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108 lines
3.2 KiB
Python
Executable File
108 lines
3.2 KiB
Python
Executable File
#!/usr/bin/env python
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import bme680
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import time
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print("""Estimate indoor air quality
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Runs the sensor for a burn-in period, then uses a
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combination of relative humidity and gas resistance
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to estimate indoor air quality as a percentage.
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Press Ctrl+C to exit
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""")
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try:
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sensor = bme680.BME680(bme680.I2C_ADDR_PRIMARY)
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except IOError:
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sensor = bme680.BME680(bme680.I2C_ADDR_SECONDARY)
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# These oversampling settings can be tweaked to
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# change the balance between accuracy and noise in
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# the data.
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sensor.set_humidity_oversample(bme680.OS_2X)
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sensor.set_pressure_oversample(bme680.OS_4X)
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sensor.set_temperature_oversample(bme680.OS_8X)
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sensor.set_filter(bme680.FILTER_SIZE_3)
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sensor.set_gas_status(bme680.ENABLE_GAS_MEAS)
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sensor.set_gas_heater_temperature(320)
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sensor.set_gas_heater_duration(150)
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sensor.select_gas_heater_profile(0)
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# start_time and curr_time ensure that the
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# burn_in_time (in seconds) is kept track of.
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start_time = time.time()
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curr_time = time.time()
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burn_in_time = 300
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burn_in_data = []
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try:
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# Collect gas resistance burn-in values, then use the average
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# of the last 50 values to set the upper limit for calculating
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# gas_baseline.
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print('Collecting gas resistance burn-in data for 5 mins\n')
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while curr_time - start_time < burn_in_time:
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curr_time = time.time()
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if sensor.get_sensor_data() and sensor.data.heat_stable:
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gas = sensor.data.gas_resistance
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burn_in_data.append(gas)
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print('Gas: {0} Ohms'.format(gas))
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time.sleep(1)
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gas_baseline = sum(burn_in_data[-50:]) / 50.0
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# Set the humidity baseline to 40%, an optimal indoor humidity.
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hum_baseline = 40.0
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# This sets the balance between humidity and gas reading in the
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# calculation of air_quality_score (25:75, humidity:gas)
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hum_weighting = 0.25
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print('Gas baseline: {0} Ohms, humidity baseline: {1:.2f} %RH\n'.format(
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gas_baseline,
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hum_baseline))
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while True:
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if sensor.get_sensor_data() and sensor.data.heat_stable:
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gas = sensor.data.gas_resistance
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gas_offset = gas_baseline - gas
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hum = sensor.data.humidity
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hum_offset = hum - hum_baseline
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# Calculate hum_score as the distance from the hum_baseline.
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if hum_offset > 0:
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hum_score = (100 - hum_baseline - hum_offset)
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hum_score /= (100 - hum_baseline)
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hum_score *= (hum_weighting * 100)
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else:
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hum_score = (hum_baseline + hum_offset)
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hum_score /= hum_baseline
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hum_score *= (hum_weighting * 100)
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# Calculate gas_score as the distance from the gas_baseline.
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if gas_offset > 0:
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gas_score = (gas / gas_baseline)
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gas_score *= (100 - (hum_weighting * 100))
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else:
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gas_score = 100 - (hum_weighting * 100)
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# Calculate air_quality_score.
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air_quality_score = hum_score + gas_score
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print('Gas: {0:.2f} Ohms,humidity: {1:.2f} %RH,air quality: {2:.2f}'.format(
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gas,
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hum,
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air_quality_score))
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time.sleep(1)
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except KeyboardInterrupt:
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pass
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