Button controls an LEDTinkerPieCircuit tutorial 9 of 24 · Beginner · 10 minutes

Read a push button with INPUT_PULLUP and light an LED only while it is pressed.

Open this circuit in TinkerPieCircuit (free, runs in your browser)

What you will learn

• Digital inputs and INPUT_PULLUP
• Why a pressed button reads LOW
• if / else decisions in code

Parts

TinkerPie V1 board1 push button1 LED1 resistor, 220 Ω

Steps

1. Build the LED

   Wire S1 → resistor → LED (+), and LED (−) → GND, just like the Blink tutorial.

2. Add the button

   Click Push button. Wire one side to pin P10 and the other side to GND.

3. Use the pull-up

   pinMode(P10, INPUT_PULLUP) keeps the pin at HIGH (3.3 V) until the button joins it to GND. A pressed button therefore reads LOW.

4. Write the decision

   In loop(), if (digitalRead(P10) == LOW) turn the LED on, otherwise turn it off.

5. Try it

   Press ▶ Start, then press and hold the red cap of the button with your mouse or finger.

The code

function setup() {
  pinMode(P10, INPUT_PULLUP);
  pinMode(S1, OUTPUT);
}

function loop() {
  if (digitalRead(P10) == LOW) {
    digitalWrite(S1, HIGH);
  } else {
    digitalWrite(S1, LOW);
  }
}

Copy this into the Code tab. It is Arduino-style JavaScript. The real board uses the same pin names (S1, P10…) in TinkerPie Studio.

How it works

The board has a small resistor inside that pulls the pin up to 3.3 V. Pressing the button connects the pin to GND (0 V), so the program sees LOW.

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