Trying to see how a DFRobot capacitive soil moisture sensor works.
http://www.dfrobot.com/wiki/index.php?title=Capacitive_Soil_Moisture_Sensor_SKU:SEN0193
The logic gates allow NE555 to look like a TLC555 (which is CMOS rather than BJT's)
Use push button to get peak detector near its stable output voltage.
The 100pF is for adding soil moisture which changes the capacitance of the sensor. 100pF is more than what the sensor will change when put in a swimming pool but it does show the analog output changes some.
