Moisture sensor devices and methods associated with operation of the moisture sensor devices are disclosed herein. One embodiment includes a moisture sensor device comprising a probe forming a capacitor and adapted to be positioned within soil; a controller coupled to the probe, the controller comprising a variable frequency oscillator, the frequency of the variable frequency oscillator varies as a function of a capacitance of a capacitor, the capacitance varies as a function of a moisture content of the soil; a reference oscillator; and a circuit for comparing the frequency of the variable frequency oscillator to a frequency of the reference oscillator; and a switch coupled to the circuit and adapted to be coupled to a power output line of an irrigation controller and a power actuation line coupled to a valve.