Arduino remains a popular platform for developers who want to build practical automation projects without designing every circuit from scratch. When an application needs digital inputs, relay outputs, analog signal acquisition, temperature and humidity monitoring, and serial communication, an integrated I/O expansion board can simplify hardware development.

Eletechsup DNUNB17 is designed for this purpose. Based on the Arduino UNO R3 platform, it combines multiple I/O functions with interfaces for compatible temperature and humidity sensors, providing a flexible foundation for environmental monitoring, timer control, and customized automation projects.

Product page: https://eletechsup.com/products/dnunb17-4di-4do-4ai-digital-analog-am2301-sht20-sht30-ds18b2

1. What Makes the DNUNB17 Useful?

The DNUNB17 integrates several functions on a single expansion board:

• 4 NPN digital inputs for monitoring compatible external signals

• 4 relay outputs for switching suitable electrical loads

• 2 current input channels supporting 0/4–20 mA signals

• 2 voltage input channels supporting 0–5 V / 0–10 V signals

• Temperature and humidity sensor interfaces for compatible sensors

• RS485 interface for serial communication with compatible equipment

• Onboard LED indicator for basic status indication

• Additional expansion ports for user-developed applications

The board operates from DC 7–30 V, with 9 V, 12 V, or 24 V recommended by the manufacturer.

The DNUNB17 is an expansion board, not a standalone controller. A compatible Arduino UNO R3 development board is required.

2. GitHub Resources for Sensor Integration

Although a dedicated DNUNB17 GitHub library was not verified in the sources reviewed, several established Arduino libraries can help developers implement sensor functions.

DHT sensor library by Adafruit
https://github.com/adafruit/DHT-sensor-library

This library is a reference for compatible DHT-family temperature and humidity sensors, such as the AM2301/DHT21 family.

Adafruit SHT31 library
https://github.com/adafruit/Adafruit_SHT31

This provides software support for compatible SHT31 temperature and humidity sensors using I²C.

Arduino DallasTemperature library
https://github.com/milesburton/Arduino-Temperature-Control-Library

This library can be used with compatible DS18B20 temperature sensors, together with an appropriate OneWire library.

These repositories provide sensor-specific software building blocks. They do not automatically support the DNUNB17 board as a whole. Developers must verify the selected sensor, wiring, pin assignments, communication interface, and required pull-up resistors before using the libraries.

3. Application Example: Temperature and Humidity Monitoring

One practical application is an environmental monitoring system for a workshop, storage area, equipment cabinet, or small greenhouse.

A compatible sensor can measure temperature and humidity, while the Arduino program processes the readings and applies user-defined thresholds.

A typical workflow is:

1. Read the sensor data at regular intervals.

2. Check whether the measurements are valid.

3. Compare temperature and humidity against configured limits.

4. Activate a relay if a control condition is met.

5. Send the measurements to an external system if network connectivity is available.

For example, a developer could configure the system to activate a ventilation fan when the temperature rises above a selected threshold.

A separate lower threshold can be used to switch the fan off, reducing unnecessary relay switching.

The sensor itself, its software library, and the board's wiring must all be compatible. Temperature and humidity monitoring is an application to be implemented in firmware, not a complete software feature supplied automatically by the expansion board.

4. Application Example: Analog Sensor Acquisition

The DNUNB17 also supports current and voltage input signals, allowing developers to experiment with compatible analog sensors.

Possible applications include:

• Reading a compatible 0–10 V sensor

• Acquiring a 4–20 mA transmitter signal

• Monitoring process variables through suitable sensors

• Applying software thresholds to measured values

• Combining analog measurements with relay control

For example, a compatible industrial transmitter could provide a current signal representing a configured measurement range. The Arduino program can convert that signal into an engineering value using the sensor's scaling parameters.

Before connecting a sensor, verify the input range, wiring, polarity, and electrical specifications. Calibration may be necessary for accurate measurements.

5. Application Example: Relay-Based Timer Control

The four relay outputs make the DNUNB17 suitable for customized switching applications.

With user-written Arduino firmware, developers can implement:

• Delayed switching

• Timed on/off sequences

• Trigger-based relay control

• Repeating timer cycles

• Interlocked output logic

• Simple multi-step automation

For example, a developer could create a programmable power sequencer that activates several compatible loads in a defined order, with a configurable delay between each relay operation.

The timing logic is implemented in software. Developers should verify the output behavior during startup, reset, and power loss before connecting actual equipment.

Relay ratings also depend on the load type and electrical conditions. Motors and other inductive loads may require additional protection.

6. Application Example: RS485 Communication

RS485 enables the DNUNB17 to be incorporated into systems with compatible serial devices.

With suitable firmware, the Arduino UNO R3 can exchange data with external controllers, instruments, or remote I/O modules.

Potential projects include:

• Testing serial communication between controllers

• Reading data from compatible instruments

• Implementing a Modbus RTU master or slave

• Combining local sensor measurements with external device data

• Developing a small automation controller with multiple interfaces

RS485 is an electrical interface, not a complete communication protocol. If Modbus RTU is required, the application must implement the appropriate protocol and device configuration, including baud rate, parity, addressing, and register mapping.

7. How to Start Developing with DNUNB17

A practical development process is to test one function at a time.

Step 1 — Prepare the hardware. Install a compatible Arduino UNO R3 and supply the expansion board with the correct DC voltage.

Step 2 — Verify the sensor interfaces. Select the appropriate sensor and test its library independently before integrating it into the complete application.

Step 3 — Test the digital inputs and relay outputs. Confirm the correct pin mapping and electrical behavior using safe test conditions.

Step 4 — Test the analog inputs. Use known input values to check signal scaling before connecting external sensors.

Step 5 — Configure RS485. Verify serial settings and communication with the intended device.

Step 6 — Combine the functions. Add the control logic, timing rules, and any required external communication after individual functions work correctly.

The manufacturer provides basic hardware test sketches. More advanced application functions require user-developed code.

Conclusion

The Eletechsup DNUNB17 combines Arduino UNO R3 programmability with digital inputs, relay outputs, analog signal acquisition, temperature and humidity sensor interfaces, and RS485 communication.

Its main advantage is the integration of several useful hardware functions into one expansion board. This makes it a practical starting point for developers building environmental monitoring systems, timer controllers, sensor acquisition projects, and customized automation prototypes.

Open-source Arduino sensor libraries can help developers implement individual functions, while the board's documented interfaces provide the hardware foundation for combining them into a complete application.

Explore the DNUNB17:
https://eletechsup.com/products/dnunb17-4di-4do-4ai-digital-analog-am2301-sht20-sht30-ds18b2

Related GitHub resources:

• https://github.com/adafruit/DHT-sensor-library

• https://github.com/adafruit/Adafruit_SHT31

• https://github.com/milesburton/Arduino-Temperature-Control-Library

These are independent sensor libraries, not official DNUNB17 integrations. Confirm hardware compatibility, pin assignments, and electrical limits before use.