2 · Inputs & sensors
Read a push button
Beginner12 min
Goal
Light the LED only while the button is pressed.
Why it matters
Understanding INPUT_PULLUP avoids the classic “floating input” mistake.
What you need
- Arduino UNO board
- 5 mm LED
- 220 Ω resistor
- Push button
Nothing to buy: every component below is simulated in the browser.
Steps
- 01Add a button on pin 2 and declare pinMode(2, INPUT_PULLUP).
- 02Read it with digitalRead(2).
- 03An if/else drives the LED on pin 13.
This tutorial runs inside the Circuitly simulator: your wiring and your code are checked automatically at every step.
Frequently asked questions
- Do I need to buy hardware for this tutorial?
- No. Everything runs in the browser: Circuitly simulates the board, the components and the code. Real hardware is optional if you want to rebuild the circuit afterwards.
- Which components are used?
- Arduino UNO board, 5 mm LED, 220 Ω resistor, Push button. They are already available in the simulator library.
- How long does it take?
- About 12 minutes, beginner level, in 3 guided steps.
- What should I know before starting?
- The previous tutorial in the series, “Blink without delay() (millis)”, is enough preparation. No software install is required.
- Is the code provided and checked?
- The simulator checks your wiring and your code automatically at every step, and shows the commented solution if you get stuck.
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In the same series
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One press turns on, the next turns off — with no contact bounce.
- Read a potentiometer
Print the analog value of A0 on the serial monitor.
- Convert to volts (map & float)
Turn the ADC's 0–1023 into a 0.00–5.00 V reading.
- Light sensor (LDR)
Turn the LED on automatically when the room gets dark.