JPH057677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a snow sensor that detects the occurrence of snow on the roof of a house in a snowy area.

[Prior Art] Conventionally, in snowy areas, a large amount of snow accumulates on the roofs of houses due to snowfall during the winter. For this reason, it is necessary to remove snow several times a year, and many people die each year from falling from the roof during this process. Recently, in order to prevent such accidents, there has been a trend of installing snow processing equipment on rooftops, which uses heaters, snow melting methods using water sprinklers, and mechanical snow removal methods.

Since it is desirable for these processing devices to process roof snow when it exceeds a certain amount in order to save energy, various snow detection sensors have been devised to detect the state of a certain amount of snow. . Among them, snow sensors that use infrared rays are
It is widely used because of its high reliability.
This type of infrared sensor determines the amount of snow by emitting infrared rays in the direction of the snow surface and detecting the intensity of the amount of light reflected by the snow surface.

[Problems to be Solved by the Invention] Therefore, with conventional infrared sensors, when the amount of snow increases and the amount of snow reaches a set value that requires processing, the infrared sensor detects light other than light reflected from the snow surface. Reflected light from snowflakes falling nearby will enter the infrared sensor, and if the amount of variation in the received light level is greater than the hysteresis range of the sensor circuit, a signal with many errors will be output. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a snow sensor that can reliably determine the amount of snow even during snowfall.

[Means for Solving the Problems] A snow sensor according to the present invention includes a photoelectric conversion circuit that receives reflected light of periodically transmitted light and converts it into an electrical signal, and an output of the photoelectric conversion circuit. A snow sensor configured to include a comparator that compares and determines levels, an integrating circuit that is connected to the output side of the comparator and integrates the output of the comparator, and an integration circuit that is connected to the output side of the comparator that integrates the output of the comparator. an inverting circuit that performs inversion; a monostable circuit that receives the output of the inverting circuit and generates a pulse synchronized with the fall of the output of the comparator to reset the integrating operation of the integrating circuit; The present invention is characterized in that a second comparator is connected to the integrated circuit and compares and determines the output level of the integrating circuit.

[Function] According to the present invention, when the reflected light is received not from the snow surface but from the snowflakes, the first comparator operates, but when the reflected light disappears, the output of the first comparator is reversed. , the output of the monostable circuit via the inverting circuit resets the integrator circuit. Therefore, the output of the integrating circuit returns to zero and the second comparator is not activated, thereby preventing malfunctions caused by temporary reflected light from snowflakes or the like.

[Embodiments of the Invention] Next, a snow sensor according to the present invention will be described with reference to the drawings.

First, in order to facilitate comparison with the embodiment according to the present invention, a configuration example of a conventional snow sensor will be described with reference to the block in FIG. 2. In this figure, a periodic output obtained from an oscillation circuit 1 is amplified by an amplifier circuit 2 and applied to a light emitting diode 3. The light emitting diode 3 is turned on by the input and emits light toward the snow covered surface A. The reflected light from the snow is received by a phototransistor 4 which is set in advance to receive the reflected light, converted into an electrical signal, amplified by an amplifier circuit 5, and detected by a detection circuit 6. The DC voltage obtained by detection by the detection circuit 6 is compared with a reference voltage of a reference voltage source 8 by a comparator 7, and if it is larger than the reference voltage, the output of the comparator 7 operates the relay 14. However, in such a configuration, when it snows, malfunctions occur due to reflected light from snowflakes falling between the light emitting diode 3 and the snow surface, and the determination result cannot be trusted.

FIG. 1 is a block diagram showing an embodiment of a snow sensor according to the present invention. In this example, the functions from the oscillation circuit 1 to the reference voltage source 8 and including the relay 14 are indicated by the same reference numerals in FIG. 2 and have the same functions.
An integrating circuit 9 and a comparator 12 with a reference voltage source 13 are connected between the comparator 7 and the relay 14, and an inverting circuit 12 is connected to the output side of the comparator 7 to reset the integrating circuit 9. and a monostable circuit 11 are added.

Now, in FIG. 1, when the phototransistor 4 detects reflected light from the snow surface that has reached a predetermined level, the comparator 7 generates a predetermined voltage.
Integrating circuit 9 starts an integrating operation. When the output of the integrating circuit 9 becomes higher than the reference voltage of the reference voltage source 13, the comparator 12 operates and the relay 14
Activate.

Separately from the above, when reflected light from a snowflake enters the phototransistor 4, the comparator 7 is activated and the integration circuit 9 starts integrating, but when the reflected light disappears, the output of the comparator 7 is reversed. This inverted output is given to the inverting circuit 10, and a reset pulse is obtained by operating the monostable circuit 11 with the rising output. If the integration operation of the integration circuit 9 is reset with this output, the output of the integration circuit 9 will return to zero, so the comparator 12 will not operate and the relay 14 will not operate. In this way, temporary malfunctions caused by snowflakes can be prevented.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, the snow surface can be determined without error even during snowfall, and the effect of improving reliability is significant. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of the configuration of a conventional snow sensor. In the above diagram, 1 is an oscillation circuit, 2 and 5 are amplifier circuits, 3 is a light emitting diode, 4 is a phototransistor, 6 is a detection circuit, 7 and 12 are comparators,
8 and 13 are reference voltage sources, 9 is an integrating circuit, 10 is an inverting circuit, 11 is a monostable circuit, and 14 is a relay.

Claims (1)

[Claims] 1. In a snow sensor configured to include a photoelectric conversion circuit that receives reflected light of periodically transmitted light and converts it into an electrical signal, and a comparator that compares and determines the output level of the photoelectric conversion circuit. ,
an integrator circuit connected to the output side of the comparator to integrate the output of the comparator; an inverting circuit connected to the output side of the comparator to invert the output of the comparator; a monostable circuit that resets the integrating operation of the integrating circuit by generating a pulse synchronized with the fall of the output of the integrating circuit; and a second monostable circuit that is connected to the output side of the integrating circuit and that compares and determines the output level of the integrating circuit. A snow sensor characterized in that a comparator is added.