Why this page exists 2 min
Almost every EV3 lesson that goes wrong goes wrong in the same two places: something is in the wrong port, or the Brick never really connected. Neither is a programming mistake, and neither shows up as an error message.
The Brick will not tell you that your motor is in port 1 instead of port A. EV3 Classroom will not tell you that you paired with the group at the next table. Both will simply do nothing, or do something strange, and it will look exactly like a bug in your program.
So there are two screens worth learning properly — the Brick’s Port View and EV3 Classroom’s port row — and one habit worth building: check the machine before you blame the blocks.
The question these screens answer is always the same one: does what the software can see match the robot in front of you?
The Brick’s four tabs 3 min
Switch the Brick on with the dark grey centre button and wait for the startup sound. Across the top of the screen are four tabs. The left and right buttons move between them.
Tab 2 is file navigation, and you will rarely need it. The second entry on tab 3, Brick Program, lets you build a tiny program on the Brick itself with no computer at all — worth knowing exists, but this course programs in EV3 Classroom.
Port View — what is actually plugged in 8 min
Port View is the Brick telling you what it can see. Not what you meant to plug in — what is really there, right now.
Get to it with tab 3 → Port View. The screen is laid out like the Brick itself:
- the top row is the four sensor ports, 1 2 3 4
- the bottom row is the four motor ports, A B C D
- the middle shows the port you have selected, in full, with its live reading
A port showing --- has nothing on it. If a port you have wired reads ---, the problem is the cable, and no amount of editing your program will help.
Reading a sensor
Move to a port with the arrow buttons. The reading updates as you move the robot, so you can test a sensor with your hands before a single block runs.
One sensor, several things to measure
A sensor often measures more than one thing, and Port View lets you choose. Press the centre button on a port and you get its list of modes.
Reading a motor
Motors report the degrees they have turned. Turn the wheel by hand and the number moves — which is the quickest way there is to prove a motor is on the port you think it is.
Read that letter before the dash: L-MOTOR or M-MOTOR. It is the Brick telling you which motor you actually built in — and more than one lesson in this course turns on knowing the difference. If your lesson says Medium and the Brick says L-MOTOR, trust the Brick.
Your check, every lesson, before any program
- Open Port View.
- Does every port your model uses show something other than
---? - Is each one on the letter or number your lesson asked for? Sensors go in 1 2 3 4, motors in A B C D. They are not interchangeable.
- Move each part by hand — press the sensor, turn the wheel — and watch its number change. A port that reads but never moves is a part that will never work.
Motor Control — move a motor with no program 3 min
Also on tab 3. Motor Control drives the motors straight from the Brick’s buttons, which is the fastest way to find out whether a mechanism is jammed, geared the wrong way, or simply not connected.
Use this before you blame a program. If the arm will not lift here, with no program involved at all, then the problem is in the build — a gear out of mesh, something rubbing, or a motor that is not plugged in.
And the third entry, IR Control — which this course does not use
Name your Brick — do this first 4 min
Every Brick leaves the factory called EV3. In a room with six of them, that is six devices with the same name in the pairing list, and no way to tell which is yours.
Name it before you turn Bluetooth on, not after. This is the single change that prevents the commonest Bluetooth problem in a classroom — driving a robot that belongs to another group.
EV3.Pick a name nobody else will pick. Your group’s name, your table number, something silly — it does not matter, as long as you would recognise it instantly in a list. Then write it on a sticker and put it on the Brick.
Turn Bluetooth on 3 min
Still in Settings. Move to Bluetooth and press the centre button.
Confirm with the tick at the bottom. Back on the main screen, a small Bluetooth symbol appears in the top-left corner — that corner is your at-a-glance check for the rest of the lesson.
Pair EV3 Classroom with your Brick 8 min
Now to the computer. Open EV3 Classroom. Top-left of the programming area is a small Brick icon — it is your connection, and it has a coloured dot.
Choose the right Brick — carefully
Read the name before you click Connect. Connecting to the wrong Brick is not an error — it works perfectly, on somebody else’s robot.
The passkey, and accepting it on the Brick
Pairing takes a handshake at both ends. The computer asks, and the Brick has to say yes — so after clicking Connect, look at the Brick.
Confirm it — do not take the cable’s word for it 5 min
A plugged-in cable is not a connected Brick, and a connected Brick is not a correctly wired robot. This is the step that turns “it doesn’t work” into a diagnosis.
Click the Brick icon for the full picture — firmware, battery, and every port drawn where it physically sits.
The check is one question: does this screen agree with the robot in front of you? If your lesson says a Touch Sensor on 1 and a Medium Motor on A, and this panel says the same, you can start programming. If it does not, fix the cables — not the program.
Watch the battery here too. A Brick below about 20 % behaves in a way that will waste your whole lesson: motors run slower than the number you asked for, and the Bluetooth connection starts dropping. If a robot that worked yesterday is sluggish today, look at this reading before you change anything.
When it goes wrong 4 min
| What you see | What it usually is |
|---|---|
| My Brick is not in the list | Bluetooth or Visibility is unticked, or the Brick has gone to sleep. Press a button to wake it and check the top-left corner for the Bluetooth symbol. |
Several Bricks called EV3 | Nobody has named theirs. Go back and name yours — you cannot tell them apart otherwise, and neither can anyone else. |
| It connected, then dropped | Usually battery, sometimes distance. Check the percentage in the hub panel. A USB cable is the reliable fallback when a room is busy. |
A port reads --- | Nothing is on that port. Reseat both ends of the cable — including the end at the sensor, which is the one people forget. |
| The robot does the opposite of what I wrote | Two cables swapped. Two sensors of the same kind are physically identical and only the port tells them apart. Swap the cables rather than editing the program. |
Port View says L-MOTOR, my lesson says Medium | You built the other motor in. The Brick is right. Either swap the motor or use the port your Brick actually has. |
| Nothing moves, but everything looks connected | Try Motor Control on the Brick. If it will not move there, with no program at all, the fault is in the build. |
Check the machine before you blame the blocks. Almost every time, the machine is what changed.