• System Details
• ToDo-List

The 3 analogue signals from the MiCS6814 are read by the channels 0 till 2 of an ADC type ADS1115.
Till the availablity of a simple, local calibration & scaling, these ADC-signals initially will be scaled on the 10 bits of the ADC => 0 till 1024 units,
directly compatible with the setting for readout of ADS1115: fullscale = 1024mV => 1unit = 1mV
When calibration has been found, either the controlling ESP8266, or the next stage in Domoticz for each type of gas will translate/scale the measured amount of units into microgram/m³.
Adjacent to the gassensor an extra (simple) thermosensor LM35 measures the temperature of the air flowing over the gassensor:
the sensor LM35 is physically fitted close and hovering over the gassensor for a local measurement of temperature as close as possible.
It's analogue output is a linear voltage of 10mV/degree, read by channel 3 of the same ADS1115:
also this 3rd channel of the ADC applies the setting of fullscale = 1024mV => 1unit = 1mV => resolution = 0.1 degree
anticipating the measurement of positive temperatures.
For setup the MiCS6814-Gassensor is combined with the GP2Y10-Dustsensor, housed in a cabinet as normally used for an alarm:
that cabinet provides solid metal walls, but still free airflow incl. metal gaze against intrusion of insects etc.
Outside antenna required to assure Wifi-communication for the controlling ESP8266.
Power regulator for ESP8266 also takes care for the sensors.
General measurement of temperature, humidity and pressure by a BME280-sensor at the bottom of the housing.
The cluster of Gassensor+Thermosensor is free-hanging within the housing in front of the dustsensor:
no protection against fluctuating temperature, moisture and dust from ambient air, as would be required for more stable measurements.

• Calibration concept =
  data logging => offsets + transfer function,
  to become compatible with RIVM's AQI-classsification.
• Environmental control =
  stable air flow circuit with control for heating/drying and for filtering of the air/gas for gassensor & dustsensor,
  to compensate effects of temperature & humidity, respectively dust (related to gas measurements):
  
  First feasible approach seems:
  • a tube/canal in front of the entry of the GP2Y10-sensor,
  • enclosing the cluster of gassensor MiCS6814 + thermosensor LM35,
  • with heater at entry of tube/canal,
  • with heater power PWM-controlled from the LM35-info
  • NO dustfilter, being too complicated to fit & maintain
    [Such filter should be positioned in the air flow 'before' the gas-sensor:
    however conflicting with the present position of the gas-sensor cluster in front of the dust-sensor,
    would block good operation of the dust-sensor,
    which is now located 'behind' the gassensor]
• Replace BME280 by BME680 and relocate in the airflow between the MiCS6814 and the GP2Y10 =
  addition of very basic VOC-measurement for awareness of outdoor VOC-level.
  VOC is becoming an important aspect for indoor environment, but might also be significant outdoors.
  The BME680 is equivalent to BME280 for Temperature/Humidity/Pressure.
  Addition of this measurement to this setup is a first step extending the measurement catalogue to roughly cover the VOC-aspect.

For an 'Extended Configuration' the concept must be developed from scratch:
still in infancy.

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