thirds of the 8 2 volt power supply at line 32 when the flip flop internal to timer device 27 resets the actual delay time in the charging of capacitor c1 is determined by the setting of rheostat r2 by knob 22 when capacitor c1 becomes charged a comparator internal to said timer device 27 and connected to pin d thereof causes the flip flop of timer device 27 to reset whereupon capacitor c1 discharges through pin e and drives pin b to near ground potential through a reversal of the previously described steps the current from resistor r1 takes the lower potential path to ground through pin b of timer device 27 flows through diode d3 and drops to near zero and the leakage current through said diode flows through resistor r9 to ground whereupon triac device q lacking control current becomes non conducting de energizing solenoid coil 28 and thus closing valve 12 until sensor 16 again dries and causes resistance to increase to the preselected value determined by the setting of knob 23 pin g of timer device 27 is connected to the flip flop internal to said timer device 27 to provide means to reset said flip flop on command such.