Little Nightlight Schematic Circuit Diagram
In this explanation, we will introduce a straightforward, cost-effective, and lightweight automatic nightlight designed to operate on a 230V AC mains power source. This nightlight can serve as an upscale addition to your children’s bedroom, and the author’s suggested setup is depicted in Figure 1.
Fig. 1
Circuit and working of Little Nightlight
Circuit diagram for the nightlight is shown in Fig. 2. It is built around three resistors (R1 through R3), two light-emitting diodes (LED1 and LED2), a light-dependent resistor (LDR1), a BC548 transistor (T1) and a capacitor (C1). Here LED1 is blue and LED2 is RGB with rainbow effect.
Fig. 2
The circuit is designed to function on a 230V AC power supply while consuming minimal current. It employs a standard 5mm LDR to control the rainbow LED (LED2) by utilizing an npn transistor, T1. To prevent excessive current through LED2, there’s a series resistor, R3, with a value of 150 ohms. The sensor circuit is responsible for activating the rainbow light in low-light conditions and turning it off when ambient light is sufficient. If necessary, you can adjust the light detection threshold by modifying the value of the 47-kilo-ohm resistor, R2.
Resistor R1, which has a value of 100 kilo-ohms, along with diode D1 (1N4007) and the 4.7µF, 16V electrolytic capacitor C1, serves the purpose of stepping down the input supply voltage from 230V AC to a very low DC level. In addition to acting as a constant pilot lamp, the 5mm blue LED (LED1) maintains the voltage across the buffer capacitor C1 at approximately 3V. When the circuit is active, typically in low-light conditions, LED1 generates a waving effect that corresponds to the overall current consumption of the circuit.
The rainbow LED used here is an affordable flashing LED equipped with an integrated driver chip. Upon powering up, it goes through a sequence of flashing red, blue, and green colors, each displayed for several seconds. Subsequently, it gradually blends these colors together to produce various other colors, as demonstrated in the author’s lab experiments shown in Fig. 3.
Fig. 3
Construction and testing
An actual-size PCB layout for the little nightlight is shown in Fig. 4 and its components layout in Fig. 5. After assembling the circuit, enclose it in a suitable box.
Fig. 4
Fig.5
Fix CON1 so that you can connect 230V AC easily. Connect LDR1 such that light from LED1 and LED2 doesn’t fall on it. After proper assembly and connections, your little nightlight circuit is ready to use. Proposed enclosure is shown in Fig. 6.
Fig. 6.