XL9535 4-Channel I2C Expansion Relay Module - 5V Opto-Isolated

Specifications:

• Operating Voltage (VCC): 5V DC
• Communication Protocol: I2C (Inter-Integrated Circuit)
  
• Logic Voltage: 3.3V to 5V (Compatible)
  
• Channels: 4 Independent Channels
  
• Relay Rating: 10A @ 250VAC / 10A @ 30VDC
  
• Output Type: SPDT (Single Pole Double Throw) - NO, NC, COM
  
• Address Selection: Configurable via hardware jumpers (A0, A1, A2)
  
• Indicators: Power LED + 4 Status LEDs for individual relays

Applications:

• ESP8266 Home Automation: Control 4 appliances using an ESP-01 module (which only has 2 usable GPIOs).
  
• PLC-Style Industrial Controls: Daisy-chain multiple modules to control dozens of actuators from a single Raspberry Pi.
  
• Robotics Power Distribution: Switch motors, lights, and sensors on/off individually on a rover without consuming the main controller's interrupt pins.
  
• Smart Gardening Systems: Control water valves, grow lights, and air pumps simultaneously.

Project Evolution

• Prerequisites: You have likely worked with a standard 1-Channel Relay, toggling a light with a simple digitalWrite(High).
  
• The Upgrade: This module unlocks Scalability. You can now build a Centralized Home Control Hub. Instead of needing an Arduino Mega just for the extra pins, you can stick with a compact, cheap, and Wi-Fi-enabled ESP8266 or ESP32.
  
• Effort Level: Intermediate. Requires installing an I2C library (like the standard Wire library or specific XL9535 libraries) and understanding binary/hex addressing.
  
• Minimum Hardware: An Arduino Uno, Nano, or ESP32, and 4 jumper wires.

Virtual Technician: Wiring Guide ????️
Warning: Always handle mains voltage (220V) with extreme caution. Disconnect power before wiring.

Pin Mapping:

Package Including:

1 X XL9535 4-Channel I2C Expansion Relay Module - 5V

1 X Jumper wire Connector

Frequently Asked Questions (FAQ)

1. Does this relay module work with Raspberry Pi?
   Yes, it works perfectly with Raspberry Pi via the I2C bus (3.3V logic safe).
2. What is the I2C address of the XL9535 relay module?
   The default address varies usually around 0x20-0x27, but is configurable via A0-A2 jumpers.
3. Do I need a separate power supply for this module?
   For stability, we recommend a separate 5V 1A/2A supply if switching all 4 relays simultaneously, though USB power often suffices for testing.
4. Can I control this using an ESP8266 ESP-01?
   Yes, this is the ideal use case as the ESP-01 only exposes GPIO 0 and 2, which can be used as SDA/SCL.
5. Is there an Arduino library for the XL9535?
   Yes, standard XL9535 libraries or general PCF8575-style expansion libraries are often compatible or easily adapted.
6. Can I daisy-chain multiple modules?
   Yes, by changing the I2C address jumpers, you can connect multiple modules to the same two wires.
7. What is the maximum current per channel?
   The relays are rated for 10A, but for continuous loads, we recommend keeping it under 7A to prevent overheating.
8. Does it support 3.3V logic inputs?
   Yes, the XL9535 is compatible with 3.3V logic levels from ESP32 and STM32.
9. Are the relays optically isolated?
   This specific module uses the I2C expander for isolation but does not always feature separate optocouplers per channel; the chip provides the buffer.
10. Can I use this for PWM dimming?
    No, mechanical relays are too slow for PWM. They are for On/Off switching only.
11. What happens to the relays if the microcontroller resets?
    The XL9535 has a reset state; usually, all outputs default to OFF, ensuring safety.
12. How fast can I switch the relays?
    Mechanical relays should not be switched faster than 1-2Hz (once per second) to preserve lifespan.
13. Does it include flyback diodes?
    Yes, the module circuitry includes protection against back EMF from the relay coils.
14. Can I use this with Home Assistant?
    Yes, via ESPHome or Tasmota on an ESP board connected to this module.
15. What wire gauge should I use for the relay terminals?
    For AC loads, use at least 14-16 AWG wire depending on the current draw.
16. Is the XL9535 better than the PCF8574?
    The XL9535 typically offers more pins (16 vs 8) and often better drive capability, though here it is used similarly for 4 channels.
17. How do I change the I2C address?
    Soldering or jumpering the A0, A1, A2 pads on the PCB changes the address bits.
18. Can I drive 12V relays with this?
    This specific board comes with 5V relays installed. You must supply 5V to VCC.
19. Does the module have mounting holes?
    Yes, it features standard M3 mounting holes for easy chassis integration.
20. Is the code different from a standard relay?
    Yes, instead of digitalWrite(), you send I2C commands (bytes) to the address of the module.