Air pump control circuit for gas detector

Abstract

The utility model relates to the technical field of air pump control, and discloses an air pump control circuit for a gas detector. The technical problems that in the prior art, an air pump pressure detection method is difficult to achieve accurate control over an air pump, precision is low, and stability is poor are solved. The device comprises an air pressure sensor for detecting the pressure of an air inlet pipeline of an air pump, a pressure signal output end of the air pressure sensor is connected with a main control chip, a control signal output end of the main control chip is connected with the air pump, and a power supply line of the air pump is connected with a boosting module and a current sampling operation module. The output end of the current sampling operation module is connected with the main control chip. According to the invention, PWM pulse width modulation is used to modulate the power supply of the air pump, so that the power supply voltage of the air pump is adjustable, and the gas collection flow is adjustable; the air pressure sensor is used for detecting and judging air path pressure to prevent air path blockage, and the current sampling operation module is used for detecting and judging air pump power supply current to prevent overhigh locked-rotor current of an air pump motor.

Description

Technical Field

[0001] The utility model relates to the technical field of air pump control, in particular to an air pump control circuit for a gas detector. Background Art

[0002] Gas detectors can be divided into free diffusion type and pump suction type according to the way they collect contact sample gas. Free diffusion gas detectors detect by naturally diffusing sample gas into the sensor, while pump suction gas detectors detect by sucking sample gas into the sensor through an air pump. Handheld all-in-one gas detectors with pump suction sampling method are widely used in the industry, while traditional handheld all-in-one gas detectors usually use a simple switch control method to control the start and stop of the gas pump by turning the switch on and off. This control method is simple, but it does not meet the application scenarios of high precision and high stability.

[0003] The Chinese patent document in the prior art: 201720152153.7 discloses a control circuit of a gas detector suction pump. It includes a PWM_FLOW signal terminal and an ADC_FLOW signal terminal, the PWM_FLOW signal terminal is connected to the 1st pin of the transistor Q9 through the resistor R42, the 2nd pin of the transistor Q9 is grounded, the 3rd pin of the transistor Q9 is connected to the current sampling resistor R60, the current sampling resistor R60 has three connecting branches, one branch is connected to the ADC_FLOW signal terminal through the resistor R61, another branch is connected to the resistor R88 through a diode D5, and another branch is connected to the No. 1 connection terminal of the suction pump, and the No. 2 connection terminal of the suction pump is connected between the diode D5 and the resistor R88.

[0004] However, during the implementation of the above scheme, there are at least the following technical problems: the traditional air pump pressure detection method is difficult to achieve precise control of the air pump. Usually, a fixed voltage is given to the air pump to drive the air pump to pump air through the pipeline for detection. The air pump power supply voltage is fixed and cannot be adjusted, and the gas collection flow rate remains unchanged; there is a lack of state detection of the air pump and the air path, and there is no signal feedback. It is impossible to detect faults such as air pump air path blockage and motor stalling, which can easily cause damage to the expensive air pump. In addition, the instrument detection results also have technical problems of low accuracy and poor stability when there is no normal air extraction. Therefore, it is urgent to propose an air pump control circuit for a gas detector. In order to improve the accuracy and stability of the gas detector, improve the maintainability and reliability of the equipment, reduce the failure rate, and thus extend the service life of the equipment. Summary of the invention

[0005] In view of the above technical problems, the present invention provides an air pump control circuit for a gas detector, which solves the problem that the traditional air pump pressure detection method in the prior art is difficult to achieve precise control of the air pump. Usually, a fixed voltage is applied to the air pump to drive the air pump to draw air through a pipeline for detection. The air pump power supply voltage is fixed and cannot be adjusted, and the gas collection flow rate remains unchanged. There is a lack of status detection of the air pump and the air path, and there is no signal feedback. Faults such as air path blockage and motor stalling of the air pump cannot be detected, which can easily cause damage to the expensive air pump. In addition, in the absence of normal air extraction, the detection results of the instrument also have the technical problems of low accuracy and poor stability.

[0006] The present application uses PWM pulse width modulation to modulate the power supply of the air pump, thereby achieving adjustable power supply voltage of the air pump and adjustable gas collection flow rate; uses an air pressure sensor to detect and judge the air circuit pressure to prevent air circuit blockage, and uses a current sampling operation circuit to detect and judge the air pump power supply current to prevent the air pump motor from stalling due to excessive current.

[0007] According to one aspect of the present disclosure, there is provided an air pump control circuit for a gas detector, comprising an air pressure sensor capable of detecting the pressure of an air pump intake pipe, wherein a pressure signal output end of the air pressure sensor is connected to a main control chip, a control signal output end of the main control chip is connected to the air pump, a boost module and a current sampling operation module are connected to the power supply line of the air pump, and an output end of the current sampling operation module is connected to the main control chip.

