Uno Voltage (V)
The push that moves electricity. The Uno's pins give 5 volts when they're on and 0 when they're off. Voltage is always measured between two points, usually a pin and GND.
Learn electronics by doing
From your first LED
to your first robot.
You don't need to know anything about electronics to start. Each project teaches one or two new ideas, and the simulator shows what's really happening in the wires.
How the lab works
Four steps, every project
- 1
Wire it
Put parts on the breadboard and tap two pins to add a wire. The checklist ticks each step off. Stuck? Show me draws the wire for you, and the voice can read each step aloud.
- 2
Code it
Snap blocks together: “when Uno starts”, “turn pin 13 on”, “wait 1000 ms”. The lab shows the real Arduino C++ they make, and you can switch to typing code yourself.
- 3
Test it
Press Run. The simulator works out the real voltages, so LEDs glow as brightly as they would, and it warns you about missing resistors and short circuits before they cost a part.
- 4
Build it for real
Build the same circuit on your desk, plug in your Uno with a USB cable, and upload the code straight from Chrome or Edge. No Arduino IDE needed.
Your learning path
12 projects in four levels
Starter2 projects
Your first circuits: make lights blink in order.
- 1Blink an LED
- 2Traffic Light
Explorer2 projects
Buttons and buzzers: the Uno starts listening.
- 3Button Lamp
- 4Buzzer Doorbell
Maker6 projects
Knobs, sensors, colours and displays.
- 5Knob Dimmer
- 6Night Light
- 7Colour Mixer
- 8Digital Dice
- 9Intruder Alarm
- 10Parking Sensor
Inventor2 projects
Motors and servos: make things move.
- 11Smart Fan
- 12Servo Pointer
Electronics basics
The ideas behind every project
Current (mA)
How much electricity flows, in milliamps. An LED is happy with about 15 mA. An Uno pin can give 20 mA safely, which is why motors need a transistor.
Resistance (Ω)
How hard a part makes it for current to flow, in ohms. Resistors have colour bands: 220 Ω is red, red, brown. The lab has a colour code calculator.
Ohm's law
V = I × R
Know two, find the third. An LED on 5 V needs a resistor of about (5 − 2) ÷ 0.015 = 200 Ω, so you use the next size up: 220 Ω.
LEDs have a side
Current only flows one way through an LED: in the long leg (+) and out the short leg (−). Every LED needs a resistor, or it takes too much current and burns out.
The breadboard
Each short column of 5 holes is joined inside, like a hidden wire. Parts whose legs share a column are connected without any wire. Legs of one part go in different columns.
Digital and analog
Digital pins are either on or off, HIGH or LOW. Analog pins A0 to A5 read anything in between, from 0 to 1023, which is how a knob or a light sensor reports how far it's turned or how bright it is.
PWM (~ pins)
Pins marked ~ (3, 5, 6, 9, 10, 11) flick on and off very fast. Changing how long they stay on makes an LED look dimmer or brighter, or a motor spin slower or faster.
Tools in the lab
Real tools, on screen
Multimeter
Touch two points with the probes. It reads volts while the Uno runs, ohms while it's off, and beeps when two points are connected.
Resistor calculators
Find the right resistor for an LED, turn colour bands into a value and back, and work out Ohm's law.
Voice guide
Reads each step aloud, shows where the wire goes, and says well done when you get it right.
Serial Monitor
See the messages your program prints, from the simulator or from your real Uno over USB.
Build it for real
What you need on your desk
- Chrome or Edge on Windows, macOS, Linux or a Chromebook. They can talk to the Uno over USB.
- An Uno board and a USB cable. Blue clone boards work too.
- On Windows with a blue clone board: install the free CH340 driver once (download CH341SER.EXE), then plug the board in again. Macs, Chromebooks and Linux already have it.
- A starter kit: breadboard, jumper wires, LEDs, resistors and a few sensors. The lab's My parts box tells you what each project needs and what to buy.
Ready to make something light up?
Your first project takes about 10 minutes.