Dust sensor controlling the amount of light emission by controlling the light emission time

Abstract

The utility model discloses a dust detector through control luminous time to control luminous quantity, including setting in the detection area's luminous element, light receiving element and be used for to the light current signal of light receiving element in producing amplification amplifier circuit, control and detect light emission and light receiving signal's singlechip, the drive circuit of luminous element adopts transistor switch circuit to control luminous time, the drive circuit includes transistor and current -limiting resistance, luminous element, transistor and current -limiting resistance series connection with power supply and form the electric loop, the transistor trigger control end is controlledly connected in the singlechip, the utility model discloses dust sensor through control luminous time realizes to luminous element luminous quantity control, through the luminous quantity of luminous element accurate control, can improve dust sensor measurement result's accuracy and reliability.

Description

Technical Field

[0001] This utility model relates to a dust sensor, and more particularly to a dust sensor that controls the amount of light emitted by controlling the light emission time. Background Technology

[0002] Dust sensors are widely used in industrial production, environmental monitoring, and building safety. They detect the content / concentration of particulate matter in the environment by detecting changes in the electrical signal caused by dust or smoke within a relatively enclosed detection area. The dust sensor's control unit (MCU) drives a light-emitting element to emit light as the detection light source through a light-emitting element driving circuit. The detection light source is located on one side of the detection chamber, which is used to shield external light sources, while a light-receiving element is located on the other side.

[0003] In practical applications, the amount of light emitted by the light-emitting element of a dust sensor (which depends on the light intensity and duration) directly affects the detection results. The accuracy of this light emission / intensity control directly impacts the sensor's detection precision and sensitivity for dust particles. Improper light emission control, such as excessively strong or weak light, or too low or too high light levels, can lead to unstable or distorted data output from the dust sensor, thus affecting the final detection results. Therefore, in practical applications, it is essential to ensure that the light emission control of the dust sensor is optimal to improve detection accuracy and reliability.

[0004] Current dust sensors (such as) Figure 1 As shown, there are few or no dedicated control circuits for controlling the amount of light emitted by the light-emitting element, making it impossible to adjust the amount of light emitted by the light-emitting element and making it difficult to ensure the accuracy of the dust sensor measurement results.

[0005] Existing dust sensor drive circuits have the following problems: ① Due to variations in the drive circuit and temperature characteristics, the luminous current changes, causing variations in the luminous output. ② Even if the luminous current remains unchanged, the luminous output will still change due to variations in the output of the luminous element itself, degradation, and temperature characteristics. This, in turn, leads to a decrease in the detection accuracy of the dust sensor. Utility Model Content

[0006] This invention addresses the shortcomings of existing technologies by proposing a dust sensor that controls the amount of light emitted by controlling the light emission time, thus solving the problem of unstable light emission caused by changes in the light emission current in existing dust sensors.

[0007] By controlling the emission time of the light-emitting element, the emission amount of the light-emitting element can be controlled. In turn, by accurately controlling the emission amount of the light-emitting element, the accuracy of the dust sensor measurement results can be improved.

[0008] A dust sensor that controls the amount of light emitted by controlling the emission time includes a light-emitting element (101) disposed in the detection area, a light-receiving element, and an amplification circuit for amplifying the photocurrent signal generated in the light-receiving element, and a microcontroller for controlling and detecting the light emission and light reception signals. The driving circuit of the light-emitting element adopts a transistor switching circuit to control the emission time. The driving circuit includes a transistor and a current-limiting resistor. The light-emitting element, the transistor, and the current-limiting resistor are connected in series with the power supply to form an electrical loop. The trigger control terminal of the transistor is controlled to be connected to the microcontroller.

[0009] The dust sensor uses an NMOS transistor. The positive terminal of the power supply is connected to the light-emitting element through a resistor R1. The negative terminal of the light-emitting element is connected to the source terminal of the NMOS transistor. The drain terminal of the NMOS transistor is grounded. The gate terminal of the NMOS transistor is connected to the microcontroller.

[0010] The dust sensor described herein uses two NMOS transistors connected in parallel. The source of the first NMOS transistor is connected to the microcontroller via resistor R2, and the drain of the first NMOS transistor is grounded. The source terminal of the first NMOS transistor is also connected to the gate of the second NMOS transistor. The drain output terminal of the second NMOS transistor is connected to the gate of the first NMOS transistor, and the drain output terminal is also grounded via resistor R3. The source terminal of the second NMOS transistor is connected in series with the light-emitting element and the power supply.

[0011] The dust sensor described above uses a PMOS transistor. The drain terminal of the PMOS transistor is connected to a light-emitting element via a resistor and then grounded. The source terminal of the PMOS transistor is connected to the positive terminal of the power supply, and the gate terminal of the PMOS transistor is connected to a microcontroller.

