BOM using Digikey mylist: 

Link:

https://www.digikey.in/en/mylists/list/TSIVIDT023

1. Physical Assembly

Step 1 – Prepare breadboard & power

• Place the Arduino UNO R4 WiFi on your workbench and connect the USB Type-C cable for programming.
• Place the OLED display, DHT11 sensor, and Soil Moisture sensor on the breadboard.
• Connect all common grounds (GND) together.
• Connect all positive (VCC/5V) lines together.

Step 2 – Hook up sensors

Soil Moisture Sensor (Capacitive type):

• VCC → 5V
• GND → GND
• AO (Analog Output) → A0

DHT11 Sensor:

• VCC → 5V
• GND → GND
• DATA → D2

OLED Display (SSD1306, I²C):

• SDA → Arduino SDA
• SCL → Arduino SCL
• VCC → 5V
• GND → GND

Step 3 – Connect the Relay Module

• Relay VCC → 5V (Arduino Uno R4 WiFi)
• Relay GND → GND (Arduino Uno R4 WiFi)
• Relay IN → D3 (Arduino Uno R4 WiFi)

Step 4 – Connect the Pump & Power

• Use a separate power supply for the pump (match the pump’s rated voltage, e.g., 5V to 12V).
• Connect the pump negative (−) → Pump power supply negative (−) connect the pump power supply negative (−) to Arduino Uno R4 WiFi GND (common ground).
• Connect pump positive (+) → Relay COM terminal.
• Connect the pump power supply positive (+) → Relay NO terminal.

Step 5 – Safety Checks

• Verify the relay rating is equal or higher than your pump current.
• For mains/AC pumps, use a proper AC-rated relay or SSR and ensure full electrical isolation.

• Insulate all exposed terminals with heat-shrink or electrical tape.

   

2. Software / Uploading Code

Open Arduino IDE and select Arduino UNO R4 WiFi as your board.

Install required libraries (if not already installed):

• WiFiS3
• PubSubClient
• DHT Sensor Library
• Adafruit GFX
• Adafruit SSD1306

Paste the final Arduino code (relayPin = D3, soil sensor = A0).

Update your WiFi SSID and password, as well as your ThingsBoard token.

Upload the sketch.

Open Serial Monitor (9600 baud) to check debug messages.

3. Calibrate Soil Sensor & Set Threshold

• Place the sensor in dry air → Note the analog value (near 1023).
• Place the sensor in wet soil → Note the analog value (around 300–400).
• Choose one moistureThreshold of these two.
• Example: Dry = 950, Wet = 300 → Threshold ≈ 600–700.
• Update this line in code:

                           const int moistureThreshold = XXX;

• Re-upload the sketch.

4. Verify Pump Control

• Open the Serial Monitor and watch the soil moisture value.
• Remove the sensor from the soil (simulate dryness).

                  The pump turns ON using a relay.

• Insert the sensor into moist soil.

        Pump turns OFF using a relay.

• Use a multimeter to confirm relay NO/COM switching.

5. OLED Pump ON/OFF Display

• The OLED shows:
• Soil Moisture
• Temperature (°C)
• Humidity (%)
• Raw Value

6. Troubleshooting Checklist

• Relay clicks, but the pump doesn’t run → The Pump supply is not connected properly.
• Pump runs when not expected → Threshold set incorrectly. Adjust moistureThreshold.
• OLED blank → Check I²C wiring (SDA=A4, SCL=A5) and address (0x3C).
• DHT shows nan → Bad wiring or missing pull-up resistor.

[Soil Moisture Sensor]
        |
      (A0)
        |
  [Arduino UNO R4 WiFi]-----------(D2)---[DHT11 Sensor]
     |              |               
[Relay Module] (SDA/SDA, SCL/SCL)
         |          |               
         |        [OLED SSD1306]
         |
         |__[Pump Power/Relay Output]---[Water Pump]
         |
         |__[Dedicated Pump Supply (Common Ground)]