CN215375086U - Photoelectric air pollution degree detection system - Google Patents
Photoelectric air pollution degree detection system Download PDFInfo
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- CN215375086U CN215375086U CN202121412867.XU CN202121412867U CN215375086U CN 215375086 U CN215375086 U CN 215375086U CN 202121412867 U CN202121412867 U CN 202121412867U CN 215375086 U CN215375086 U CN 215375086U
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Abstract
The utility model discloses a photoelectric air pollution degree detection system, which comprises an air turbidity detection circuit, a constant current control circuit and a light emitting diode LED1, wherein the air turbidity detection circuit receives an illumination intensity signal of a light emitting diode LED1 penetrating through air, converts the illumination intensity signal into a voltage signal and outputs the voltage signal to a controller, the controller detects the air pollution degree according to the received voltage signal and outputs a pulse width modulation signal to the constant current control circuit, and the constant current control circuit outputs constant current according to the received pulse width modulation signal to drive the light emitting diode LED 1. The photoelectric air pollution degree detection system can achieve the purpose of driving the light emitting diode LED1 to output stable illumination intensity by constant current, and further improves the accuracy of air pollution degree detection.
Description
Technical Field
The utility model relates to the field of air pollution degree detection devices, in particular to a photoelectric air pollution degree detection system.
Background
In recent years, people are increasingly unsatisfied with the quality of living air, and particulate matters harmful to human bodies in the air are continuously increased. In order to control the increasingly deteriorated air, people invent a plurality of methods for detecting air turbidity, a photoelectric detection method is the most common method, the driving signal used by the method is mostly in a constant value voltage or pulse voltage form, the constant value voltage or pulse voltage is converted into different current values through the self impedance of a light emitting diode device to drive a light source to work, and light of the light source passes through the turbid air and is received by a phototriode to complete photoelectric signal conversion. However, the light emitting diode device used for measuring turbidity by the photoelectric method is a current-driven type, illumination linear change can be realized by changing current, and the current fixed value voltage or pulse voltage cannot effectively ensure that the light emitting diode outputs stable illumination intensity, so that the detection of air turbidity is inaccurate.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a photoelectric air pollution degree detection system capable of ensuring the stable output of the illuminance of a photoelectric device.
The photoelectric air pollution degree detection system comprises an air turbidity detection circuit, a controller and a constant current control loop;
the air turbidity detection circuit receives an illumination intensity signal of the light emitting diode LED1 penetrating through the air, converts the illumination intensity signal into a voltage signal and outputs the voltage signal to the controller;
the controller detects the air pollution degree according to the received voltage signal and outputs a pulse width modulation signal to the constant current control loop;
the constant current control loop outputs constant current to drive the light emitting diode LED1 according to the received pulse width modulation signal.
The photoelectric air pollution degree detection system outputs constant current to drive the light emitting diode LED1 through the pulse width modulation signal output by the controller according to the received pulse width modulation signal by the constant current control loop, the air turbidity detection circuit receives the illumination intensity signal of the light emitting diode LED1 penetrating through the air, converts the illumination intensity signal into a voltage signal and outputs the voltage signal to the controller, and the controller detects the air pollution degree according to the received voltage signal so as to achieve the purpose of driving the light emitting diode LED1 to output stable illumination intensity by constant current and further improve the accuracy of air pollution degree detection.
The air turbidity detection circuit comprises a phototriode Q1 and an emitter follower isolation chip U1;
a collector of the phototriode Q1 is connected with a positive terminal of a direct-current power supply VCC _12V, a base receives an illumination intensity signal of the LED1 penetrating through air, and an emitter is respectively connected with a resistor R1 and a positive input end of an emitter follower isolation chip U1;
the reverse input end and the output end of the emitter follower isolation chip U1 are connected, the output end is connected with the controller, and the power supply end is connected with the positive end of a direct-current power supply VCC _ 5V;
the constant current control loop comprises an RC shaping circuit and a negative feedback loop;
the RC shaping circuit shapes and outputs a direct current voltage signal to a negative feedback loop according to the received pulse width modulation signal;
and the negative feedback loop receives the direct current voltage signal and outputs constant current to drive the light emitting diode LED1 according to the current signal fed back by the sampling circuit in the negative feedback loop.
The RC shaping circuit comprises a resistor R2, a resistor R3, a capacitor C1 and a capacitor C2;
one end of the resistor R2 is respectively connected with one end of the resistor R3 and the PWM end of the controller, and the other end of the resistor R2 is grounded;
the capacitor C1 and the capacitor C2 are connected in parallel, one end of a parallel node is connected with the other end of the resistor R3 and the input end of the negative feedback loop respectively, and the other end of the parallel node is grounded.
