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Level 3 · The Build

The Build.

Off the screen, onto the bench.

A plastic block full of holes, a handful of parts, and real devices you wire yourself — starting with the Beacon and growing from there.

Fathohm Field Guide · Volume 3 of 3 · 2026
Fathohmfathohm.com
Level 3 · Contents

Theory you
can hold.

The rules and the parts were the why. This is the how: the bench you work on, the first device you build, and the shelf of projects waiting after it.

The bench
The projects
The Buildi
Build · A

The Breadboard.

Your workbench is a plastic block full of holes. Three rules and you can build anything in this book.

A column is one wire. The five holes stacked in each little column are joined together inside the board. Drop two legs into the same column and they're connected — no solder, no fuss.

The side rails carry power. The long + and stripes down each edge run the full length of the board. Feed them from your battery once, and every column can tap in.

In one loop, order is free. The same current flows through everything in a series loop, so a resistor before or after the LED limits it identically. Position is tidiness, not function — a freeing thing to learn early.

What has a direction, and what doesn't

The battery, LED, and diode have a + and end — put them in the right way round. A resistor or jumper doesn't care which way it goes. When something won't light, check polarity first.

Column = one node. Rails = power. Order is free; polarity isn't.
The Breadboard2
Build · B · the first project

The Beacon.

One device, built across the whole course — a flashing signal light you engineer part by part.

Every chapter quietly adds to one machine. You light an LED (Chapter 1), size its resistor so it doesn't burn out (Chapter 3), add more lights in series and parallel (Chapter 2), store charge to make it fade (Chapter 4), drive it harder with a transistor (Chapter 6), protect it with a diode (Chapter 7), and finally give it a heartbeat with a 555 (Chapter 10). The result is the Beacon: a bright, blinking signal that runs all night on a 9-volt battery.

The shopping list

A breadboard, three red LEDs, a 555 timer, an NPN transistor, a signal diode, an assortment of resistors and capacitors, two pushbuttons, a 9 V battery and clip, jumper wires, and a light sensor. A few dollars, all common parts — Adafruit, SparkFun, and DigiKey each stock everything.

You don't learn the parts and then build. You build, and the parts teach themselves.
The Beacon3
Build · C · the shelf

What's next
to build.

The Beacon is the first project, not the last. Each one below reuses the same bench and parts you already know — and teaches one new trick.

Once the Beacon blinks, the same skills carry straight into bigger devices. The shelf grows; each project is self-contained, with its own parts list and its own payoff.

The Beacon A flashing signal light  live
The Spinner Make a motor turn & control its speed
The Sequencer A chasing row of lights
The Mood Lamp A smooth fade you can dial
The Buzzer Make a sound — the 555 as a tone

Each project lives on its own page at fathohm.com, with a live design bench, a parts list, and a printable build card — just like the Beacon.

Same bench, same parts, one new idea each time. That's how a hobby becomes a habit.
The Project Shelf4
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Now go build something.

The whole course — animations, sliders, quizzes, and every project bench — is free at fathohm.com. These three guides are yours to keep, mark up, and pass on.

Fathohm · How to engineer · First edition
Fathohm · Level 3 of 3fathohm.com