C1 is output as a signal for instructing switching of the current amount to be adjusted by the current adjustment circuit 6.

  Since an output that goes high from the RS flip-flop 41 is input to one input terminal of the AND gate A1, the signal value of the smoke detection signal from the amplifier circuit 3 is supplied to the comparator C2 via the AND gate A1. , C3. Therefore, in each of the comparators C2 and C3, the signal value of the smoke detection signal from the amplifier circuit 3 is compared with the first and third threshold values Vth1 and Vth3. Since the input to one input terminal of the AND gate A2 (the output from the RS flip-flop 41) is high, the output from the comparator C3 input to the other input terminal is connected to the output terminal of the AND gate A2. Will appear.

  At this time, when the signal value of the smoke detection signal from the amplifier circuit 3 becomes larger than the first threshold value Vth1, the output from the comparator C2 switches to high. Then, the output from the comparator C <b> 2 that becomes high is output to the alarm determination / control circuit 5 as a smoke detection signal indicating that the amount of smoke is large.

  On the other hand, when the signal value of the smoke detection signal from the amplifier circuit 3 becomes smaller than the third threshold value Vth3, the output from the comparator C3 switches to high. Since the output from the comparator C2 that becomes high is input to the reset terminal of the RS flip-flop 41 via the AND gate A2, the output from the RS flip-flop 41 is switched to low. As a result, the outputs from the AND gate A1 to the comparators C2 and C3 are low, and the outputs from the comparators C2 and C3 are always low.

  Further, a high output from the comparator C3 is output to the alarm determination / control circuit 5 as a reset signal for resetting the operation state to the initial state. That is, when a high output is given from the comparator C2, and the alarm determination / control circuit 5 starts the alarm determination operation, it functions as a reset signal for stopping the alarm determination operation. Further, a high output from the AND gate A2 is output as a signal for instructing switching of the amount of current to be adjusted by the current adjustment circuit 6.

1-3. Reporting determination / control circuit The reporting determination / control circuit 5 includes a counter circuit 51 that performs a counting operation based on an output from the comparator C2, and an output signal that is output when a predetermined number is counted by the counter circuit 51. And an alarm control circuit 52 that instructs the speaker SP to issue an alarm. The output from the comparator C3 is input to the counter circuit 51 and the alarm control circuit 52 as a reset signal for resetting.

  In the alarm determination / control circuit 5 configured as described above, the counter circuit 51 performs a counting operation to add “1” each time the smoke detection signal that goes high from the comparator C2 is input. When the count value by the counter circuit 51 becomes equal to or greater than the predetermined number N, a signal that becomes high from the counter circuit 51 is input to the alarm control circuit 52. The counter circuit 51 has a circuit configuration capable of counting up to a predetermined number N, such as a circuit configured by connecting N stages of T flip-flops in series or an N stage shift register. That's fine.

  In this way, when receiving a high output from the counter circuit 51, the alarm control circuit 52 issues an alarm for notifying the occurrence of a fire in order to recognize that the environment has a large amount of smoke. Next, an instruction is given to the speaker SP. Thereafter, in the counter circuit 51, the count value exceeds the predetermined number N, but the output is held high. On the other hand, when a high output (reset signal) is input from the comparator C3, the count value of the counter circuit 51 is reset to 0 and the output from the counter circuit 51 is also switched to low.

  When the counter circuit 51 receives the high smoke detection signal from the comparator C2 and starts the counting operation, the smoke detection signal from the comparator C2 becomes low until the high reset signal from the comparator C3 is received. Even the current count value is retained. In addition, when the alarm control circuit 52 instructs the speaker SP to issue an alarm, if the reset signal that goes high from the comparator C3 is received, the alarm control circuit 52 stops the alarm issuing to the speaker SP. To instruct.

  Alternatively, the counter circuit 51 may be reset once the output from the comparator C2 goes low. That is, the counter circuit 51 outputs a high signal to the alarm control circuit 52 only when the number of times the signal value of the smoke detection signal continuously exceeds the first threshold value Vth1 becomes N times. By doing in this way, the occurrence of a fire is confirmed and an alarm by the speaker SP can be issued only when the smoke amount exceeding the predetermined concentration is continuously detected during the time N × T. .

