A laser dust particle counter for measuring dust particles in a clean environment

Abstract

The present application discloses a laser dust particle counter for measuring dust particles in a clean environment, including a processor circuit, a communication circuit, a laser diode drive circuit, a photoelectric detection circuit, a power supply circuit, an air pump motor drive circuit and a gas flow detection circuit, wherein the processor circuit is connected to the communication circuit, the laser diode drive circuit, the photoelectric detection circuit, the air pump motor drive circuit and the gas flow detection circuit, and the power supply circuit supplies power to each module. The invention has the following advantages: the use of a 100mW high-power laser light source and light source intensity supports automatic control, enhances the detection capability of micro-particles, supports accurate measurement of larger particle sizes, expands the measurement range of the counter, ensures that accurate sampling flow is maintained under different measurement environments, is more suitable for long-term online dust particle measurement, and realizes more accurate air cleanliness calculation.

Description

Technical Field

[0001] The invention relates to a laser dust particle counter for measuring dust particles in a clean environment, belonging to the technical field of automatic testing. Background Art

[0002] Laser dust particle counter is an instrument used to measure the number and size distribution of dust particles per unit volume in a clean environment. It can be widely used in laser dust particle counters, blood centers, epidemic prevention stations, disease control centers, quality supervision institutions and other authoritative institutions, electronics industry, pharmaceutical workshops, semiconductors, optical or precision machining, plastics, spray painting, hospitals, environmental protection, inspection institutes and other production enterprises and scientific research departments to monitor the purification effect and cleanliness level of workbenches, clean rooms and clean workshops of various cleanliness levels to ensure product quality.

[0003] Laser dust particle counter is an instrument used to measure the number and size distribution of dust particles per unit volume in a clean environment. Its basic principle is that the detection laser of the optical sensor is scattered by dust particles and received by the photosensitive element to generate a pulse signal, which is output and amplified, and then processed digitally. By comparing with the standard particle signal, the comparison result is expressed by different parameters.

[0004] Existing laser dust particle counters have the following disadvantages:

[0005] 1. The measurement capability of micro-particles and large dust particles is limited, and the application scope is not wide enough;

[0006] 2. It is not possible to maintain accurate sampling flow under different measurement environments, which is not suitable for long-term online dust particle measurement, and the air cleanliness calculation is not accurate enough;

[0007] 3. The anti-interference ability is low, and the motor is not stable enough when running at low speed, which affects the service life and accuracy of the counter. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a laser dust particle counter for measuring dust particles in a clean environment in view of the above shortcomings. The laser dust particle counter uses a 100mW high-power laser light source and supports automatic control of the light source intensity, thereby enhancing the ability to detect micro-particles. It can also support accurate measurement of larger particle sizes, expand the measurement range of the counter, and ensure that accurate sampling flow is maintained under different measurement environments. The counter is more suitable for long-term online dust particle measurement and realizes more accurate air cleanliness calculation.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A laser dust particle counter for measuring dust particles in a clean environment comprises a processor circuit, a communication circuit, a laser diode drive circuit, a photoelectric detection circuit, a power supply circuit, an air pump motor drive circuit and a gas flow detection circuit. The processor circuit is connected to the communication circuit, the laser diode drive circuit, the photoelectric detection circuit, the air pump motor drive circuit and the gas flow detection circuit, and the power supply circuit supplies power to each module.

[0011] Further, the processor circuit includes a chip U3, the model of the chip U3 is STM32F405RG, the 5th pin of the chip U3 is connected to one end of the crystal oscillator X1 and one end of the capacitor C17, the 6th pin of the chip U3 is connected to the other end of the crystal oscillator X1 and one end of the capacitor C18, the other end of the capacitor C17 and the other end of the capacitor C18 are grounded, the 7th pin of the chip U3 is connected to one end of the resistor R14 and one end of the capacitor C20, the other end of the resistor R14 is connected to the VCC power supply, the other end of the capacitor C20 is grounded, the 17th pin of the chip U3 is connected to one end of the resistor R43 and one end of the resistor R42, the other end of the resistor R43 is grounded, the other end of the resistor R42 is connected to the base of the transistor Q8, the emitter of the transistor Q8 is grounded, the collector of the transistor Q8 is connected to one end of the buzzer, and the other end of the buzzer is connected to the VDD power supply;

[0012] The processor circuit also includes a chip U4, the model of which is NC AT24C64D-SSHM-B. Pin 5 of chip U4 is connected to one end of resistor R16 and pin 33 of chip U3, pin 6 of chip U4 is connected to one end of resistor R15 and pin 34 of chip U3, the other end of resistor R15 and the other end of resistor R16 are grounded, pin 8 of chip U4 is connected to one end of capacitor C19 and to VDD power supply, and the other end of capacitor C19 is grounded.

[0013] Furthermore, the laser diode driving circuit includes a chip U1, wherein pin 1 of the chip U1 is connected to one end of a capacitor C3 and pin 20 of the chip U3, pin 3 of the chip U1 is connected to one end of a resistor R2, one end of a capacitor C4 and the S pole of a MOS tube Q1, the other end of the resistor R2 and the other end of the capacitor C4 are grounded, the G pole of the MOS tube Q1 is connected to pin 4 of the chip U1, the D pole of the MOS tube Q1 is connected to pin 1 of the socket CN1, pin 2 of the socket CN1 is connected to one end of the capacitor C1 and one end of the capacitor C2, and are connected to a 3V7 power supply, and the other end of the capacitor C1 and the other end of the capacitor C2 are grounded.

