5V 1 Channel Relay Active low
5V 1 Channel Relay Module (Active Low Trigger)
Low-level triggered single relay module with optocoupler isolation for Arduino/Raspberry Pi projects
Introduction
The 5V 1 Channel Relay Module is an electrically operated switch that allows you to control high voltage/high current devices (up to 250VAC/10A) with low voltage circuits (5V). This version uses an active low trigger signal, meaning the relay activates when the control pin goes LOW (0V).
Key Features
Active Low Trigger
Activates when control signal goes LOW (0V)
High Power Control
10A @ 250VAC or 30VDC
Optoisolation
️4N25 optocoupler protects control circuit
Status LEDs
Power + Relay activation indicators
Technical Specifications
| Trigger Voltage | 5V DC (Active LOW signal) |
|---|---|
| Trigger Current | ~15-20mA |
| Max Switching Current | 10A @ 250VAC or 30VDC |
| Default State | Normally Open (NO) |
| Contact Type | 1 Form A (SPST – Single Pole Single Throw) |
| Optocoupler | 4N25 (or equivalent) |
| Operating Temperature | -40°C to +70°C |
| Module Dimensions | 50mm x 26mm x 18mm (L×W×H) |
Pin Configuration
| Pin Label | Description | Connection |
|---|---|---|
| VCC | 5V Power Input | Connect to 5V supply |
| GND | Ground | Connect to system ground |
| IN | Control Signal (Active LOW) | Connect to microcontroller pin |
| NO | Normally Open Contact | Load connection (open when relay off) |
| COM | Common Contact | Load power input |
| NC | Normally Closed Contact | Load connection (closed when relay off) |
Wiring with Arduino
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
// Arduino Active LOW Relay Control const int relayPin = 8; // Connected to IN pin void setup() { pinMode(relayPin, OUTPUT); digitalWrite(relayPin, HIGH); // Start with relay OFF (active LOW) } void loop() { digitalWrite(relayPin, LOW); // Activate relay delay(2000); digitalWrite(relayPin, HIGH); // Deactivate relay delay(2000); } |
Trigger Logic Explained
Active LOW Mode
Relay activates when:
Control Pin: LOW (0V)
LED turns ON when activated
Default State
Module starts with:
Relay: OFF
Control pin should be HIGH (5V) initially
Application Examples
Home Automation
Control lights, fans, or appliances
Irrigation Systems
Automatic watering control
Power Switching
Safe control of high voltage devices
Automotive Projects
Remote starter or accessory control
Safety Precautions
- ⚠️ High Voltage Warning: Use extreme caution when working with mains voltage
- 🔧 Use proper insulation for all high voltage connections
- 📏 Maintain adequate clearance between low and high voltage sections
- 💡 Always disconnect power before making wiring changes
- 🔍 Double-check all connections before applying power
