JPS5949638B2 - Dimming smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a dimming type smoke detector that issues an alarm by detecting the amount of light attenuation caused by smoke entering an optical path in which a light emitting element and a light receiving element are arranged facing each other. The invention relates to a sensor equipped with an automatic balancing circuit, and its purpose is to eliminate the effects of circuit contamination, changes due to temperature of circuit elements, and drift such as aging deterioration through automatic balancing.

Attenuation type (light transmission attenuation type) smoke detectors have light transmitting and receiving elements facing each other via an optical path, and the amount of light attenuation between them is 5 to 15%.
/m decreases, an alarm signal is sent to the receiver.

However, light-emitting devices are required to have a long life and high electrical-to-optical conversion efficiency, and a method of emitting pulsed light from an infrared light emitting diode is generally used;
0 to +50°C), and the amount of light changes by about 70% over a long period of time. Furthermore, if the optical system is contaminated, the light will be attenuated by about 50%. The present invention is based on the 100% level of the amplified light receiving output pulse voltage and the constant reduced pressure level (hereinafter referred to as 8
A level comparator circuit using two programmable unijunction transistors (hereinafter referred to as PUT) whose anodes are pressurized with a voltage of 5% level), and a DC voltage of the same voltage as the 85% level of the output pulse voltage that is always applied. When the voltage is held and this holding voltage drops, the capacitor is charged and boosted by the PUT output pulse of the 85% level pressurization, and when this increased voltage exceeds the holding voltage, the capacitor is discharged and the PUT gate is controlled. The main circuit is an analog voltage holding circuit that performs automatic balancing with the level comparison circuit and sets the charging rate and discharge rate of the capacitor to be different. A timer circuit is provided to issue an alarm, and the circuit is configured to minimize power consumption at all times. Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram showing the overall configuration of the attenuation type smoke detector of the present invention, where LD is a pulse generated by a PG pulse generator, and LD is a pulse generated by a pulse generator PG. A light-emitting diode (RD) that is driven to generate pulsed light is a light-receiving diode that faces the light-emitting diode LD (1:1) via an optical path and receives the pulsed light and converts the light into electricity. Receiving light intensifier, LC
Y is a comparison circuit for the 100% level of the output voltage of the light receiving amplifier AM, LC2 is a comparison circuit for the 85% level, VH is an analog voltage holding circuit that performs automatic balancing with the level comparison circuit LC2, and T is a timer. The circuit SW is a switch circuit that triggers a thyristor using the output of the timer circuit T to short-circuit the line ends and generate an alarm signal.

Note that there are two line terminals, and current only for circuit operation is always supplied to the circuit from the center. FIG. 2 shows an example of a specific circuit representing the main part of the present invention.

Pulse generator PGij. A well-known pulse generator that is composed of a PNPN switch element and an LC series resonant circuit and can obtain a large current peak value generates pulses to drive the light emitting diode LD.
For example, infrared pulsed light 1 is emitted from the light source. The pulsed light 1 is received by the opposing light receiving diode RD, converted into an electric pulse, and amplified by the light receiving amplifier AM. The light receiving amplifier AM is a linear amplifier that uses C-MOS (complementary metal oxide semiconductor device) to reduce power consumption, and amplifies the photocurrent pulse flowing through the light receiving diode RD to increase the voltage v.
outputs a positive pulse of The block LC surrounded by a dotted line is a level comparison circuit in which the level comparison circuits LCl and LC2 shown in FIG.
) is applied with an 85% level voltage obtained by reducing the level of the output voltage of the light receiving amplifier AM by a resistor R1, and a 100% level voltage is applied to the anode of the transistor PUT2. The analog voltage holding circuit VH includes a MOS field effect transistor MOS1, field effect transistors MOS2 and MOS3 constituting a C-MOS amplifier circuit, and a capacitor Cl. It consists of resistors R2, R3, etc.

