Compact Light Dependent Resistor (LDR) sensor module designed for detecting ambient light levels.
The module uses a transistor switching stage with adjustable sensitivity and is implemented on a 25 mm x 25 mm single-layer PCB.
It can be used for automatic lighting systems, light/dark detection circuits, and microcontroller interfacing projects.
| Parameter | Value |
|---|---|
| PCB Size | 25 mm x 25 mm |
| PCB Layers | Single Layer |
| Mount Type | Through Hole |
| Sensitivity Control | Adjustable (Potentiometer) |
| Tool used | Proteus 8 Professional |
- Compact 25 mm x 25 mm PCB footprint
- Adjustable light sensitivity
- Transistor-based switching output
- LED status indicator
| Reference | Component |
|---|---|
| LDR1 | Light Dependent Resistor |
| RV1 | Potentiometer |
| Q1 | NPN Transistor (BC547 or equivalent) |
| R1 | Current Limiting Resistor |
| D1 | LED Indicator |
The LDR changes resistance based on incident light intensity.
High light intensity results in low LDR resistance.
Low light intensity results in high LDR resistance. OR vice versa.
The LDR and potentiometer controls the base of the NPN transistor. When the light level crosses the set threshold:
- The transistor switches ON or OFF
- The LED indicates module status
- The OUT pin provides a switching signal for external circuits
Sensitivity can be adjusted using RV1.
- Automatic street light systems
- Light and dark detection circuits
- Energy saving lighting control
- Arduino and microcontroller projects
- Security lighting systems
Images
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PCB Layout.png
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3D Render.png
- Connect VCC to power supply.
- Connect GND to ground.
- Adjust RV1 to set the desired light detection threshold.