Gas sensors to 1-wire

You got my attention, cannot help you with the schema, but would like to see the end result :-).

H.

This is good idea.
You can use this board: http://www.hobby-boards.com/catalog/product_info.php?cPath=22&products_id=91
There is also schema for ds2438 from this device: http://www.hobby-boards.com/catalog/links/ts3-r1/Humidity-Temp-Solar%20v3.2%20Schematic.pdf

I did a little research.
MQ-135 Sensor detect air particles from 10ppm to 300ppm (1000ppm benzene). 10ppm is high value - I think it is more applicable to alarms.
So we need more sensitive sensor.
TSG 2602 works from 1 to 10ppm - it is much better.
It seems that these sensors are more suitable for measuring indoor air quality. In datasheets don’t see information about sensitivity to S0x, NOx, C0x …etc, despite I think that because of their general sensitivity, will work in outdoor environment.
I created wiring diagram (see attachment, but circuit is untested) and formula for temperature compensation - these gas sensors is sensitive to temperature and slightly to humidity.

Schema is taken from hobby-boards Temperature/Sun sensor. I do not know whether I chose the optimal resistor values, but trimmer solves everything. :smiley:

Compensation formula (only for TSG2602):

Vcomp = Vin*(-0,028*T+1,6)

Where:
“Vin” is meausred voltage
“T” is Temperature in Celsius deg

Then for implemenation to SW is also needed know voltage for clear air (0,9~xV - depends on trimmer position) and voltage for contamined air (0.11V~xV depends on trimmer) - it will be simply readed from OneWireViewer.

Probably in the near future I’ll try to order parts and test it. :slight_smile:

EDIT: Added URLs, fixed bad ppm values (oh my memory… :))

EDIT2: Schema is moved to: http://discourse.weather-watch.com/

I don’t think that the amount of Ozone refers to the overall air quality. Respectively for high value of ground ozone must be present hydrocarbons and/or nitrogen oxides (both present eq. in exhausts) and must be high solar radiation/activity. I think that Carbon Dioxide sensor will be closer to overall air quality.
Nevertheless, these sensors have low sensitivity - at least I think - It starts from 10ppm. See datasheet for MQ 131 or MQ 135 and others similar.

I found great gas sensor test at Explore the World With US -

BTW: MQ-135 is also on e-bay http://www.ebay.co.uk/itm/MQ135-sensor-Air-quality-sensor-Hazardous-gas-detection-/180713997925?pt=LH_DefaultDomain_0&hash=item2a1364c665

Wow, nice guys,

I am very interested in this, would it be possible to get a “turn key” solution and use WD to log the data?

H.

TSG 2602 arrived yesterday (bought at rs-online.com).
Works very well. Detects cigarette smoke, some fumes, VOCs etc… :hello1:
I modified the scheme for maximal sensitivity. See attachment.
The output voltage depends on the quality of air and is between approx 0,4 - 4,7V.

Now we need support for Air Quality sensor in WD.
If possible:

  • field for AQ ROM at 1-Wire reader in “Main setup” tab
  • Checkbox for AQ sensor temperature compensation - on these measured values will be applied temperature compensation for TSG2602: Vout = Vin*(-0,028*T+1,6) where: “Vin” is meausred voltage and “T” is Temperature in Celsius deg. Or this checkbox may be replaced with field where will be added equation for specific sensor.
  • Output can be Air Quality index (check box in 1-wire reader):
    • configuration at 1-Wire reader in “Other settings” tab where will be fields for minimal and maximal voltage.
    • Air Quality Index = (Vmax-Vmin)/500*(Vmax-Vact) where “Vact” is actual measured value.
  • New column “1_wire_Air_Quality” for WDMySQL
  • WD Graphs for AQ
  • WD Main window may include AQI number and status word.

And then we have another weather value that can be measured and used in WD. 8)

What do you think?


Turn Key, is the same as plug and play.

Whole kid assembled, you simply plug it in and configure WD to use it.

H.

I think it is brilliant :-).

H.

With this sensor can be measured a Particulate Matter (PM10 or even smaller particles). But reading data from this sensor isn’t easy (10ms pulses). How did you solved it? Do you have a schematic?

Hello,

(Sorry for English, it is about a translator)

I am interested by this project, WD is you it compatible?
Thank you.
Serge

Currently WD not able to reasonably use the data from this sensor.
But I can to try ask Brian if he would do something with it.

Ok Merci Rad-X

I have done some deeper research. It seems that TSG2600 is for air quality measuring slightly better than TSG2602 - higher sensitivity for standard city outdoor air contaminants.
See basic classification at http://www.directindustry.com/prod/figaro-engineering/semiconductor-air-quality-sensors-29357-147448.html
info and links at http://lekernel.net/blog/2009/07/toxic-gas-sensors-at-tmplab/
Especially measuring results at http://lekernel.net/blog/2009/09/sanobot-data-for-the-first-half-of-september/
But TSG2602 detect VOCs - eg. leaks of dangerous gases from factory…

I ordered TSG2600 and MQ-135.
Once the parts arrive, I’ll try to compare them.

However, some donation for development would be nice. These sensors are not the cheapest.

Hello,
Simply it would be interesting initially if Brian will integrate the probe in WD. Do you have answers?

Thank you
Serge

I forgot to send PM to Brian. I sent him message today.

Still looking for TGS2600 or TGS2602 in UK?
I bought them at cz.rs-online.com. Both in stock in most xx.rs-online.com eshops. See:
TGS2600 in uk.rs-online.com
TGS2602 in uk.rs-online.com

En France,
http://www.rs-particuliers.com/WebSearch/Capteurs_de_temperature_et_thermocouples-120110.aspx?Page=9&NavigationEx=&Manufacturer=&Price=

Serge

If used with the solar sensor. Where would you place it? High (8-10Meters) or low near the ground?

I’m following this tread very closely as I would also like to do AQI at my station. It’s not very common i Denmark.

Flemming

The sensor should be optimally placed at a height where they move people. About 2 meters above ground.
Sensor must be also well ventilated, not only because they need good air exchange for measuring, but because of its inner portion is heated up to 400 deg C - temperature of sensor surface is about 50 deg C in room temperature. So if is gas sensor placed into a small box with poor heat exchange without temperature sensor (for calculating of heat deviation), measuring will be very inaccurate.

Good evening RAD-X,

You have news of Brian for the project.

Cordially
Serge