烟雾传感器mq2的python代码

以下是烟雾传感器mq2的Python代码示例：

import time
import math
import smbus

# Define some constants from the datasheet
MQ_PIN = 0        # Define which analog input channel you are going to use (MCP3008)
MQ_SAMPLE_TIMES = 5  # Define how many times you are going to sample in each loop
MQ_SAMPLE_INTERVAL = 0.1  # Define the interval between samples (in seconds)
MQ_RL_VALUE = 10  # Define the load resistance on the board, in kilo ohms
MQ_RO_CLEAN_AIR_FACTOR = 9.83  # RO_CLEAR_AIR_FACTOR=(Sensor resistance in clean air)/RO,
                                # which is derived from the chart in datasheet
MQ_RO = 10  # Assume initially that the sensor is calibrated with clean air

# Define the calibration function
def MQCalibration():
    val = 0
    for i in range(MQ_SAMPLE_TIMES):
        val += MQResistanceCalculation(analogRead(MQ_PIN))
        time.sleep(MQ_SAMPLE_INTERVAL)
    val = val/MQ_SAMPLE_TIMES
    MQ_RO = val/MQ_RO_CLEAN_AIR_FACTOR
    return MQ_RO

# Define the gas concentration function
def MQGasPercentage():
    val = 0
    for i in range(MQ_SAMPLE_TIMES):
        rs = MQResistanceCalculation(analogRead(MQ_PIN))
        ratio = rs/MQ_RO
        val += ratio
        time.sleep(MQ_SAMPLE_INTERVAL)
    val = val/MQ_SAMPLE_TIMES
    val = math.pow(10, ((math.log10(val)-1.897)/-0.288))
    return val

# Define the resistance calculation function
def MQResistanceCalculation(raw_adc):
    return ((MQ_RL_VALUE*(1023-raw_adc)/raw_adc))

# Define the analog read function
def analogRead(channel):
    bus = smbus.SMBus(1)
    adc = bus.read_i2c_block_data(0x48, 0x40+channel)
    data = (adc[0] * 256 + adc[1])
    return data

# Call the calibration function
MQCalibration()

# Print the gas concentration value every 2 seconds
while True:
    print("Gas Concentration : ", MQGasPercentage(), "ppm")
    time.sleep(2)

在代码中，我们使用了树莓派的GPIO接口和PCF8591模块来读取烟雾传感器MQ2的模拟输出值，并通过MQResistanceCalculation函数将其转换为传感器的电阻值。然后，我们使用MQCalibration函数对传感器进行校准，然后使用MQGasPercentage函数计算出气体浓度并将其输出到终端。您可以根据自己的需求和硬件配置进行适当的修改。