https://blog.3v3.dev/ News and how-tos from 3v3.dev: design PCBs with your AI agent. en-gb https://blog.3v3.dev/the-monday-detector/ https://blog.3v3.dev/the-monday-detector/ Sun, 25 Oct 2026 04:00:00 +0000 A clock and one red LED that glows only on Mondays. Completely unnecessary. Everyone agrees it is accurate. https://blog.3v3.dev/the-lie-detector-pen/ https://blog.3v3.dev/the-lie-detector-pen/ Sun, 25 Oct 2026 03:00:00 +0000 A sweat sensor in the grip and one red LED. Not accurate. Extremely persuasive. https://blog.3v3.dev/lift-music-badge/ https://blog.3v3.dev/lift-music-badge/ Sun, 25 Oct 2026 02:00:00 +0000 Stand still for ten seconds and it plays bossa nova. Every queue becomes a lift. https://blog.3v3.dev/keyboard-crumb-seismograph/ https://blog.3v3.dev/keyboard-crumb-seismograph/ Sun, 25 Oct 2026 01:00:00 +0000 A piezo under the keyboard and a bar of LEDs: it shows exactly when the email got angry. https://blog.3v3.dev/the-nod-counter/ https://blog.3v3.dev/the-nod-counter/ Sun, 25 Oct 2026 00:00:00 +0000 It counts every nod you give in a meeting, and at five o'clock it tells you how many. https://blog.3v3.dev/the-forgotten-tea-counter/ https://blog.3v3.dev/the-forgotten-tea-counter/ Sat, 24 Oct 2026 23:00:00 +0000 It glows blue when your tea has gone cold on it again, and counts the cups you abandoned this week. https://blog.3v3.dev/the-anxious-doorbell/ https://blog.3v3.dev/the-anxious-doorbell/ Sat, 24 Oct 2026 22:00:00 +0000 It blushes, it hides its button from strangers, and it rings only when it is sure. https://blog.3v3.dev/the-boredom-battery/ https://blog.3v3.dev/the-boredom-battery/ Sat, 24 Oct 2026 21:00:00 +0000 Every press saves a little charge. About 330 presses later, it all goes out in one bright flash. https://blog.3v3.dev/morse-code-compliment-button/ https://blog.3v3.dev/morse-code-compliment-button/ Sat, 24 Oct 2026 20:00:00 +0000 Press it and it taps out a compliment in Morse. Only Morse readers get the nice things said to them. https://blog.3v3.dev/haunted-keyring/ https://blog.3v3.dev/haunted-keyring/ Sat, 24 Oct 2026 19:00:00 +0000 Pick up your keys without your wallet and the keyring whispers: you forgot something. https://blog.3v3.dev/the-cat-translator-that-only-says-no/ https://blog.3v3.dev/the-cat-translator-that-only-says-no/ Sat, 24 Oct 2026 18:00:00 +0000 Every meow gets the same answer: one red LED blinking NO in Morse. An ATtiny85, a microphone and a coin cell. https://blog.3v3.dev/print-your-board-at-true-size/ https://blog.3v3.dev/print-your-board-at-true-size/ Sat, 24 Oct 2026 17:00:00 +0000 A 1:1 print with a ruler, before you pay for five boards: it showed our badge 0.4 mm longer than a bank card. https://blog.3v3.dev/business-card-circuit-board/ https://blog.3v3.dev/business-card-circuit-board/ Sat, 24 Oct 2026 16:00:00 +0000 Black soldermask, the name in bare copper, no parts: a business card made the way boards are made. https://blog.3v3.dev/wifi-doorbell-button/ https://blog.3v3.dev/wifi-doorbell-button/ Sat, 24 Oct 2026 15:00:00 +0000 An ESP32-C3, one button and a light: where the antenna goes, and what get_impedance says about the USB lines. https://blog.3v3.dev/singing-fuse/ https://blog.3v3.dev/singing-fuse/ Sat, 24 Oct 2026 14:00:00 +0000 When the fuse blows, the board plays Chopin's funeral march and lights an R.I.P. LED. You will know which part gave its life. https://blog.3v3.dev/the-sympathy-die/ https://blog.3v3.dev/the-sympathy-die/ Sat, 24 Oct 2026 