How to Describe a PCB to an AI (With Examples That Work)

Ask ten people to describe a PCB to an AI and you get ten very different boards back — usually because eight of those requests left out something a board cannot be designed without. Text to PCB works now: you type a description and minutes later you have a schematic, a routed board, a 3D model and factory files. The brief decides how good they are.

Here is the checklist we wish every new BuildPCB user read first: the six questions a good brief answers, four examples you can copy, and what not to specify.

The six things every text-to-PCB brief must answer

No engineering vocabulary needed — six answers, one paragraph. Miss one and the engine guesses, and a guess about power or size costs you a board order.

1. What the board must DO

Behaviour, not components. "A battery-powered temperature logger that sends a reading over Wi-Fi every ten minutes and sleeps in between" implies deep sleep, an antenna, a charge path and a low-quiescent regulator. "An ESP32 board with a sensor" implies nothing.

2. How it is POWERED

The most commonly skipped item, and the most damaging. Name the source and the numbers: USB-C at 5 V, a single-cell LiPo with USB-C charging, a 12 V barrel jack, a CR2032 coin cell. Say what the board must produce (3.3 V at 500 mA) and whether it runs with the battery removed. "Battery powered" is not an answer: a coin cell and a 2S LiPo give completely different boards.

3. The main chip or module, if you have a preference

If your firmware already targets an ESP32-S3, an RP2040, an STM32G0 or an ATtiny, say so: it becomes a hard constraint. If you do not care, say "no preference, pick something cheap and in stock" — that beats a part number you half-remember.

4. INPUTS and OUTPUTS

List everything a human touches and every wire that crosses the board edge: buttons, LEDs and what they mean, sensors and their bus (I2C, SPI, analog), displays, motor outputs with their current, relays, and the connectors you own — JST-PH, XT30, 2.54 mm headers.

5. SIZE limit and mounting

Give a maximum, not a wish: "must fit inside 50 × 25 mm", "two M2 holes 40 mm apart", "round, 32 mm diameter". If it goes into an enclosure you own, say which edge each connector sits on. Mechanical limits are cheap to state and expensive to discover later.

6. Special constraints

Anything that would make you reject a board that otherwise works: "must run three months on 2000 mAh", "it has a Wi-Fi antenna, keep copper away from it", "hand-solderable, nothing smaller than 0603". These change part selection, not just layout.

Four AI PCB prompt examples: weak brief vs. strong brief

Each strong version is copyable: swap in your numbers and paste it into the BuildPCB studio.

Example 1 — A USB-C LED keychain

What improved: the weak version never says how many LEDs, how they behave, or how it hangs on a keyring. The strong one adds the current budget, the programming header and the hole.

Example 2 — An ESP32-S3 sensor board with a battery

What improved: "runs on a battery" leaves chemistry, charging, connector and runtime undefined. The three-month target turns sleep current into a design driver, which justifies the switchable divider.

Example 3 — A motor-driver board for a small robot

What improved: motor boards fail on the numbers. Stall current, pack voltage and "1.5 A continuous per channel" size the H-bridge and the copper; the hole pattern makes the board bolt onto your chassis.

Example 4 — A USB-C charging board for a LiPo battery

What improved: the weak brief leaves out the cell size, the charge current, whether the cell is protected, and what comes out of the board.

Say this, not this

Say this	Not this
"One 3.7 V LiPo with USB-C charging at 500 mA"	"Battery powered"
"1.5 A continuous per motor channel"	"Use 40 mil traces on the motor outputs"
"An ESP32-S3 module with an integrated antenna"	"ESP32"
"Maximum 50 × 25 mm, two M2 holes 40 mm apart"	"Small"
"A temperature sensor on I2C, ±0.5 °C is fine"	"A good temperature sensor"
"Any dual H-bridge rated 1.5 A per channel, in stock"	A part number you are not sure exists
"Must last three months on 2000 mAh"	"Make it low power"

What not to include in an AI circuit design prompt

A brief describes intent and constraints. Implementation is the engine's job, and over-specifying it makes the result worse.

• Trace widths, via sizes and layer counts. State the current and voltage instead; widths follow from them and are checked automatically. The exception is a real constraint: "two layers only, my fab charges more".
• Routing and exact placement. Give the constraint behind the instruction — "keep copper away from the antenna", "the USB connector has to reach the edge" — and let placement follow.
• Part numbers you are unsure about. A misremembered suffix pulls in the wrong package or no stock. But do state a part when it is mandatory — "it must be the CH340N, my driver expects it" — and it is treated as fixed.
• Two boards in one request. A transmitter and a receiver are two projects; separate ones keep the files clean.
• Pasted datasheets. Forty pages of PDF add noise; one line — "the sensor needs 3.3 V and 10 kΩ pull-ups" — adds signal.

How to iterate after you generate a PCB from a description

The first board is a draft, and changing it is conversational. In the same project, say what you want: "move the USB-C connector to the short edge", "make the board 40 × 20 mm", "add a second LED next to the first one", "use a 3.3 V regulator that can supply 1 A".

Two habits help: name which part ("move the button next to the module", not "move the button"), and keep unrelated changes in separate messages.

After every change the board is re-checked, not patched — electrical and design rules, connectivity, track widths against your currents, parts inside the outline, connector orientation, regenerated factory files. You can also drag parts yourself in the board view and the traces follow. For a variant that keeps the original intact, start a new project; the BuildPCB manual covers the full flow.

A better brief is not a substitute for reviewing the board

A precise brief raises the odds of a board you can order, but it does not make review optional. BuildPCB is in beta, and every design should be treated as a strong first version, not a certified product.

Before sending anything to a factory, spin the 3D view and check that every connector opening faces outward and can take a cable, measure the outline and holes against your enclosure, and read the bill of materials to confirm ratings and packages. For mains voltage, high currents, batteries, motors, radio or high-speed signals — or any board that could hurt someone if it fails — have a qualified professional review it, and order a prototype before a batch.

For what happens between your paragraph and the Gerbers, read how AI PCB design works. If you are new to boards, how to make a PCB covers idea to hardware, and the other guides go deeper.

Frequently asked questions

How long should my text-to-PCB brief be?

One short paragraph, roughly 60 to 150 words. Length is not what matters — answering the six questions (function, power, main chip, I/O, size, constraints) is.

What if I do not know which microcontroller to use?

Say exactly that. "No preference, pick something cheap and in stock" is a perfectly good line, and the engine will choose a real, available part and tell you what it picked and why.

Should I name exact part numbers in my prompt?

Only when a part is genuinely mandatory — a chip your firmware needs, a module you already own, a footprint you must match. Otherwise describe the function and rating and let the engine pick from the live parts catalog.

Can I change the board after it has been generated?

Yes. Ask in plain language in the same project ("make it 40 × 20 mm", "move the connector to the short edge"), and the board is re-checked and its manufacturing files regenerated after every change.

Does a good brief mean the board is ready to manufacture?

It makes a usable first version far more likely, but BuildPCB is in beta. Review the 3D view, the outline and the bill of materials yourself, and get a professional review before ordering anything complex or safety-critical.