XL9535 2 Channel I2C Relay Module Expansion Board 5V

Specifications:

• Operating Voltage: 5V DC
  
• Channels: 2 Independent Relay Channels
• Communication Protocol: I2C (Inter-Integrated Circuit)
  
• Logic Voltage: 3.3V / 5V Compatible (Check pull-up requirements)
  
• Relay Rating: 10A @ 250VAC / 10A @ 30VDC
  
• Output Type: SPDT (NC, COM, NO)
  
• Indicators: Power LED and individual Status LEDs for each relay
  
• Isolation: Optocoupler isolation for signal integrity

Applications:

• Smart Home Nodes: Control lights and fans using an ESP8266/ESP32 where pins are scarce.
• PLC-Style Control: Daisy-chain multiple modules to create a massive bank of relays controlled by a single Raspberry Pi.
• Robotics: Switch high-current motors or solenoids without using up the PWM pins needed for speed control.
• Industrial Automation: Retrofit existing machines with digital control via I2C.

Project Evolution

• The Prerequisite (Where you started): You likely started with a standard 5V 2-Channel Relay Module. It was great, but it occupied Digital Pins 7 and 8. As you added an LCD screen and a WiFi shield, you suddenly had no pins left to add more features.
• The Upgrade (What this unlocks): By switching to the XL9535 I2C Relay, you reclaim those digital pins. This module sits on the I2C bus (sharing pins with your OLED display or RTC). This upgrade unlocks the ability to build Distributed Control Systems—you can now have a display, a sensor array, and high-voltage control all running off an ESP-01 or an ATtiny85.

Virtual Technician: Wiring & Safety
⚠️ Safety Warning: This module is rated for switching mains voltage (AC). If working with 110V/220V, ensure the board is disconnected from power before touching terminals. Use a proper enclosure.

Pin Mapping:

• VCC: Connect to 5V (Must be stable, relays draw current).
  
• GND: Connect to Common Ground.
  
• SDA: I2C Data (A4 on Uno, D21 on ESP32).
  
• SCL: I2C Clock (A5 on Uno, D22 on ESP32).

Package Including : 

1 X XL9535 2 Channel I2C Relay Module Expansion Board 5V

1 X Jumper Wire Connector

Frequently Asked Questions (FAQ)

1.How many pins does this relay module use?
It strictly uses 2 pins (SDA and SCL) regardless of how many relays are on the board, plus VCC and GND.

2. Can I use this with an ESP32?
Yes, the ESP32 handles I2C natively. You may need to ensure your library supports the XL9535 chip.

3. Does this work with Raspberry Pi?
Yes, you can control it via Python using SMbus or specific I2C libraries for the XL9535.

4. What is the I2C address of this module?
The default address varies by batch but is often configurable via solder pads on the back. Run an I2C scanner sketch to confirm.

5. Can I change the I2C address?
Most XL9535 modules have A0, A1, A2 address selection pads allowing up to 8 unique addresses.

6. Do I need an external power supply?
Yes, while the I2C bus carries data, the coils need stable 5V. Do not power the coils directly from a weak 3.3V microcontroller pin.

7. Is the XL9535 compatible with the PCF8574 library?
No, they are different chips. You must use a library specifically written for the XL9535 or generic I/O expander libraries that support it.

8. Can I daisy chain multiple modules?
Yes, as long as you configure each module to a unique I2C address, you can connect multiple units to the same two wires.

9. What is the maximum current for the relays?
The relays are rated for 10A at 250VAC or 30VDC. For continuous loads, we recommend keeping it under 7A.

10. Does it utilize Optocouplers?
Yes, this module features optocoupler isolation to protect your microcontroller from high-voltage switching noise.

11. Can I use this with 3.3V logic?
Yes, the I2C bus is generally tolerant, but ensure you supply 5V to the VCC pin for the relay coils to actuate properly.

12. What happens if the I2C signal is lost?
The relays will maintain their last state until the chip is reset or power is cycled.

13. Does this module support high-speed switching?
No, mechanical relays are slow (ms). Do not use for PWM or high-frequency switching; use a MOSFET module for that.

14. Why is the LED on but the relay not clicking?
This usually means the VCC voltage is too low to energize the coil. Ensure a solid 5V supply.

15. Can I control the relays individually?
Yes, the software library allows you to address and toggle each channel independently.

16. Is there a "flyback" diode protection?
Yes, the module includes protection components to prevent back EMF from damaging the driver chip.

17. What is the wire gauge for the terminal blocks?
The screw terminals typically accept 14-22 AWG wire suitable for mains connections.

18. Can I use this for Home Assistant?
Yes, via ESPHome or Tasmota (if supported in their I/O expander list), making it great for custom smart switches.

19. Does the XL9535 generate heat?
The chip itself runs cool. The relay coils will generate slight warmth when active for long periods, which is normal.

20. Where can I find the library?
We provide links to verified Arduino/PlatformIO libraries in our Resources section (or search "XL9535 Arduino" on GitHub).