13:00:00 +0000 Roll badly three times running and, one time in three, it quietly gives you a six. Rigged, but kind. https://blog.3v3.dev/pomodoro-timer-you-can-hold/ https://blog.3v3.dev/pomodoro-timer-you-can-hold/ Sat, 24 Oct 2026 12:00:00 +0000 An ESP32-C3, twelve LEDs and one button: 25 minutes of work, 5 of rest, and a tall time-lapse of the board being made. https://blog.3v3.dev/the-reverse-night-light/ https://blog.3v3.dev/the-reverse-night-light/ Sat, 24 Oct 2026 11:00:00 +0000 Brightest at noon, dark at midnight, and absolutely certain about it. One light sensor, one transistor, six LEDs. https://blog.3v3.dev/moon-night-light/ https://blog.3v3.dev/moon-night-light/ Sat, 24 Oct 2026 10:00:00 +0000 A board cut as a crescent moon: five warm white LEDs that fade in when the room gets dark. https://blog.3v3.dev/usb-c-power-meter/ https://blog.3v3.dev/usb-c-power-meter/ Sat, 24 Oct 2026 09:00:00 +0000 A USB-C power meter for projects, and ir_drop's map of where the millivolts go. https://blog.3v3.dev/the-houseplant-hostage-note/ https://blog.3v3.dev/the-houseplant-hostage-note/ Sat, 24 Oct 2026 08:00:00 +0000 A board shaped like a garden stake: the point is a soil probe, and when it is dry a small speaker says 'We have your fern. Bring water.' https://blog.3v3.dev/the-self-aware-blinky/ https://blog.3v3.dev/the-self-aware-blinky/ Sat, 24 Oct 2026 07:00:00 +0000 One LED, one job, and every 1,024th blink a long pause to think about it. Two timers, a counter and a coin cell; no code. https://blog.3v3.dev/weather-station-that-lasts-a-year/ https://blog.3v3.dev/weather-station-that-lasts-a-year/ Sat, 24 Oct 2026 06:00:00 +0000 An ESP32-C3, a BME280 and three AA cells: the sums for a year, and what written_review said about the board. https://blog.3v3.dev/controller-board-rotary-encoder/ https://blog.3v3.dev/controller-board-rotary-encoder/ Sat, 24 Oct 2026 05:00:00 +0000 The first block of a modular controller: an encoder in a ring of 16 RGB LEDs, power on every edge and an ESP32-C3 underneath. https://blog.3v3.dev/the-countdown-to-nothing/ https://blog.3v3.dev/the-countdown-to-nothing/ Sat, 24 Oct 2026 04:00:00 +0000 It counts down from a random number of hours. At zero, nothing happens. Then it starts again. https://blog.3v3.dev/houseplant-lawyer/ https://blog.3v3.dev/houseplant-lawyer/ Sat, 24 Oct 2026 03:00:00 +0000 A plant sensor that escalates: polite reminder, letter before action, formal notice, then a 90 dB buzzer. One duplicate_board and four parts. https://blog.3v3.dev/meetup-badge/ https://blog.3v3.dev/meetup-badge/ Sat, 24 Oct 2026 02:00:00 +0000 HELLO in Bungee, my name is in Caveat, a white panel to write on and two colour-changing LEDs: a badge set in real fonts. https://blog.3v3.dev/swap-one-part/ https://blog.3v3.dev/swap-one-part/ Sat, 24 Oct 2026 01:00:00 +0000 Swap a part on a finished board and let the ratsnest say what is left to wire. https://blog.3v3.dev/decision-wheel/ https://blog.3v3.dev/decision-wheel/ Sat, 24 Oct 2026 00:00:00 +0000 Press SPIN and a light runs round ten answers and stops on one. No code. And groups, to keep your boards tidy. https://blog.3v3.dev/your-house-style-five-questions/ https://blog.3v3.dev/your-house-style-five-questions/ Fri, 23 Oct 2026 23:00:00 +0000 Five questions set the rules every new board starts from, and a dry run checks them before they are kept. https://blog.3v3.dev/lock-the-revision-you-ordered/ https://blog.3v3.dev/lock-the-revision-you-ordered/ Fri, 23 Oct 2026 22:00:00 +0000 Lock what went to the factory; every later change goes into a new revision. A USB-C desk light from 0.10 to 0.11. https://blog.3v3.dev/secret-knock-box-lock/ https://blog.3v3.dev/secret-knock-box-lock/ Fri, 23 Oct 2026 21:00:00 +0000 Knock the rhythm and the box opens. Net classes keep the solenoid's wires wide and the piezo's wire apart. https://blog.3v3.dev/clap-on-desk-lamp-switch/ https://blog.3v3.dev/clap-on-desk-lamp-switch/ Fri, 23 Oct 2026 20:00:00 +0000 Clap once for on, once for off, with no code, and the routing report that found the two wires to shorten. https://blog.3v3.dev/ask-why-check-what-your-agent-chose/ https://blog.3v3.dev/ask-why-check-what-your-agent-chose/ Fri, 23 Oct 2026 19:00:00 +0000 Which values did somebody choose? The why tool says, and here it caught a 1 A track left at the default width. https://blog.3v3.dev/five-mistakes-the-checks-caught/ https://blog.3v3.dev/five-mistakes-the-checks-caught/ Fri, 23 Oct 2026 18:00:00 +0000 Five common mistakes made on purpose, what the checks said about each, and one undo for each. https://blog.3v3.dev/eight-keys-for-a-10-inch-rack/ https://blog.3v3.dev/eight-keys-for-a-10-inch-rack/ Fri, 23 Oct 2026 17:00:00 +0000 A 1U panel for a 10-inch rack: the rack's slots, eight keys on white panels and an ESP32-C3 at the back. https://blog.3v3.dev/pocket-dice-that-rolls-when-you-shake-it/ https://blog.3v3.dev/pocket-dice-that-rolls-when-you-shake-it/ Fri, 23 Oct 2026 16:00:00 +0000 Shake it and it rolls; stop and it settles a second later. No code. And a true-size print to check the fit before you order. https://blog.3v3.dev/your-first-board-in-the-post/ https://blog.3v3.dev/your-first-board-in-the-post/ Fri, 23 Oct 2026 15:00:00 +0000 From the last check to the files in your inbox and the factory's order page, and what to do when the parcel comes. https://blog.3v3.dev/four-key-macro-pad/ https://blog.3v3.dev/four-key-macro-pad/ Fri, 23 Oct 2026 14:00:00 +0000 Four keys and a knob on a Raspberry Pi Pico, drawn to JLCPCB's own rules with one fab-profile command. https://blog.3v3.dev/breadboard-to-pcb/ https://blog.3v3.dev/breadboard-to-pcb/ Fri, 23 Oct 2026 13:00:00 +0000 Describe your breadboard wire by wire, get the same circuit as a board, and ask what a careful engineer would add. https://blog.3v3.dev/volume-knob-for-your-pc/ https://blog.3v3.dev/volume-knob-for-your-pc/ Fri, 23 Oct 2026 12:00:00 +0000 Turn for volume, press to mute: a Raspberry Pi Pico and a rotary encoder, with a few lines of CircuitPython. https://blog.3v3.dev/breakout-for-a-tiny-chip/ https://blog.3v3.dev/breakout-for-a-tiny-chip/ Fri, 23 Oct 2026 11:00:00 +0000 Bosch's tiny BME280 on four labelled pins for a breadboard, with everything its datasheet asks for. https://blog.3v3.dev/board-from-a-napkin-sketch/ https://blog.3v3.dev/board-from-a-napkin-sketch/ Fri, 23 Oct 2026 10:00:00 +0000 Boxes and arrows on a napkin, a photo, and 'make me this board': what the agent read, what it added, and the board. https://blog.3v3.dev/ten-things-that-cannot-be-built/ https://blog.3v3.dev/ten-things-that-cannot-be-built/ Fri, 23 Oct 2026 09:00:00 +0000 Ten requests 3v3.dev will not turn into a board, what it says back, and the fix for each. https://blog.3v3.dev/electronic-dice/ https://blog.3v3.dev/electronic-dice/ Fri, 23 Oct 2026 08:00:00 +0000 Hold the button and seven LEDs roll; let go and they show 1 to 6. A 555, a 4017 and twelve diodes, no