12V 4 Channel Relay Module with Optocoupler Isolation - 10A 250V AC

Specifications:

• Operating Voltage: 12V DC (Relay Coil Voltage)
  
• Channels: 4 Independent Channels
  
• Load Capacity (AC): Max 10A @ 250V AC
  
• Load Capacity (DC): Max 10A @ 30V DC
  
• Isolation: Optocoupler Protection (protects microcontroller from back EMF)
  
• Indicators: Individual Status LEDs for each channel (Red/Green) + Power LED
  
• Interface: Standard TTL Logic (Compatible with Arduino, Raspberry Pi, ESP32, PLC)
  
• Mounting: 4x Screw holes for secure chassis mounting
  
• Output Terminals: Heavy-duty screw terminals (Normally Open, Common, Normally Closed)

Applications:

• Home Automation: Control 4 separate lights or fans in a room using an ESP8266/ESP32.
  
• Industrial PLC Control: Interface low-voltage PLC signals to heavy AC contactors.
  
• Robotics: Switch high-current motors (forward/reverse H-bridge logic) or solenoids.
  
• Gardening: Control 4 independent water pumps or valves for automated irrigation.
  
• Safety Systems: Trigger alarms, hooters, or emergency shut-off mechanisms.

Project Evolution

• The Prerequisite: If you have mastered blinking an LED or controlling a small servo motor...
  
• The Upgrade: this 4-Channel Relay Module unlocks the world of Mains Voltage Automation. You are no longer limited to 5V USB gadgets. You can now build a system that controls your ceiling fan, coffee machine, desk lamp, and heater simultaneously.
  
• Effort Level: Intermediate. Requires understanding of external 12V power sources and careful handling of AC mains voltage.
  
• Hardware Needed: 12V DC Adapter (for the relay coils), Microcontroller (Arduino/Pi), and Jumper Wires.

Virtual Technician: Wiring & Safety

• ⚠️ SAFETY WARNING: If using this to switch 110V/220V AC Mains, ensure you disconnect power before touching the board. The bottom of the PCB has exposed high-voltage traces. Always mount inside a plastic enclosure.
  
• Powering the Board: Connect a regulated 12V DC source to the VCC and GND terminals. Do NOT try to power the relay coils directly from an Arduino's 5V pin; it will not work.
  
• Connecting Logic: Connect the IN1, IN2, IN3, IN4 pins to your microcontroller's digital outputs.
  
• Jumper Selection (If equipped): Place jumper on High or Low to select trigger type.
   

Package Including : 1 X 12V 4 Channel Relay Module with Optocoupler Isolation - 10A 250V AC

Frequently Asked Questions (FAQ)

1. Can I power this directly from the Arduino's 5V pin?
   No, this is a 12V relay module. The coils require 12V to activate. You need an external 12V power supply. The Arduino ground must be shared with the 12V ground.
2. Will this work with a 3.3V microcontroller like ESP32 or Raspberry Pi? Yes, the input signal is isolated via optocouplers. A 3.3V signal is usually sufficient to trigger the optocoupler LED, making it compatible with 3.3V logic.
3. Is this module Active High or Active Low?
   Most standard versions are Active Low (Relay turns ON when signal is LOW). However, some "Pro" versions have a jumper to select High or Low trigger. Please check the board markings.
4. Can I control the speed of a fan or dim a light with this?
   No. Relays are simple ON/OFF switches. They cannot dim lights or control speed (PWM). Rapid switching will damage the relay.
5. What is the maximum current this board can handle?
   The relays are rated for 10A, but for continuous safe operation, we recommend keeping the load under 7A to prevent overheating traces.
6. Does this provide complete optical isolation?
   Yes, if you remove the JD-VCC jumper (on supported boards) and power the coils separately, you achieve full galvanic isolation between your microcontroller and the relay power.
7. Why do I hear a 'click' sound when it works?
   That is the mechanical armature inside the relay physically moving to make contact. It is normal and indicates the relay is working.
8. Can I use this to switch DC voltages like 24V or 48V?
   Yes, it is rated for up to 30V DC at 10A. It works perfectly for switching 12V or 24V DC loads.
9. Do I need a flyback diode for my circuit?
   No, the module has built-in flyback protection diodes for the relay coils, and optocouplers provide further isolation.
10. Can I use all 4 channels at the same time?
    Yes, provided your 12V power supply can provide enough current (approx. 60-70mA per channel, so ~300mA total).
11. How do I mount this board?
    There are 4 mounting holes at the corners standard for M3 screws/spacers.
12. Can I use this with a Raspberry Pi without a driver?
    Yes, the GPIO pins of a Pi can drive the input signal pins of this module directly.
13. What happens if I connect the polarity backwards?
    The logic inputs often have protection, but reversing the main 12V VCC/GND power can damage the board components immediately.
14. Is this waterproof?
    No, this is an open PCB module. If used outdoors or in humid environments, it must be placed inside a waterproof enclosure (IP65 recommended).
15. Why is the LED on but the relay not clicking?
    This usually happens if you provide the logic signal but forget to connect the main 12V power source to the JD-VCC/VCC pins. The LED runs on logic power; the relay needs 12V.
16. Can I switch AC and DC loads on different channels?
    Yes, the 4 relays are completely independent dry contacts. You can switch 220V AC on Channel 1 and 12V DC on Channel 2 simultaneously.
17. What is the lifespan of the relays?
    Mechanical relays typically have a lifespan of 100,000 electrical cycles at rated load and 10 million mechanical cycles.
18. Can I use this for a 3-phase motor?
    No, this is for single-phase control only. For 3-phase motors, use this relay to trigger a heavy-duty 3-phase contactor.
19. Does it support PWM (Pulse Width Modulation)?
    No. Do not use PWM on mechanical relays. It will destroy the relay mechanics within minutes.
20. What is the difference between NC, NO, and COM?
    COM: Common (Power in). NO: Normally Open (Connects when relay is ON). NC: Normally Closed (Disconnects when relay is ON).