** This device is an airbag air pressure control device, mainly composed of STM32F103C8T6 microcontroller, BMP388 air pressure sensor, OLED display module, elastic button, TB6612 drive module, and air pump , solenoid valve and air bag.
Among them, one end of the air guide pipe is connected to the air pump, and the other end is connected to one end of the one-way valve to prevent air flow in the opposite direction. The air guide pipe led from the other end of the one-way valve is connected to the three air guide pipes through a multi-way joint, and one is connected to the pressure sensor, One is connected to the solenoid valve and the other is connected to the air bag.
**2. Function description** This air pressure control device detects the air pressure value in the air bag through the BMP388 air pressure sensor, and displays the detection results on the OLED screen in real time. This device can set the target air pressure value, inflate the air bag through the air pump or open the solenoid valve to deflate so that the air pressure in the air bag reaches the set value, and adjust the inflation speed by adjusting the speed of the motor in the air pump. When the sensor detects that the air pressure value deviates from the set value, the air pump is used to inflate again or the solenoid valve is opened to deflate to suppress changes in air pressure and maintain dynamic stability. The air pressure range that this device can accurately measure is 30.0~125.0kPa, and the target air pressure range that can be adjusted is the current atmospheric pressure (approximately 101.3 kPa)~125.0kPa. In addition, this device also has a Bluetooth module to facilitate connection with a smartphone, thereby enabling detection and adjustment of the air bag pressure through the mobile app ( the Bluetooth function is not implemented ).
**3. Program flow chart**
![2.png]
**4. Debugging and test results** * The test comparison of different flow rates at the same target pressure (110.0Kpa) is as follows | | | | | | | -- - | --- | --- | --- | --- | | Flow rate | Starting air pressure | Target air pressure | Ending air pressure | Average time | | Weak | 101.3Kpa | 110.0Kpa | 110.0±0.1Kpa | 40s | | Medium | 101.3Kpa | 110.0Kpa | 110.0±0.1Kpa | 9s | | Strong | 101.3Kpa | 110.0Kpa | 110.0±0.1Kpa | 3.5s | | --- | --- | --- | --- | --- | | Flow rate | Starting air pressure | Target air pressure | Ending air pressure | Average time | | Weak | 101.3Kpa | 105.0Kpa | 105.0±0.1Kpa | 19s | | weak | 101.3Kpa | 110.0Kpa | 110.0±0.1Kpa | 40s | | weak | 101.3Kpa | 115.0Kpa | 114.9±0.1Kpa | 110s | | | Medium | 101.3Kpa | 110.0Kpa | 110.0±0.1Kpa | 9s | | Medium | 101.3Kpa | 115.0Kpa | 115.0±0.1Kpa | 13s | | 101.3Kpa | 105.0Kpa | 105.0±0.1Kpa | 2.5s | | Strong | 101.3Kpa | 110.0Kpa | 110.0±0.1Kpa | 3.5s | | Strong | 101.3Kpa | 115.0Kpa | 115.0±0.1Kpa | 6.0s | | Strong | 101.3Kpa | 120.0Kpa | 120.0±0.1Kpa | 7.3s | * Result Analysis
After many times of debugging and testing, this device has basically achieved the functions required by the question. At the same time, it was found that under weak flow rates, it is difficult for the air pressure in the air bag to continue to rise after reaching 115Kpa; under medium and strong flow rates, it will become difficult for the air pressure inside the air bag to rise after reaching 121 Kpa. If further improvement is needed in maintaining stable air pressure: the air duct connection can be sealed to improve the air tightness of the device. If you have different requirements on the air pressure adjustment range: you can replace the BMP388 with an air pressure sensor with the required range, and select an air bag with appropriate pressure resistance.
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