[0014] Further, the photoelectric detection circuit includes an amplifier U2A, pin 3 of the amplifier U2A is connected to one end of the photocell PD1, one end of the capacitor C9, one end of the capacitor C10, one end of the resistor R11 and one end of the resistor R8, the other end of the capacitor C9, the other end of the capacitor C10 and the other end of the resistor R11 are grounded, the other end of the resistor R8 is connected to the VDDA power supply, pin 2 of the amplifier U2A is connected to the other end of the photocell PD1, one end of the resistor R5 and one end of the capacitor C5, the other end of the resistor R5 and the other end of the capacitor C5 are connected to pin 1 of the amplifier U2A, pin 8 of the amplifier U2A is connected to one end of the capacitor C6 and one end of the capacitor C11, and is connected to the VDDA power supply, The other end of capacitor C6 and the other end of capacitor C11 are grounded, pin 1 of amplifier U2A is connected to one end of capacitor C7, the other end of capacitor C7 is connected to one end of resistor R6, one end of resistor R10 and one end of resistor R9, the other end of resistor R6 is connected to VDDA power supply, the other end of resistor R10 is grounded, the other end of resistor R9 is connected to pin 5 of amplifier U2B, pin 6 of amplifier U2B is connected to one end of resistor R3 and one end of resistor R4, the other end of resistor R3 is grounded, the other end of resistor R4 is connected to pin 7 of amplifier U2B and one end of resistor R7, the other end of resistor R7 is connected to one end of capacitor C8 and pin 14 of chip U3, and the other end of capacitor C8 is grounded.

[0015] Further, the power supply circuit includes a chip U7, the model of the chip U7 is LMR14006, the 5th pin of the chip U7 is connected to one end of the resistor R23, one end of the capacitor C30, one end of the capacitor C29, one end of the capacitor C28, one end of the capacitor C27 and the 2nd pin of the MOS tube Q2, the other end of the resistor R23 is connected to the 4th pin of the chip U7, the other end of the capacitor C30, the other end of the capacitor C29, the other end of the capacitor C28 and the other end of the capacitor C27 are grounded, the 3rd pin of the MOS tube Q2 is connected to one end of the resistor R26, one end of the fuse F3, one end of the diode D2 and one end of the diode D8, the other end of the fuse F3 is connected to the 2nd pin of the interface CN3, the 1st pin of the interface CN3 is grounded, the other end of the diode D2 and the diode The other end of the tube D8 is connected to the 2nd pin of the interface CN2 and one end of the resistor R44, the other end of the resistor R44 is connected to one end of the resistor R45 and the 22nd pin of the chip U3, the other end of the resistor R45 is grounded, the 1st pin of the MOS tube Q2 is connected to one end of the resistor R27, the other end of the resistor R27 is connected to the other end of the resistor R26, one end of the diode D4 and the collector of the transistor Q3, the other end of the diode D4 is connected to one end of the diode D5 and the 1st pin of the interface XH5, the other end of the diode D5 is connected to the 27th pin of the chip U3, the base of the transistor Q3 is connected to one end of the resistor R29, the other end of the resistor R29 is connected to the 26th pin of the chip U3 and one end of the resistor R31, the other end of the resistor R31 and the emitter of the transistor Q3 are grounded;

[0016] Pin 3 of the interface XH5 is connected to pin 3 of the MOS tube Q7, pin 1 of the MOS tube Q7 is connected to one end of a resistor R36, the other end of the resistor R36 is connected to one end of a resistor R35 and the collector of the transistor Q6, pin 2 of the MOS tube Q7 is connected to the other end of the resistor R35 and connected to +5V, the base of the transistor Q6 is connected to one end of a resistor R40, the other end of the resistor R40 is connected to pin 25 of the chip U3, and the emitter of the transistor Q6 is grounded.

[0017] Furthermore, the 1st pin of the chip U7 is connected to one end of the capacitor C26, the 6th pin of the chip U7 is connected to the other end of the capacitor C26, one end of the diode D3 and one end of the inductor L2, the other end of the diode D3 is grounded, the other end of the inductor L2 is connected to one end of the capacitor C33, one end of the resistor R25, one end of the resistor R48, one end of the capacitor C25, one end of the capacitor C34 and the 1st pin of the chip U6, and connected to the 3V7 power supply, the other end of the resistor R25 is connected to one end of the LED lamp LED1, and the other end of the LED lamp LED1 is connected to the ground. Pin 5 of chip U6 is connected to one end of capacitor C31 and one end of capacitor C32, and are connected to the VCC power supply. The other end of capacitor C31 and the other end of capacitor C32 are grounded. The model of chip U6 is LP5907-3.3. Pin 3 of chip U7 is connected to one end of resistor R28 and one end of resistor R24. The other end of resistor R27 is grounded, and the other end of resistor R24 ​​is connected to the 3V7 power supply.

[0018] Furthermore, the power supply circuit also includes a chip U8, wherein pin 3 of chip U8 is connected to one end of a resistor R30, one end of a capacitor C36, one end of a resistor R46 and pin 5 of chip U7, the other end of resistor R46 is connected to pin 23 of chip U3 and one end of a resistor R47, the other end of resistor R47 is grounded, the other end of resistor R30 is connected to pin 5 of chip U8, the other end of capacitor C36 is grounded, pin 6 of chip U8 is connected to one end of capacitor C35, pin 2 of chip U8 is connected to the other end of capacitor C35, one end of a diode D6 and one end of an inductor L3, the other end of diode D6 is grounded, the other end of inductor L3 is connected to one end of resistor R32, one end of capacitor C38 and one end of capacitor C37, and are connected to a +5V power supply, the other end of capacitor C38 and the other end of capacitor C37 are grounded, pin 4 of chip U8 is connected to the other end of resistor R32 and one end of resistor R33, and the other end of resistor R33 is grounded.

