energy-saving porch light - switches itself on (and off)

switches itself on (and off) This circuit forms a switch that can be triggered on (or off) at the onset of darkness and remain active for a period that is variable from thirty minutes to five hours. The main design consideration was that of .keeping power consumption to a minimum while retaining a fair degree of versatility. The primary purpose was to provide an economical porch light but the circuit can obviously be used for any short- term switching application that is referenced to ambient light levels. In spite of its simplicity the circuit is relatively sophisticated. The basis of the circuit is a 14-stage ripple counter with an internal clock oscillator contained in the 4060 (IC1) which does most of the work. The frequency of the oscillator is deter- mined by C3, R6, and potentiometer P1 which enables the frequency to be adjusted. The clock is started when a logic 0 reaches the reset in- put of IC1. This is achieved by the light-dependent resistor R14 and the components asso...