Hello everyone I'm assisting on an investigation, an agronomist wants to make some calculations to improve an irrigation system he has on his greenhouse, I live in a kinda delayed country in terms of education, I need to measure the moisture (obviously with common moisture sensors) in different points at the same time, I was helped here in this forum before with a PLX DAQ problem; speaking of which is for getting the results on M Excel, so my question is this:
since It's a large greenhouse, can I use any kind of wiring? do I need amplifiers? coaxial or any other kind of cable? any adaptor?
It depends entirely on how the data is traveling that 82 feet - but that's long enough that you can't ignore it. Tell us a bit more about how the data's being sent - serial? analog voltage? How fast?
The description on that Amazon listing isn't very clear but it seems like it's got an analog output (probably 0-5V) and a digital output which is probably just on/off based on the threshold set by the trimpot.
You will have trouble trying to sense the analog voltage 82 feet away but the digital will be fine.
Reading the reviews, it looks like this is applying a DC voltage to the sensor pins and it will corrode the pins very quickly, like within a week. I would not use it, for that reason.
That's how all those garbage moisture sensors work - it's a conductivity sensor.
If you want them to last at all, you can't apply the voltage constantly, only in pulses, but operating life is still poor. Expect to routinely replace them. Tinning the copper, like one review suggested, is not really a solution, though I'll bet it would help. It would also introduce tin ions (and lead ions if you use leaded solder - particularly undesirable if the soil has your vegetables growing in it) to the soil (plus the copper ions from the traces themselves dissolving).
I don't understand why you need a sensor board for that.
Arduino has all the ingredients that a cheap sensor has.
I am thinking of using a 50% PWM output, and connecting that to one electrode (burried length of iron rod) via a 100n capacitor.
That gives the electrode a 2.5volt AC signal. Less corrosion.
A second parallel iron rod could pick more or less of that signal up, depending on the moisture.
Has that been done before?
Leo..