[0008] The main control chip includes an STM32 single-chip microcomputer.

[0009] The pressure signal output end of the air pressure sensor is connected to the SCL1 and SDA1 pins of the STM32 single-chip microcomputer.

[0010] The control signal output end of the STM32 single-chip microcomputer is connected to the air pump via a transistor, the base of the transistor is connected to the PB9 pin of the STM32 single-chip microcomputer to receive the PWM control signal output by the STM32 single-chip microcomputer, and the emitter of the transistor is connected to the air pump.

[0011] The boost module includes a SGM6603 boost chip, a voltage input end of the SGM6603 boost chip is connected to a 3.7v battery, and the SGM6603 boost chip outputs a 4.5v voltage connected to an air pump.

[0012] The current sampling operation module includes an OPA2330 operational amplifier, and the amplified signal output terminal CH9 pin of the OPA2330 operational amplifier is connected to the AIN9 pin of the STM32 microcontroller through an RC filter module.

[0013] The beneficial effects of the utility model are:

[0014] The adjustable power supply voltage and flow rate of the air pump provide a suitable air pressure and airflow environment for the instrument to use the detection gas, which can reduce power consumption, prevent the air pump from working for a long time in fault conditions such as air path blockage or motor stalling, reduce the chance of air pump damage, extend its life, achieve air path blockage and motor stalling protection, and improve the accuracy of the instrument's detection of gas concentration.

[0015] By detecting the air pump intake pipeline pressure through the air pressure sensor, the working pressure of the air pump can be obtained in real time and accurately, thus providing accurate data for subsequent control.

[0016] The boost module is used to boost the battery voltage to 4.5V, ensuring that the air pump can work normally even under low voltage conditions, thus improving the efficiency and reliability of the equipment.

[0017] The current sampling operation module can monitor the working current of the air pump in real time, and connect the amplified signal to the main control chip, so that the main control chip can control the air pump more accurately according to the current signal.

[0018] Using STM32 MCU as the main control chip can realize complex control logic and ensure the stability and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the schematic diagram of the air pump control circuit used for the gas detector;

[0020] Figure 2 Main control chip circuit schematic diagram

[0021] Figure 3 Schematic diagram of the air pump control and current sampling module circuit

[0022] Figure 4 Schematic diagram of the boost module circuit

[0023] Figure 5 Schematic diagram of the air pressure sensor interface circuit

[0024] Figure 6 Schematic diagram of filter circuit

[0025] Figure 7 Gas sensor interface circuit schematic

[0026] Figure 8 It is a gas circuit block diagram of a gas pump control circuit for a gas detector;

[0027] The names of the components in the figure are: J4 is the gas sensor interface; J5 is the pump interface; J6 is the sensor interface. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. Example 1

[0029] This example discloses a gas pump control circuit for a gas detector, see Figures 1 to 8 ,

[0030] It includes an air pressure sensor capable of detecting the pressure of the air pump intake pipeline. The pressure signal output end of the air pressure sensor is connected to the main control chip. The control signal output end of the main control chip is connected to the air pump. The power supply line of the air pump is connected to a boost module and a current sampling operation module. The output end of the current sampling operation module is connected to the main control chip.

[0031] The main control chip includes an STM32 microcontroller.

[0032] The pressure signal output end of the air pressure sensor is connected to the SCL1 and SDA1 pins of the STM32 microcontroller.

[0033] The control signal output end of the STM32 microcontroller is connected to the air pump via a transistor, the base of the transistor is connected to the PB9 pin of the STM32 microcontroller to receive the PWM control signal output by the STM32 microcontroller, and the emitter of the transistor is connected to the air pump.

[0034] The boost module includes a SGM6603 boost chip. The voltage input end of the SGM6603 boost chip is connected to a 3.7v battery, and the SGM6603 boost chip outputs a 4.5v voltage connected to an air pump.

[0035] The current sampling operation module includes an OPA2330 operational amplifier, and the amplified signal output terminal CH9 pin of the OPA2330 operational amplifier is connected to the AIN9 pin of the STM32 microcontroller through an RC filter module.

[0036] This application introduces an air pressure sensor to detect the air pump intake line pressure in real time and accurately, providing accurate data for subsequent control. By boosting the battery voltage to 4.5V through the boost module, the air pump can be ensured to work normally even under low voltage conditions, thereby improving the stability and reliability of the equipment. The working current of the air pump is an important parameter reflecting its working state. Through the current sampling operation module and the use of closed-loop control technology, the working current of the air pump can be monitored in real time, and the amplified signal can be fed back to the main control chip to achieve precise control of the air pump.

