We stopped melting metal to try an idea. A block of holes with hidden clips inside, and any circuit could be built in a minute and taken apart the next. Here is the block. Learn where its clips run.
⟨ transmission ends ⟩By the end of this page you will build any small circuit on a breadboard and know it is wired the way you meant: which holes are joined inside, where the power rails run and where they break, and the habits that keep a build readable when it does not work.
Below is a breadboard: a block of holes with metal clips hidden underneath, so that some holes are joined to each other. The meter from The Meter is on its beep setting, with the black probe already in hole 12c. Find every hole the board joins to it.
A 60-column full-size board on a wide screen; on a phone the same lesson on a 17-column mini board, which has no rails. Columns numbered, rows a to e above the trench and f to j below. A clip reads 0.1 Ω end to end; two different clips read OL. The x-ray lens draws the metal that is really there under the plastic.
Four holes beeped, the rest stayed silent, and the trench cut the column in two. That is the whole board: short clips of 5, one per half-column, and a part’s 2 legs in 2 different clips are 2 different points of a circuit.
The long rows along the edges, red and blue, are the power rails: one clip the whole length of the board, as the x-ray showed. The trench is the other thing to own. Nothing crosses it unless you cross it. The black probe is now in 12e; a short jumper waits on the bench.
The jumper spans any 2 holes one row apart, and the meter reads whatever it really joins: dropped inside a clip it changes nothing. A wire from e to f is how a column is carried across the trench, and how a chip’s 2 rows of pins get their own columns. One caveat for other boards: many full-size boards split each power rail at the middle; this one’s rails run whole. Beep a new board’s rail end to end once.
Now a build. First Light again, on the board this time: a 9 V battery, a 470 Ω resistor, a red LED, and 2 jumpers. The battery’s red lead is already plugged in as + and its black lead as −. A part lies along a row with its legs in 2 columns; a jumper reaches from the battery’s clip to a column. Make one path: +, jumper, resistor, LED, jumper, −. The LED’s longer leg is the + side; click the LED to turn it round.
Battery 9 V with 2 Ω inside, resistor 470 Ω, red LED 1.9 V when lit: 15 mA when the loop is right, as in First Light. On the wide board the battery feeds the top rails; on the phone’s mini board, which has no rails, its leads sit in column 1, the a-side as + and the f-side as −. The resistor spans 4 columns and the LED 1, each with its legs in 2 column clips; the LED’s + leg is on the left until you turn it; each jumper’s 2 ends drag separately and snap into any hole. An LED wired straight across + and − with no resistor takes about 3.5 A and dies at once, loudly.
It lights because every joint is a clip you can name: rail to resistor leg, resistor leg to LED leg in one column, LED leg to jumper, jumper to rail. A build that fails is debugged the same way, clip by clip with the beep. The habits below are what make that fast.
Now meet the board properly, as it looks on the bench.
When you are ready, test yourself:
You push an LED’s 2 legs into 14c and 14d. Power is on. It stays dark. Why?
A resistor’s legs go into 10c and 10h. Are its 2 legs joined to each other by the board?
On a full-size board your battery feeds the left end of the top + rail, and an LED circuit at the right end gets no power. The fastest check?
You can now put any small circuit on a board and name every joint in it. The next fragment, The Schematic, gives you the drawing those joints come from, so that a circuit on paper and a circuit on the board become the same thing read 2 ways.
Lesson 5 done.
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