The Journal of David A. Johnson, P.E., page 5

Last Updated on: Wednesday, December 31, 2008 03:16 PM

Soil Percolation Test  --  I got an interesting call from a guy who has a soil testing service in California.  He wanted to automate the soil “percolation” test, which is required for new construction, in homes which use a sanitary septic system, instead of the conventional city sewage connection.  The soil conditions must meet certain minimum requirements before a septic system can be approved.  The most important characteristic of the soil is its ability to absorb water.  The percolation test measures the rate in which the soil can take in the water.  I put my thinking cap on and came up with a method to make it fully automated.  Instead of requiring a person to monitor the test for an 8 hour period, the person only needed a few minutes to install the system and switch it on.  The system would control the water flow into a perforated pipe and a battery powered data accusation system would record all the data of the test for later viewing. But, as is often the case, the guy who wanted the system could not afford my consulting fees.  It is too bad, for it would have been an interesting project, but I have to eat, so it will just not get done now.

Solar Energy Research  --  Colorado is blessed with lots of sun and wind.  Some of the best wind energy sites in the nation are north of me, along the Colorado-Wyoming border. I would love to have some land and the resources to work on some new wind generator concepts.  I have some ideas how a grid-connected generator could cope with varying wind speeds.  I also have some thoughts about solar trough thermal energy collectors.  The beauty of these systems is that you could store the excess energy in the form of hot oil in big insulated metal tanks.  The amount of energy stored could be enough for a week of overcast weather.  The heat energy could be used to heat domestic water, heat a house in winter or run a heat engine for electricity.

Cassette Tape to MP3  --  I like to listen to a good audio book during my sometimes long soldering sessions and my 2 hour walks.  The wife and I have been buying used books through eBay for years.  We buy used audio books; convert them to MP3, before reselling them. This buy and resell cycle usually means we can get to listen to a good book for about $5.  There are lots of great books available on eBay but many of the older books are only available on cassette tapes.  Tapes are rather inconvenient for my walks, so I’m going to try and set up a small recording station in one of my spare bedrooms.  I’ll be looking for a quality cassette tape player with an automatic reversing action.  This will allow me to convert a whole tape at a time to MP3 tracks. I’ll use my old computer to store the tracks and later break up the massive 60 minute MP3 tracks into smaller ones.

Laser Light Receiver for Robot --  I started working on a sensitive laser light receiver design for a company who makes robotic law mowers.  Their mowers are big machines and by using some sophisticated computer controls and carefully positioned light reflectors, can mow large lawns without human intervention.  It should be an interesting project.

Variable Speed Wind Generator  --  I have been reading a lot about wind generators lately.  I frequently visit the website at www.otherpower.com and read about many of their grassroots developments of some of their simple generator designs.  Many years ago I had worked on an unsuccessful 6KW variable pitch grid tied generator.  The variable pitch propeller did a great job for adjusting to different steady state wind speed conditions; but it suffered from a long reaction time lag which often resulted in the system being kicked off the grid connection during heavy wind gusts.  I think a better way to deal with these sudden changes is by using a more intelligent alternator excitation field controller.

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