8 Channel Relay Module 5V DC with light coupling

The 8-Channel 5V Relay Module with Optocoupler Light-Coupling Isolation is one of the most popular and versatile relay boards for makers, hobbyists, engineers, and industrial automation projects. It allows your low-voltage microcontroller, Raspberry Pi, ESP32, or PLC to safely switch high-voltage AC or DC devices — such as lights, fans, motors, pumps, water valves, heaters, and household appliances — while keeping your sensitive control electronics fully protected from electrical noise and voltage spikes.

Why Optocoupler Isolation Matters

The defining feature of this relay module is the optocoupler (opto-isolator) on every channel. The optocoupler uses light to transfer the control signal between the microcontroller side and the relay coil side, completely separating the two electrical circuits. This provides three major benefits:

1. Electrical Safety — Even if a high-voltage spike occurs on the load side, your microcontroller stays safe
2. Noise Immunity — Electrical noise from motors, fluorescent lights, or relay contact bouncing cannot reach your sensitive logic circuits
3. Ground Loop Prevention — Logic ground and load ground can be kept separate when needed (using JD-VCC jumper)

This makes the optocoupler-isolated version far safer and more reliable than basic relay modules without isolation — essential for industrial environments, mains AC switching, or any project where reliability and electrical safety matter.

Powerful 8-Channel Switching Capability

The module features eight independent SPDT (Single Pole Double Throw) relays, each with three connection terminals:

• NC (Normally Closed) — Connected to COM when the relay is OFF
• NO (Normally Open) — Connected to COM when the relay is ON
• COM (Common) — The pole that switches between NC and NO

Each relay can switch up to:

• 10A at 250V AC (suitable for most household appliances)
• 10A at 125V AC
• 10A at 30V DC (motors, lights, solenoids)
• 10A at 28V DC

This gives the module a total switching capacity that can handle a substantial portion of a small smart home, industrial control panel, or multi-channel automation system.

Easy to Control

Each channel is controlled by a simple digital input pin:

• HIGH (5V or 3.3V): Relay OFF (default with active-low module)
• LOW (0V): Relay ON (engages relay coil)

(Note: Most 8-channel relay modules are active-LOW, meaning the relay engages when the input pin is pulled to GND. Some modules can be configured as active-HIGH via solder pads. Always check your specific module's documentation.)

The module supports both 3.3V logic (Raspberry Pi, ESP32, ESP8266, STM32) and 5V logic (Arduino Uno, Mega, Nano) thanks to the optocoupler input circuit, which works reliably across this voltage range.

Visual Feedback

Each channel features a dedicated red LED indicator, which lights up when its corresponding relay is energized. This provides instant visual confirmation of relay activity, making debugging, testing, and troubleshooting straightforward — especially valuable in complex automation setups.

Robust and Practical Design

The module is built on a high-quality PCB with:

• Heavy-duty screw terminal blocks for secure load wire connections
• High-current copper traces for the relay output side
• Standard 0.1" pin headers for control and power connections
• Mounting holes for screw-mounting in enclosures
• Built-in flyback diodes to protect against inductive load spikes
• Quality electromechanical relays rated for 100,000+ operation cycles

Common Applications

This module is at the heart of countless projects, including:

• Smart home automation — control lights, fans, AC, water heaters, kettles
• Smart greenhouse systems — automated irrigation, ventilation, heating
• Aquarium controllers — pumps, lights, heaters, CO2 valves
• 3D printer enclosures — lighting, fans, heaters, filters
• Industrial control panels — motors, solenoids, indicator lamps
• Pool and spa controllers — pumps, heaters, lighting
• Server room automation — fans, alarm beacons
• Brewing and fermentation control — heating elements, agitators
• Remote switching systems — using ESP32/ESP8266 with WiFi or LoRa
• Security and access control — door strikes, magnetic locks, sirens
• Educational STEM projects for teaching automation concepts

Power Configuration

The module typically has two power input options:

1. VCC + GND — Powers both the input/control side and the relay coil side from the same 5V supply (default with VCC/JD-VCC jumper installed)
2. VCC + JD-VCC + GND — When the jumper is removed, the input/control side and the relay coil side can be powered from separate, isolated supplies, providing true galvanic isolation for maximum safety

For mains AC switching applications, the isolated power configuration is strongly recommended.

Specifications

Relay Specifications

• Number of Channels: 8
• Relay Type: SPDT (Single Pole Double Throw) Electromechanical
• Maximum Switching Current: 10A
• Maximum AC Switching Voltage: 250V AC (also rated 125V AC at 10A)
• Maximum DC Switching Voltage: 30V DC (also rated 28V DC at 10A)
• Operation Cycles: 100,000+ (typical for quality relays)
• Switching Time: ~10 ms (typical)

Control / Logic

• Logic Level Compatibility: 3.3V and 5V (TTL)
• Activation Logic: Active LOW (typical — verify per module)
• Optocoupler Isolation: Yes — full optical isolation per channel
• Supply Voltage: 5V DC
• Current Draw (per relay active): ~70–80 mA per relay (~600 mA all 8 active)
• Idle Current: ~30 mA

Indicators

• Power LED: 1 (board power indicator)
• Channel LEDs: 8 (one per relay, lights when relay active)

Mechanical

• PCB Material: FR-4 with double-sided routing
• Screw Terminal Blocks: Heavy-duty, suitable for AC/DC wiring
• Mounting Holes: Yes (4 corners, typical)

Pinout

Applications

Home Automation

• Smart lighting — control multiple light circuits
• Smart kitchen — coffee makers, kettles, microwaves
• HVAC control — fans, AC units, heaters
• Smart blinds and curtains — motorized window treatments
• Garage door automation
• Entry door electric strikes
• Outdoor lighting — pathway, garden, security lights
• Christmas / festival decorations — automated light shows

Industrial & Commercial

• Control panels and PLCs replacement / supplementation
• Motor and pump control (with proper interface)
• Solenoid valve actuation — water, gas, pneumatic
• Industrial alarm systems — beacons, sirens
• Production line automation
• Conveyor belt controls
• Heater and oven control
• Lab equipment switching
• Display and signage power control

Smart Garden / Agriculture

• Automated irrigation systems — multiple zones
• Greenhouse fans and heaters
• Grow light scheduling
• Hydroponic pumps and aerators
• Rainwater collection valves

Aquarium / Pond

• Lighting (day/night cycles)
• Water pumps and protein skimmers
• Heaters and chillers
• Auto top-off systems
• CO2 solenoid control

Robotics & Maker Projects

• High-current motor switching (with appropriate driver circuitry)
• Powerful electromagnets for pick-and-place projects
• Pneumatic / hydraulic actuator control
• Educational STEM and university research projects
• DIY home server power management
• Battery management and load switching

Security & Access

• Door strike and magnetic lock control
• Surveillance camera power switching
• Alarm sirens and indicators
• RFID-triggered access systems
• Smart doorbell relay extensions

IoT & Smart Devices

• WiFi-controlled smart plugs (multi-channel)
• Voice-controlled appliances (Alexa, Google Home, Siri integration)
• Remote-controlled devices over MQTT, Node-RED, Home Assistant
• LoRa / NB-IoT remote switching stations
• Cloud-controlled industrial devices