The negative feedback loop comprises an operational amplifier U2, a triode Q2 and a sampling resistor R4;
the positive input end of the operational amplifier U2 is connected with the parallel connection node of the capacitor C1 and the capacitor C2, the output end is connected with the base electrode of the triode Q2 through the resistor R5, and the reverse input end is respectively connected with one end of the sampling resistor R4 and the emitter electrode of the triode Q2;
the collector of the triode Q2 is connected with the cathode of the light-emitting diode LED1, the emitter of the triode Q2 is grounded through the sampling resistor R4, and the anode of the light-emitting diode LED1 is connected with the positive end of the direct-current power supply VCC _ 12V.
Drawings
FIG. 1 is a schematic diagram of a photoelectric air pollution level detection system according to the present invention;
FIG. 2 is a circuit diagram of an air turbidity detecting circuit according to the present invention;
fig. 3 is a circuit diagram of a constant current control loop according to the present invention.
Detailed Description
A photoelectric air pollution degree detection system is shown in figure 1 and comprises an air turbidity detection circuit, a controller and a constant current control loop, wherein the air turbidity detection circuit receives an illumination intensity signal of a light emitting diode LED1 penetrating through air, converts the illumination intensity signal into a voltage signal and outputs the voltage signal to the controller, the controller detects the air pollution degree according to the received voltage signal and outputs a pulse width modulation signal to the constant current control loop, and the constant current control loop outputs constant current to drive a light emitting diode LED1 according to the received pulse width modulation signal.
The air turbidity measuring principle of the photoelectric air pollution degree detection system is that the air turbidity degree is judged by utilizing the change of illumination intensity after the light emitting diode LED1 emits fluorescence and penetrates through turbid air. As shown in fig. 2, the light emitting diode LED1 is driven by a constant current to emit fluorescence, the fluorescence irradiates the phototransistor Q1 through turbid air and is received, the phototransistor Q1 outputs different currents Ie according to different emitters receiving illumination intensity, the currents Ie flows through a resistor R1 and is converted into a voltage signal Ue = Ie × R1, the voltage signal Ue flows into an emitter follower isolation chip U1, the voltage signal Ue is received by a controller after being isolated, the controller detects air pollution degree according to the received voltage signal, and the controller is a single chip microcomputer controller, such as a single chip microcomputer controller STM 32.
The constant current control loop receives a pulse width modulation signal with a duty ratio of N transmitted by the controller, a rectangular wave with a peak-to-peak value of U passes through an RC shaping circuit consisting of a resistor R2, a resistor R3, a capacitor C1 and a capacitor C2, the rectangular wave is gradually changed into direct current voltage by utilizing the charge-discharge characteristic of a large capacitor in an RC combination, the amplitude of the direct current voltage is the peak-to-peak value (U multiplied by N) V, the direct current voltage passes through an operational amplifier U2, a triode Q2 and a sampling resistor R4 to form a negative feedback loop, and the sampling resistor R4 feeds back the current of a load light emitting diode LED1 in real time, when the load current becomes larger, the voltage at the reverse input terminal of the operational amplifier U2 becomes higher, the difference from the positive input terminal becomes smaller, the differential voltage value at the output terminal becomes smaller, further, the base current of the output control transistor Q2 decreases, the internal resistance of the transistor Q2 increases, the voltage drop between the emitter and the collector increases, and the load current decreases. When the load current is reduced, the voltage of the reverse input end of the operational amplifier U2 is reduced, the difference value between the voltage and the same-direction input end of the operational amplifier U2 is increased, the output differential voltage value of the operational amplifier U2 is increased, the base current of the output control triode Q2 is increased, the internal resistance of the triode Q2 is reduced, the voltage drop between the emitter and the collector is reduced, and the load current is increased. Therefore, the load current is fed back through the sampling resistor R4 in real time to finally achieve a constant stable current, as shown in fig. 3. The calculation formula for driving constant current by the light emitting diode LED1 is: IL = (U × N) ÷ R4.
The triode Q2 is an NPN type triode, when in actual use, a proper triode is selected according to the actual current and voltage requirements, or the triode is replaced by other power devices (such as MOS (metal oxide semiconductor) tubes or IGBT (insulated gate bipolar transistor) devices), and if the power meets the requirement of considering heat dissipation, heat dissipation measures are taken.