[0019] Furthermore, the air pump motor drive circuit includes a chip U9 and a chip U10, the model of the chip U9 is LMR14006, the model of the chip U10 is LMV321, the pin 1 of the chip U10 is connected to the pin 21 of the chip U3, the pins 3 and 4 of the chip U10 are connected to one end of the resistor R39, the other end of the resistor R39 is connected to the pin 3 of the chip U9, the pin 5 of the chip U10 is connected to one end of the capacitor C43 and connected to the VDD power supply, the other end of the capacitor C43 is grounded, the pin 5 of the chip U9 is connected to one end of the capacitor C42 and connected to the IN+ power supply, the other end of the capacitor C42 is grounded, and the pin 4 of the chip U9 is connected to the IN+ power supply. The pin is connected to one end of resistor R34 and pin 24 of chip U3, and the other end of resistor R34 is grounded, pin 1 of chip U9 is connected to one end of capacitor C39, pin 6 of chip U9 is connected to the other end of capacitor C39, one end of diode D7 and one end of inductor L4, and the other end of diode D7 is grounded, the other end of inductor L4 is connected to one end of resistor R37, one end of capacitor C40, one end of capacitor C41 and pin 1 of interface CN6, pin 3 of chip U9 is connected to one end of resistor R38 and the other end of resistor R37, and the other end of resistor R38, the other end of capacitor C40, the other end of capacitor C41 and pin 2 of interface CN6 are grounded.

[0020] Furthermore, the gas flow detection circuit includes a chip U11, the model of chip U11 is XGZP190, pin 1 and pin 8 of chip U11 are connected to pin 1 of amplifier U12B, pin 2 and pin 3 of amplifier U12B are connected to one end of resistor R40, the other end of resistor R40 is connected to one end of resistor R42, one end of capacitor C45 and pin 2 of amplifier U13A, pin 3 of chip U11 is connected to pin 1 of amplifier U12A, pin 2 and pin 4 of amplifier U12A are connected to one end of resistor R30, the other end of resistor R30 is connected to pin 1 of amplifier U13A, one end of resistor R41 and one end of capacitor C44, the other end of resistor R41 and the other end of capacitor C44 are connected to +1V2 power supply, pin 3 of amplifier U13A is connected to the other end of resistor R42, the other end of capacitor C45 and one end of resistor R43, and the other end of resistor R43 is connected to ADC acquisition of chip U3.

[0021] Further, the communication circuit includes a chip U5, the model of the chip U5 is SP3485, the pin 1 of the chip U5 is connected to one end of a resistor R18 and the pin 30 of the chip U3, the other end of the resistor R18 is connected to a VDD power supply, the pins 2 and 3 of the chip U5 are connected to one end of a resistor R19 and the collector of a transistor Q5, the other end of the resistor R19 is connected to the VDD power supply, the base of the transistor Q5 is connected to one end of a resistor R21, the other end of the resistor R21 is connected to one end of a resistor R20 and the pin 29 of the chip U3, and the other end of the resistor R20 is connected to the VDD power supply;

[0022] Pin 6 of the chip U5 is connected to a TVS diode D1, one end of a resistor R22 and one end of a fuse F2, the other end of the resistor R22 is connected to a VDD power supply, the other end of the fuse F2 is connected to pin 3 of an interface XH3, pin 7 of the chip U5 is connected to a TVS diode D1, one end of a resistor R17 and one end of a fuse F1, the other end of the resistor R17 is grounded, the other end of the fuse F1 is connected to pin 2 of the interface XH3, pin 8 of the chip U5 is connected to one end of a capacitor C21 and to a VDD power supply, and the other end of the capacitor C21 is grounded.

[0023] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0024] 1. Use 100mW high-power laser light source to enhance the detection capability of micro particles (particle diameter 0.3μm).

[0025] 2. The light source intensity supports automatic control. In addition to the standard measurement mode, it can support accurate measurement of larger particle sizes (>20μm).

[0026] 3. Use high-speed ADC to collect particle detection signals. While supporting standard 6-channel counting, 128 additional custom counting channels can be inserted.

[0027] 4. Support closed-loop flow control of sampling airflow, which can ensure accurate sampling flow in different measurement environments, eliminating frequent manual adjustments, and is more suitable for long-term online dust particle measurement, achieving more accurate air cleanliness calculation.

[0028] 5. The motor is controlled by DC voltage control, which produces less interference and has a larger torque and is more stable when the motor runs at low speed.

[0029] 6. It adopts dual power supply and built-in large-capacity lithium battery. The continuous battery power supply can work for no less than 10 hours, which is convenient for mobile measurement of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0031] Figure 1 is a circuit diagram of a processor circuit in the present invention;

[0032] Figure 2 is a circuit diagram of the communication circuit in the present invention;

[0033] Figure 3is a circuit diagram of a laser diode driving circuit in the present invention;

[0034] Figure 4 is a circuit diagram of the photoelectric detection circuit in the present invention;

[0035] Figure 5 is a circuit diagram of a power supply circuit in the present invention;

[0036] Figure 6 is a circuit diagram of the air pump motor driving circuit in the present invention;

[0037] Figure 7 It is a circuit diagram of the gas flow detection circuit in the present invention. DETAILED DESCRIPTION

[0038] Embodiment 1, a laser dust particle counter for measuring dust particles in a clean environment, includes a processor circuit, a communication circuit, a laser diode drive circuit, a photoelectric detection circuit, a power supply circuit, an air pump motor drive circuit and a gas flow detection circuit, the processor circuit is connected to the communication circuit, the laser diode drive circuit, the photoelectric detection circuit, the air pump motor drive circuit and the gas flow detection circuit, and the power supply circuit supplies power to each module.

[0039] like Figure 1 As shown, the processor circuit includes a chip U3, the model of the chip U3 is STM32F405RG, the 5th pin of the chip U3 is connected to one end of the crystal oscillator X1 and one end of the capacitor C17, the 6th pin of the chip U3 is connected to the other end of the crystal oscillator X1 and one end of the capacitor C18, the other end of the capacitor C17 and the other end of the capacitor C18 are grounded, the 7th pin of the chip U3 is connected to one end of the resistor R14 and one end of the capacitor C20, the other end of the resistor R14 is connected to the VCC power supply, the other end of the capacitor C20 is grounded, the 17th pin of the chip U3 is connected to one end of the resistor R43 and one end of the resistor R42, the other end of the resistor R43 is grounded, the other end of the resistor R42 is connected to the base of the transistor Q8, the emitter of the transistor Q8 is grounded, the collector of the transistor Q8 is connected to one end of the buzzer, and the other end of the buzzer is connected to the VDD power supply.

