The automatic night light is an automation system in lighting. The circuit, with the help of LDR, automatically turns ON the 6 LEDs connected to it as soon as the main lights of a room are down.
Hardware Components
The following components are required to make an Automatic Night Lamp Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | AC power supply | – | 1 |
| 2. | Diodes | 1N4007, 1N4148 | 4, 2 |
| 3. | IC | LM7812 | 1 |
| 4. | LDR | – | 1 |
| 5. | IC | NE555 Timer | 1 |
| 6. | LEDs | 5mm | 6 |
| 7. | Resistor | 68Ω,1KΩ,1MΩ/1W | 2,1,1 |
| 8. | Variable resistor | 50KΩ | 1 |
| 9. | Electrolytic capacitor | 220µF/16V, 100µF/25V | 1,1 |
| 10. | Ceramic Capacitor | 330nF/400V, 0.01µF | 1,1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
LM7812 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM7812
Automatic Night Lamp Circuit
Working Explanation
The circuit of the automatic night light takes an AC power supply as its power input. A 330nF capacitor, in the circuit, drops the voltage of the AC supply. Furthermore, the voltage coming from the capacitor is rectified by the full wave rectifier circuit. Four 1N4007 diode makes up this full wave bridge rectifier. The full wave rectification thus converts the AC voltage to DC voltage. During this conversion, ripples get included, hence, a 220µF capacitor helps remove these ripples. Moreover, the voltage further passes through a voltage regulator IC LM7812. LM7812 steps down the voltage further to 12V in order to operate the night light switch.
The timer IC NE555 and the photoresistor build up the night light circuit. The LDR detects the light in the room. Until the LDR detects the main lighting, its resistance remains low, hence, NE555 output PIN remains LOW. But, as soon as lights in the room are turned OFF, the LDR resistance becomes high so does the output PIN of the IC. Hence, with the output PIN being HIGH the 6 LEDs light up. Furthermore, a 50K variable resistor adjusts the sensitivity of the circuit.
Extra care must be taken as the circuit operates directly with the AC main supply.
Application
- Home automation
