that pump 62 is not activated by transient signals attributable to stimuli other than a gradual darkening or lightening of ambient light to a predetermined u201c trigger u201d level so called u201c dusk u201d and u201c dawn u201d discriminators u 4 then compare the signal being received from light sensor 18 to predetermined signal values consistent with u201c dusk u201d and u201c dawn u201d ambient light conditions parallel nand gates receive the signals from the discriminators and assuming that the pump start criteria has been met signal pump controller module 86 to start pump 62 optionally a manual override push button switch sw 2 is provided for use in manually starting pump 62 at a time other than as determined by light level discrimination module 84 referring to fig5 and 6 b power supply module 90 preferably comprises a 110 volt or 220 volt ac input current a step down transformer to reduce the current to 12v a rectifier to convert the 12v from alternating to direct current a filter and a regulator the 12v dc current is then fed to the circuitry on pc board 66 fig3 and 110 volt ac line current upstream of the transformer is desirably fed to pump 62 fig3 as shown in fig6 c an on off power switch sw 1 60 in fig2 and fuse f 1 are desirably provided between the inlet power plug p 2 fig6 b and transformer 68 fig3 referring to fig4 and 6 c pump start module 86 preferably comprises a misting duration selector a misting duration timer and a controller for the ac pump 62 fig3 referring to fig6 c the desired duration.