[0040] The processor circuit also includes a chip U4, the model of which is NC AT24C64D-SSHM-B. Pin 5 of chip U4 is connected to one end of resistor R16 and pin 33 of chip U3, pin 6 of chip U4 is connected to one end of resistor R15 and pin 34 of chip U3, the other end of resistor R15 and the other end of resistor R16 are grounded, pin 8 of chip U4 is connected to one end of capacitor C19 and to VDD power supply, and the other end of capacitor C19 is grounded.

[0041] The processor circuit uses the STM32F401RCT6 microprocessor, which can run at 84 MHz and provide 105 DMIPS / 285 CoreMark performance. It also has a built-in 2.4 MSPS 12-bit ADC and multiple USART serial data ports.

[0042] According to Shannon's theorem, a 2.4MSPS ADC can theoretically sample a 1.2MHz sine wave. If the maximum concentration of the sampling signal is below 50k / L and the gas flow rate is designed to be no more than 10L / min, the maximum frequency of the pulse signal is approximately equal to 8.3k / s, which is much smaller than 1.2M / s. The processor circuit can accurately sample the pulse waveform.

[0043] like Figure 2 As shown, the communication circuit includes a chip U5, the model of the chip U5 is SP3485, the pin 1 of the chip U5 is connected to one end of a resistor R18 and the pin 30 of the chip U3, the other end of the resistor R18 is connected to a VDD power supply, the pins 2 and 3 of the chip U5 are connected to one end of a resistor R19 and the collector of a transistor Q5, the other end of the resistor R19 is connected to the VDD power supply, the base of the transistor Q5 is connected to one end of a resistor R21, the other end of the resistor R21 is connected to one end of a resistor R20 and the pin 29 of the chip U3, the other end of the resistor R20 is connected to the VDD power supply.

[0044] Pin 6 of the chip U5 is connected to a TVS diode D1, one end of a resistor R22 and one end of a fuse F2, the other end of the resistor R22 is connected to a VDD power supply, the other end of the fuse F2 is connected to pin 3 of an interface XH3, pin 7 of the chip U5 is connected to a TVS diode D1, one end of a resistor R17 and one end of a fuse F1, the other end of the resistor R17 is grounded, the other end of the fuse F1 is connected to pin 2 of the interface XH3, pin 8 of the chip U5 is connected to one end of a capacitor C21 and to a VDD power supply, and the other end of the capacitor C21 is grounded.

[0045] The communication circuit uses an RS485 interface for data transmission.

[0046] like Figure 3 As shown, the laser diode driving circuit includes a chip U1, pin 1 of the chip U1 is connected to one end of a capacitor C3 and pin 20 of the chip U3, pin 3 of the chip U1 is connected to one end of a resistor R2, one end of a capacitor C4 and the S pole of a MOS tube Q1, the other end of the resistor R2 and the other end of the capacitor C4 are grounded, the G pole of the MOS tube Q1 is connected to pin 4 of the chip U1, the D pole of the MOS tube Q1 is connected to pin 1 of the socket CN1, pin 2 of the socket CN1 is connected to one end of a capacitor C1 and one end of a capacitor C2, and are connected to a 3V7 power supply, and the other end of the capacitor C1 and the other end of the capacitor C2 are grounded.

[0047] The laser diode is a light-emitting device driven by a constant current. The laser diode is connected to the socket CN1. The circuit uses the chip U1 and the MOS tube Q1 as output control, and the current feedback is performed through the resistor R2. The voltage signal generated by the 1st pin of the chip U1 controls the driving current. The control relationship is V DAC1 = I OUT *R2.

[0048] The circuit uses DAC as the control signal of the output current, and the processor can be used to quantitatively control the output power of the laser diode. The present invention uses a 200mW infrared laser diode to generate the detection light source. The photoelectric parameters of the laser diode have certain discreteness. In the counter production and metering link, the laser intensity of each device needs to be corrected. The driving circuit that is completely automatically controlled by the processor can correct the light intensity more accurately. At the same time, because no adjustable resistor is used, the long-term stability of the device is greatly reduced by the influence of vibration and temperature and humidity.

[0049] like Figure 4 As shown, the photoelectric detection circuit includes an amplifier U2A, and the 3rd pin of the amplifier U2A is connected to one end of the photocell PD1, one end of the capacitor C9, one end of the capacitor C10, one end of the resistor R11 and one end of the resistor R8, the other end of the capacitor C9, the other end of the capacitor C10 and the other end of the resistor R11 are grounded, and the other end of the resistor R8 is connected to the VDDA power supply, the 2nd pin of the amplifier U2A is connected to the other end of the photocell PD1, one end of the resistor R5 and one end of the capacitor C5, the other end of the resistor R5 and the other end of the capacitor C5 are connected to the 1st pin of the amplifier U2A, the 8th pin of the amplifier U2A is connected to one end of the capacitor C6 and one end of the capacitor C11, and is connected to the VDDA power supply, The other end of capacitor C6 and the other end of capacitor C11 are grounded, pin 1 of amplifier U2A is connected to one end of capacitor C7, the other end of capacitor C7 is connected to one end of resistor R6, one end of resistor R10 and one end of resistor R9, the other end of resistor R6 is connected to VDDA power supply, the other end of resistor R10 is grounded, the other end of resistor R9 is connected to pin 5 of amplifier U2B, pin 6 of amplifier U2B is connected to one end of resistor R3 and one end of resistor R4, the other end of resistor R3 is grounded, the other end of resistor R4 is connected to pin 7 of amplifier U2B and one end of resistor R7, the other end of resistor R7 is connected to one end of capacitor C8 and pin 14 of chip U3, and the other end of capacitor C8 is grounded.

