In this tutorial, we will demonstrate a dark-activated LED fader and its working. This dark-activated switch will activate the relay to operate the AC light at sunset. The light stays on until morning and then goes off. This eliminates the need to switch porch lights or backyard lights on and off every day and also helps to illuminate the premises of the house when the occupants are not present.
This is an easy and simple circuit that will use the light-sensing property of LDR ( Light Dependent Resistor) to fade in and fade out 3 LEDs. LDR will act as a potential divider that will provide variable voltage. During daytime, LDR will get sunlight and act as a conductor to reduce voltage level whereas during night time LDR ceases to conduct and voltage level increases to activate the relay.
Hardware Components:
The following components are required to make a dark-activated LED Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Battery | 9V-12V | 1 |
| 2. | Resistors | 390,1K,10K | 1 |
| 3. | Capacitors | 100uf, 3.3uf | 1 |
| 4. | Transistors | 2N3904, 2N4403 | 1,1 |
| 5. | LED | – | 3 |
| 6. | IC | NE555 Timer | 1 |
| 7. | LDR | – | 1 |
| 8. | Variable Resistor | 100K, 1M | 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Dark Activated LED Circuit
Working Explanation:
The working of this circuit is simple and easy. We divided this circuit into two parts. The first part would be the dark sensor circuit and the second part of the LED fader circuit. The circuit around transistor 2N3904 acts as a dark sensor circuit. When Light is absent on the surface of LDR its resistance increases due to which the transistor will activate an LED circuit consisting of 555 timer IC. In this circuit, a 100K variable resistor will be used to adjust the sensitivity of the dark sensor the fading of the LED can be adjusted by a 1M variable resistor.
We can increase the number of LEDs by using current limiting resistors and this circuit can also be operated on low voltages starting from 4.5V.
Applications and Uses:
- This Can be used to illuminate areas automatically.
- This can be used in automatic street lights.
