Just like my previous circuit using LM358 this is also very cheap,also under 100 rupees. This is a circuit for controlling the street lights,garden lights,automatically. You don’t need to turn it on and turn it off again and again, just turn on the circuit once and forget, it will automatically manage itself by sensing the available brightness in the garden or street.
In this circuit the IC LM358 is working as a comparator. The transistor BC548 is wired as a switch to turn on the relay. The 10K pot is used to adjust the sensitivity of the circuit. When the darkness goes below a certain level (this level can be controlled by varying the 1oK pot) the voltage at pin 3 (of LDR) will become greater than the voltage at pin 2 (set by 10K pot) and the comparator output goes high. This turns on the transistor and relay connected to it.
You can connect any type or any number of lamps. You should choose the relay according the the current rating of the lamps.