A breadboard joins the five holes in each numbered column (a–e, and separately f–j) with a metal strip; the rails along the edges join along their length. Each leg of a part must be in a different strip, and the loop goes from strip to strip through the parts.
Real parts don't snap together like Tinkercad's. A breadboard holds them with hidden metal strips underneath. Put a leg in the wrong hole and the circuit quietly doesn't work. Which holes are joined?
In a breadboard, the five holes of each numbered column are joined (a to e, and separately f to j: the gap down the middle splits them). The rails along the top and bottom are joined along the board's length: + for power, − for GND. Rows (a, b, c…) are not joined.
Predict: Read the problem and decide what you think before you try anything. A wrong guess is fine: it shows you what to look for.
Try: Try it on the board and compare the result with your prediction.
Investigate: Work out why it happens, one step at a time.
Modify: Change the problem on purpose and see what happens.
Practise: A few on your own, to check you have it.
Make: Make your own problem using what you have learned. Expect a few tries; that is normal.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
PredictRead the problem and decide what you think before you try anything. A wrong guess is fine: it shows you what to look for.
One column
TryTry it on the board and compare the result with your prediction.
Try: find the strips
Was your prediction right?
Try it yourselfYour edits are saved in this browser.
Click a hole in column 8. Which holes light up?
Use the board. This ticks when you get there.
Move the LED's short leg (−) so the LED lights.
Use the board. This ticks when you get there.
InvestigateWork out why it happens, one step at a time.
Worked example: trace the strips
Worked exampleBefore each step, say what you think comes next.
resistor: b3→b7One leg in column 3, one in column 7: it joins the two strips.
LED: c7 (+)→c8 (−)Long leg in column 7, short leg in column 8.
d8→GNDThe GND wire takes column 8 back to the Uno.
one loop, four stripsEvery part bridges two strips; no part has both legs in one.
Now: which holes are joined to a3?
Sam thinks this LED (long leg c7, short leg c8) is shorted out. It isn't. Click the line where Sam's reasoning first goes wrong.
ModifyChange the problem on purpose and see what happens.
Vary: the gap and the rails
Try it yourselfYour edits are saved in this browser.
This LED straddles the gap (e7 and f7), but stays dark. Move the GND wire so it lights.
Use the board. This ticks when you get there.
5V and GND are on the top rails. Move the free ends of W3 and W4 so the LED lights.
Use the board. This ticks when you get there.
Modify TypicalChange the problem on purpose and see what happens.
Build it for real
Before you plug in the USB cable: check that 5V and GND are never in the same strip.
PractiseA few on your own, to check you have it.
Which holes?
MakeMake your own problem using what you have learned. Expect a few tries; that is normal.
Build it from scratch
Try it yourselfYour edits are saved in this browser.
Need a hint?
Plan the strips first: pin 13's strip, a middle strip, a GND strip.
Another hint
Resistor from pin 13's strip to a new strip; LED long leg in that strip, short leg in the GND wire's strip.
Another hint
For example: resistor in i2 and i8, LED long leg in h8 and short leg in h4.
The wires to pin 13 and GND are in. Place the resistor and the LED so the LED lights safely.
Use the board. This ticks when you get there.
For teachers
Students click breadboard holes to see the hidden strips, fix an LED whose legs share a strip, trace a loop strip by strip, straddle the gap and use the rails, build the circuit on a real breadboard and upload the blink, then place every part themselves. About 45 minutes.
I can place parts so each leg is in a different strip.
I can build a circuit on a real breadboard and upload a sketch.
Before class
The board treats the named pin as HIGH (the blink sketch's on moment) and shows a short circuit or missing resistor as a warning. Some breadboards split each rail in the middle: check yours and say so.
Uploading: Arduino IDE (install, admin rights) or Arduino Cloud Editor (browser plus the Create Agent, an account). Choose before the lesson and test one board on the school network. Tinkercad remains the no-kit route.
Kit per pair: Uno and USB cable, breadboard, a 220 Ω resistor, an LED, two jumper wires.
Running the lesson
Predict: show a real breadboard turned over (or a photo) after the reveal: the metal strips.
Find the mistake: ask a student to trace with a finger which holes are joined to c7.
Real hardware: nothing is plugged into USB until a partner has traced the loop.
The hard part (on purpose)
Students build what looks like the diagram, not what is joined. Before they plug in, have them trace the loop strip by strip with a finger.
When students get stuck
An LED won't light on the real board. Ask: Which strips are its legs in? Which way round is it? Fix: Different strips, long leg towards the resistor.
A student thinks rows are joined. Ask: Click a hole: which ones light up? Fix: Columns of five.
Stretch and support
Stretch: Put a second LED and resistor on pin 12, using the GND rail for both LEDs.
Support: A printed breadboard map with the strips shaded.
Where it leads
Next: A small system (a brief, criteria, and tests on the boundary).
one column: Committing to what happens when both LED legs share a column tests the new move: legs in the same strip are joined to each other, so the current goes round the part.
Try: find the strips: Clicking holes shows the strips directly, which settles the prediction; then students fix the LED by moving one leg.
Worked example: trace the strips: Tracing the loop strip by strip models the move; Sam's 'rows are joined' is planted after the method.
Vary: the gap and the rails: Two more pieces of breadboard: a part can straddle the gap (its legs in two strips), and the rails carry power and GND along the board.
Build it for real: Building the same circuit on a real breadboard and uploading the blink sketch is the step from simulator to hardware; the strips are the first thing to check when it doesn't work.
which holes?: Reading connectivity without the board, including the gap and the rails.
build it from scratch: Placing every part from scattered positions puts the whole idea together: each part bridges two strips, and the loop runs from pin 13 back to GND.
Now you can
Say which breadboard holes are joined.
Place parts so each leg is in a different strip.
Build a circuit on a real breadboard and upload a sketch.