How to Make Automatic Street Light Controller


Automatic street light controllers are essential part of modern cities as they not only save energy but also provide convenience and safety of pedestrians and drivers by providing proper street lighting. In this article, we will guide you on how to make an automatic street light controller using the LM358 IC, BC547 transistor, 10k LDR and a 10k trimpot with other miscellaneous components. We will also provide separate descriptions of these components.By utilizing these components, you can create a cost-effective and reliable controller for street lights, saving energy and contributing to a greener environment.

Introduction to Major Components:

LM358 IC:

The LM358 is a dual operational amplifier integrated circuit (IC) that is widely used in various applications such as voltage amplification, signal processing, and voltage comparators. It consists of two independent, high-gain, internally frequency-compensated operational amplifiers. The LM358 functions with a wide supply voltage range and has a low power consumption, making it ideal for low voltage applications.

The LM358 IC is readily available in the market and can be easily incorporated into electronic circuits. It has a high open-loop gain and a common mode input voltage range that includes ground. The IC also exhibits low input bias and offset currents, allowing precise control of the connected system.

BC547 Transistor:

The BC547 is a general-purpose NPN transistor that is commonly used for amplification and switching purposes in electronic circuits. It is a low power transistor with a maximum collector current of 100mA and a maximum collector-emitter voltage of 45V.

The BC547 transistor has three terminals, namely the base, collector, and emitter. It is designed to operate in the active region, where a small current at the base can control a larger current flowing through the collector and emitter. This feature makes it suitable for amplification purposes.

10k Trimpot:

A trimpot, also known as a trimmer potentiometer, is a three-terminal variable resistor that can be adjusted with a small screwdriver or any other suitable tool. The 10k trimpot is a type of trimpot with a resistance of 10,000 ohms. It is primarily used for fine-tuning circuits and adjusting the output parameters.

The trimpot acts as a variable voltage divider, allowing the user to set the desired resistance value within its specified range. It is commonly employed in applications where precise adjustments are required, such as calibration or offset compensation in electronic systems.

10 LDR:

A 10K LDR (Light Dependent Resistor) is a type of electronic component that exhibits a change in resistance with respect to the amount of light falling on its surface. Here are the specifications of a typical 10K LDR:

  • Resistance Range: The LDR can vary its resistance between 10,000 ohms (10K ohms) to a very high value (in the megaohm range) depending on the amount of light it receives.
  • Photosensitivity: It has a high photosensitivity, meaning it effectively reacts to changes in the intensity of light falling on its surface.
  • Dark Resistance: In dark conditions, the LDR has a typical resistance value of several megaohms (e.g., around 10M ohms).
  • Illuminated Resistance: When exposed to bright light, the LDR’s resistance decreases significantly, typically reaching around 10K ohms.
  • Response Time: The response time of a 10K LDR is relatively quick, allowing it to effectively capture changes in light intensity.
  • Operating Voltage: It can generally operate within a wide voltage range, often between 1V and 10V.
  • Physical Size: These LDRs are typically small in size, often in the range of a few millimeters in diameter.
  • Spectral Range: A 10K LDR is sensitive to a wide range of light wavelengths, typically covering the visible spectrum and parts of the infrared range.

These specifications may vary slightly depending on the specific manufacturer or model of the 10K LDR.

How to Make Automatic Street Light Controller
Automatic Street Light Controller

Circuit Diagram of Automatic Street Light Controller

This project can be designed using a few basic components. The circuit diagram of this project is shown below.

How to Make Automatic Street Light Controller Circuit Diagram
Automatic Street Light Controller Circuit Diagram
How to Make Automatic Street Light Controller Schematic
Automatic Street Light Controller Schematic

More Circuit Layouts

Components List of Automatic Street Light Controller

Following is the list of all components used in this project:

  • 1X LM358 IC
  • 1X 1N4148 DIODE
  • 1X LED
  • 1X 1OK LDR
  • 1X 12V RELAY

Gerber Files:

Explanation of Automatic Street Light Controller

Now that we have an understanding of the LM358 IC, BC547 transistor, and 10k trimpot, let’s discuss how to make an automatic street light controller.

Working Principle:

The automatic street light controller works on the principle of utilizing the varying resistance of the LDR due to ambient light conditions. The LM358 IC amplifies the voltage fluctuation across the LDR and provides an output signal. This output signal is then fed to the base of the BC547 transistor, which acts as a switch.

When the light intensity is low, the resistance of the LDR increases, resulting in a higher voltage at the output of the LM358 IC. This turns on the BC547 transistor, allowing current to flow through the relay and activating the street light. As the light intensity increases, the resistance of the LDR decreases, causing a decrease in voltage at the IC’s output. This turns off the transistor and turns off the street light.

The trimpot is used to adjust the switching point based on the desired light intensity. By adjusting the trimpot, the sensitivity of the LDR can be fine-tuned, ensuring accurate control of the street light.

Making the Automatic Street Light Controller:


  1. Gather the Components: To begin, gather all the necessary components for the project. These include the LM358 IC, BC547 transistor, 10k trimpot, resistors, capacitors, relays, and a few connecting wires. Ensure that the components are of high quality and compatible with each other for optimal functioning. A complete list of material is already provided in the Components List section.
  2. Circuit Design: Carefully design the circuit for the automatic street light controller. Start by connecting the LM358 IC as a comparator to detect the light intensity and switch the street lights accordingly. Use the BC547 transistor as a switching device to control the relay, which in turn will control the street lights. Incorporate the 10k trimpot to adjust the sensitivity of the light sensor as desired. Follow the circuit diagram provided above and make the necessary connections with precision.
  3. Power Supply: Provide a stable power supply to the circuit. Use a reliable power source, such as a 12V battery or a regulated power supply unit. Ensure that the voltage and current ratings are suitable for the circuit’s requirements. This will ensure smooth and uninterrupted functioning of the street light controller.
  4. Calibration: Calibrate the 10k trimpot to adjust the sensitivity of the light sensor. This will enable the controller to accurately detect the ambient light intensity and switch the street lights accordingly. Adjust the trimpot until the desired switching threshold is achieved, minimizing false triggers and optimizing energy efficiency.
  5. Testing and Troubleshooting: After completing the circuit assembly, thoroughly test the automatic street light controller. Connect the street lights to the relay and simulate different light conditions to observe the switching behavior. Engage in a systematic troubleshooting process to identify and rectify any issues that may arise. Ensure that all connections are secure and components are functioning correctly.

Conclusion of Automatic Street Light Controller

In conclusion, creating an automatic street light controller using the LM358 IC can greatly improve the efficiency and functionality of street lighting systems. By using this controller, energy consumption can be optimized by automatically adjusting the street lights based on ambient light levels. Moreover, the use of high-quality components ensures reliability and longevity. By following the steps outlined in this article, you can successfully assemble and implement an automatic street light controller, contributing to safer and more environmentally friendly communities.

More projects, You may like:

For more project and circuit diagrams, you can go through the Schematics in the main menu where you can find many interesting projects and circuit diagrams like audio amplifier circuits, voltage booster circuitbattery charger circuit and timer circuits etc., which are all beginner circuit projects. Feel free to check them out!

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