[0012] The dust sensor's final amplifier output signal is converted to an A / D converter and then connected to a microcontroller. The microcontroller outputs a control signal to control the on / off time of the light-emitting ON / OFF switch circuit based on the amount of analog electrical signal (203) detected by receiving light.

[0013] The dust sensor includes a temperature sensor, which is a built-in temperature sensor of a microcontroller. The microcontroller performs temperature compensation by controlling the light emission time width or the light emission duty cycle of the flashing light according to the received temperature information.

[0014] The dust sensor includes a temperature sensor, which is located adjacent to the light-emitting element. The temperature sensor outputs a signal to a microcontroller. The microcontroller performs temperature compensation by controlling the light-emitting time width or the light-emitting duty cycle of the flashing light based on the received temperature information.

[0015] 1. This utility model of a dust sensor includes an on / off control circuit for emitting light. The MCU controls the emitting time of the light-emitting element to provide a stable amount of illumination, thereby improving the accuracy of the dust sensor's measurement results. Furthermore, by controlling the ON / OFF of the MCU's I / O terminals, precise control of the emitting time of the light-emitting element / the equivalent electrical signal quantity controlling the emitted light quantity can be easily achieved. Controlling the emitting light quantity by outputting an electrical signal quantity equivalent to the emitting light quantity from the MCU is easy to implement, easy to adjust, and has low circuit cost.

[0016] 2. The dust sensor of this utility model provides a stable amount of light for dust detection by controlling the on / off time of the light emission. Since it does not require a circuit to adjust the absolute value of the current flowing through the light emission element, it can obtain a signal quantity equivalent to the absolute value of the light emission current, thus simplifying the light emission circuit.

[0017] 3. This dust sensor, based on temperature information from the MCU's built-in temperature sensor or a separately provided temperature sensor, performs temperature compensation by controlling the flashing light emission time width or emission duty cycle (301). Since the light intensity of the light-emitting element decreases at high temperatures, the light intensity can be corrected by increasing the current flowing through the light-emitting element at high temperatures. By changing the flashing light emission time width or emission duty cycle (PWM control) for temperature compensation, the operating temperature range of the dust sensor can be expanded. Attached Figure Description

[0018] Figure 1 The diagram shown is a schematic of a dust sensor in the prior art.

[0019] Figure 2 The diagram shown is a schematic diagram of the dust sensor of this utility model.

[0020] Figure 3 , Figure 4 , Figure 5 The figures shown are one, two, and three specific embodiments of the light-emitting driving circuit for the dust sensor of this utility model.

[0021] Figure 6 The following is an example waveform 1 for controlling the light emission of the dust sensor of this utility model;

[0022] Figure 7 The following is an example 2 of the waveform for controlling the light emission of the dust sensor of this utility model;

[0023] Figure 8 The figure shown is an example 1 of the waveform of the light emission control and analog electrical signal of the dust sensor of this utility model;

[0024] Figure 9The following is an example 2 of the waveform of the analog electrical signal of the dust sensor of this utility model;

[0025] Figure 10 The image shows an example of temperature characteristic correction of the light output of the dust sensor of this invention using temperature compensation. Detailed Implementation

[0026] To make the technical concept and advantages of this utility model in achieving its inventive purpose clearer, the technical solution of this utility model will be further described in detail below with reference to the accompanying drawings. It should be understood that the following embodiments are only preferred embodiments for explaining and illustrating this utility model, and should not be regarded as and do not constitute a limitation on the scope of patent protection claimed by this utility model.

[0027] See Figure 2 This utility model is a dust sensor that controls the amount of light emitted by controlling the light emission time. It includes a light-emitting element 101, a light-receiving element 102, and an amplifier circuit 103 for amplifying the photocurrent signal generated in the light-receiving element, all disposed in the detection area. It also includes a microcontroller 104 (hereinafter referred to as "MCU") for controlling and detecting the light emission and light reception signals. Figure 2 ) and existing technology ( Figure 1 The difference lies in that: the driving circuit of the light-emitting element adopts a transistor switching circuit to control the light-emitting time; the driving circuit includes a transistor and a current-limiting resistor, the light-emitting element, the transistor and the current-limiting resistor are connected in series with the power supply to form an electrical circuit, and the transistor trigger control terminal is controlled to be connected to the microcontroller.

[0028] The output signal of the final stage amplifier of the amplifier circuit is connected to the microcontroller after being converted by A / D. The microcontroller outputs a control signal to control the on / off time of the light-emitting ON / OFF switch circuit based on the analog electrical signal 203 detected by receiving light.