1-4. Current Adjustment Circuit The current adjustment circuit 6 includes an RS flip-flop 61 in which the output from the comparator C1 is input to the set terminal (S) and the output from the AND gate A2 is input to the reset terminal (R), and the transistor Tr1. An npn transistor Tr2 having a collector connected to a connection node between the emitter and the resistor R1 and an output terminal (Q) of the RS flip-flop 61 connected to the base, and one end connected to the emitter of the transistor Tr2 and the other end Is provided with a grounded resistor R2.

  The RS flip-flop 61 switches the output from the output terminal at the rising edge when the input to each of the set terminal and the reset terminal switches from low to high, like the RS flip-flop 41 in the signal processing circuit 4. Further, when the RS flip-flop 61 is set to the initial state, the output from the output terminal becomes low.

  In the current adjustment circuit 6 configured as described above, when a high output from the comparator C1 is input to the set terminal of the RS flip-flop 61, the output from the RS flip-flop 61 is switched to high and is applied to the base of the transistor Tr2. As a result, the transistor Tr2 is turned on. As a result, a parallel circuit composed of the resistors R1 and R2 is configured, so that the value of the current flowing through the light emitting diode LD via the transistor Tr1 increases, and the amount of current supplied to the light emitting diode LD is set to the second current amount Ib. The

  When an output that goes high from the AND gate A2 is input to the reset terminal of the RS flip-flop 61, the output from the RS flip-flop 61 is switched to low and input to the base of the transistor Tr2, and the transistor Tr2 is turned off. . As a result, the connection between the resistor R2 and the emitter of the transistor Tr1 is disconnected, so that the value of the current flowing through the light emitting diode LD via the transistor Tr1 decreases, and the amount of current supplied to the light emitting diode LD is the first current amount Ia. Set to

  When each part is configured as described above, in the signal processing circuit 4, when the signal value of the smoke detection signal from the amplifier circuit 3 is equal to or lower than the second threshold value Vth2, and the output from the comparator C1 becomes low, the standby mode Works as. At this time, in the signal processing circuit 4, the comparison operation by the comparators C2 and C3 is not performed, and the outputs from the comparators C2 and C3 remain low. Further, in the current adjustment circuit 6, since the transistor Tr2 is turned off, the amount of current flowing through the light emitting diode LD by the LED drive circuit 1 becomes the first current amount Ia.

  On the other hand, in the signal processing circuit 4, when the signal value of the smoke detection signal from the amplifier circuit 3 is larger than the second threshold value Vth2 and the output from the comparator C1 becomes high, the signal processing circuit 4 operates as a detection mode. At this time, in the signal processing circuit 4, the comparator C2 and C3 perform a comparison operation between the signal value of the smoke detection signal and the threshold values Vth1 and Vth3. Further, in the current adjustment circuit 6, since the transistor Tr2 is turned on, the amount of current flowing through the light emitting diode LD by the LED drive circuit 1 becomes the second current amount Ib.

2. Example of operation when alarm is issued An example of operation in the alarm device having each unit as described above will be described below. First, an operation when an alarm is issued after shifting from the standby mode to the sensing mode will be described with reference to FIG. In the standby mode, as described above, since the output from the RS flip-flop 61 is low, the transistor Tr2 is turned OFF, and the amount of current (LED light emission current) flowing through the light emitting diode LD via the transistor Tr1 is the first amount. The current amount is Ia. Further, since the signal value of the smoke detection signal that is the output from the amplifier circuit 3 is equal to or less than the second threshold value Vth2, the output from the comparator C1 remains low.

  Then, as shown in FIG. 3 (a), when the indoor smoke density increases at time Ta and the amount of scattered light received by the photodiode PD increases, smoke detection that is an output from the amplifier circuit 3 is detected. The signal value of the signal becomes larger than the second threshold value Vth2. Therefore, the output from the comparator C1 becomes high, and the standby mode is shifted to the sensing mode. Accordingly, the outputs of the RS flip-flops 41 and 61 become high, the smoke detection signal is allowed to be input to the comparators C2 and C3, and the transistor Tr2 is turned on. Since the transistor Tr2 is turned on, the amount of current (LED emission current) flowing through the light emitting diode LD becomes the second current amount Ib at time Ta + T, which is the next cycle.

