Project Soil

Project Soil is an extremely cheap & easy to use system to collect & manage soil data on a global scale. On a planet with more than 7 billion people, it is essential to control the conditions of the soil & understand how to sustain it. Project Soil’s cheap digital soil testing kit & light infrastructure (data collection & fruition via web & SMS) will allow all growers to understand their land, crops & choose suitable seeds for their soil, thereby yielding better crops with less pesticides.

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I’ve been working on the hardware to allow us to log soil moisture and temperature at extremely low cost. The first generation of sensors has been made for £8 each, bearing in mind that this is low quantity costing that really increases the value for money.

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Soldering the ATmega8U2 processor was fun in itself due to the Quad-Flat No Leads (QFN) package. Soldering required a steady hand, solder paste, a hot-air rework station and a stereo microscope. Soldering surface mount packages by hand is wildly improved with the use of a stereo microscope. It allows you to check connections, look for solder bridges and ensure there are no dry joints. As always the other magic tool for soldering is flux. Flux is the magneto of the soldering world and just seems to make solder go to the right places, whether that’s to your pins when soldering or to a piece of solder braid when desoldering.

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A view through the microscope, much easier to see what you’re soldering with this!

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A view through the microscope, you can see spekled bits of solder paste balls here on the left hand side (on the white silkscreen).

The 8u2 is extremely similar to it’s predecessor, the AT90USB82 to the point where avrdude, when used to flash the device does not have a part for the 8u2. Instead the following command is used to erase the device for example using the Force argument -F


avrdude -P /dev/tty.usbserial -c avrispmkII -p AT90USB82 -F erase

A makefile has been used based on a template by Jon Sowman to compile and then flashed to the device using avrdude and an avrISP mark 2.

More information to come as the project progresses.

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