Pulsed infrared dust concentration detection circuit

Abstract

The invention discloses a pulsed infrared dust concentration detection circuit, which is composed of an analog circuit and a digital circuit. The analog circuit comprises four stages of operational amplifiers connected in order. The non-inverting end and inverting end of a first stage operational amplifier are connected by a phototube. The infrared luminous tube of the phototube is connected between the collector electrode and digital ground of a triode, an infrared receiving tube is connected between the non-inverting end and inverting end of the first stage operational amplifier. A capacitor C1 is connected between a power supply and the digital ground, a resistor R1 is connected between the power supply and the emitting electrode of the triode, a capacitor C2 is connected between the emitting electrode of the triode and the digital ground, and a resistor R3 is connected between the PWM port of the digit circuit and the base electrode of the triode. A single chip microcomputer emits PWM pulse to drive the triode by the resistor R3. Step-by-step amplification is employed to conduct signal processing, precisely control the effective signal amplitude, and maximumly reduce noise interference. The circuit is internally added with a charge storage and driving part circuit, can realize autonomous driving, and has no need for an additional external power supply.

Description

technical field [0001] The invention relates to a dust concentration detection instrument, especially a detection circuit therein. Background technique [0002] The dust concentration detector is mainly composed of a detection circuit, a detection hole, etc. After the light-emitting tube in the detection circuit emits light, the emission optical axis formed in the optical path structure passes through the detection hole. When there is no dust in the detection hole, the emission optical axis will propagate along a straight line. ; When there is dust in the detection hole, the dust will scatter the light, and the light passing through the detection hole will scatter around, so that the light will change and the output signal will change. The detection circuit adopts a four-stage amplifier integrated chip to amplify the signal received by the light-emitting tube, and finally outputs an analog signal. The main problems of the dust concentration detection circuit are: [0003] ...

AI Technical Summary

Problems solved by technology

[0003] 1. The dust concentration detection circuit is only a passive detection circuit, which does not have the functions of signal processing and key information storage

[0004] 2. The luminous tube is a passive device and must be driven by an external PWM signal to work. The power supply for driving the luminous tube must be provided by an external circuit alone, which is equivalent to a detector product that needs to provide two power sources to work.

[0005] 3. The light-emitting tube works under the drive of an external PWM signal, and outputs an analog signal. The analog signal is greatly affected by the power supply voltage and the driving signal, and the accuracy is low.

[0006] 4. The accuracy of dust concentration detection depends too much on the accuracy of integrated chips, and the controllability is low

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