5V RELAY Module with LDR

Description

Description

The 5V Relay Module with LDR is a complete, self-contained light-activated switching solution that combines a photoresistor (Light Dependent Resistor) with a powerful relay output on a single compact board. Unlike separate sensor and relay modules that require additional wiring and programming, this integrated module provides a simple “plug-and-play” system — when ambient light crosses the adjustable threshold, the relay automatically activates or deactivates, allowing you to directly control lights, fans, alarms, or any other high-power AC or DC equipment.

At the heart of the module is an LDR (photoresistor) that detects ambient light intensity. As light levels change, the resistance of the LDR changes proportionally. An onboard LM393 comparator processes this signal against a reference voltage set by the blue potentiometer, providing clean, stable switching without the jitter or noise associated with simple transistor-based circuits.

The module features an SPDT relay (Single Pole Double Throw) with screw terminals for COM (Common), NO (Normally Open), and NC (Normally Closed). The relay contacts are rated for 10A at 250V AC or 30V DC, making it capable of switching most common loads directly — from LED strip lights and household lamps to exhaust fans, pumps, and small motors.

Key features include a red power indicator LED, a blue relay status LED, an onboard potentiometer for precise sensitivity adjustment, and four mounting holes for secure installation. The module operates directly from a 5V DC power supply (USB charger, Arduino 5V pin, or dedicated 5V adapter) and requires no microcontroller or programming for basic operation — though it can easily be interfaced with one if more complex logic is needed.

This module is ideal for automatic night lights, garden lighting control, security lighting, darkroom equipment, automatic plant grow lights, daylight-responsive ventilation systems, and any application where light level triggers an action. It is suitable for both hobbyist projects and commercial installations such as signage lighting control and display case lighting.

Features

• All-in-one design — LDR sensor and relay on a single PCB, no external components required

• Adjustable light sensitivity via onboard blue potentiometer — set any brightness threshold

• LM393 comparator for stable, jitter-free switching

• SPDT relay contacts — COM, NO, NC terminals for flexible load wiring

• High load capacity — 10A at 250V AC or 30V DC, suitable for most household and industrial loads

• Dual LED indicators — Red LED for power, Blue LED for relay status

• Standalone operation — works with just a 5V power supply, no microcontroller needed

• Four mounting holes (3mm) for secure panel or enclosure installation

• Screw terminal blocks for reliable, tool-free wiring

• Compact PCB design — fits easily into project boxes and control panels

Technical Parameters