[0029] By controlling the emission time of the light-emitting element, the MCU provides a stable amount of illumination, thereby improving the accuracy of dust sensor measurements. Furthermore, by controlling the ON / OFF of the MCU's I / O terminals, precise adjustment of the emission time / equivalent electrical signal quantity controlling the emitted light quantity can be easily achieved (the MCU outputs an electrical signal quantity equivalent to the emission quantity). This is easy to implement, easy to adjust, and has low circuit cost. Example

[0030] See Figure 3In the dust sensor of this embodiment, the light-emitting ON / OFF switch circuit uses an NMOS transistor. The positive terminal of the power supply is connected to the light-emitting element through a resistor R1. The negative terminal of the light-emitting element is connected to the source terminal of the NMOS transistor. The drain terminal of the NMOS transistor is grounded. The gate terminal of the NMOS transistor is connected to the microcontroller. Example

[0031] See Figure 4 In this embodiment of the dust sensor, the ON / OFF switch circuit uses two NMOS transistors connected in parallel. The current is reduced by limiting the opening of the drive pulse, thus ensuring the safety of each MOS transistor. The source of the first NMOS transistor is connected to the microcontroller via resistor R2, and its drain is grounded. The source terminal of the first NMOS transistor is also connected to the gate of the second NMOS transistor. The drain output terminal of the second NMOS transistor is connected to the gate of the first NMOS transistor, and its drain output terminal is also grounded via resistor R3. The source terminal of the second NMOS transistor is connected in series with the light-emitting element and then to the power supply. Example

[0032] See Figure 5 In the dust sensor of this embodiment, the light-emitting ON / OFF switch circuit uses a PMOS transistor. The drain terminal of the PMOS transistor is connected to the light-emitting element through a resistor and then grounded. The source terminal of the PMOS transistor is connected to the positive terminal of the power supply, and the gate terminal of the PMOS transistor is connected to the microcontroller.

[0033] This utility model dust sensor includes a temperature sensor, which is either a built-in temperature sensor of a microcontroller or a temperature sensor (using a digital temperature sensor, with the output signal connected to the microcontroller) placed adjacent to the light-emitting element. The microcontroller performs temperature compensation by controlling the light-emitting time width or the light-emitting duty cycle of the flashing light according to the received temperature information.

[0034] By adjusting the irradiation amount through a light emission control circuit controlled by a microcontroller (MCU), a stable amount of light can be provided for the dust sensor / light emission element, which helps to ensure the accuracy and stability of the measurement results.

[0035] Figure 6The figure shows a waveform example 1 for controlling the light intensity of the dust sensor of this utility model. This figure illustrates that the average light intensity of each of cases 1 to 3 (light intensity 1 to light intensity 3) can be obtained through on / off time width control (the light emission duty cycle 301 is variable). In example 1, the microcontroller adjusts the electrical signal quantity equivalent to the light intensity by controlling the timing of the ON / OFF switch of the light emission to provide the stable illumination light intensity required for dust detection. In example 2, for the on / off time control of the light emission, repeated flashing is performed with a period (202) shorter than the desired light signal pulse light emission time width 201, and the amount of analog electrical signal 203 detected by receiving light is read. Since a circuit equivalent to the signal quantity when controlling the absolute value of the light emission current can be obtained without adjusting the absolute value of the current flowing through the light-emitting element, the light emission circuit can be simplified. In example 3, for the on / off time control of the light-emitting element, the flashing period 202 of the flashing light emission is set to half or less of the desired light signal pulse light emission time width 201, and the light emission duty cycle 301 of the flashing light emission is changed. The same effect can be achieved without changing the circuitry on the light receiving side. Figure 6 In the above, the light emission duty cycle (301) = light emission time width (302) / flicker period (202) = light emission time width (302) / (light emission time width (302) + non-light emission time width (303)).

[0036] Figure 7 The diagram shows an example waveform 2 for controlling the light emission intensity of the dust sensor of this invention; this figure illustrates the case where the emission time width 302 is variable and the non-emission time width 303 is fixed (duty cycle is variable). Furthermore, similar effects can be obtained even when the emission time width 302 is fixed and the non-emission time width 303 is variable. The emission time width and non-emission time width are not limited.

[0037] Figure 8 The diagram shows the waveform example 1 of the emission intensity control and analog electrical signal for Examples 1-3 above. For the emission intensity 1 to 3 in Examples 1-3, the average emission intensity 1 to 3 can be obtained by controlling the ON / OFF time width (the emission duty cycle 301 is variable), and the light can be received and converted into an electrical signal. This is a diagram illustrating how the amount of analog electrical signal 203 corresponding to cases 1 to 3 is obtained. Since the analog electrical signal 203 is an electrical signal through the photocurrent signal amplification circuit 103, which is optimized to the desired pulse time width 201, the flicker pulse becomes muffled, as shown in the waveform above.

