Plant Saver

Discussing and introducing questions:

• What is Arduino? Explain that it is the “brain” of the project. Like a human brain receives signals from the skin (touch) and tells the hand to move, Arduino receives signals from sensors and tells LEDs to light up.
• Input vs. Output: * Inputs: Sensors (Soil moisture, buttons, light sensor
• Outputs: Actuators (LEDs, buzzers, motors).

• The Software: Introduce the Arduino IDE. Explain that we use “sketches” (code) to tell the brain what to do.
• Key Terminology:
• Digital: Only two states—ON (High) or OFF (Low).
• Analog: A range of values (e.g., 0 to 1023) used for measuring “how much” moisture is in the soil.

Safety First: Explain why we use resistors (to prevent the LED from “blowing up” from too much current).

Polarity: Teach students that LEDs have a long leg (Positive/Anode) and a short leg (Negative/Cathode).

The Code: Introduce the Blink sketch.

void setup() {

 pinMode(13, OUTPUT);

}

void loop() {

 digitalWrite(13, HIGH); // Turn LED on

 delay(1000);      // Wait 1 second

 digitalWrite(13, LOW); // Turn LED off

 delay(1000);

}

Activity: Students must successfully make their LED blink before moving to the main project.

1. The Hardware Setup

Students will now expand their circuit to include:

• The Sensor: A Capacitive Soil Moisture Sensor (v1.2). Unlike resistive sensors, these don’t corrode as quickly.

• Two LEDs: Green (Moist) and Red (Dry).

• Wiring Guide: Sensor: VCC to 5V, GND to GND, and AUOUT to Analog Pin A0. LEDs: Green to Digital Pin 2, Red to Digital Pin 3 (using resistors for both).

2. The Logic (Programming)

Explain the if/else logic: If the soil is dry, then turn on the Red LED. Otherwise, turn on the Green LED.

const int sensorPin = A0;

const int redLED = 3; 

const int greenLED = 2;

void setup() {

Serial.begin(9600);

 pinMode(redLED, OUTPUT);

 pinMode(greenLED, OUTPUT);

}

void loop() {

int sensorVal = analogRead(A0);

Serial.println(sensorVal);

if( sensorVal > 450) {

   digitalWrite(redLED, HIGH);

  digitalWrite(greenLED, LOW);

}

else{

   digitalWrite(redLED, LOW);

  digitalWrite(greenLED, HIGH);

}

}