AVR-Chat

Generally speaking, moisture measurement in soil is accomplished 
thro0ugh the use of resistance
measurement.  A pair of probes is stuck into the soil, and the 
resistance is measured.  IKn a digital
approach,  an empirically determined lookup table is then used to 
convert the resistance to a moisture
percentage measurement.  I built a lumber moisture meter about 30 years 
ago, but it used an analog
meter movement, anbd was calibrated by borrowing a commercial lumber 
moisture meter and making
comparative measurements on a wide range of lumber.  Worked fine.

   As for your USB, the EASIEST approach would be to look up FTDIChip, 
and use one of their
serial <-> USB converter chips.  Alternatively, you could check 
www.atmel.com for applications
notes on implementing USB on either a USB enabled AVR (relatively 
expensive) or on a regular
AVR (inexpensive, but restricted to 12 Mbps speeds.

Teo wrote:
>
> Hello,
>
> I would like to develop a sistem based on Atmel to measure the moisture
> level of soil. Can you recommend me, please, one good and cheap sensor ?
>
> I would also like to communicate via USB.
>
> __
> .
>
>