JPS5922910B2 - Battery-powered photoelectric smoke detector light emitting diode abnormality detection and battery voltage drop detection circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a battery-powered photoelectric buried sensor that uses a built-in battery as a power source to periodically cause a light emitting diode to emit light, and detects changes in the light caused by smoke. ,
It is configured to be able to detect an abnormality in the light emitting diode and a drop in battery voltage as a power source.

Conventionally, in photoelectric smoke detectors, constant monitoring of the light emitting source has been required for the purpose of improving reliability.

Furthermore, in a battery-powered photoelectric buried sensor that uses a built-in battery as a power source, constant monitoring of the power supply voltage is also required. Therefore,
The battery-powered photoelectric buried sensor of the present invention satisfies the above two demands at the same time, and will be described in detail below with reference to drawings of embodiments.

FIG. 1 is a diagram showing the configuration of a general battery-powered photoelectric buried sensor, in which a light emitting diode LED is connected to a pulse generator P.
The light is lit in pulses periodically due to the output of the The scattering or attenuation of the light beam generated from this light emitting diode LED due to smoke is detected by the light receiving element PD, and the signal is amplified by amplifier A and then input to comparison circuit H. When the detected signal exceeds the set value, It is configured to drive an alarm M. This sensor operates using the built-in battery B as a power source. FIG. 2 shows only the light emitting part of the present invention, which is the circuit of FIG. 1 added with a light emitting diode abnormality detection circuit and a battery voltage drop detection circuit. ) Periodic pulse lighting is performed via the first transistor Trl which is ON/OFF controlled.

This light emitting diode LED has two resistors R2 in parallel,
A voltage dividing circuit consisting of R3 is connected, and a gap is connected between the voltage dividing point P1 of this voltage dividing circuit and the reference voltage point P2 of the reference voltage circuit consisting of resistor R6 and Zener diode ZD. A second transistor Tr2 that controls the impedance of a circuit that bypasses the output of P via a resistor R4.
The emitter-base circuit of is connected to the resistor R5.
This bypassing circuit consists of resistor R3 and second transistor Tr.
It consists of two emitter-collector circuits, the output of which is converted into an abnormality alarm signal via an inverter I. The operation of the light emitting diode abnormality detection and battery voltage drop detection circuit of the present invention configured as described above will be explained based on the waveform diagram of each part shown in FIG. In normal normal times [section 1], the voltage between the voltage dividers R2 and R3 is the same as that of the light emitting diode LE.
Since there is only a very small voltage drop due to D, the emitter voltage c of the second transistor Tr2 connected to the voltage dividing point is higher than the base voltage f, so it is in the 0N state and the V1 first voltage is higher than the base voltage f. Since the collector voltage d of the transistor Trl is always a high voltage, the pulse voltage b generated in the first transistor Trl is routed through the emitter-collector circuit of the resistor R3 and the second transistor Tr2 and the resistor R4. Therefore, no signal is generated at the output g of the inverter I.

Next, when the light emitting diode LED is disconnected [section], the light emitting current does not flow, so the emitter voltage c of the second transistor Tr2 is at the voltage dividing point P, which is determined by the voltage dividing ratio of the voltage dividing resistors R2 and R3. voltage, which is lower than the base voltage f.

Then, the second transistor Tr2 becomes 0FF state and V
1. The pulse voltage b generated at the first transistor Tr is not bypassed, so the pulse voltage b generated at the first transistor Trl is input to the inverter I and generates a pulse signal at the output g. Furthermore, when the power supply voltage e decreases [section], the voltage drop across the resistor R6 connected in series with the Zener diode ZD decreases, and as a result, the base voltage f of the second transistor Tr2 becomes the emitter voltage c. Since the apparent increase occurs in comparison, the second transistor Tr2
becomes the 0FF state, and the pulse voltage b generated in the first transistor Trl is inputted to the inverter I without being bypassed, similar to when the light emitting diode LED is disconnected, and the output g
generates a pulse signal.

As described above, the light emitting diode abnormality detection and battery voltage drop detection circuit of the present invention can simultaneously monitor the disconnection of the light emitting diode and the drop in battery voltage as a power source with a simple configuration. Since the monitoring timing is when the light emitting diode is emitting light and when the power consumption is high, it is possible to detect a value close to the actual remaining capacity of the battery, which is highly reliable. Since it also serves as the pulse generator of the light emitting circuit, it has a small number of parts and can be manufactured at low cost, making it very useful in the disaster prevention industry.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a general battery-powered photoelectric smoke detector. FIG. 2 is a circuit diagram showing a light emitting diode abnormality and battery voltage drop detection circuit of the present invention. FIG. 3 is a waveform diagram showing waveforms of various parts in the circuit of FIG. B...Battery, P...Pulse generator, LED...Light emitting diode, R3, Tr2/R4...Circuit for bypassing output, R1-6...Resistor, Trl/Tr2... Transistor, ZD... Zener diode.

Claims (1)

[Claims] 1. In a battery-powered photoelectric smoke detector that has a built-in battery as a power source and uses a light-emitting diode as a light source driven by a pulse generator, a circuit that bypasses the output of the pulse generator and a circuit that bypasses the output of the light-emitting diode. means for comparing the divided voltage of the voltage dividing circuit connected between the two poles with a reference voltage and controlling the impedance of the bypassing circuit; A circuit for detecting an abnormality in a light emitting diode and detecting a battery voltage drop in a battery-powered photoelectric smoke detector.