The night light circuit works by utilizing two functions. The first is the fact that LDR changes resistance when light levels change. When it is dark, the resistance of LDR will rise.

If the resistance rises, the voltage will rise, and because the transistor requires 0.7 Volts to turn on, the voltage across the LDR will rise until it reaches 0.7 Volts. At this point, the transistor becomes a wire and connects the LED to the battery, so the LED lights up.

The 1M variable resistor can be adjusted to enable different levels of light to turn on the LED. This makes the circuit more or less sensitive to light.

Test circuit

By covering the LDR and pretending it is dark, you increase the resistance of the LDR. This may be sufficient to illuminate the LED. If not, try adjusting the variable resistor with a screwdriver to make the circuit more or less sensitive to light.

Ninghai Haohua Electronics is an     LED Night Light Factory     from China. For more information and information about LED night lights, please visit us: https://www.nhhx.net