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, Light sensor (LDR). They are already available in the simulator library.

How long does it take?

About 15 minutes, intermediate level, in 4 guided steps.

What should I know before starting?

The previous tutorial in the series, “Convert to volts (map & float)”, 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.

All tutorials

2 · Inputs & sensors

Light sensor (LDR)

Intermediate15 min

Goal

Turn the LED on automatically when the room gets dark.

Why it matters

The voltage divider turns a variable resistance into a measurable voltage.

What you need

Arduino UNO board
5 mm LED
220 Ω resistor
Light sensor (LDR)

Nothing to buy: every component below is simulated in the browser.

Steps

01Add a light sensor on A0.
02Pick a threshold (e.g. 400) and compare it to the reading.
03Light the LED below the threshold, switch it off above.
04Change the light level in the Scenario panel while running.

This tutorial runs inside the Circuitly simulator: your wiring and your code are checked automatically at every step.

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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, Light sensor (LDR). They are already available in the simulator library.
How long does it take?: About 15 minutes, intermediate level, in 4 guided steps.
What should I know before starting?: The previous tutorial in the series, “Convert to volts (map & float)”, 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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