[0037] During operation, the boost module boosts the 3.7v battery voltage to 4.5v to supply power to the air pump. The air pressure sensor detects the pressure of the air pump intake pipe and inputs the pressure signal to the STM32 microcontroller. The STM32 microcontroller adjusts the output PWM (pulse width modulation) control signal according to the received pressure signal, and controls the transistor-driven air pump by adjusting the duty cycle of the PWM signal. At the same time, the current sampling operation module is also working. The OPA2330 operational amplifier collects the working current of the air pump, and then connects the amplified signal to the AIN9 pin of the STM32 microcontroller. Through collaborative work, the detection and control of the air pump intake pipe pressure, as well as the sampling and amplification of the current, are realized.

[0038] U13 and its peripheral circuits form a boost circuit, which raises BT's 3.7V to the maximum operating power supply voltage of 4.5V for the air pump. PB9 is the PWM signal output terminal from the STM32 microcontroller, which controls the on-off duty cycle of Q13 and then controls the power supply voltage of the air pump. For example, the voltage of 3.5V-4.5V can be controlled. Different voltages will result in different gas collection flow rates (300mL / min-800mL / min), thus achieving adjustable flow rate.

[0039] The pressure sensor interfaces SCL1 and SDA1 in the circuit diagram come from the IIC interface of the STM32 microcontroller. The J6 connector is connected to a digital air pressure sensor. The STM32 microcontroller controls the air pressure sensor through the IIC interface to read the air pressure of the intake pipeline. If the air path is blocked, the air pressure will increase significantly, and the air path blockage fault will be judged. The instrument will display a fault prompt, and the PB9 of the STM32 microcontroller will promptly control and shut down the air pump to prevent damage to the air pump. The air path system block diagram shows the relative position order of each device in the air path system.

[0040] In the circuit diagram, R76, R77, R78, R79, R80, C54 and U14 form a current acquisition operation circuit. The voltage output CH9 of the operation circuit is connected to the RC filter and the analog-to-digital conversion interface of the STM32 microcontroller. The STM32 microcontroller calculates the current, determines that the motor is blocked according to the abnormal increase in current, and shuts down the air pump in time to prevent damage to the air pump.

[0041] The adjustable power supply voltage and flow rate of the gas pump provide a suitable air pressure and airflow environment for the instrument to use to detect gases. For example, detecting certain gases requires a flow rate of about 500mL / min. Too large or too small a flow rate will affect the accuracy of gas concentration detection. The rated working voltage or maximum working voltage of the gas pump is relatively high. If it works at these voltages, the flow rate is generally large and the power consumption is also high. Adjustable flow rate can reduce power consumption.

[0042] The air pump is a relatively expensive device with a limited lifespan (about a few thousand decimals). If it works for a long time in a fault state such as air path blockage or motor stalling, it will inevitably cause direct damage to the air pump or reduce its lifespan. Therefore, air path blockage and motor stalling protection are very necessary. In addition, when the air pump is not pumping normally, the instrument detects abnormal gas concentration, the instrument determines the fault, and displays the fault to prevent false detection.

[0043] Although some preferred embodiments of the utility model have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the utility model.

[0044] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of this application and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An air pump control circuit for a gas detector, characterized in that: It includes an air pressure sensor that can detect the pressure of the air pump intake pipe. The pressure signal output end of the air pressure sensor is connected to the main control chip, the control signal output end of the main control chip is connected to the air pump, the boost module and the current sampling operation module are connected to the power supply line of the air pump, and the output end of the current sampling operation module is connected to the main control chip.

2. The air pump control circuit for a gas detector according to claim 1, wherein: The main control chip includes an STM32 single-chip microcomputer.

3. The air pump control circuit for a gas detector according to claim 2, wherein: The pressure signal output end of the air pressure sensor is connected to the SCL1 and SDA1 pins of the STM32 microcontroller.

4. The air pump control circuit for a gas detector according to claim 2, wherein: The control signal output end of the STM32 single-chip microcomputer is connected to the air pump via a transistor, the base of the transistor is connected to the PB9 pin of the STM32 single-chip microcomputer to receive the PWM control signal output by the STM32 single-chip microcomputer, and the emitter of the transistor is connected to the air pump.

5. The air pump control circuit for a gas detector according to claim 1, wherein: The boost module includes an SGM6603 boost chip, a voltage input end of the SGM6603 boost chip is connected to a 3.7V battery, and the SGM6603 boost chip outputs a 4.5V voltage to be connected to an air pump.

6. The air pump control circuit for a gas detector according to claim 2, wherein: The current sampling operation module includes an OPA2330 operational amplifier, and the amplified signal output terminal CH9 pin of the OPA2330 operational amplifier is connected to the AIN9 pin of the STM32 microcontroller through an RC filter module.

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