Modern automation projects increasingly combine local control, sensor monitoring, and network connectivity. Developers want hardware that can handle real-world I/O signals while remaining flexible enough for custom firmware and open-source software.

Eletechsup ESS3B18 is an ESP32-S3-based I/O expansion board designed for this type of application. With relay outputs, analog signal interfaces, temperature and humidity-related functions, and RS485 communication, it provides a hardware foundation for smart building control, remote monitoring, and industrial IoT prototypes.

1. ESS3B18 Hardware for Connected Automation

The ESS3B18 is listed with the following features:

• ESP32-S3-based control platform

• 4 relay outputs, rated up to 10 A under specified conditions

• Analog signal interfaces supporting 4–20 mA and 0–10 V applications

• Temperature and humidity-related monitoring functions

• RS485 communication

• Wi-Fi connectivity through the ESP32-S3 platform

• DC 7–28 V supply range, according to the product listing

The combination of local I/O and network connectivity allows developers to create application-specific control systems without designing every interface from scratch.

Please confirm the exact channel counts, measurement ranges, and output ratings against the selected hardware version and its official documentation before installation.

2. GitHub Inspiration: ESP32-S3, Modbus and MQTT

A useful open-source reference is:

GitHub: ESP32-S3 Modbus-MQTT Bridge
https://github.com/whitehawk1979/esp32-modbus-mqtt-bridge

This project demonstrates an ESP32-S3-based architecture that connects Modbus RTU relay controllers to Home Assistant through MQTT. Its documented features include network configuration, device control, MQTT discovery, and firmware updates.

The project targets other hardware, not the ESS3B18. Nevertheless, it illustrates a practical architecture that developers can study when planning their own ESS3B18 application.

A similar system could be designed around the following workflow:

1. Read input signals and sensor measurements.

2. Process the measurements and control rules on the ESP32-S3.

3. Publish selected data through MQTT.

4. Display the data in Home Assistant or another compatible dashboard.

5. Receive authorized commands and control the appropriate outputs.

The ESS3B18 would require its own verified pin mapping and hardware-specific firmware. The GitHub repository should not be treated as a ready-to-flash firmware image for this board.

3. Application Example: Smart Building Monitoring

One possible application is a smart building monitoring system.

Compatible sensors can provide temperature, humidity, or other environmental information. The ESP32-S3 can process the readings and publish them to a dashboard through a configured network connection.

A developer could implement features such as:

• Monitoring environmental conditions

• Displaying readings on a central dashboard

• Recording historical values through an external service

• Sending alerts when readings exceed configured limits

• Controlling compatible ventilation or other equipment through relay outputs

For example, a ventilation system could switch on when a temperature threshold is exceeded and switch off after the temperature falls below a separate lower threshold.

The control rules and dashboard integration must be implemented in software. Actual temperature and humidity sensing capabilities depend on the board's fitted sensors and supported interfaces.

4. Application Example: Analog Signal Monitoring

Industrial sensors often provide voltage or current outputs rather than digital GPIO signals.

With compatible analog inputs, the ESS3B18 can serve as the hardware foundation for a monitoring application involving signals such as 0–10 V or 4–20 mA.

A typical project could:

1. Connect a compatible sensor.

2. Read the analog input using the appropriate hardware interface.

3. Convert the raw measurement into an engineering value.

4. Publish the value through MQTT.

5. Display the result on a remote monitoring dashboard.

Potential applications include process monitoring, equipment status monitoring, and sensor-data collection.

The accuracy and supported range depend on the board's analog circuit, configuration, calibration, and the connected sensor. Confirm electrical compatibility before applying an external signal.

5. Application Example: Relay Control with Remote Status

The four relay outputs can be used to switch compatible loads under firmware control.

For example, an application might use local input signals and sensor readings to control lighting, ventilation, or other suitable equipment.

The software could also expose control commands through an authenticated web interface or MQTT.

A reliable implementation should include:

• Defined output states at startup

• Input validation for remote commands

• Communication-loss handling

• Appropriate access control

• Suitable electrical protection for the connected loads

Relay ratings must be assessed for the actual voltage, current, and load type. A resistive-load rating should not automatically be assumed to apply to motors or other inductive loads.

6. Application Example: RS485 and Industrial IoT

RS485 provides a way to connect compatible equipment using a differential serial interface. When combined with an ESP32-S3 network connection, it can help bridge local devices and network-based monitoring software.

A possible architecture is:

Field device → RS485 → ESP32-S3 application → Wi-Fi → MQTT broker → Dashboard

For Modbus RTU equipment, the firmware must implement the correct protocol and register mapping. Baud rate, parity, device addressing, and electrical wiring must match the connected device.

Developers can use this architecture as a starting point for monitoring compatible instruments or connecting local control hardware to a larger automation system.

7. Getting Started with Development

A practical development workflow is to test the hardware incrementally.

Step 1: Verify the board and power supply. Confirm the correct supply voltage and hardware revision.

Step 2: Test each interface. Verify relay operation, digital inputs, analog measurements, and the available temperature or humidity functions individually.

Step 3: Choose a firmware framework. Use a suitable ESP32-S3 development environment, such as Arduino or ESP-IDF, according to the project's requirements.

Step 4: Add communication. Implement Wi-Fi and MQTT for network access, and configure RS485 for the required serial protocol.

Step 5: Integrate the dashboard. Connect the application to Home Assistant or another suitable platform only after the hardware functions have been verified.

Step 6: Test failure scenarios. Check behavior after power loss, network disconnection, sensor failure, and invalid control commands before deploying the system.

Conclusion

The Eletechsup ESS3B18 combines ESP32-S3 programmability with relay control, analog signal interfaces, environmental monitoring capabilities, and RS485 communication.

It is a promising hardware foundation for developers building smart building controllers, sensor-monitoring systems, and connected automation prototypes.

Open-source projects such as the ESP32-S3 Modbus-MQTT Bridge demonstrate how ESP32-based hardware can connect industrial I/O systems with MQTT and Home Assistant. Although the referenced project does not directly support the ESS3B18, its architecture offers a useful starting point for planning a customized implementation.

Explore Eletechsup products:
https://eletechsup.com/

Related GitHub project:
https://github.com/whitehawk1979/esp32-modbus-mqtt-bridge

The GitHub project is an independent reference for a different hardware platform, not official ESS3B18 firmware. Verify the ESS3B18 specifications, wiring, and software compatibility before use.