The transistor used in the project is an NPN BJT transistor. It is used to provide the relay its sufficient driving current. I used a 12 V relay in the project. The value of POT and R depends on the specification of the LDR. Use BJT transistor DC analysis to solve for your needed value. The POT in the circuit serves a mean of adjusting the sensitivity of the LDR. It can also be used to make the lamps initially off or on. The Switch is a single pole double throw (SPDT) switch. It is used to change the mode of the lamp (i.e. Dark activated and Light activated).
