Electronics enthusiasts love experimenting with simple yet practical projects. Today, we’re building a smart light-controlled fan using a light-dependent resistor (LDR) and a 10393 comparator. This project is perfect for beginners who want to understand how a fan can be controlled based on ambient light levels without using any microcontroller or programming.

Project Overview

This project will automatically turn on a small fan when the surrounding light intensity decreases, such as during the evening or in a dim environment. The LDR detects the change in light, and the 10393 comparator determines whether the fan should be switched on or off.

Why This Project?

●  It’s a simple, practical automation project.
●  No coding or microcontroller is required.
●  It demonstrates the working principles of a comparator circuit.
●  Can be applied in various scenarios, such as cooling systems for enclosed areas.

Components Required

To build this project, you’ll need the following components:

1. LDR (Light Dependent Resistor) – Detects light intensity.
2. 10393 Comparator (LM393 equivalent) – Compares voltage levels and switches the fan on or off.
3. Potentiometer (10kΩ) – Adjusts the sensitivity of light detection.
4. Transistor (BC547 or similar) – Acts as a switch to control the fan.
5. Diode (1N4007) – Prevents reverse voltage damage.
6. Resistors (1kΩ, 10kΩ, 100Ω, etc.) – Limits current in the circuit.
7. Small 5V DC Fan – The main load of our circuit.
8. Relay Module (5V) – Controls the switching of the fan.
9. Battery or Power Adapter (5V-12V) – Provides power to the circuit.
10. Connecting Wires and PCB or Breadboard – For assembling the circuit.

How It Works

1. Light Detection with LDR

●  The LDR is a resistor whose resistance decreases when light intensity increases and vice versa.
●  When it is bright, the resistance of the LDR is low, keeping the fan off.
●  When it gets dark, the resistance increases, triggering the comparator to switch the fan on.

2. Comparator Action (10393 IC)

●  The 10393 comparator has two inputs: inverting (-) and non-inverting (+).
●  It compares the voltage across the LDR and the reference voltage set by the potentiometer.
●  When the LDR voltage crosses the threshold, the comparator output changes state.
●  The comparator output then drives the transistor, which in turn controls the relay for the fan.

3. Fan Activation

●  If the comparator detects low light, it sends a signal to the transistor.
●  The transistor acts as a switch and activates the relay.
●  The relay allows current to flow to the fan, turning it on.
●  When the light increases again, the comparator output reverses, switching the fan off.

Step-by-Step Assembly Guide

Step 1: Placing Components on the Breadboard

1. Insert the LDR and connect one leg to VCC (positive) and the other to the input pin of the 10393 comparator.
2. Attach a 10kΩ potentiometer to create a reference voltage for the comparator.
3. Connect the comparator's output pin to the transistor’s base via a 1kΩ resistor.

Step 2: Adding the Relay and Fan

1. Connect the transistor’s collector to the relay’s input pin.
2. Connect the relay’s output terminals to the fan and power supply.
3. Place a diode (1N4007) across the relay coil to protect against voltage spikes.

Step 3: Powering the Circuit

1. Connect the positive power rail to VCC (5V-12V, depending on your fan’s voltage requirement).
2. Ground all necessary components properly to ensure a stable circuit.

Testing and Adjustments

1. Power on the circuit and observe the behavior of the fan.
2. Adjust the potentiometer to set the light threshold for fan activation.
3. Use a flashlight or cover the LDR with your hand to see if the fan turns on/off correctly.
4. If necessary, tweak resistor values to fine-tune the circuit’s responsiveness.

Potential Applications and Enhancements

Applications

●  Automatic Cooling System: Can be used in electronic cabinets or small enclosures.
●  Smart Home Integration: Can be combined with other home automation projects.
●  Greenhouses: Helps maintain airflow based on daylight levels.

Enhancements

●  Multiple Fans: Extend the circuit to control more than one fan.
●  Humidity or Temperature Sensors: Add extra functionality for climate control.
●  Solar Power: Make it eco-friendly by running it on a small solar panel.

Conclusion

This DIY light-controlled fan project is a simple yet effective way to automate cooling based on ambient light conditions. By using an LDR, 10393 comparator, and a transistor-driven relay, we can create a system that intelligently responds to changes in light.
This project not only helps in understanding the working of comparator circuits but also serves as a stepping stone for more advanced automation systems.