Moisture Sensor with Arduino & Bluetooth Low Energy (BLE)

## Hardware Requirements

- Arduino board with BLE support  
  *(e.g. Arduino Nano 33 BLE, MKR WiFi 1010, etc.)*
- Capacitive moisture sensor (soil sensor)
- USB cable
- Arduino IDE

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## The Script

```cpp
#include 

const int sensorPin = A0;   // Sensor pin
int minWert = 1023;         // Minimum value for moisture
int maxWert = 0;            // Maximum value for moisture
bool isAdvertising = false; // Advertising state

// UUIDs for the service and characteristic
const char* serviceUuid = "12345678-1234-1234-1234-123456789012";
const char* charUuid    = "12345678-1234-1234-1234-123456789013";

BLEService customService(serviceUuid); 
BLEIntCharacteristic humidityCharacteristic(charUuid, BLERead | BLENotify);

void setup() {
  Serial.begin(9600);
  while (!Serial);

  // Initialize BLE
  if (!BLE.begin()) {
    Serial.println("Starting BLE failed!");
    while (1);
  }

  BLE.setLocalName("Sensor01");
  customService.addCharacteristic(humidityCharacteristic);
  BLE.addService(customService);
  
  BLE.advertise();
  isAdvertising = true;

  Serial.println("Bluetooth device is ready to send humidity");
}

void loop() {
  int sensorValue = analogRead(sensorPin);

  // Update maximum and minimum values
  if (sensorValue > maxWert) maxWert = sensorValue;
  if (sensorValue < minWert) minWert = sensorValue;

  // Calculate humidity
  float humidity = map(sensorValue, minWert, maxWert, 100, 0);
  humidity = constrain(humidity, 0, 100);

  humidityCharacteristic.writeValue((int)humidity);

  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.println("%");

  // Check connection
  if (BLE.connected()) {
    if (isAdvertising) {
      Serial.println("Device connected, stopping advertising.");
      isAdvertising = false;
    }
  } else {
    if (!isAdvertising) {
      BLE.advertise();
      Serial.println("Advertising restarted");
      isAdvertising = true;
    }
  }

  delay(2000);
}

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Script Structure

The script consists of two main parts:

• setup() Initialization of BLE, service, and characteristic, as well as starting advertising

• loop() Reading the sensor, calculating moisture, transmitting data, and status checking

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Reading Data

There are different ways to receive the data via Bluetooth.

The easiest is to use Bluetooth LE scanner apps, for example:

• BLE Scanner (iOS)
• BLE Scanner (Android)

There you will find your Arduino device under the name "Sensor01" and can read the moisture values live.

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Use Cases

This script serves as a foundation for many projects:

• Home and garden automation
• Smart home systems
• Environmental monitoring
• Notifications on thresholds (e.g. too dry soil)

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Conclusion

With this script, you have a solid starting point to reliably transmit sensor data via Bluetooth Low Energy.

The step from a simple moisture sensor to a comprehensive smart home solution is much smaller than you might initially think.