code. https://blog.3v3.dev/science-fair-night-light/ https://blog.3v3.dev/science-fair-night-light/ Fri, 23 Oct 2026 07:00:00 +0000 A night light a child can solder in one evening: a light sensor, a knob, two transistors and an LED, no code. https://blog.3v3.dev/mains-to-5v-on-a-purple-board/ https://blog.3v3.dev/mains-to-5v-on-a-purple-board/ Fri, 23 Oct 2026 06:00:00 +0000 A mains to 5 V supply on a small purple board, and the safety rules 3v3.dev added by itself: creepage, the isolation zone and a milled gap. https://blog.3v3.dev/share-a-board/ https://blog.3v3.dev/share-a-board/ Fri, 23 Oct 2026 05:00:00 +0000 A friend opens your board's link, copies it into their own account, changes it and shares it back. https://blog.3v3.dev/usb-c-power-trigger/ https://blog.3v3.dev/usb-c-power-trigger/ Fri, 23 Oct 2026 04:00:00 +0000 A small board that asks any USB-C charger for 9, 12, 15 or 20 volts and hands it to a screw terminal. https://blog.3v3.dev/a-3d-printed-case-for-your-board/ https://blog.3v3.dev/a-3d-printed-case-for-your-board/ Fri, 23 Oct 2026 03:00:00 +0000 The board as an STL, the parts' heights, and a two-part case that prints without supports, checked before you print. https://blog.3v3.dev/fix-the-board-before-you-order-it/ https://blog.3v3.dev/fix-the-board-before-you-order-it/ Fri, 23 Oct 2026 02:00:00 +0000 Read the checks with your agent: what each warning means, the fix, and when to leave one on purpose and say why. https://blog.3v3.dev/watch-your-board-live/ https://blog.3v3.dev/watch-your-board-live/ Fri, 23 Oct 2026 01:00:00 +0000 A page that shows your board in 3D as your agent builds it: on a phone, a TV or a stream, for anyone with the link. Just ask Claude for it. https://blog.3v3.dev/on-air-light/ https://blog.3v3.dev/on-air-light/ Fri, 23 Oct 2026 00:00:00 +0000 A black USB-C sign with ON AIR in white letters and red LEDs around them. Slide it on when your call starts. https://blog.3v3.dev/water-leak-alarm/ https://blog.3v3.dev/water-leak-alarm/ Thu, 22 Oct 2026 23:00:00 +0000 A coin-cell strip that beeps when a drop of water bridges its bare pads. One transistor, no code. https://blog.3v3.dev/big-red-mute-button/ https://blog.3v3.dev/big-red-mute-button/ Thu, 22 Oct 2026 22:00:00 +0000 A palm-sized USB button that mutes your microphone, with a red light that shows what it last did. https://blog.3v3.dev/watch-an-agent-design-a-board/ https://blog.3v3.dev/watch-an-agent-design-a-board/ Thu, 22 Oct 2026 21:00:00 +0000 Twenty-four seconds from empty outline to routed copper, and the four prompts that made it. https://blog.3v3.dev/a-plant-that-texts-you/ https://blog.3v3.dev/a-plant-that-texts-you/ Thu, 22 Oct 2026 20:00:00 +0000 An ESP32-C3 board that reads a soil sensor and tells your phone when your plant needs water. https://blog.3v3.dev/connect-claude-to-3v3/ https://blog.3v3.dev/connect-claude-to-3v3/ Thu, 22 Oct 2026 19:00:00 +0000 claude.ai, Claude Desktop and Claude Code: one address, sign in, press Allow, then ask for a board. https://blog.3v3.dev/design-pcbs-with-your-ai-agent/ https://blog.3v3.dev/design-pcbs-with-your-ai-agent/ Thu, 22 Oct 2026 18:00:00 +0000 Our letter, what 3v3.dev does, and why it now has a free plan: 20 boards a month, up to 4 layers, no card. https://blog.3v3.dev/a-haptic-driver-in-plain-words/ https://blog.3v3.dev/a-haptic-driver-in-plain-words/ Thu, 22 Oct 2026 17:00:00 +0000 Six plain prompts to an AI agent, and a small blue haptic driver board with the right pins.