  After the time Ta + T, the comparator C2 compares the signal value of the smoke detection signal with the first threshold value Vth1, thereby determining whether or not the smoke concentration has exceeded the concentration necessary for alarming. At this time, as shown in FIG. 3A, when the smoke concentration in the room increases and the signal value of the smoke detection signal exceeds the first threshold value Vth1, a high smoke detection signal is output from the comparator C2. . Note that the comparator C3 determines whether to return to the standby mode by comparing the signal value of the smoke detection signal with the third threshold value Vth3.

  From this time Ta + T to time Tb (= Ta + 6 × T), if the smoke concentration remains in excess of the concentration necessary for alarming, a high smoke detection signal is sent to the alarm determination / control circuit 5. It will be output 6 times. If the count value of the counter circuit 51 becomes “6” in the notification determination / control circuit 5, a signal that goes high is output to the notification control circuit 52. At time Tb, the counter circuit 51 Is output to the alarm control circuit 52. Therefore, at time Tb, the alarm control circuit 52 to which a high output is given instructs the speaker SP to issue a fire alarm, and the speaker SP issues a fire alarm.

3. Example of Returning Operation to Standby Mode First, an operation for returning to the standby mode after shifting from the standby mode to the sensing mode will be described with reference to FIG. Similar to the operation example of FIG. 3A described above, in the standby mode in which the signal value of the smoke detection signal from the amplifier circuit 3 is equal to or lower than the threshold value Vth2, the output from the comparator C1 is low. Output is low. Further, since the output from the RS flip-flop 61 becomes low and the transistor Tr2 is OFF, the amount of current (LED emission current) flowing through the light emitting diode LD is the first current amount Ia.

  When the indoor smoke density increases at time Ta and the signal value of the smoke detection signal output from the amplifier circuit 3 becomes larger than the second threshold value Vth2, the output from the comparator C1 becomes high, and the detection is started from the standby mode. Enter mode. Therefore, after the time Ta + T, the transistor Tr2 is turned on, and the amount of current (LED light emission current) flowing through the light emitting diode LD increases to the second current amount Ib. Further, the comparator C2 determines whether or not the smoke concentration exceeds the concentration necessary for alarming by comparing the signal value of the smoke detection signal with the first threshold value Vth1, while the comparator C3 It is determined whether or not to return to the standby mode by comparing the signal value of the smoke detection signal with the third threshold value Vth3.

  After the transition to such a sensing mode, the amplifier circuit at time Tc (Tc <Tb) before the number of times the smoke detection signal that goes high is output to the alarm determination / control circuit 5 exceeds six times. When the signal value of the smoke detection signal from 3 falls below the third threshold value Vth3, the output from the comparator C3 becomes high. As a result, the output from the AND gate A2 becomes high and is input to the reset terminal to each of the RS flip-flops 41 and 61, whereby the output from the RS flip-flops 41 and 61 becomes low. Therefore, the mode shifts from the detection mode to the standby mode, the smoke detection signal to the comparators C2 and C3 is prohibited, and the amount of current (LED emission current) flowing through the light emitting diode LD is reduced to the first current amount Ia. .

  Thus, in this embodiment, since the light emitting diode LD is driven with the first current amount Ia in the standby mode, the power consumption is suppressed by operating in the standby mode when the amount of smoke is small. Can do. In the sensing mode, it is possible not only to determine whether or not to issue an alarm, but also to determine whether or not it is necessary to return to the standby mode, and the third threshold value Vth3 is expressed by the above equation (4). By setting a small value, it is possible to prevent the operation from becoming unstable due to repeated switching between the standby mode and the sensing mode.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing details of the internal configuration of the alarm device in the present embodiment. FIG. 5 is a timing chart for showing the operation state of each part in the alarm device configured as shown in FIG. 4, and shows the operation when the alarm is not issued. In the alarm device in FIG. 4, parts used for the same purpose as the alarm device shown in FIG.

