AVR-Chat

On Thu, 18 Oct 2007 12:27:59 -0500  you (Thomas Keller <tjkeller1@alltel.net>)
wrote:

I was wondering how a simple resistance measurement could differentiate between
a moist soil with low nutrient content and a drier soil containing a lot of
soluble nutrients.

>   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.
>>
>> __
>> .
>>
>>  
>
>
>
> 
>Yahoo! Groups Links
>
>
>

--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
FZAOINT http://www.fzaoint.net