LDR Circuit design

Updated 12/05/2020

In this project, we will be looking at a simple LDR Circuit. A LDR is defined as a Light Dependant Resistor; quite self explanatory. We will be using this component, along side a few others, to turn ON a LED when there is no light. Let's get right into it.

Components Required:

1. 9-Volt DC Power Supply

2. BC547 NPN Transistor

3. 1x LED

4. 1x 50k Ohm Resistor

5. 1x 1k Ohm Resistor

6. 1x LDR03

We will be using the BC547 NPN transistor as a switch to toggle the LED ON and OFF. When the Light Dependant Resistor detects darkness, it will send a positive signal to the transistor, turning on the LED. Similarly, if the LDR detects light, a logic 0 signal is sent to the transistor; turning the LED off. Take a look at the circuit schematic diagram to understand how the components will perform this operation.

Circuit Schematic:

Note: 1=collector, 2=base, 3=emitter

The above diagram shows how simple this circuit is to operate, but has many applications; for example, street lights would replicate this project to automatically switch on as the sunsets. We continue on and design a PCB with Through-hole Technology components.

PCB Design:

To design the PCB for this circuit, we have switched up our design software and now use 'KiCAD'. This software allows high quality, professional PCBs to be designed, which are simpler and more convenient to manufacture. That's all for this project! Share with your friends and electronic enthusiasts and stay tuned for more.

By Zaqyas Mahmood, Electronic Engineer