1. Configuration of Alarm Device As shown in FIG. 4, the alarm device in this embodiment is configured such that the output from the comparator C3 and the output from the counter circuit 51 are input to the configuration of the alarm device (FIG. 2) in the first embodiment. The two-input one-output OR (logical sum) gate O1 and the output from the RS flip-flop 41 are input to the set terminal (S) and the output from the OR gate O1 is input to the reset terminal (R). A configuration in which a flip-flop 7, a timer circuit 8 that starts timer measurement using the output terminal (Q) of the RS flip-flop 7, and a clock oscillation circuit 80 that supplies a clock for timer measurement by the timer circuit 8 are further added. Become.

  Further, the signal processing circuit 4a (corresponding to the signal processing circuit 4 in FIG. 1) in the alarm device shown in FIG. 4 includes an output signal from the timer circuit 8 and a comparator in the configuration of the signal processing circuit 4 in the first embodiment. The configuration further includes a 2-input 1-output OR gate O2 that receives an output from C3 and outputs an output signal to the AND gate A2. Further, the output from the OR circuit O1 is supplied to the timer circuit 8 as a reset signal for resetting the measurement time measured by the timer in the timer circuit 8. Although not shown in the first embodiment, the clock oscillation circuit 80 may be the same as the clock oscillation circuit that generates a clock used for the timing control operation in the timing control circuit 11.

  Unlike the alarm device of the first embodiment, the alarm device of the present embodiment configured as described above is input from the standby mode because the output from the timer circuit 8 is input to the AND gate A2 via the OR gate O2. Even when a predetermined time has elapsed after the transition to the sensing mode, it is possible to return to the standby mode again. In the signal processing circuit 4a, since the output from the comparator C3 is input to the AND gate A2 via the OR gate O2, as in the first embodiment, as shown in FIG. After the transition to, the standby mode can also be restored when the signal value of the sensing signal becomes smaller than the third threshold value Vth3.

  In other words, in the present embodiment, the OR gate O1, the RS flip-flop 7, the timer circuit 8, and the clock oscillation circuit 80, which are further added to the configuration of the alarm device shown in FIG. This is different from the alarm device of the first embodiment. Therefore, hereinafter, the timer measurement operation after the transition to the sensing mode by the OR gate O1, the RS flip-flop 7, the timer circuit 8, and the clock oscillation circuit 80 will be described in detail. The RS flip-flop 7 and the timer circuit 8 are switched in output and timer set (start of timer measurement) / reset when the input rises from low to high.

2. Example of Return Operation to Standby Mode by Timer Measurement Hereinafter, an operation when returning to the standby mode by timer measurement after shifting from the standby mode to the sensing mode will be described with reference to FIG. In this operation example, when the time T1 (= 11 × T) is measured by the timer circuit 8, a high signal is output from the timer circuit 8 to the OR gate O2 to return to the standby mode. To do.

  Similar to the operation example of FIG. 3A in the first embodiment, as shown in FIG. 5, in the standby mode in which the signal value of the smoke detection signal from the amplifier circuit 3 is equal to or lower than the threshold value Vth2, the output from the comparator C1 Is low, the outputs from the comparators C2 and C3 are low, and the comparison operation is not performed. Further, since the output from the RS flip-flop 61 becomes low and the transistor Tr2 is OFF, the amount of current (LED emission current) flowing through the light emitting diode LD is the first current amount Ia.

  When the indoor smoke density increases at time Ta and the signal value of the smoke detection signal output from the amplifier circuit 3 becomes larger than the second threshold value Vth2, the output from the comparator C1 becomes high, and the detection is started from the standby mode. Enter mode. At this time, since the output from the RS flip-flop 41 is switched to high, the input to the set terminal of the RS flip-flop 7 rises from low to high, and the output of the RS flip-flop 7 is switched to high. As a result, the set input to the timer circuit 8 rises high, and timer measurement by the timer circuit 8 starts.

  Thereafter, by the time Td (= Ta + T1), the number of times the signal value of the smoke detection signal output from the amplifier circuit 3 exceeds the first threshold Th1 is less than N (= 6) times, and the amplifier circuit When the signal value of the smoke detection signal output from 3 remains equal to or greater than the third threshold Th3, the timer circuit 8 measures the time T1 and outputs a high signal. A high signal from the timer circuit 8 is input to the AND gate A2 via the OR gate O2. Therefore, the input to the reset terminal of each of the RS flip-flops 41 and 61 rises to high, the output of each of the RS flip-flops 41 and 61 is switched to low, and the standby mode is restored.

