Nuts and Volts - August 2015

Just run this once. It will create a relational database for log entries. The database table is named “GAS.” In GAS, the entries are sampletime, COVOLTS, COPPM, LPGVOLTS, LPGPPM, VOCVOLTS, and VOCPPM

• SQLITE_LOG_INSERT.PY. This code takes the current log file and loads its contents into the database.

• SQLITE_EXAMPLE_QUERY.PY. This is a query example to be run against the database once you have updated it with some log file data. It queries all COVOLTS>0. This is run independent of all other files, and serves as an example of what the database query can do for you (but does not represent the complete functionality). Please refer to Python SQLITE for a more complete set.

• The entire application launches under IDLE as the Python module GASGUIVER11.PY.

*The ISaAC board needs to be integrated with the Raspberry PI GPIO serial port. The process is straightforward and appears in the August 2014 article mentioned earlier. It’s detailed in the freely downloadable ISaAC Tech Manual.

SYSMAIL.PY needs to be updated with your personal email address and password. Placement variable definitions are provided in code.

Current Prototype

Figure 10 shows our current bench implementation.

As you can see, our version of the sensor board and its connections to ISaAC (sitting on top of the Raspberry Pi) uses a solderless breadboard. Again, simple enough. Since ISaAC implements an Arduino compatible form factor, one may choose a more compact implementation that could be realized by integrating all the sensor board electronics onto an Arduino shield.

The present configuration has been successively moved around my house and gas measurements have been collected. A substantial database of these recordings is now in place.

One area remaining to be addressed is calibration. That will be an additional project. The literature indicates a number of ways in which this can be accomplished, so given that the entire design is open and readily modified, I’ll leave that up to you. For my purposes, this current configuration captures what I need for now in terms of gas indications.

What’s Next?

In this article, we introduced you to tools and techniques to understand and apply gas sensors within an indoor environment. The hardware and software for this open implementation can serve as a model for your own DIY system. It is expandable, so you can first start with a single sensor and then add on the others. Our discussion on gas sensors should also help you apply other sensor types in your design.