Zed-King Institute

    Online Arduino Simulator

    Free · No board needed · No login

    Run Arduino sketches on a virtual Uno — LEDs, buttons, sensors, LCD and servo motors. Pick a sketch on the side, copy it into the simulator and press play. Built for NIELIT O Level M4 & PR-4 (IoT).

    Free Editor Practice Questions
    1

    Pick a sketch and copy it

    Wiring

    LED long leg (anode) → 220Ω resistor → pin 13. LED short leg (cathode) → GND. Or use the Uno's built-in LED — no wiring needed.

    sketch.ino

    void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}
    2

    Paste it in the simulator and press ▶

    Open in new tab

    How: press the blue + to add parts → drag from pin to pin to wire → paste your code in sketch.ino → press the green ▶.

    Practice Questions — Arduino / IoTA new question every time, checked instantly. Easy, medium and hard levels.

    How to Use the Arduino Simulator

    1. The simulator on this page is already open: a blank Arduino Uno with a code editor next to it.
    2. Choose a sketch from Practice sketches and press Copy.
    3. In the simulator, select all the code in sketch.ino and paste yours in its place.
    4. Add the parts listed under Wiring with the + button and connect their pins.
    5. Press the green play button. Change a delay() or a pin number and run again to see the effect.

    Arduino Topics Covered for O Level M4 (IoT)

    NIELIT O Level M4-R5.1 Internet of Things and its Applications tests the same handful of building blocks, and each one has a sketch in the side panel:

    • pinMode, digitalWrite and delay — LED blink and traffic light
    • digitalRead with INPUT_PULLUP — push button input
    • analogWrite (PWM) — LED fading and motor speed
    • analogRead and the Serial Monitor — potentiometers and analog sensors
    • pulseIn — the HC-SR04 ultrasonic distance sensor
    • Libraries — LiquidCrystal for a 16x2 LCD and Servo for a servo motor

    Frequently Asked Questions

    Can I practice Arduino without buying a board?

    Yes. The simulator on this page is a virtual Arduino Uno. You place LEDs, buttons, sensors and displays, wire them, paste your sketch and press play — the LED blinks and the LCD prints exactly as real hardware would.

    Is this Arduino simulator free?

    Yes. It uses Wokwi, a free online electronics simulator, and needs no account for practice. Nothing is installed on your computer.

    How do I add an LED or a sensor?

    In the simulator, press the blue + button above the board, search for the part (LED, resistor, pushbutton, HC-SR04, LCD 16x2, servo), then drag from a part's pin to an Arduino pin to draw a wire. Each example in the side panel lists the exact connections.

    Where do I see Serial.println() output?

    When the simulation is running, the Serial Monitor opens below the code in the simulator. Make sure your sketch has Serial.begin(9600) in setup().

    Is this enough for the O Level PR-4 (IoT) practical?

    It covers the programming side of NIELIT O Level M4-R5.1 (Internet of Things): digital and analog input/output, PWM, sensors, LCD and servo. Practice the sketches here, then attempt our free PR-4 practical mock test, which checks your sketch automatically.

    The simulator does not load. What should I do?

    Use the Open in new tab button — some networks and older phones block embedded pages. The simulator needs a modern browser and works best on a laptop or desktop.