  In addition, after shifting to the sensing mode at time Ta, as shown in FIG. 3A, when a high signal is output from the counter 51 at time Tb and an alarm is issued from the speaker SP, the counter 51 A high signal from is input to the reset terminal of the RS flip-flop 7 and the timer circuit 8 through the OR gate O1. Further, as shown in FIG. 3B, when the signal value of the smoke detection signal falls below the third threshold value Vth3 at time Tc, a high signal from the comparator C3 is sent to the RS flip-flop via the OR gate O1. 7 and the timer circuit 8. In the operation example as shown in FIG. 3A or 3B, since the output from the OR gate O1 becomes high, the output of the RS flip-flop 7 is switched to low and the timer circuit 8 performs measurement. Time is reset.

  As described above, in this embodiment, by adding a timer function to the configuration of the first embodiment, even when the alarm is not issued for a predetermined time, the standby mode is restored. Power consumption can be reduced. In the present embodiment, by providing the comparator C3 and the OR gate O2 in the signal processing circuit 4a, the return to the standby mode is performed either when the signal value of the smoke detection signal decreases or time elapses. However, the comparator C3 and the OR gate O2 may be omitted. That is, the return to the standby mode may be performed only when the timer circuit 8 measures the passage of a predetermined time after the transition to the sensing mode.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram showing details of the internal configuration of the alarm device in the present embodiment. In the alarm device shown in FIG. 6, parts used for the same purpose as the alarm device shown in FIG.

  As shown in FIG. 6, the alarm device in the present embodiment is a light emitting diode LD by measuring the signal value of the smoke detection signal from the amplifier circuit 3 in the configuration of the alarm device (FIG. 4) in the second embodiment. The light quantity measuring circuit 9 for estimating the amount of emitted light is added. Further, instead of the LED drive circuit 1 and the current adjustment circuit 6 in the configuration of FIG. 4, the LED drive circuit 1a and the current adjustment circuit 6a in which the resistors R1 and R2 are changed to variable resistors R1a and R2a (LED drive in FIG. 1). Circuit 1 and current adjustment circuit 6).

  That is, in the alarm device shown in FIG. 6, the resistance values of the variable resistors R1a and R2a in the LED drive circuit 1a and the current adjustment circuit 6a are changed based on the estimation result of the light emission amount of the light emitting diode LD by the light amount measurement circuit 9. The With this added configuration, the alarm device in the second embodiment can be accompanied by a function for compensating for a decrease in the light emission amount of the light emitting diode LD due to deterioration over time or environmental deterioration. Therefore, hereinafter, the configuration and operation related to the function for compensating for the decrease in the light emission amount of the light emitting diode LD will be described in detail.

1. First Example of Light Amount Measurement Circuit The light amount measurement circuit 9a (corresponding to the light amount measurement circuit 9 in FIG. 6) in this example receives a clock from the clock oscillation circuit 80 as shown in FIG. An average value calculation circuit 91 for calculating an average value of the smoke detection signal for each predetermined period, and an average value of the smoke detection signal output from the average value calculation circuit 91 is input to the inverting input terminal (−) to be a non-inverting input terminal The resistance value of the variable resistors R1a and R2a in the LED driving circuit 1a and the current adjustment circuit 6a is changed based on the output from the comparator C4 compared with the voltage Vth4 serving as a threshold applied to (+) and the comparator C4. And a resistance value switching control circuit 92.

  In the light quantity measurement circuit 9 a configured as described above, the average value calculation circuit 91 measures a predetermined period based on the number of clocks from the clock oscillation circuit 80. The average value calculation circuit 91 integrates the signal value of the smoke detection signal from the amplifier circuit 3 within a predetermined period, and then, with respect to the integrated value of the smoke detection signal, the predetermined period of the smoke detection signal from the amplifier circuit 3. The average value of the smoke detection signal after a predetermined period is calculated by dividing by the number of times of output.

