step up output voltage vo2 developed on the collector of transistor tr4 as output voltage vo2 is sufficiently stepped up transistor tr6 following second schmitt trigger 30 is subsequently turned on as can be seen from fig1 there is a relay k1 arranged in the collector circuit of transistor tr6 when relay k1 is energized by turning on transistor tr6 the normally opened contacts 1 and 2 in the power supplying circuit are actuated to turn on the light b being controlled since resistor r3 has been shorted out by transistor tr3 the electric potential ve developed on the emitter of transistor tr1 is now reduced to equ2 accordingly it can be appreciated that transistor tr1 will be turned off when light sensing element cds senses daylight increase at dawn and the electric potential developed across light sensing element cds drops below the sum of the emitter potential v 39 e the barrier voltage vr of transistor tr1 as indicated at vl at time t2 in fig2 a once transistor tr1 is turned off transistors tr2 and tr3 are subsequently turned off at this duration the energy stored in capacitor c1 discharges through adjustable resistor vr3 diode d2 and resistors r4 and r5 however capacitor c1 still has sufficient energy allowing second schmitt trigger 30 to remain enabled and the light b being controlled is continuously energized by 110 vac power source through contacts 1 and 2 actuated by relay k1 as capacitor c1 discharges sufficiently field effect.