[0038] Figure 9The image shows an example 2 of the waveform of the analog electrical signal of the dust sensor of this invention; when the light-emitting element flashes for a short period of time, ripple is generated in the light-receiving electrical signal. By synchronizing the MCU's reading timing with the flashing period, the influence of ripple can be reduced, and stable reading can be achieved.

[0039] Figure 9 This is a diagram depicting the ripple of the analog electrical signal 203 generated by the switching on / off of light emission. Based on the frequency band characteristics of the photocurrent signal amplifier circuit 103, the waveform of the analog electrical signal 203 may produce significant ripple within the same period as the flickering period 202 of the light emission. Figure 9 In this example, the timing for MCU reading is set to the on / off timing indicated by the arrow above. Synchronization allows for a more stable value. The timing indicated by the arrow is an example and is not limited to any particular timing for synchronized reading.

[0040] Since the light emission of the light-emitting element decreases at high temperatures, temperature compensation can be achieved by increasing the current flowing through the light-emitting element at high temperatures, thereby expanding the operating temperature range of the dust sensor. The operating temperature of the light-emitting element is detected using a built-in temperature sensor in the MCU or a separately provided temperature sensor, and the MCU can perform temperature compensation by controlling the amount of light emitted.

[0041] Figure 10 The illustration shows an example of temperature characteristic correction of the light emission output of the dust sensor of this invention using temperature compensation; typically, the light emission output of the light-emitting element has a negative temperature characteristic 601. A curve 602 is derived to counteract this value, a curve 603 is determined to change the light emission duty cycle 301, and temperature correction is performed. As a result, as shown in the temperature-corrected line 604, the temperature characteristic of the dust sensor's light emission output is reduced, and the temperature dependence of the dust detection quantity is significantly reduced. The change in the light emission duty cycle 301 is controlled by the MCU based on temperature information from a temperature sensor integrated in the MCU or a separately provided temperature sensor.

Claims

1. A dust sensor for controlling the amount of light emission by controlling the light emission time, comprising a light emitting element (101) disposed in a detection area, a light receiving element, and an amplification circuit for amplifying a photoelectric current signal generated in the light receiving element, a single-chip microcomputer for controlling and detecting light emission and light receiving signals, characterized in that: The driving circuit of the light-emitting element adopts a transistor switching circuit to control the light-emitting time; the driving circuit includes a transistor and a current-limiting resistor, the light-emitting element, the transistor and the current-limiting resistor are connected in series with the power supply to form an electrical loop, and the transistor trigger control terminal is controlled to be connected to the microcontroller. ​ 2. The dust sensor according to claim 1, characterized in that: The transistor is an NMOS transistor. The positive terminal of the power supply is connected to the light-emitting element through a resistor R1. The negative terminal of the light-emitting element is connected to the source terminal of the NMOS transistor. The drain terminal of the NMOS transistor is grounded. The gate terminal of the NMOS transistor is connected to the microcontroller.

3. The dust sensor according to claim 1, characterized in that: The transistor is composed of two NMOS transistors connected in parallel. The source of the first NMOS transistor is connected to the microcontroller through resistor R2, and the drain of the first NMOS transistor is grounded. The source terminal of the first NMOS transistor is also connected to the gate of the second NMOS transistor. The drain output terminal of the second NMOS transistor is connected to the gate of the first NMOS transistor, and the drain output terminal is also grounded through resistor R3. The source terminal of the second NMOS transistor is connected in series with the light-emitting element and the power supply.

4. The dust sensor according to claim 1, characterized in that: The transistor is a PMOS transistor. The drain terminal of the PMOS transistor is connected to the light-emitting element through a resistor and then grounded. The source terminal of the PMOS transistor is connected to the positive terminal of the power supply. The gate terminal of the PMOS transistor is connected to the microcontroller.

5. The dust sensor according to any one of claims 1-4, characterized in that: The output signal of the final stage amplifier of the amplifier circuit is connected to the microcontroller after being converted by A / D. The microcontroller outputs a control signal to control the on / off time of the light-emitting ON / OFF switch circuit based on the amount of analog electrical signal (203) detected by receiving light.

6. The dust sensor according to claim 5, characterized in that: It includes a temperature sensor, which is a built-in temperature sensor of a microcontroller. The microcontroller performs temperature compensation by controlling the light emission time width or the light emission duty cycle based on the received temperature information.

7. The dust sensor according to claim 5, characterized in that: The device includes a temperature sensor, which is located adjacent to the light-emitting element. The output signal of the temperature sensor is connected to a microcontroller. The microcontroller performs temperature compensation by controlling the light-emitting time width or the light-emitting duty cycle of the flashing light based on the received temperature information.

8. The dust sensor according to any one of claims 1-4, characterized in that: A temperature sensor is placed adjacent to the light-emitting element. The temperature sensor is a digital temperature sensor, and the output signal of the temperature sensor is connected to the microcontroller.

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