Have you ever wondered about the mechanism behind the automatic activation of streetlights at night and their automatic deactivation in the morning? Is there an individual responsible for manually switching these lights on and off? While there are various methods to control streetlights, the following circuit demonstrates an Automatic Street Light Controller Circuit that achieves automation by utilizing an LDR (Light Dependent Resistor) and a relay.
The circuit employed in this scenario is a straightforward light-sensitive switch with a relay at its output. This switch effectively controls the operation of streetlights and can be extended to control various electrical appliances within a household as well.
- Circuit Diagram of Automatic Street Light Controller Switch Circuit
- Components used in this Circuit
- Components Description
- Testing of LDR
- Factors for Selecting an appropriate Relay
- Automatic Street Light Controller Circuit Simulation Video (Old Circuit)
- Working of Automatic Street Light Controller Switch Circuit
- Automatic Street Light Controller Project Output Video
For those who experience fear in the dark, we have outlined a straightforward circuit designed to automatically activate a street light equipped with LEDs or a bulb coupled with a relay. This illumination is sufficient to provide visibility of nearby objects.
This circuit is user-friendly in terms of both setup and operation, running on battery power. Its low power consumption can be attributed to the circuit’s minimal component count.
The core of the entire circuit is the IC LM358, functioning as a voltage comparator configured as an operational amplifier. The key component for light detection is the LDR (Light Dependent Resistor), which exhibits resistance proportional to the incident light intensity.
Circuit Diagram of Automatic Street Light Controller Switch Circuit
Components used in this Circuit
- IC LM358 – 1
- Resistor 10KΩ – 1
- Potentiometer 10KΩ – 1
- 5V Relay Module – 1
- Small LED Strip
- 9V Battery
- LDR – 1
- Connecting Wires
It is an Operational Amplifier IC. It is available ib 8-pin DIP Package and can be used in several configurations like Amplifier, oscillator, comparator etc.
The sensitivity of an LDR relies on the amount of light it receives. As the light intensity on the LDR intensifies, its resistance decreases, whereas if the light intensity decreases, the resistance of the LDR increases.
During periods of darkness or when there is no light, the LDR’s resistance falls within the mega ohms range. Conversely, in the presence of light or in well-lit conditions, its resistance decreases by a few hundred ohms.
Testing of LDR
It is advisable to verify the proper functioning of each component before installing it in the circuit, as this can save time during troubleshooting. To test the LDR, set the multimeter to the resistance measurement mode.
Measure the resistance of the LDR in the presence of light or brightness, and the reading should be low. Then, carefully shield the LDR from any light exposure and measure its resistance once more. The reading should be high. If you obtain these expected results, you can conclude that your LDR is functioning correctly.
A two-terminal passive component employed for regulating current within a circuit is known as a resistor. The voltage observed across a resistor is directly correlated to the current passing through it.
Resistors come in two primary categories:
I. Fixed Resistor: This type of resistor maintains a constant resistance value.
II. Variable Resistor: A variable resistor, on the other hand, allows for adjustment of its resistance value. For instance, a 5K resistor permits resistance variation within the range of 0 to 5K.
To determine the resistance value, you can either use a multimeter or refer to the color code markings on the resistor.
This component provides a means of isolation between the controller and the device. Devices are versatile, capable of operating on both AC and DC, while microcontrollers, which operate on DC, transmit signals to them. Hence, a relay serves as a necessary bridge to connect these different signal types. When you need to control a substantial amount of current or voltage using a small electrical signal, a relay proves to be quite useful.
Factors for Selecting an appropriate Relay
- The voltage and current required to strengthen the coil.
- The maximum voltage which we will acquire in the output.
- Amount of the armature.
- Amount of contacts for the armature.
- Number of electrical associates (N/O and N/C).
Automatic Street Light Controller Circuit Simulation Video (Old Circuit)
Working of Automatic Street Light Controller Switch Circuit
Understanding the operation of the circuit is straightforward. In this design, we incorporated the IC LM358, essentially an operational amplifier. Within this IC, pins 2 and 3 are employed to compare voltages, and they furnish a high or low output based on the voltage levels at the input pins.
The circuit combines the LDR and the 10K Resistor to create a potential divider pair. This pair generates an adjustable voltage at the non-inverting input (Pin 3). Simultaneously, another potential divider is created around the inverting input (Pin 2) using a 10K potentiometer. This inverting input will receive half of the supply voltage.
As we know the property of LDR that during the day time, its resistance is low, the voltage at the non-inverting input (i.e. pin 3) is higher than the voltage at the inverting input (pin 2). Hence, the output at the pin 1 is high. As a result, the relay is OFF and the LED (or the bulb) will not glow.
But in dimness or at night time, we know that resistance of LDR is high. Hence, the voltage at non-inverting input pin 3 of the IC LM358 decreases than the inverting input pin 2. As a result, the output pin 1 moves to low state, which further makes the relay to activate and the LED or bulb associated to it will glow.