EnviroDylos


A History of the EnviroDylos and its short evolution.
An environmentally controlled enclosure for the Dylos DC1100 Particle Counter.

The Objective:
To make an off-the-shelf Dylos Particle Counter report reliable and reasonably accurate PM2.5 approximation values that track regional air quality monitors through challenging weather conditions.

The weakness of the Dylos Particle counter is its inability to distinguish between micro-fine water particles and fine particulate matter (PM). As a result, when air temperatures approach freezing and the relative humidity rises well above 40 percent, the particle counter tends to count the micro-fine water and/or ice particles that get suspended. This results in falsely high readings that are easily challenged by air quality authorities.

The Goal:
1) Keep the Particle Counter well within specified operating limits.
2) Keep the ambient air sample Relative Humidity below 35 percent at all times at temperatures below 50 degrees F.

The Solution:
Simply by warming the ambient air sample, as is done with most instrument grade PM air monitors, the relative humidity is reduced significantly. This causes a change of state for the airborne water from a micro-fine solid droplet to a vapor which will not be detected by the particle counter.


Concept - Dew Point and Relative Humidity Reduction
Concept - Dew Point and Relative Humidity Reduction


EnviroDylos Communications
EnviroDylos Communications


EnviroDylos Power
EnviroDylos Power


EnviroDylos System Overview
EnviroDylos System Overview

EnviroDylos Construction



Heater Testing
Heater Bench Test
Bench Testing of the EnviroDylos Heater:

80mm PC Box Fan,
Home Made Thermal Couple,
PID Controller and
Solid State Relay

(Pid Controller configured for Celsius)

Heater Test



EnviroDylos Completed


Data Plot - Active Area PM2.5 and EnviroDylos (Home)
EnviroDylosPM


Data Plot - Active Ambient:Environmental Dylos Ratio
EnviroDylosAEratio

Operational January 04, 2015
Additional modification includes a framed box screen cover for the air inlet.
Later added screen sock to air outlet.

EnviroDylosExternal

Hourly Data Plots are posted to:
http://aqi.crharper.com

Update June 2015
The EnviroDylos system has worked surprisingly well over the winter and through the spring season without interference from tree pollen or mold spores. With the onset of the warmer weather, where the enclosure continues to operate without the heater, PM counts are observed to still be lower than the Ambient/Reference Dylos. Also, we also experienced fairly heavy wood smoke one evening and the resulting data showed that the Ambient Dylos reported very high large particle counts where the EnviroDylos did not. The Ambient Dylos also appeared to have over-scaled for the small particle counts. These recent findings seem to indicate that with the very low air flow rate and baffling of the EnviroDylos, the enclosure essentially attenuates the larger particulate matter to the point that the Dylos doesn't see it. Yet, the EnviroDylos still seems to report fairly realistic readings roughly equal to PM2.5 for the industrial sources in our region during the summer months.

Eight Days in May - 2016
An interesting correlation using ESDR, CREATE Lab's Environmental Sensor Data Repository.

Update July 2016 - All your CO2 are belong to us.
Addition of CO2meter's AirSense K30 CO2 sensor placed in the flow path and communicating by I2C bus. The purpose being to observe ambient CO2 levels under various weather and seasonal conditions and the effects of industrial plumage during our frequent surface inversions. So, can abnormally high CO2 levels also be an indicator of 'bad air', not from the CO2 itself, but what may also accompany it?

EnviroDylosK30

CO2 EnviroDylos Services:
* k30d (daemon)
* DylosPiClientCO2

CO2 Host Services:
* DylosPiServerCO2
* (plot services)

NOTE: For reliable I2C communications with the K30 sensor, which uses a software based interface, the I2C clock must be slowed down from the Raspberry Pi's default clock rate. But, even with this slower I2C clock, some communication errors will still occur and must be tolerated. Accepting this limitation, the K30 can still operate within acceptable limits without excessive retries. An alternate solution would be to use the available serial port interface but this would require an additional USB to serial adapter.