[chbot] Just when I thought I had a good soil moisture solution...
markaren1 at xtra.co.nz
Wed Nov 18 04:01:45 GMT 2015
I will Barrel over and help.
Can't help to wonder if you wouldn't have this problem if you stopped
Rifling through these messages.
Mind you, that is of course the Stock response...
Careful you don't Trigger more Punishment.
On 18/11/2015 4:06 p.m., Andy ZL3AG wrote:
> Shoot me. Please.
> On 18/11/2015, at 2:05 PM, Robin Gilks wrote:
>> Well I was going to write something like that - but my ideas just sort of
>> If I keep coming back to this project at the correct Frequency, I'll find
>> out if I have the Capacity for it to get finished.
>> After all my work, it appears that Resistance is futile...
>>> Shouldn't the subj be 'Just when I though I had a Solution for soil
>>> Moisture" ? :)
>>> On 18/11/2015 12:40 p.m., Robin Gilks wrote:
>>>> ... I discovered that rather than resistive I should be looking at high
>>>> frequency capacitive sensors.
>>>> Commercial ones run at up to 70MHz, this one based on am ATTINY441 AVR
>>>> chip runs at the system clock rate of 16MHz and has an I2C interface.
>>>> Very simple mode of operation, its basically using the PCB as the two
>>>> plates of a capacitor and as the dielectric constant around it changes
>>>> (due to moisture) so does the capacitance.
>>>> This is measured by driving a high frequency clock to the cap through a
>>>> series resistor and measuring the peak voltage swing across the cap with
>>>> couple of diodes and long(ish) time constant RC network providing a
>>>> differential output to the A/D inputs of the micro.
>>>> Think I'll go this route...
>> Robin Gilks
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