I’ve checked the codeshare, wiki, and forum, and can’t find any information on the gas sense module. I see that I need to turn on the heater and that it takes 10 seconds before it is ready to give a good reading, but I don’t see any documentation about how to make a usable value from ReadVoltage. Any tips?
Also, any problem with turning on the heating element and keeping it on all the time?
I see he is graphing the voltages, but that doesn’t give the values “meaning”. Meaning would be more along the lines of PPMs, or 3.13 is safe but 3.17 is dangerous, etc.
Those are sensor specific so the best is to see what voltages mean.
I had gas sensors where I left the heater on for days at a time without any problem. In my code share sample I have one timer that kicks off a reading process and another that runs the pre-heat, so it looks something like this:
timer1 = 60 seconds
timer2 = 20 seconds – this is the pre heat
timer1.tick
turn on sensor heaters
start timer 2
timer2.tick
stop timer2
grab a reading
turn off sensor heaters
Now as to what do the voltages mean, that is a little more difficult to answer as really these are cheap sensors and sensors you would base your life on, cost orders of magnitude more then these and take a lot of maintenance and expense to keep calibrated etc. There are charts available for these sensors however, which sensor are you using? Typically I don’t bother with this as I’m looking at relative readings, ie I’m interested more in the delta then the actual reading.
The source code etc for my demo gas sensor project http://www.tinyclr.com/codeshare/entry/607
@ Duke Nukem - first, what is that great brown board you have everything attached to?
For the rest of it:
I have the MQ-3 that came with it because I haven’t gotten a different one yet. I plan to get CO/Combustable (MQ-9 I think) next week when I am back near my electronics store (there isn’t one really close to home, so it’s a special occasion when I get to go).
I’m not looking at these as primary sensors, I have smoke & CO pre-wired in my home plus a combustible detector in my mechanical room. The Gadgeteer connected sensors are supplemental for times I’m not at home, hopefully good enough to help save the cats lives if we are on vacation and there is some problem (we would call friends to check it out in person and see if the big detectors are screaming).
I am just interested in understanding what the represented values really are instead of just having a baseline voltage and reading deviations.
@ Gus - I figured it would be specific to each sensor since each measures different things and I’m guessing some are in different orders of magnitude.
Guess I have research to do to convert the voltages to something else, I’ll be sure to post the code to the Codeshare when I have something useful.
For project boards I bought a number of Tamiya 70172 Universal Plate L (210x160mm), which is what I used for this project
and these Tamiya 70157 Universal Plate Set (2pcs.)
However now you might want to have a look at http://devonboard.com/ and Gus has mentioned they have something coming.
The spec sheet for the MQ-3 can be found here:
http://www.winsensor.com/English/photo/product/20110923162329742974.pdf
Which has the reference charts I mentioned.
I assume you want the MQ-9 for CO detection which is problematic given the heater for CO runs at 1.5v so it won’t work for CO gas given the module is setup for 5v heaters, spec sheet here:
http://www.winsensor.com/English/photo/product/20110926164252365236.pdf
I’ve been running some experiments with shorten heat cycles to simulate that lower sensor temperature, but I’m thinking its a no go really.
We did look at upgrading to the ME series of gas sensors, but the cost of the sensors scared us off for anything other then custom builds, but who know if there is enough interest I would think there are a couple of module makers who might consider making these modules.
Thanks Duke Nukem.
I did a YouTube video overview of my Gas Sensor Project here which you might find interesting
Great overview!