Improving the Accuracy of Gas Sensors

If you need a sensor to detect gasses of some sort, you’ll probably be looking at the MQ series of gas sensors. These small metal cylinders contain a heater and some electrochemical sensor. Wire the heater up to a voltage, and connect one end of the resistor to an ADC, and you have a sensor for alcohol vapors, hydrogen sulfide, carbon monoxide, or ozone, depending on which model of sensor you’ve picked up.

These are simple analog devices, and as you would expect they’re sensitive to both temperature and humidity. [Davide Gironi] wanted a more accurate gas sensor, so he’s diving into a bit of overengineering and correlating the output of these sensors against temperature and humidity.

There’s a difference between accuracy and precision, and if you want to calibrate gas sensors, you’ll need to calibrate them against something. Instead of digging out a gas sensor of known precision, [Davide] took the easy way out: he graphed the curves on the datasheets for these sensors. It’s brilliant in its simplicity.

These numbers were thrown into R, and with a bit of work, [Davide] had a look up table of various concentrations of gasses plotted against certain resistances. In testing these sensors, he found a higher correlation between humidity and temperature and gas concentrations, which one would expect.

The files for these sensors are available on [Davide]’s website, and he included a neat little video showing everyone what went into these calculations. You can check that out below.

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Raspberry Pi and R


[Stephen] picked up a Raspberry Pi to do a little hardware hacking and add a blinking LED to the many feathers in his software development hat. He picked up an analog to digital converter and a temperature sensor that would serve him well in a few projects he wanted to put together, including a weather station and a small Pi-controlled home brewing setup. He ended up not liking Python, and didn’t like the C-ness of wiringPi. He’s a scientist, so he’s most comfortable with R and Matlab. Of course, playing around with a R and a Raspberry Pi means replicating his sensor-reading code in R.

[Stephen] put together a neat little package that will allow him to read his sensors over an SPI bus with his Raspberry Pi. Yes, this functionality can easily be duplicated with Python, but if you’re looking to generate beautiful graphs, or just do a whole lot of statistics on something, R is the tool you need.

It’s a cool project, even if it is only measuring the temperature. Using R for the nerd cred isn’t bad, either.

BeagleBoard Cluster

What do you do after you make a BeagleBoard graphing calculator? [Matt] over at Liquidware Antipasto made a BeagleBoard Elastic R Cluster that fits in a briefcase. Ten BeagleBoards, are connected to each other though USB to ethernet adapters and a pair of ethernet switches connected to a wireless router. The cost for this cluster comes in around $2000 and while consuming less than 40 watts of power, out-paces a $4500 laptop. How might you use this cluster? What improvements would you make? Continue reading “BeagleBoard Cluster”