Electronic Circuits

Automatic LED Night Light

Automatic LED Night Light

Inspired by a Chinese design, recently I built a small automatic LED night light with the help of a few generally available inexpensive components. Shown below is the base schematic of that automatic White LED night light runs on AC230V. Needless to say, an ambient light sensor is used in the design for day & night detection. Well, my prototype is still in its infancy – no tidying for the camera!

Automatic LED Night Light - Schematic

The first part of the design is based on capacitive topology particularly suitable for power supply in the milliwatt range as it’s simple, compact and economical. Rest of the design is a dark-activated white LED driver, realized with an LDR, and an NPN transistor as key components. All resistors used here are ¼ w type, and the voltage-limiting component – the 5V6 zener diode is a 500mW one (BZX55C5V6).

The main component (C1) in the capacitive potential divider power supply section should be a CBB22 type (i.e. CBB22 474J 400V). Remember, the circuit handles in excess of 230VAC which could be lethal. Construction should only be attempted by those experienced with fatal-level voltages and safety procedures.

Finally, since this is a little project still under development, if you make/modify this, I’m especially interested to see how it came out. Take pictures/videos of your experiments and send them my way!

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