[0050] The laser dust particle counter utilizes the Tyndall effect. Dust particles of different sizes will produce scattered light of different intensities when passing through a laser beam. By detecting the number of light pulses of different intensities, the number of dust particles can be accurately counted.

[0051] Photocell PD1, resistor R5, capacitor C5, and amplifier U2A form a transimpedance amplifier, which is used to convert the weak current signal generated by photocell PD1 into a voltage signal output. The conversion relationship is Vout = -(I PD1 *R5), the input impedance of the amplifier circuit is too high, and the low-pass filtering effect of capacitor C5 increases the stability of the circuit.

[0052] After the weak photoelectric signal is amplified through transimpedance, it is converted into a voltage signal with sufficient driving capability. Due to the dark current of the photocell PD1 and the inability of the detection cavity itself to completely extinguish light, the transimpedance amplifier will have a large DC signal offset. When coupled to the next stage through capacitor C7, the capacitor's DC isolation and AC passing function is utilized to extract only the useful pulse voltage signal from the signal. After amplifier U2B performs secondary amplification on the signal, the signal is directly sent to the high-speed ADC pin of the processor for digital sampling.

[0053] After the pulse signal is digitized by ADC and digital operations are performed, a more accurate counting model can be established. For example, when two particles pass through the signal at the same time, only one count can be made when using the comparator threshold comparison, but the digital processing can distinguish the characteristics of the double particle waveform.

[0054] like Figure 5 As shown, the power supply circuit includes a chip U7, the model of the chip U7 is LMR14006, the 5th pin of the chip U7 is connected to one end of the resistor R23, one end of the capacitor C30, one end of the capacitor C29, one end of the capacitor C28, one end of the capacitor C27 and the 2nd pin of the MOS tube Q2, the other end of the resistor R23 is connected to the 4th pin of the chip U7, the other end of the capacitor C30, the other end of the capacitor C29, the other end of the capacitor C28 and the other end of the capacitor C27 are grounded, the 3rd pin of the MOS tube Q2 is connected to one end of the resistor R26, one end of the fuse F3, one end of the diode D2 and one end of the diode D8, the other end of the fuse F3 is connected to the 2nd pin of the interface CN3, the 1st pin of the interface CN3 is grounded, the other end of the diode D2 and the diode The other end of D8 is connected to pin 2 of interface CN2 and one end of resistor R44, the other end of resistor R44 is connected to one end of resistor R45 and pin 22 of chip U3, the other end of resistor R45 is grounded, pin 1 of MOS tube Q2 is connected to one end of resistor R27, the other end of resistor R27 is connected to the other end of resistor R26, one end of diode D4 and the collector of transistor Q3, the other end of diode D4 is connected to one end of diode D5 and pin 1 of interface XH5, the other end of diode D5 is connected to pin 27 of chip U3, the base of transistor Q3 is connected to one end of resistor R29, the other end of resistor R29 is connected to pin 26 of chip U3 and one end of resistor R31, the other end of resistor R31 and the emitter of transistor Q3 are grounded.

[0055] Pin 3 of the interface XH5 is connected to pin 3 of the MOS tube Q7, pin 1 of the MOS tube Q7 is connected to one end of a resistor R36, the other end of the resistor R36 is connected to one end of a resistor R35 and the collector of the transistor Q6, pin 2 of the MOS tube Q7 is connected to the other end of the resistor R35 and connected to +5V, the base of the transistor Q6 is connected to one end of a resistor R40, the other end of the resistor R40 is connected to pin 25 of the chip U3, and the emitter of the transistor Q6 is grounded.

[0056] Pin 1 of the chip U7 is connected to one end of capacitor C26, and pin 6 of the chip U7 is connected to the other end of capacitor C26, one end of diode D3 and one end of inductor L2. The other end of diode D3 is grounded. The other end of inductor L2 is connected to one end of capacitor C33, one end of resistor R25, one end of resistor R48, one end of capacitor C25, one end of capacitor C34 and pin 1 of chip U6, and connected to 3V7 power supply. The other end of resistor R25 is connected to one end of LED lamp LED1, and the other end of LED lamp LED1 is connected to Ground, the other end of resistor R48 is connected to pin 2 of chip U6, the other end of capacitor C25 and the other end of capacitor C34 are grounded, pin 5 of chip U6 is connected to one end of capacitor C31 and one end of capacitor C32, and connected to VCC power supply, the other end of capacitor C31 and the other end of capacitor C32 are grounded, the model of chip U6 is LP5907-3.3, pin 3 of chip U7 is connected to one end of resistor R28 and one end of resistor R24, the other end of resistor R27 is grounded, and the other end of resistor R24 ​​is connected to 3V7 power supply.

[0057] The power supply circuit also includes a chip U8, wherein pin 3 of chip U8 is connected to one end of a resistor R30, one end of a capacitor C36, one end of a resistor R46 and pin 5 of chip U7, the other end of resistor R46 is connected to pin 23 of chip U3 and one end of a resistor R47, the other end of resistor R47 is grounded, the other end of resistor R30 is connected to pin 5 of chip U8, the other end of capacitor C36 is grounded, pin 6 of chip U8 is connected to one end of capacitor C35, pin 2 of chip U8 is connected to the other end of capacitor C35, one end of a diode D6 and one end of an inductor L3, the other end of diode D6 is grounded, the other end of inductor L3 is connected to one end of resistor R32, one end of capacitor C38 and one end of capacitor C37, and are connected to a +5V power supply, the other end of capacitor C38 and the other end of capacitor C37 are grounded, pin 4 of chip U8 is connected to the other end of resistor R32 and one end of resistor R33, the other end of resistor R33 is grounded.

[0058] The present invention has dual power interfaces, one power interface CN2 is a charger interface, and one power interface CN3 is a battery pack interface. The battery pack is placed inside the device by default.

