JPS6256724A - Automatic ventilation fan - Google Patents

Abstract

PURPOSE:To effect high accuracy ventilation fan control by constituting an automatic ventilation fan control system with a nonstable multivibrator circuit which outputs a detection signal according to the resistance value of a smoke sensing resistance element, reference time generation circuit, switching element which drives a ventilation fan using the output signal of a microcomputor. CONSTITUTION:The resistance value of a smoke sensing resistance element 1 is changed into a square shaped off time by means of a nonstable multi-vibrator circuit 2, and it is inputted to a microcomputor 4 via a wave shape forming circuit 3. This input is converted into a relative number at a microcomputor 4 by comparison with the square shaped wave off time of the reference time generated from another nonstable multi-vibrator circuit 5. In order to prevent unstability at the start of energizing the smoke sensing element 1 the resistance value of the smoke sensing resistance element 1 after a certain time has passed and the sensor 1 has become stable is taken in as a reference value,and then it is converted into a relative value to be taken is as a reference relative value. After this the resistance value of the smoke sensing resistance element 1 is converted into a relative value by the microcomputer 4, an by its difference from the reference relative value a motor 7 is driven through a switching element 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic ventilation fan that is operated by sensing smoke.

2. Description of the Related Art Conventionally, a control circuit for this type of ventilation fan has a configuration as shown in FIG. 2, although no specific literature is cited. That is, the resistance value of the smoke sensing resistive element 101 changes due to changes in the concentration of smoke in the air, and the change in resistance value is expressed as resistance 1o2. Variable resistor 103, resistor 104. resistance 1o5
．． A bridge circuit consisting of a resistor of 106° and a resistor of 107 performs comparison detection. When the concentration of smoke in the air increases, the resistance value of the smoke sensing element 101 decreases, the bridge circuit becomes unbalanced, and a small current flows through the base of the transistor 108. This minute current is amplified by a transistor 109, a switching operation is performed by a transistor 110, a relay 111 is activated, and a motor 112 is activated.
It was configured to drive the

Problems to be Solved by the Invention In such a conventional configuration, the smoke sensing resistor element 101 operates very unstablely when the current is started, and does not become stable until several minutes have passed after the start of the current. Therefore, it was necessary to adjust the variable resistor 103 and take in the reference value when the air conditioner stabilized after several minutes in the normal air condition, which required a lot of effort. Further, since the adjustment is done manually, there is a problem in that it is difficult to obtain highly accurate reference values.

The present invention is intended to solve these problems, and aims to: - Automatically take in the resistance value of a smoke sensing resistance element under stable normal air conditions as a reference value, and perform highly accurate control of a ventilation fan. That is.

Means for Solving the Problem In order to solve this problem, the present invention provides an astable multi-function device that outputs a detection signal that changes according to the resistance value of a smoke sensing resistor element whose resistance value changes in response to smoke. a vibrator circuit, a reference time generation circuit, and a microcontroller that takes in the resistance value of the smoke sensing resistor element in normal air conditions after a predetermined time as a reference value, and outputs a signal when the detection signal exceeds the reference value. It consists of a computer and a switching element that drives a ventilation fan using the output signal of this microcomputer.

Function: With this configuration, the microcomputer receives a signal from the reference time generation circuit, measures when to take in the stable resistance value of the smoke sensing resistor element as a reference value, takes that resistance value after a predetermined period of time has elapsed, and sets the value to zero. The detection signal from the stable multivibrator circuit is compared, and the switching element is operated based on the result to control the operation of the ventilation fan, allowing highly accurate operation control of the ventilation fan.

Example Hereinafter, one embodiment of the present invention will be described based on FIG.

In FIG. 1, reference numeral 2 denotes an astable multivibrator circuit which outputs a detection signal according to the change in resistance value of the smoke sensing resistor element 1 whose resistance value changes in response to smoke. It is connected to the. 5
is another astable multivibrator which generates a square wave reference time and is connected to the microcomputer 4. A triac 6 is connected between the output section of the microcomputer 4 and the motor of the ventilation fan.

The operation of the automatic ventilation fan in the above configuration will be explained below.

The resistance value of the smoke sensing resistive element 1 is varied during the off-time of the square wave by the astable multivibrator circuit 2.

The square wave is inputted to the microcomputer 4 via the waveform shaping circuit 3. This input is converted into a relative number by the microcomputer 4 by comparing it with the off time of the square wave of the reference time generated by another astable multivibrator circuit 5. In order to prevent instability at the start of energization of the smoke sensing element 1, the microcomputer 4 measures the time, and when it stabilizes after a predetermined period of time, the resistance value of the smoke sensing resistive element 1 is taken in as a reference value, and the microcomputer 4 calculates the relative value. Convert it to a value and automatically import it as a reference relative number. Thereafter, the resistance value of the smoke sensing resistance element 1, which changes from time to time, is converted into a relative number by the microcomputer 4, and the motor is driven through the switching element 6 based on the difference from the reference relative number.

In the embodiment, the astable multivibrator 5 is used to convert the reference relative number, but it goes without saying that there is no limit to the method of generating the reference time.

Effects of the Invention As is clear from the above description of the embodiments, according to the present invention, a stable reference resistance value of a smoke sensing element can be obtained by using a smoke sensing element, an astable multivibrator circuit, and a microcomputer. This allows for highly accurate ventilation fan control. Automatic importing eliminates the need for human intervention, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of an automatic ventilation fan according to an embodiment of the present invention, and FIG. 2 is a control circuit diagram of a conventional automatic ventilation fan. 1...Smoke sensing resistor element, 2...Astable multivibrator circuit, 4...Microcomputer, 6...Switching element.

Claims (1)

[Claims] an astable multivibrator circuit that outputs a detection signal that changes according to the resistance value of a smoke sensing resistive element whose resistance value changes in response to smoke; a reference time generating circuit; Consisting of a microcomputer that takes in the resistance value of the sensing resistive element as a reference value and outputs a signal when the detection signal exceeds the reference value, and a switching element that drives the ventilation fan using the output signal of this microcomputer. automatic ventilation fan.