  The average value of the smoke detection signal calculated by the average value calculation circuit 91 is given to the comparator C4, so that the comparator C4 compares the average value of the smoke detection signal with the threshold value Vth4. That is, in the comparator C4, when the average value of the smoke detection signal is equal to or higher than the threshold value Vth4, the output of the comparator C4 becomes low, and when the average value of the smoke detection signal falls below the threshold value Vth4, the output of the comparator C4 becomes high. .

  When the average value of the smoke detection signal falls below the threshold value Vth4 and an output that becomes high from the comparator C4 is given to the resistance value switching control circuit 92, the resistance value switching control circuit 92 causes the light emitting diode LD to deteriorate over time. It is determined that the amount of light received by the photodiode PD has decreased due to the deterioration of the environment inside the smoke sensing housing 101. Therefore, the resistance value switching control circuit 92 performs switching control of the resistance values so as to reduce the resistance values of the variable resistors R1a and R2a in the LED driving circuit 1a and the current adjusting circuit 6a. That is, the resistance values of the variable resistors R1a and R2a can be switched so that the first and second current amounts Ia and Ib flowing to the light emitting diode LD are increased, thereby compensating for the decrease in the light receiving amount of the photodiode PD. .

  Thus, when the resistance value switching control circuit 92 switches the resistance values of the variable resistors R1a and R2a, the average value of the smoke detection signal output from the average value calculation circuit 91 is predetermined with respect to the threshold value Vth4. The resistance values of the variable resistors R1a and R2a are set so as to exceed the voltage value ΔV. When the resistance values of the variable resistors R1a and R2a are switched, the output from the comparator C4 becomes low until the average value of the smoke detection signal from the average value calculation circuit 91 falls below the threshold value Vth4 again. The resistance values of the variable resistors R1a and R2a are maintained. When the comparator C4 confirms that the average value of the smoke detection signal from the average value calculation circuit 91 is below the threshold value Vth4, the resistance value switching control circuit 92 further reduces the resistance values of the variable resistors R1a and R2a. Switch to value.

2. Second Example of Light Quantity Measurement Circuit The light quantity measurement circuit 9b (corresponding to the light quantity measurement circuit 9 in FIG. 6) in this example is an average value calculation circuit in the configuration shown in FIG. 7A, as shown in FIG. 7B. Instead of 91, a minimum value calculation circuit 93 is provided which calculates the minimum value of the smoke detection signal every predetermined period by inputting a clock from the clock oscillation circuit 80. Since the other configuration is the same as that of the light quantity measurement circuit 9a shown in FIG. 7A, details thereof are omitted as referring to the description of the first example.

  With the configuration as shown in FIG. 7B, the light quantity measurement circuit 9b of the present example is different from the light quantity measurement circuit 9a of the first example configured as shown in FIG. Then, the minimum value of the smoke detection signal within a predetermined time measured based on the number of clocks from the clock oscillation circuit 80 is calculated. When the calculated smoke detection signal is given to the comparator C4, it is compared with the threshold value Vth4, and the resistance value switching control unit 92 performs a control operation for switching the resistance value based on the comparison result.

  Specifically, in the minimum value calculation circuit 93, each time the smoke detection signal from the amplifier circuit 3 is input, the smoke detection signal falls below the minimum value of the smoke detection signal detected last time. In this case, the signal value of the input smoke detection signal is stored as a new minimum value. Thereafter, the stored minimum value of the smoke detection signal is compared with the signal value of the smoke detection signal from the amplifier circuit 3 to search for a further minimum value. Then, the signal value of the smoke detection signal stored in the minimum value calculation circuit 93 when the predetermined time has elapsed is output to the comparator C4 as the minimum value of the smoke detection signal at the predetermined time.

  In this example, in order to make the minimum value calculation in the minimum value calculation circuit 93 more reliable, in the minimum value calculation circuit 93, the smoke value becomes a signal value lower than the minimum value of the smoke detection signal detected last time. When the number of detection signal inputs reaches a predetermined number, the signal value of the smoke detection signal may be replaced with the minimum value of the smoke detection signal and stored.