[0059] When the counter is working, the power supply needs to be turned on. When the counter stops working, the battery needs to be disconnected to ensure that the battery does not discharge at will. The circuit uses MOS tube Q2 as the power switch device. Compared with the mechanical power switch, the electronic switch has a longer service life and better environmental resistance. When turned on, the button generates a conduction signal to the MOS tube Q2 through the diode D4, the power is turned on, and it starts to run and generates a power hold signal by controlling the triode Q3 until it is turned off. The program releases the signal to keep the power on and the power is disconnected.

[0060] The power supply circuit uses two DCDCs, one of which is switched by chip U7 and then stabilized by secondary linear voltage by chip U6 before the circuit is powered. Because the power input voltage is 12V, the processor and sampling circuit use a voltage of 3.3V, and the sampling circuit has high requirements for power supply noise. The use of DCDC voltage stabilization in conjunction with LDO can effectively reduce the thermal dissipation power of LDO and reduce the switching noise of DCDC. The other DCDC voltage stabilization is the power supply for the thermal printer. The thermal printer has lower requirements for power supply noise. After switching voltage stabilization by chip U8, it directly powers the thermal printer.

[0061] like Figure 6 As shown, the air pump motor drive circuit includes a chip U9 and a chip U10, the model of the chip U9 is LMR14006, the model of the chip U10 is LMV321, the pin 1 of the chip U10 is connected to the pin 21 of the chip U3, the pins 3 and 4 of the chip U10 are connected to one end of a resistor R39, the other end of the resistor R39 is connected to the pin 3 of the chip U9, the pin 5 of the chip U10 is connected to one end of a capacitor C43 and connected to the VDD power supply, the other end of the capacitor C43 is grounded, the pin 5 of the chip U9 is connected to one end of a capacitor C42 and connected to the IN+ power supply, the other end of the capacitor C42 is grounded, the pin 4 of the chip U9 is One end of resistor R34 is connected to pin 24 of chip U3, and the other end of resistor R34 is grounded, pin 1 of chip U9 is connected to one end of capacitor C39, pin 6 of chip U9 is connected to the other end of capacitor C39, one end of diode D7 and one end of inductor L4, and the other end of diode D7 is grounded, the other end of inductor L4 is connected to one end of resistor R37, one end of capacitor C40, one end of capacitor C41 and pin 1 of interface CN6, pin 3 of chip U9 is connected to one end of resistor R38 and the other end of resistor R37, and the other end of resistor R38, the other end of capacitor C40, the other end of capacitor C41 and pin 2 of interface CN6 are grounded.

[0062] The counter of the present invention uses a flow rate of 2.83L / min for gas sampling, and the air pump motor driving circuit adopts a DC closed-loop control circuit.

[0063] The driving circuit of the air pump motor can control the output voltage of the interface CN6 by controlling DAC2 through the program. The circuit is a DC output. Compared with the PWM driving mode, the DC voltage control mode produces less interference, and the motor has a large torque and is more stable when running at a low speed.

[0064] like Figure 7 As shown, the gas flow detection circuit includes a chip U11, the model of the chip U11 is XGZP190, the 1st and 8th pins of the chip U11 are connected to the 1st pin of the amplifier U12B, the 2nd and 3rd pins of the amplifier U12B are connected to one end of the resistor R40, the other end of the resistor R40 is connected to one end of the resistor R42, one end of the capacitor C45 and the 2nd pin of the amplifier U13A, the 3rd pin of the chip U11 is connected to the 1st pin of the amplifier U12A, the 2nd and 4th pins of the amplifier U12A are connected to one end of the resistor R30, the other end of the resistor R30 is connected to the 1st pin of the amplifier U13A, one end of the resistor R41 and one end of the capacitor C44, the other end of the resistor R41 and the other end of the capacitor C44 are connected to the +1V2 power supply, the 3rd pin of the amplifier U13A is connected to the other end of the resistor R42, the other end of the capacitor C45 and one end of the resistor R43, and the other end of the resistor R43 is connected to the ADC acquisition of the chip U3.

[0065] The gas flow detection circuit measures the pressure difference at both ends of the metal gas pipe and calculates the gas flow through the gas pipe. The chip U11 of the micro-pressure difference sensor with a range of 1kpa is used. After the signal is amplified by the operational amplifier, it is sent to the single-chip microcomputer for digital sampling. After the sampled signal is digitally integrated, the gas flow is calculated. PRES_S+ and PRES_S- are the signals after the impedance of the pressure difference sensor becomes low. Reducing the impedance can ensure that the signal is not distorted after entering the amplifier U13A for differential amplification. PRES_ADC is the signal collected by the single-chip microcomputer ADC. After collecting the analog quantity, the current pressure difference is calculated. The diameter of the copper tube sample can calculate the current gas flow rate, and then calculate the gas flow.

[0066] Finally, the PID calculation method is used to perform closed-loop control of the air pump, which can ensure accurate sampling flow in different measurement environments, eliminate frequent manual adjustments, and is more suitable for long-term online dust particle measurement.

[0067] The description of the present invention is given for the purpose of illustration and description, and is not intended to be exhaustive or to limit the invention to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for particular uses.

