XL9535 16-Channel I2C Relay Module with IO Expansion - 5V Opto-Isolated

Specifications:

• Operating Voltage: 5V DC 
  
• Channels: 16 Independent Channels
• Communication Protocol: I2C (Two-Wire Interface)
• Logic Voltage: 3.3V / 5V Compatible (Works with ESP32, STM32, Arduino)
  
• Relay Rating: 10A @ 250VAC / 10A @ 30VDC
  
• Isolation: Optocoupler isolation for every channel
  
• Address Selection: Onboard Jumpers (A0, A1, A2) allowing up to 8 boards on the same bus (128 Relays total!)
  
• Indicators: LED Status indicators for Power and Individual Relay State

Applications:

• Smart Home Hubs: Control lights, fans, and locks for an entire floor from a single ESP32.
  
• Industrial PLC Replacements: Build cost-effective logic controllers for machinery.
  
• Hydroponics Systems: Manage pumps, valves, and grow lights simultaneously.
  
• Holiday Lighting: Sequence 16 different light strings with precise timing.
  Escape Rooms: Control maglocks and effects centrally.

Project Evolution

• The Prerequisites: You have likely used a single relay or a 4-channel module, directly driving the pins with digitalWrite(). You understand the basics of switching high voltage safely.
  
• The Upgrade: This module unlocks Scalability. It introduces you to Bus Architecture, where devices share communication lines rather than hogging ports. This is how professional automotive and industrial systems are designed.
  
• Effort Level: Intermediate. You will need to install an I2C library (like the standard Wire.h or specific XL9535 libraries) and manage external 5V power, as your USB port cannot supply enough current for 16 relays.

Virtual Technician: Wiring & Safety
⚠️ Probots Logic-Safe™ ????️: While the relays need 5V to switch, the I2C lines are generally 3.3V friendly. However, always ensure your external power supply shares a common Ground (GND) with your microcontroller.

Pinout Guide:

• VCC: Connect to External 5V 2A+ Power Supply (Do NOT power from Arduino 5V pin).
  
• GND: Connect to Power Supply GND AND Microcontroller GND.
  
• SDA: Connect to Microcontroller SDA (e.g., GPIO 21 on ESP32).
  
• SCL: Connect to Microcontroller SCL (e.g., GPIO 22 on ESP32).

Package Including:

1 X XL9535 16-Channel I2C Expansion Relay Module - 5V Opto-Isolated

1 X Jumper wire Connector

1 X Jst extension cable

Frequently Asked Questions (FAQ)

1. How many wires do I need to control all 16 relays?
   You only need 2 wires for data (SDA, SCL) plus 2 wires for power (5V, GND). Total 4 wires.
2. Can I use this with an ESP32 or ESP8266?
   Yes, it is fully compatible with 3.3V logic levels found on ESP boards.
3. Do I need a special library for Arduino?
   Yes, we recommend using a standard XL9535 or PCA9535 library available in the IDE.
4. Can I chain multiple boards together?
   Yes, by changing the A0-A2 address jumpers, you can connect up to 8 boards (128 relays) on one I2C bus.
5. What is the default I2C address?
   It depends on the jumper configuration, usually 0x20 to 0x27. Use an I2C scanner sketch to verify.
6. Can I power this directly from my Arduino's 5V pin?
   No. 16 relays draw too much current (~1A). You risk burning your Arduino. Use an external 5V 2A supply.
7. Does it remember the relay state after power loss?
   No, standard relays will reset to the "Normally Open" state when power is cut.
8. Are the relays "Active Low" or "Active High"?
   This depends on the library and board revision, but typically writing a '0' to the register turns the relay ON (Active Low).
9. What is the maximum voltage for the relays?
   The relays are rated for 250VAC or 30VDC.
10. Can I switch DC motors with this?
    Yes, but we recommend adding a flyback diode across the motor terminals to prevent back-EMF noise.
11. Is the XL9535 better than the PCF8575?
    The XL9535 usually offers more robust drive capability and different address ranges, but functionality is very similar.
12. Why is the power LED on but relays won't click?
    Check that your external power supply is providing a full 5V. If voltage drops under load, relays won't engage.
13. Can I use this with a Raspberry Pi?
    Yes, enable I2C in raspi-config and use Python libraries (like smbus) to control the registers.
14. Does it support PWM or dimming?
    No, these are mechanical relays. They connect or disconnect; they cannot dim lights.
15. What happens if the I2C signal is lost?
    The relays will remain in their last state until power is cycled or a new command is sent.
16. Are the screw terminals removable?
    Typically no, they are soldered to the PCB for high-current reliability.
17. How do I isolate the noise?
    The board has built-in optocouplers. For extreme noise, use a separate power supply for the relays vs the microcontroller.
18. Can I mount this on a DIN rail?
    The PCB usually has mounting holes, but you may need a separate DIN rail carrier/clip.
19. Does this work with Home Assistant?
    Yes, via ESPHome or Tasmota (configured as an I2C expander).
20. What is the switching speed?
    Mechanical relays are slow (approx 10ms). Do not use for high-speed switching (>1Hz).