The foregoing is a more detailed description of the utility model in connection with specific preferred embodiments and it is not intended that the utility model be limited to these specific details. For those skilled in the art to which the utility model pertains, several simple deductions or substitutions can be made without departing from the spirit of the utility model, and all shall be considered as belonging to the protection scope of the utility model.
Claims (5)
1. A photoelectric air pollution degree detection system is characterized by comprising an air turbidity detection circuit, a controller and a constant current control loop;
the air turbidity detection circuit receives an illumination intensity signal of the light emitting diode LED1 penetrating through the air, converts the illumination intensity signal into a voltage signal and outputs the voltage signal to the controller;
the controller detects the air pollution degree according to the received voltage signal and outputs a pulse width modulation signal to the constant current control loop;
the constant current control loop outputs constant current to drive the light emitting diode LED1 according to the received pulse width modulation signal.
2. The photoelectric air pollution degree detection system according to claim 1, wherein the air turbidity detection circuit comprises a phototriode Q1 and an emitter follower isolation chip U1;
a collector of the phototriode Q1 is connected with a positive terminal of a direct-current power supply VCC _12V, a base receives an illumination intensity signal of the LED1 penetrating through air, and an emitter is respectively connected with a resistor R1 and a positive input end of an emitter follower isolation chip U1;
and the reverse input end and the output end of the emitter follower isolation chip U1 are connected, the output end is connected with the controller, and the power supply end is connected with the positive end of a direct-current power supply VCC _ 5V.
3. The photoelectric air pollution degree detection system according to claim 1, wherein the constant current control loop comprises an RC shaping circuit and a negative feedback loop;
the RC shaping circuit shapes and outputs a direct current voltage signal to a negative feedback loop according to the received pulse width modulation signal;
and the negative feedback loop receives the direct current voltage signal and outputs constant current to drive the light emitting diode LED1 according to the current signal fed back by the sampling circuit in the negative feedback loop.
4. The photoelectric air pollution degree detection system according to claim 3, wherein the RC shaping circuit comprises a resistor R2, a resistor R3, a capacitor C1, a capacitor C2;
one end of the resistor R2 is respectively connected with one end of the resistor R3 and the PWM end of the controller, and the other end of the resistor R2 is grounded;
the capacitor C1 and the capacitor C2 are connected in parallel, one end of a parallel node is connected with the other end of the resistor R3 and the input end of the negative feedback loop respectively, and the other end of the parallel node is grounded.
5. The photoelectric air pollution degree detection system according to claim 4, wherein the negative feedback loop comprises an operational amplifier U2, a triode Q2 and a sampling resistor R4;
the positive input end of the operational amplifier U2 is connected with the parallel connection node of the capacitor C1 and the capacitor C2, the output end is connected with the base electrode of the triode Q2 through the resistor R5, and the reverse input end is respectively connected with one end of the sampling resistor R4 and the emitter electrode of the triode Q2;
the collector of the triode Q2 is connected with the cathode of the light-emitting diode LED1, the emitter of the triode Q2 is grounded through the sampling resistor R4, and the anode of the light-emitting diode LED1 is connected with the positive end of the direct-current power supply VCC _ 12V.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121412867.XU CN215375086U (en) | 2021-06-24 | 2021-06-24 | Photoelectric air pollution degree detection system |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202121412867.XU CN215375086U (en) | 2021-06-24 | 2021-06-24 | Photoelectric air pollution degree detection system |
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| CN215375086U true CN215375086U (en) | 2021-12-31 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114857733A (en) * | 2022-04-29 | 2022-08-05 | 广州市微生物研究所有限公司 | Air purifier plasma concentration control method and control circuit |
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2021
- 2021-06-24 CN CN202121412867.XU patent/CN215375086U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114857733A (en) * | 2022-04-29 | 2022-08-05 | 广州市微生物研究所有限公司 | Air purifier plasma concentration control method and control circuit |
| CN114857733B (en) * | 2022-04-29 | 2023-11-03 | 广州市微生物研究所集团股份有限公司 | Plasma concentration control method and control circuit for air purifier |
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Address after: 510663 1 Pinnacle Road, Luogang District, Guangzhou, Guangdong Patentee after: Guangzhou Institute of Microbiology Group Co.,Ltd. Address before: 510663 1 Pinnacle Road, Luogang District, Guangzhou, Guangdong Patentee before: Guangzhou Institute of Microbiology Co.,Ltd. |
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