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By tbitson
#193925
Greetings,
Is anyone working with the CCS811 VOC/CO2 sensor? I'm running the example code ported to a Photon (very minor changes), and the results I'm getting doesn't look right. The voc and co2 response looks identical, just scaled differently. I've tried exposing the sensor to volatiles (alcohol) and pure co2, but both channels respond. Overlaying the plots of time sequenced data shows the response to changes are identical, except for scaling (co2 is about a factor of 7 higher than voc, but does vary). In fresh air co2 = ~410, voc = 0, so it appears to be working. I've walked through Nate's example code and I don't see anything that stands out.

Has anyone got this sensor to work? Am I missing something?

- Tim

Plot:
Image
https://www.dropbox.com/s/00iv1sa76z74i ... .jpeg?dl=0
By MysterELane
#194744
I've noticed a similar behavior. I was going to ask about some results I got, but it would be interesting to plot these against each. I think I will do that next using Vernier's Logger Pro, anyways....

I mesaured in several locations. All results are CO2/VOC

Greenhouse with plants growing: 430/3
Empty Classroom: 450/7
Indoor Turf Field: 4802/670
Upstairs in the building with the turf field, in a room with a laser cutter and 3D printers: 7693/1111 (Pegged reading?)

None of these readings were adjust for environmental conditions. I've got the BME280 on order to sample again with environmental input. Right now I have my circuit wired up on a sparkfun Inventors kit Arduino w/breadboard, outputting the readings to an LCD screen. It should be noted, in the same locations, I used a vernier CO2 sensor and got the following readings:

Greenhouse w/ plants: 357 ppm
empty classroom: 530 ppm
Indoor Turf field: 449 ppm

If this thing is working, I'm wondering if I should be concerned about the Sparkfun readings.
By MysterELane
#194756
Just read that there is a 48 hour burn in time on the sensor, so none of those readings I took are reliable. Still, once its burned in with the recommend 48 hour period, it will be interesting to plot the CO2 value versus the tVOC value in Logger Pro.
By MysterELane
#194762
ALSO, from a sparkfun video....

This is a tVOC sensor, NOT a CO2 sensor. So yes, it is based on the same value, and the tVOC value is used to basically estimate the amount of CO2. So, it is not a reliable CO2 measurement, but is used to determine overall air quality. The tVOC value can be thought of "This is the equivalent of having this many ppm CO2"

https://www.youtube.com/watch?v=gdFb6-4 ... e=youtu.be