Gate of transistor MOS1 (q is level comparison circuit L
Connected to the cathode (5) of the transistor PUTl of C,
Also, the output side of the C-MOS amplification circuit is resistor R4,
It is connected to the gates (Q) of transistors PUTl and PUT2 via R5, and constitutes an automatic balancing circuit between the level comparison circuit LC and the analog voltage holding circuit VH.Thus, the voltage holding function of the voltage holding circuit VH is as follows. Depending on the charging and discharging of capacitor C1, capacitor C1 is charged at a constant rate (less than 1%/sec) through resistor R2 when the gate of transistor MOS1 becomes 0N, and discharged at a constant rate (less than 1%/sec) through C-MOS. The resistance R
3 is for limiting current consumption. The timer circuit T is a capacitor C2 that constitutes a time constant circuit for time setting.
and resistor R6, transistors PUT3 and Tr that constitute the discharge circuit of capacitor C2, resistors R7 and R8 for setting the voltage of the gate (Q) that regulates the conduction of transistor PUT3, and the switch circuit SW is composed of thyristor SCR. It also consists of a resistor R9, a capacitor C3, etc. for noise prevention.

Further, the rectifier RF rectifies the power supply current transmitted from the center via the line, and supplies DC power at a voltage of V to the circuit through the resistor RlO. Note that the capacitor C3 is for smoothing the rectified wave. Next, we will explain the operation of the circuit.
A pulse voltage with an amplitude v is input from the light receiving amplifier AM to the level comparison circuit LC, a pulse voltage with a level 85% V is applied to the anode of the transistor PUT1, and a pulse voltage with a level 100% V is applied to the anode of the transistor PUT2. A pulse voltage is applied.

On the other hand, the output voltage of the analog voltage holding circuit VH is 85% of the above
V, and this DC voltage decreases as capacitor C1 discharges at a rate of 5-10%/hour, thus reducing transistor PU.
Since the gate voltage of Tl also decreases, when the anode voltage of 85% V becomes higher, the transistor PUTl becomes conductive and the voltage is transferred from the cathode (T) to the transistor MO of the voltage holding circuit VH.
A pulse is sent to the gate (6) of Sl. FIG. 3 is a voltage waveform diagram when the transistor PUT1 is in operation, and when the anode voltage becomes higher than the gate voltage, a cathode output voltage is generated. As shown in the figure, the phase of the cathode output voltage is delayed due to stray capacitance due to the high impedance of the cathode circuit. Note that when the anode voltage is lower than the gate voltage, there is no output from the cathode. When the above cathode output voltage is applied to the gate of the transistor MOS1, the transistor M
A charging circuit for capacitor C1 passing through OSl is configured,
Capacitor C1 is charged at the previously mentioned rate to restore the holding voltage level.

In this way, the holding voltage is balanced between the transistor PUTl and the voltage holding circuit. Therefore, even if the output voltage V of the photoreceptor amplifier AM changes due to drift, the output voltage of the voltage holding circuit VH follows the change and is always maintained at VC.
It becomes 85%V. As a result, the gate (Qvc) of the transistor PUT2 is always applied with a voltage at the 85% level of the voltage that maintains the peak value of the output voltage V of the photodetector amplifier AM.On the other hand, the anode of the transistor PUT2 is always applied with a voltage of 100% V. A transistor PU to which a pulse voltage is applied and is supplied from an analog voltage holding circuit VH
Since the gate voltage of T2 is naturally lower than the anode voltage, a positive pulse is always generated at the output of the transistor PUT2, and the NPN transistor Tr is made conductive for each pulse to discharge the charge in the capacitor C2 through the transistor Tr.

However, smoke enters the optical path and the amount of light received decreases, causing the anode voltage applied to the transistor PUT2 to drop to the voltage holding circuit V
When the voltage becomes smaller than the gate voltage supplied from H, the comparison output of the transistor PUT2 disappears, the transistor Tr is cut off, and the capacitor C2 continues to charge. Figure 4 is a time chart explaining the operation of the circuit after the transistor PUT2, and the block diagram in Figure 1 is a time chart explaining the operation of the circuit after the level comparison circuit LCI. Figure b shows a state in which the voltage level has attenuated after the smoke infiltrated; figure b shows the same output pulse from the cathode, but the output is cut off after smoke invades for the reason mentioned above; figure c shows the charging and discharging state of capacitor C2. , the charging voltage of capacitor C2, which increases with the time constant of resistor R6 and capacitor C2, is discharged through transistor Tr every time the cathode output pulse is shown in b in the same figure, but if the cathode output pulse is cut off due to the intrusion of smoke, charging continues. and its charging voltage, that is, transistor PUT3
When the anode (8 voltage exceeds the gate (q voltage) set by resistor RT.R8, transistor PUT3 becomes conductive and discharges the charge of capacitor C2, and the thyristor SCR
is made conductive by triggering its gate, and the switch circuit SW is changed from 0FF to 0 as shown in the chart d in the same figure.
Switch to N to short-circuit the DC output side of the rectifier RF. That is, a smoke detection alarm is issued after a time period set by a time constant circuit (indicated by approximately 10 pulses in chart (c)) after smoke intrusion is detected. Next, the point that the present invention can eliminate the influence of drift will be explained. in general,
In a device like the present invention that optically detects smoke intrusion using a light emitting/receiving element, temperature changes can be detected as described above. The amount of light received changes over time due to aging deterioration, etc.
The output voltage v of M drifts as illustrated in FIG.