Claims

1. A laser dust particle counter for measuring dust particles in a clean environment, characterized in that: It includes a processor circuit, a communication circuit, a laser diode drive circuit, a photoelectric detection circuit, a power supply circuit, an air pump motor drive circuit and a gas flow detection circuit. The processor circuit is connected to the communication circuit, the laser diode drive circuit, the photoelectric detection circuit, the air pump motor drive circuit and the gas flow detection circuit. The power supply circuit supplies power to each module. The processor circuit includes a chip U3, the model of the chip U3 is STM32F405RG, the 5th pin of the chip U3 is connected to one end of the crystal oscillator X1 and one end of the capacitor C17, the 6th pin of the chip U3 is connected to the other end of the crystal oscillator X1 and one end of the capacitor C18, the other end of the capacitor C17 and the other end of the capacitor C18 are grounded, the 7th pin of the chip U3 is connected to one end of the resistor R14 and one end of the capacitor C20, the other end of the resistor R14 is connected to the VCC power supply, the other end of the capacitor C20 is grounded, the 17th pin of the chip U3 is connected to one end of the resistor R43 and one end of the resistor R42, the other end of the resistor R43 is grounded, the other end of the resistor R42 is connected to the base of the transistor Q8, the emitter of the transistor Q8 is grounded, the collector of the transistor Q8 is connected to one end of the buzzer, and the other end of the buzzer is connected to the VDD power supply; The processor circuit also includes a chip U4, the model of the chip U4 is NC AT24C64D-SSHM-B, the 5th pin of the chip U4 is connected to one end of a resistor R16 and the 33rd pin of the chip U3, the 6th pin of the chip U4 is connected to one end of a resistor R15 and the 34th pin of the chip U3, the other end of the resistor R15 and the other end of the resistor R16 are grounded, the 8th pin of the chip U4 is connected to one end of a capacitor C19 and connected to a VDD power supply, and the other end of the capacitor C19 is grounded; The laser diode driving circuit comprises a chip U1, wherein pin 1 of the chip U1 is connected to one end of a capacitor C3 and pin 20 of the chip U3, pin 3 of the chip U1 is connected to one end of a resistor R2, one end of a capacitor C4 and the S pole of a MOS tube Q1, the other end of the resistor R2 and the other end of the capacitor C4 are grounded, the G pole of the MOS tube Q1 is connected to pin 4 of the chip U1, the D pole of the MOS tube Q1 is connected to pin 1 of a socket CN1, pin 2 of the socket CN1 is connected to one end of a capacitor C1 and one end of a capacitor C2, and is connected to a 3V7 power supply, and the other end of the capacitor C1 and the other end of the capacitor C2 are grounded; The photoelectric detection circuit includes an amplifier U2A, wherein the 3rd pin of the amplifier U2A is connected to one end of the photocell PD1, one end of the capacitor C9, one end of the capacitor C10, one end of the resistor R11 and one end of the resistor R8, the other end of the capacitor C9, the other end of the capacitor C10 and the other end of the resistor R11 are grounded, the other end of the resistor R8 is connected to the VDDA power supply, the 2nd pin of the amplifier U2A is connected to the other end of the photocell PD1, one end of the resistor R5 and one end of the capacitor C5, the other end of the resistor R5 and the other end of the capacitor C5 are connected to the 1st pin of the amplifier U2A, the 8th pin of the amplifier U2A is connected to one end of the capacitor C6 and one end of the capacitor C11, and is connected to the VDDA power supply, the capacitor The other end of C6 and the other end of capacitor C11 are grounded, pin 1 of amplifier U2A is connected to one end of capacitor C7, the other end of capacitor C7 is connected to one end of resistor R6, one end of resistor R10 and one end of resistor R9, the other end of resistor R6 is connected to VDDA power supply, the other end of resistor R10 is grounded, the other end of resistor R9 is connected to pin 5 of amplifier U2B, pin 6 of amplifier U2B is connected to one end of resistor R3 and one end of resistor R4, the other end of resistor R3 is grounded, the other end of resistor R4 is connected to pin 7 of amplifier U2B and one end of resistor R7, the other end of resistor R7 is connected to one end of capacitor C8 and pin 14 of chip U3, and the other end of capacitor C8 is grounded.

2. A laser dust particle counter for measuring dust particles in a clean environment as claimed in claim 1, characterized in that: The power supply circuit includes a chip U7, the model of the chip U7 is LMR14006, the 5th pin of the chip U7 is connected to one end of a resistor R23, one end of a capacitor C30, one end of a capacitor C29, one end of a capacitor C28, one end of a capacitor C27 and the 2nd pin of the MOS tube Q2, the other end of the resistor R23 is connected to the 4th pin of the chip U7, the other ends of the capacitor C30, the other ends of the capacitor C29, the other ends of the capacitor C28 and the other end of the capacitor C27 are grounded, the 3rd pin of the MOS tube Q2 is connected to one end of a resistor R26, one end of a fuse F3, one end of a diode D2 and one end of a diode D8, the other end of the fuse F3 is connected to the 2nd pin of the interface CN3, the 1st pin of the interface CN3 is grounded, the other end of the diode D2 and the diode D8 The other end is connected to pin 2 of interface CN2 and one end of resistor R44, the other end of resistor R44 is connected to one end of resistor R45 and pin 22 of chip U3, the other end of resistor R45 is grounded, pin 1 of MOS tube Q2 is connected to one end of resistor R27, the other end of resistor R27 is connected to the other end of resistor R26, one end of diode D4 and the collector of transistor Q3, the other end of diode D4 is connected to one end of diode D5 and pin 1 of interface XH5, the other end of diode D5 is connected to pin 27 of chip U3, the base of transistor Q3 is connected to one end of resistor R29, the other end of resistor R29 is connected to pin 26 of chip U3 and one end of resistor R31, the other end of resistor R31 and the emitter of transistor Q3 are grounded; Pin 3 of the interface XH5 is connected to pin 3 of the MOS tube Q7, pin 1 of the MOS tube Q7 is connected to one end of a resistor R36, the other end of the resistor R36 is connected to one end of a resistor R35 and the collector of the transistor Q6, pin 2 of the MOS tube Q7 is connected to the other end of the resistor R35 and connected to +5V, the base of the transistor Q6 is connected to one end of a resistor R40, the other end of the resistor R40 is connected to pin 25 of the chip U3, and the emitter of the transistor Q6 is grounded.