  Further, in the present embodiment, as shown in FIGS. 7A and 7B, the comparator C4 is provided, and the LED drive circuit 1a and the current adjustment are performed each time a high output is made from the comparator C4. Although the resistance values of the variable resistors R1a and R2a in the circuit 6a are switched in a stepwise manner, a configuration in which a differential amplifier is provided instead of the comparator C4 may be adopted.

  That is, in the differential amplifier circuit, a difference value between the average value or the minimum value of the smoke detection signal output from the average value calculation circuit 91 or the minimum value calculation circuit 93 and the threshold value Vth4 is calculated. Then, the difference value calculated by the differential amplifier circuit is given to the resistance value switching control circuit 92, so that the difference value calculated by the differential amplifier circuit becomes constant, so that each of the variable resistors R1a and R2a becomes constant. The resistance value can be set. Thus, the light emission amount of the light emitting diode LD is set so that the average value or the minimum value of the smoke detection signal output from the average value calculation circuit 91 or the minimum value calculation circuit 93 always exceeds the threshold value Vth4 by the predetermined voltage value ΔV. Can be set.

<Fourth Embodiment>
A fourth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a block diagram showing details of the internal configuration of the alarm device in the present embodiment. In the alarm device shown in FIG. 8, parts used for the same purpose as the alarm device shown in FIG. 6 are given the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 8, the alarm device in this embodiment measures time based on the clock from the clock oscillation circuit 80 instead of the light amount measurement circuit 9 in the alarm device (FIG. 6) in the third embodiment. A configuration including a time measurement circuit 10 to be performed, and a resistance value switching control circuit 92 that changes the resistance values of the variable resistors R1a and R2a in the LED drive circuit 1a and the current adjustment circuit 6a based on the output from the time measurement circuit 10 It becomes.

  With this configuration, unlike the third embodiment, the time measurement circuit 10 counts the number of clocks oscillated from the clock oscillation circuit 80 and confirms that the count value has reached a predetermined value. Then, a signal is output from the time measuring circuit 10 to the resistance value switching control circuit 92. In this time measuring circuit 10, a plurality of predetermined values for comparison with the count value of the clock are stored in advance, for example, first to nth predetermined values having different values. Each time the count value of the clock reaches each of the stored first to nth predetermined values, a signal that goes high is output from the time measurement circuit 10 to the resistance value switching control circuit 92.

  In the resistance value switching control circuit 92, each time a high signal is output from the time measurement circuit 10, as in the case of the configuration of FIG. 7A or 7B in the third embodiment, LED driving is performed. The resistance values of the variable resistors R1a and R2a in the circuit 1a and the current adjusting circuit 6a are switched stepwise. That is, whenever the time measuring circuit 10 confirms that a plurality of preset times have elapsed, the resistance value switching control circuit 92 operates to change the variable resistance R1a in the LED drive circuit 1a and the current adjustment circuit 6a. , R2a can be switched stepwise.

  By operating in this way, in the present embodiment, it is possible to compensate for the aging degradation of the light emitting diode LD by measuring the time using the clock of the clock oscillation circuit 80. Therefore, in this embodiment, since it is possible to cope with the aging degradation of the light emitting diode LD with a simple configuration, it is possible to suppress an increase in the circuit scale. Also in this embodiment, the resistance value switching control circuit 92 continuously sets the resistance values of the variable resistors R1a and R2a in the LED drive circuit 1a and the current adjustment circuit 6a based on the time measured by the time measurement circuit 10. It is good also as what switches automatically.

  In each of the above-described embodiments, when the alarm is stopped and initialized by an external input operation or communication operation after the fire alarm is issued by the speaker SP, for example, the RS flip-flops 41 and 61 are used. A high signal may be input to the reset terminal. That is, by inputting a high signal to the reset terminals of the RS flip-flops 41 and 61, each of the signal processing circuit 4 and the current adjustment circuit 6 can be set to an initial state in a standby mode, and from the comparator C3. By switching the output to high, the counter circuit 51 and the alert control circuit 52 in the alert determination / control circuit 51 can be reset to the initial state.

  The present invention is not limited to a fire alarm that issues only a fire alarm as long as it is an alarm device equipped with a photoelectric smoke detector, and can also issue a gas alarm when the amount of gas increases. It can be applied to fire and gas alarms that can be used. The present invention can also be applied to a photoelectric dust sensor device including a light emitting element and a light receiving element, and an air conditioner such as an air cleaner or an air conditioner including the photoelectric dust sensor device.

