JPS6130320B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a detection signal processing circuit for a photoelectric smoke detector, in which the photoelectric smoke detector detects sudden and high-energy noise among disturbance noises caused by light, electricity, etc. If you respond to this, it will cause a false alarm, so it is necessary to operate a delayed response to the input signal, in other words, to provide a certain period of judgment for the input signal to prevent the original smoke caused by fire from occurring. The purpose is to detect only signals and generate an alarm.

That is, in this invention, among the light from the light source driven by the light emission pulse circuit, the light scattered by the smoke particles is received by the light receiving element, and the current increases as the electric resistance of the light receiving element decreases.The switching circuit detects the light scattered by the smoke particles. In photoelectric smoke detectors, when the output of the one-shot circuit is on, the discharge circuit is turned off,
A photoelectric smoke sensor characterized in that when the output of the one shot circuit is off, the discharge circuit is turned off to reset the integrating circuit, and the charging circuit is turned off so that no charging operation is performed. The present invention relates to a detection signal processing circuit for a device.

Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 will be explained. X, Y are the light emitting part and light receiving part of the photoelectric smoke detector, 1 is the level detection circuit,
2 is one shot circuit, 3 is CR time constant circuit, 4
The output circuit 5 is a discharge circuit. The one shot circuit 2 and the level detection circuit 1 are constructed to operate as follows. When the pulse voltage generated at point A becomes sufficient to make transistor Tr1 conductive, transistor Tr1 is turned on. As a result, transistors Tr2 and Tr3 are also turned on. R1 to R6 are current limiting resistors. When transistor Tr3 is turned on, capacitor C2 is connected to the path D1→C2→Tr3.
charge is discharged. At the same time, the transistor Tr4 is also turned on, and the transistor Tr5 is also turned on through the resistor R9. Even if the transistor Tr3 is turned off, the capacitor C2 is charged through the base of the transistor Tr4 → R8 → Tr5, so the transistor
Tr4 and Tr5 are turned on for a certain period of time. This time is 1
It is set between pulse and 2 pulses. next
In the CR time constant circuit 3 and output circuit 4, when the transistor Tr5 is normally off, the diode D2 is reverse biased and the transistor Tr
6 is on, the charge of capacitor C1 is transistor
It is discharged by Tr6. Transistors Tr4, Tr5
While the transistor is on, diode D2 is forward biased and diode D4 is off and the transistor
Tr6 is turned off. Therefore, Tr4→D3→R13
→Capacitor C1 is charged in the C1 path, and when it exceeds the VBE (approximately 1V) of transistors Tr7 and Tr8, transistors Tr7 and Tr8 are turned on, and resistor R14 is turned on.
VCC appears.

Next, the operating state of this invention will be described.

[] Normal state The input A of the level detection circuit 1 is at a low level and the one-shot circuit 2 is on standby. Also, when the output of the one-shot circuit 2 is off, the discharge circuit 5 is normally on, and the CR time constant is circuit 3
The charge in the capacitor C1 is always discharged with low resistance, and the output of the output circuit 4 has not yet reached the alarm level.

[] Smoke generation Since the input A of the level detection circuit 1 is at a high level, the output of the one-shot circuit 2 is turned on by the input signal of the first pulse, and the output remains unchanged until the next cycle of pulses arrives. The time constants of capacitor C2 and resistor R8 are set so as to extend the time. If the next pulse following the above pulse is also at a high level, the output of the one-shot circuit 2 continues to remain on due to that pulse. Furthermore, if high pulses come continuously, the output of the one-shot circuit 2 will remain in the on state.
Since the discharging circuit of capacitor C2 in the CR time constant circuit 3 is in the OFF state and the charging circuit of capacitor C2 is working, charge continues to be gradually stored in capacitor C2. The output circuit 4 finally reaches the alarm output due to the pulse input signal, and a smoke generation alarm sounds.

[] Noise Occurrence 1 Single Noise Occurrence The output of the one-shot circuit 2 will remain in the on state for the time span set to a level where the input A of the level detection circuit 1 does not reach the alarm level with just one pulse. After that time has elapsed, the output of the one-shot circuit 2 is turned off. When the output of the one shot circuit 2 is turned off, the discharge circuit 5 comes into operation and the output of the output circuit 4 does not reach the alarm level.

2. Continuous Noise Generation The output of the one-shot circuit 2 is turned on for a set time by the first pulse of the input A of the level detection circuit 1, and turns off after the elapse of that time. However, even if one-shot circuit 2 is turned off, capacitor C in that circuit
Since there is no discharge path for the charge of C2, even if the output of one-shot circuit C2 is turned on next time, it will remain ON for the time it takes to charge the amount of leakage from capacitor C2, and then it will turn off immediately. The situation is repeated. And when the output of one-shot circuit 2 is off,
Since the discharge circuit 5 operates, the potential of the capacitor C1 in the time constant circuit 3 does not reach the alarm level of the output of the output circuit 4.

Fig. 2 shows the operation chart of the signal processing circuit of the present invention, in which [] is the normal state, [] is when smoke is generated, and [] is when noise is generated, respectively. It represents the potential of capacitor _C1 of circuit 5 and CR time constant circuit 3.

In the detection signal processing circuit of a photoelectric smoke detector according to the present invention, when the output of the one shot circuit is on, the discharge circuit is turned off, and when the output of the one shot circuit is off, the discharge circuit is turned on and the integration circuit is turned on. At the same time as the reset, the charging circuit is turned off and no charging operation is performed, so the one-shot circuit eliminates power consumption, and once the one-shot circuit is turned on, it remains on until the next pulse following that pulse arrives. It is possible to generate an alarm by holding the state and driving the output circuit with several pulses.In other words, it detects only the original signal from smoke during a fire and generates an alarm without responding to external noise. This has the effect of increasing the reliability of smoke detector operation.

[Brief explanation of the drawing]

The drawings show an embodiment of a detection signal processing circuit for a photoelectric smoke detector according to the present invention.
The figure shows an electric circuit diagram, and FIG. 2 shows an operation chart of the signal processing circuit. X and Y are the light emitting part and light receiving part of the photoelectric smoke detector,
1 is a level detection circuit, 2 is a one shot circuit, 3
is the CR time constant circuit, 4 is the output circuit, and 5 is the discharge circuit.

Claims (1)

[Claims] 1. In a photoelectric smoke sensor that detects the presence of smoke by detecting an electrical signal generated when light from a light emitting element driven by a light emitting pulse circuit is scattered by smoke particles and enters a light receiving element, A level detection circuit that determines and outputs when the received light output exceeds a certain level, a one-shot circuit that extends the output of this level detection circuit from one cycle or more of the light emission pulse to less than two cycles, and this one-shot circuit output. a discharge circuit that instantly discharges the CR time constant circuit when the output of the level detection circuit is not continuous, and an alarm output when the output of the CR time constant circuit reaches a predetermined value. A detection signal processing circuit for a photoelectric smoke detector, characterized by being provided with an output circuit.