3. A laser dust particle counter for measuring dust particles in a clean environment as claimed in claim 2, characterized in that: Pin 1 of the chip U7 is connected to one end of capacitor C26, and pin 6 of the chip U7 is connected to the other end of capacitor C26, one end of diode D3 and one end of inductor L2. The other end of diode D3 is grounded. The other end of inductor L2 is connected to one end of capacitor C33, one end of resistor R25, one end of resistor R48, one end of capacitor C25, one end of capacitor C34 and pin 1 of chip U6, and connected to 3V7 power supply. The other end of resistor R25 is connected to one end of LED lamp LED1, and the other end of LED lamp LED1 is connected to Ground, the other end of resistor R48 is connected to pin 2 of chip U6, the other end of capacitor C25 and the other end of capacitor C34 are grounded, pin 5 of chip U6 is connected to one end of capacitor C31 and one end of capacitor C32, and connected to VCC power supply, the other end of capacitor C31 and the other end of capacitor C32 are grounded, the model of chip U6 is LP5907-3.3, pin 3 of chip U7 is connected to one end of resistor R28 and one end of resistor R24, the other end of resistor R27 is grounded, and the other end of resistor R24 ​​is connected to 3V7 power supply.

4. A laser dust particle counter for measuring dust particles in a clean environment as claimed in claim 2, characterized in that: The power supply circuit also includes a chip U8, wherein pin 3 of chip U8 is connected to one end of a resistor R30, one end of a capacitor C36, one end of a resistor R46 and pin 5 of chip U7, the other end of resistor R46 is connected to pin 23 of chip U3 and one end of a resistor R47, the other end of resistor R47 is grounded, the other end of resistor R30 is connected to pin 5 of chip U8, the other end of capacitor C36 is grounded, pin 6 of chip U8 is connected to one end of capacitor C35, pin 2 of chip U8 is connected to the other end of capacitor C35, one end of a diode D6 and one end of an inductor L3, the other end of diode D6 is grounded, the other end of inductor L3 is connected to one end of resistor R32, one end of capacitor C38 and one end of capacitor C37, and are connected to a +5V power supply, the other end of capacitor C38 and the other end of capacitor C37 are grounded, pin 4 of chip U8 is connected to the other end of resistor R32 and one end of resistor R33, the other end of resistor R33 is grounded.

5. A laser dust particle counter for measuring dust particles in a clean environment as claimed in claim 1, characterized in that: The air pump motor drive circuit includes a chip U9 and a chip U10. The model of the chip U9 is LMR14006, the model of the chip U10 is LMV321, the pin 1 of the chip U10 is connected to the pin 21 of the chip U3, the pins 3 and 4 of the chip U10 are connected to one end of a resistor R39, the other end of the resistor R39 is connected to the pin 3 of the chip U9, the pin 5 of the chip U10 is connected to one end of a capacitor C43 and connected to a VDD power supply, the other end of the capacitor C43 is grounded, the pin 5 of the chip U9 is connected to one end of a capacitor C42 and connected to an IN+ power supply, the other end of the capacitor C42 is grounded, and the pin 4 of the chip U9 is connected to One end of resistor R34 is connected to pin 24 of chip U3, and the other end of resistor R34 is grounded. Pin 1 of chip U9 is connected to one end of capacitor C39. Pin 6 of chip U9 is connected to the other end of capacitor C39, one end of diode D7 and one end of inductor L4. The other end of diode D7 is grounded. The other end of inductor L4 is connected to one end of resistor R37, one end of capacitor C40, one end of capacitor C41 and pin 1 of interface CN6. Pin 3 of chip U9 is connected to one end of resistor R38 and the other end of resistor R37. The other end of resistor R38, the other end of capacitor C40, the other end of capacitor C41 and pin 2 of interface CN6 are grounded.

6. A laser dust particle counter for measuring dust particles in a clean environment as claimed in claim 1, characterized in that: The gas flow detection circuit includes a chip U11, the model of chip U11 is XGZP190, pin 1 and pin 8 of chip U11 are connected to pin 1 of amplifier U12B, pin 2 and pin 3 of amplifier U12B are connected to one end of resistor R40, the other end of resistor R40 is connected to one end of resistor R42, one end of capacitor C45 and pin 2 of amplifier U13A, pin 3 of chip U11 is connected to pin 1 of amplifier U12A, pin 2 and pin 4 of amplifier U12A are connected to one end of resistor R30, the other end of resistor R30 is connected to pin 1 of amplifier U13A, one end of resistor R41 and one end of capacitor C44, the other end of resistor R41 and the other end of capacitor C44 are connected to a +1V2 power supply, pin 3 of amplifier U13A is connected to the other end of resistor R42, the other end of capacitor C45 and one end of resistor R43, and the other end of resistor R43 is connected to the ADC acquisition of chip U3.

7. A laser dust particle counter for measuring dust particles in a clean environment as claimed in claim 1, characterized in that: The communication circuit includes a chip U5, the model of the chip U5 is SP3485, the pin 1 of the chip U5 is connected to one end of a resistor R18 and the pin 30 of the chip U3, the other end of the resistor R18 is connected to a VDD power supply, the pins 2 and 3 of the chip U5 are connected to one end of a resistor R19 and the collector of a transistor Q5, the other end of the resistor R19 is connected to the VDD power supply, the base of the transistor Q5 is connected to one end of a resistor R21, the other end of the resistor R21 is connected to one end of a resistor R20 and the pin 29 of the chip U3, the other end of the resistor R20 is connected to the VDD power supply; Pin 6 of the chip U5 is connected to a TVS diode D1, one end of a resistor R22 and one end of a fuse F2, the other end of the resistor R22 is connected to a VDD power supply, the other end of the fuse F2 is connected to pin 3 of an interface XH3, pin 7 of the chip U5 is connected to a TVS diode D1, one end of a resistor R17 and one end of a fuse F1, the other end of the resistor R17 is grounded, the other end of the fuse F1 is connected to pin 2 of the interface XH3, pin 8 of the chip U5 is connected to one end of a capacitor C21 and to a VDD power supply, and the other end of the capacitor C21 is grounded.

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