Therefore, unlike conventional devices, the smoke detection level cannot be set to a certain level (
If it is fixed to the dot-dashed line in the figure, due to the change due to the drift, there is a risk that smoke will be erroneously detected as smoke entering even though no smoke has entered at point P1, which is below the detection level. In the case of the present invention, as described above, the voltage holding circuit V
Due to the balancing effect of the holding voltage between transistor PUT1 and transistor PUTl, the applied voltage at the gate (q) of transistor PUT2, which is the smoke detection level, is equal to 8
It is automatically adjusted to the 5% V level (double-dashed line in the figure). Therefore, even if the output voltage V of the photodetector amplifier AM changes over time due to drift as shown in the figure, the voltage at the gate (C4) of the transistor PUT2, which is the smoke detection level, will always follow the change and remain at the 85% V level, which is 15% lower. Therefore, even if the output voltage V drifts, the smoke detection level is 85%.
Since it no longer intersects with the V level, there is no false detection at the P1 point unlike the conventional fixed detection level, and shadow detection due to drift can be eliminated. When smoke enters and the output voltage V of the light receiving amplifier AM suddenly decreases, the transistor PUT2 detects this at the point P2, which is the intersection with the 85%v level, and issues a smoke detection alarm.

Figure 5 is a schematic diagram showing an example of the overall structure of this attenuation type smoke detector, with a light emitting part containing a pulse generator PG, a light emitting diode LD, etc., and a smoke introduction hole that allows smoke to enter as appropriate. Both ends of the sensor body, which consists of a light path cladding tube installed at the top of the sensor, a light receiving judgment unit containing a light receiving diode RD and other circuits, are supported by a holder mounted on a pedestal, and the pedestal is mounted on the ceiling with the entire body facing downward. This is what is shown.

As described in the above embodiments, the present invention uses analogues with different charging and discharging rates to perform automatic balancing with the level comparison circuit so as to always maintain a constant reduced pressure level of the amplified light receiving output voltage. This is a dimming type smoke detector that uses a voltage holding circuit to eliminate the effects of drift and ensure the operation of the detection circuit when smoke enters.

This smoke detector can also be directly used to warn of poor visibility due to fog, snow, etc. by emitting a laser beam over a long distance.

[Brief explanation of the drawing]

The drawings relate to embodiments of the dimming type smoke detector of the present invention.
Fig. 1 is a block diagram showing the overall configuration, Fig. 2 is an example of a specific circuit showing the main parts of the present invention, Fig. 3 is a comparison voltage waveform diagram in a level comparison circuit, and Fig. 4 is a smoke intrusion diagram. A time chart for explaining the detection operation, FIG. 5 is an external view of an example of the structure of the sensor showing the installed state, and FIG. 6 is a diagram for explaining the operation against drift.

Claims (1)

[Claims] 1 A light-emitting element and a light-receiving element are arranged facing each other so that the pulsed light of a light-emitting element driven by pulsed light is received through an optical path, and an alarm is issued by detecting that the amount of light received is attenuated due to smoke entering the optical path. A level comparison circuit using two programmable unidirectional transistors whose anodes are respectively pressurized with a 100% level of an amplified light reception output voltage and a constant reduced pressure level in a dimming type smoke detector that emits light;
A capacitor charging circuit controlled by the constant reduced pressure level comparison output of this comparison circuit and a level comparison circuit that amplifies the voltage of this capacitor and supplies voltage to the gates of the two transistors to maintain the constant reduced pressure level. An analog voltage holding circuit that automatically balances the voltage holding is provided.
A dimming type smoke detector characterized by eliminating the influence of drift on detection circuit operation when smoke enters.