Example-2

LED Control using a Push Button

Objective

Use a push button to turn an LED ON when pressed and OFF when released. Students learn about input devices, pull-down resistors, and digital input/output in Arduino.

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Learning outcomes

• Understand the difference between input and output pins.

• Learn how to wire and use a push button in Arduino circuits.

• Understand the role of pull-down resistors.

• Write an Arduino sketch to read a button press and control an LED.

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Components (Tinkercad palette)

• Arduino Uno R3

• Breadboard (small)

• 1× LED (any color)

• 1× Resistor 220 Ω (for LED)

• 1× Resistor 10 kΩ (pull-down for button)

• 1× Push button

• 5× Jumper wires

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Circuit wiring

1. Place the push button across the middle groove of the breadboard (so each pair of legs is on separate rows).

2. Connect one leg of the button → Arduino pin 2 (digital input).

3. Connect the same leg → +5V through the breadboard rail.

4. Connect the other leg of the button → GND rail.

5. Add a 10 kΩ resistor between pin 2 and GND (this acts as a pull-down, ensuring pin stays LOW when button not pressed).

6. Wire the LED:

   • LED anode (long leg) → Arduino pin 8 (digital output).

   • LED cathode (short leg) → one side of the 220 Ω resistor.

   • Other side of the resistor → GND rail.

7. Connect Arduino GND → breadboard GND rail.

8. Connect Arduino 5V → breadboard +5V rail.

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Arduino sketch

// EXP-2: LED control using a push button (pull-down resistor)
const int BUTTON_PIN = 2;  // push button input
const int LED_PIN    = 8;  // LED output

void setup() {
  pinMode(BUTTON_PIN, INPUT);  // using external 10k pull-down
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  int pressed = digitalRead(BUTTON_PIN); // LOW or HIGH
  if (pressed == HIGH) {
    digitalWrite(LED_PIN, HIGH); // LED ON while pressed
  } else {
    digitalWrite(LED_PIN, LOW);  // LED OFF when released
  }
}

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Step-by-step in Tinkercad

1. Create new circuit in Tinkercad.

2. Place Arduino, breadboard, LED, push button, and resistors.

3. Wire as explained above (keep GND wires black and 5V wires red for clarity).

4. Open Code → Text editor and paste the above sketch.

5. Start simulation → Press the button in the workspace → LED should glow while pressed.

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How it works

• Button not pressed → pin 2 is pulled LOW (through 10 kΩ resistor) → LED OFF.

• Button pressed → pin 2 connected to 5V → Arduino reads HIGH → LED ON.

• Code continuously checks the button state in loop() and updates LED accordingly.

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Common mistakes & fixes

• LED not lighting: Check if the LED is reversed (long leg should go to Arduino pin).

• Button always ON: Missing or wrong pull-down resistor connection.

• Pin mismatch: Ensure the code pin numbers match the actual wiring.

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Viva / check-your-understanding

• Why do we need a pull-down resistor with a button?

• What happens if you remove the resistor?

• Can we use Arduino’s internal pull-up resistor instead of an external one? (Yes: pinMode(BUTTON_PIN, INPUT_PULLUP), but logic will invert.)

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Extensions (mini-tasks)

• Modify code so that button press toggles LED state (LED stays ON after one press, OFF after the next).

• Use two buttons: one for LED ON, another for LED OFF.

• Try with internal pull-up resistor and adjust code accordingly.

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Lab record (suggested headings)

• Aim

• Circuit diagram (Tinkercad screenshot)

• Code listing

• Output observation (simulation screenshot)

• Inference/Conclusion

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Thinkercad Link

https://www.tinkercad.com/things/9xa0zU7wggt-example-2