Help me please with our innovation project

[kevinpascua]

I'm Kevin , an Electronics and Communication Engineering, 1st year, my professor wants me to do a simple and low-cost sensor that can water plants with a simple sensor like this to determine if the soil is wet or dry, **broken link removed**, but with that sensor the resistance goes up when the soil is dry and when the resistance goes down its wet. What am i going to do or what should i do to my circuit to have the sensor's resistance go down if the soil is dry (so that the can current flow) and resistance go up if the soil is wet. Thank to anyone who respond to my post

 

[SABorn]

Gee man if you cant figure that out you must be a poor engineer.

Perhaps the reason for your lack of knowledge is you have been spoon fed the answers from the internet and have not actually ever worked anything out for yourself.

Come up with some answers of your own and then come back and ask if they will work, put your own brain in gear.

 

[kevinpascua]

Ohh sorry, im just a student, 1st year and my professor wants me to create that kind of stuff with a low-cost budget.

 

[JimB]

So, think about it a bit.

Moisture changes the resistance of the probe, so if you have a circuit which can measure a change in resistance, you can calibrate it to measure "moisture".

Once you can measure the moisture and have a voltage which changes with moisture, you need something to switch at the voltage corresponding to the moisture where the plants need watering.

Then you need to make that switch stop and start the watering thing.

Easy!

JimB

 

[crutschow]

To minimize corrosion of the probes you may want to use an AC voltage. The AC alternating polarity reduces the transfer of metal ions and consequent loss of probe metal that a DC current can produce.

 

[alec_t]

Why do you want a sensor whose resistance is higher when wet than when dry (assuming such a sensor exists) ?