This is one of my most attracted Circuit published in Electronics for You Magazine September 2008 issue. The circuit is doing a great job. It automatically cut off the Fridge during the Peak hours from 6 pm to 9 pm saving lot of energy and money. After the peak hours, the Fridge will turn on automatically. Try it and avoid the task of manually switching off the Fridge every day during peak hours.
Lot of explanation is necessary. But only the points.
1. LDR act as switch and T1 and T2 conduct around 6 pm when day light is low
2.T2 provides working voltage for IC1 and IC2.
3. IC2 is is a Schmitt trigger which turns on and triggers T3 and relay energize.
4. IC1 is a binary counter and its out put 1 goes high after 3 hours and latches.
5. Schimitt trigger then changes it state and relay deenergize to power the Fridge again.
6. This condition remains as such till morning. When LDR illuminates again both the ICs will reset and remains off.