Welcome to electronics! Before you build anything, take a few minutes to get to know the parts in your kit and the rules that keep you and your parts safe. At the end you build your first circuit: a small light that shows your breadboard has power. Every other lesson in this path starts from this setup.
What you'll learn
- What the main parts in your kit are called and what they do
- Which parts can get hot or break, and how to avoid it
- Why the UNO is a safe 5 V power supply for learning
- How to bring power to the long strips on the edge of the breadboard
What you need
- UNO R3 board and USB cable (UNO R3 Starter Kit)
- 1 red LED (UNO R3 Starter Kit)
- 1 resistor, 220 Ω (UNO R3 Starter Kit)
- Breadboard and jumper wires (UNO R3 Starter Kit)
Meet your parts
Tip the kit out on a table and sort the parts into small groups. Egg boxes, an ice cube tray or a few small cups work well.
| Part | What it looks like | What it does |
|---|---|---|
| UNO R3 board | Blue board with a USB socket and rows of black sockets | In this path: gives you 5 V to power your circuits. Later: runs your programs |
| Breadboard | White board full of small holes | Holds parts and connects them without soldering |
| Jumper wires | Coloured wires with pins on the ends | Connect holes on the breadboard to each other and to the UNO |
| Resistors | Small beige or blue tubes with coloured stripes | Limit how much electricity flows |
| LEDs | Small coloured domes with two legs | Give light when electricity flows the right way through them |
| Push buttons | Small black squares with four legs | Connect a circuit while you press them |
| Potentiometers | Small knobs with three legs | A resistor you can turn up and down |
| 9 V battery and snap | Rectangular battery and a clip with two wires | A power source for later projects away from the computer |
The kit has many more parts: sensors, a servo motor, a screen and more. You use them in the Arduino paths. For now, keep them in the box.
Five safety rules
- Never connect + straight to −. A wire from 5V to GND, or across the two terminals of a battery, is a short circuit. Lots of current flows, wires and batteries get hot, and parts can be damaged. The UNO has a small fuse that switches off when this happens, but don't rely on it.
- Unplug before you change the circuit. Pull the USB cable out, move the parts, check, then plug it back in.
- Always use a resistor with an LED. Without one, the LED takes too much current and burns out, sometimes with a pop.
- Keep the 9 V battery in the box until a lesson tells you to use it. Its two terminals are close together, and a coin or a key in your pocket can short them.
- If something gets hot, smells or smokes, unplug at once and check the circuit. Don't touch the hot part until it has cooled down.
The voltages in this path are low (5 V or less), so they can't give you a shock. Mains electricity from a wall socket is completely different: never open or connect anything to it.
Power from the UNO
In this path the UNO is only a power supply: plug its USB cable into a computer or a USB phone charger and use its 5V and GND pins. Whatever program is on the board doesn't matter, and you don't need the Arduino IDE yet. A new board usually blinks its small L LED; that's normal.
Along the top and bottom edge of the breadboard are two long strips, marked with a red + line and a blue − line. These are the power rails. You connect the UNO's 5V pin to the + rail and its GND pin to the − rail, so every part on the board can reach power easily.
Wiring
| From | To |
|---|---|
| UNO 5V | Bottom + rail (red wire) |
| UNO GND | Bottom − rail (black wire) |
| + rail | Column 20, row j (red wire) |
| Resistor 220 Ω | Column 20 (row h) to column 24 (row h) |
| LED long leg (+) | Column 24, row f |
| LED short leg (−) | Column 25, row f |
| Column 25, row j | − rail (black wire) |
An LED only works one way round. The long leg is + (anode) and the short leg is − (cathode). If the legs have been cut, look at the rim of the LED: the side with a small flat edge is −.
Try it
- Build the circuit with the USB cable unplugged.
- Check every wire against the table.
- Plug in the USB cable. The UNO's ON LED and your red LED light up.
- Unplug the cable: both go out. Your breadboard is ready, and you have built your first circuit.
Leave the red and black power wires in place. Most lessons in this path start from them.
Try this next
- Swap the red LED for a yellow or green one. It still works with the same resistor.
- Write the names of the parts on small labels and stick them on your sorting tray.
- Read the multimeter guide to see the tool that electronics makers use to measure circuits. You don't need one for this path.
Troubleshooting
- Nothing lights up: check that the USB cable is plugged in (the UNO's ON LED is lit), that the long leg of the LED goes to the + side, and that every wire sits in the column the table says. Wiggle each wire gently; a wire that isn't pushed all the way in is the most common fault.
- The UNO's ON LED doesn't light: try another USB port or charger, or another cable. Some cables only charge and are loose in the socket.
- The UNO goes off when you plug in your circuit: 5V is connected straight to GND somewhere. Unplug and look for a wire that goes from the + rail to the − rail.
