Help needed for soil moisture sensing...

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karthi27

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I need to design a cheap soil moisture sensor using PIC 16f877.
I referred https://www.faludi.com/2006/11/02/moisture-sensor-circuit/
I simulated it in multisim. It didn't yield satisfactory results.

All that i need is to send an analog signal to the controller based on the soil resistance. I need the hardware circuitry.
I shall take care of the programming.
 

I would not trust the circuit for several realsons.

1. the sensor is run at DC. This will cause electroplatingon the electrodes and change the scale factor over time. The circuit should be excited by AC which does not have this problem.

2. I am not surprised at your results. The circuit should be a voltage divider to ground (5V, resistor, sensor, ground) with the pickoff the node between the resistor and sensor.

3. The emitter follower will then work properly.
 

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