These are block diagrams which show the internal structure of the alarm device of this invention. These are block diagrams which show the detail of the internal structure of the alarm device in the 1st Embodiment of this invention. FIG. 3 is a timing chart for showing an operation state of each part in the alarm device having the configuration shown in FIG. 2, in which (a) shows an operation when an alarm is issued, and (b) shows an alarm issue. The operation when not performed is shown. These are block diagrams which show the detail of the internal structure of the alarm device in the 2nd Embodiment of this invention. These are timing charts for showing the operating states of the respective parts in the alarm device having the configuration of FIG. These are block diagrams which show the detail of the internal structure of the alarm device in the 3rd Embodiment of this invention. These are block diagrams which show the internal structure of the light quantity measurement circuit in the alarm device of the structure of FIG. 6, (a) shows the structure provided with the average value calculation circuit, (b) has the minimum value calculation circuit. The configuration is shown. These are block diagrams which show the detail of the internal structure of the alarm device in the 4th Embodiment of this invention. These are the schematic diagrams which show the structure of the alarm device provided with a photoelectric smoke sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a LED drive circuit 2 Current voltage conversion circuit 3 Amplification circuit 4, 4a Signal processing circuit 5 Notification judgment / control circuit 6, 6a Current adjustment circuit 7, 41, 61 RS flip-flop 8 Timer circuit 9, 9a Light quantity measurement circuit DESCRIPTION OF SYMBOLS 10 Time measuring circuit 11 Timing control circuit 51 Counter circuit 52 Alert control circuit 91 Average value calculation circuit 92 Resistance value switching control circuit 93 Minimum value calculation circuit 80 Clock oscillation circuit C1-C4 Comparator R1, R2 Resistance R1a, R2a Variable resistance A1 , A2 AND (logical product) gate O1, O2 OR (logical sum) gate

Claims (4)

A light emitting element that emits light to the smoke monitoring space;
A light receiving element that receives scattered light from smoke that has entered the smoke monitoring space, based on light from the light emitting element, and outputs a smoke detection signal that is an electrical signal based on the received light amount;
A signal processing unit that compares a signal value of the smoke detection signal from the light receiving element with a first threshold value and issues a fire alarm when the signal value exceeds the first threshold value. And
A current adjusting unit that switches an amount of current supplied to the light emitting element;
In the standby mode, the signal processing unit sets the current amount supplied to the light emitting element by the current adjusting unit to a first current amount, and uses the second threshold value smaller than the first threshold value as a reference value to detect the smoke. While comparing with the signal value of the signal,
When it is determined that the signal value of the smoke detection signal is greater than the second threshold value, the mode shifts to a detection mode, and the amount of current supplied to the light emitting element by the current adjustment unit is greater than the first amount of current. Switching to a second current amount, switching a reference value to be compared with the smoke detection signal to the first threshold value, comparing a signal value of an electric signal from the light receiving element with the first threshold value, and An alarm device that issues a fire alarm when it becomes larger. In claim 1,
In the sensing mode, the signal processing unit further adds a third threshold smaller than the first threshold to a reference value, and compares the smoke sensing signal.
When the signal value of the smoke detection signal becomes smaller than the third threshold value, the mode shifts to the standby mode, and the current amount supplied to the light emitting element by the current adjustment unit is switched to the first current amount, An alarm device, wherein a threshold value to be compared with the smoke detection signal is switched to the second threshold value. In claim 1,
A timer unit for measuring time;
After the signal processing unit transitions to the sensing mode, the number of times that the signal value of the smoke sensing signal exceeds the first threshold before the time measured by the timer unit exceeds a predetermined time is a predetermined number of times. If not, the mode shifts to the standby mode, the current amount supplied to the light emitting element by the current adjustment unit is switched to the first current amount, and the reference value to be compared with the smoke detection signal is An alarm device characterized by switching to a second threshold value. In any one of Claims 1 thru | or 3,
The alarm device, wherein when the light emission amount of the light emitting element decreases to a predetermined level, the current adjusting unit increases the first and second current amounts supplied to the light emitting element.

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