Lay out the boards, chips and wires exactly as you'll build them, on a computer or a phone. The circuit runs the whole time you build.
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Build it
Solid-core wire goes hole to hole, 22 to 30 AWG, and lies on the board as it will be cut and bent: each one shows its length, climbs included. The build sheet prints every board's parts by reference and pin-1 hole, then its wires lowest first; the bill of materials comes as a CSV.
While it runs, Warnings lists what a real build gets wrong, each with its fix: an LED with no resistor, a chip with no decoupling capacitor, a switch clocking a chip with no debounce, a reset or a gate input left on nothing. Shorted and floating lines are counted and ringed on the board, and an LED shows the current through it.
Building it for real, in the guide →
Netlist to breadboard
Import the netlist from KiCad, EasyEDA, Digital, Logisim or SPICE. What the wiring still lacks is drawn as tape across the board, pin to pin; Auto-route lays it in one click, flat on the hole grid, round what's already there.
The Nets panel, in the guide →
Schematic
The Schematic view is an editor of its own, saved with the project: start it from the board, then draw with KiCad's keys and its right-click menu. Show it on the schematic takes a part from the board to its symbol.
Export a sheet as SVG, or the whole schematic as a PDF, a page a sheet. It works by touch on a phone too.
Scope
A probe on any hole keeps a minute of history: zoom from 10 µs to 60 s, cursors, Measure and triggers on four lanes, and as many as you like with UART, SPI and I²C decoded over them Maker. Save it as PNG, or as CSV or VCD Maker. Slow the circuit to a tenth, a hundredth or a thousandth of real time, or Step it a tick at a time, and watch each edge go by. Registers, counters, RAM and the EEPROM are read and set while it runs, in decimal, hex and binary.
Seeing signals with the scope, in the guide →
History
Branch opens a copy beside the original, both running in step, every change listed as it's made: commit it back as one undo step, or discard it. On every plan, versions keep the project as it was, and a share link opens this exact view for anyone, signed out.
Saving, versions and sharing, in the guide →
Arduino
A Nano, Uno or Mega 2560 runs its sketch on an emulated AVR at 16 MHz, uploaded straight from the Arduino IDE; every pin the sketch writes reaches the circuit at that very instruction. Ben Eater's EEPROM programmer sketch runs unchanged and programs the 28C16.
His 6502 computer runs too: the W65C02S, cycle by cycle, with the 65C22 VIA, the 65C51 ACIA, the AT28C256 EEPROM and the 62256 RAM.
Going further, in the guide →
MCP
Claude, ChatGPT or any MCP client, signed in with OAuth, as you: it finds the sign-in on its own, you allow it on a consent page, and there is no key to copy. Every change it makes is in the audit log as made via MCP, with the client's name.
It runs the circuit too. With BBRouter open in your tab, its simulations run there, in a background worker that leaves the page as it is.
Parts
Everything simulated, by part number: 211 chips.
Price
Free to start
Everything in Free, and
The guide is public
FAQ
Yes: a 3D breadboard editor in the browser that simulates the circuit as it's wired, hole by hole, the whole time you build.
No: it runs in the browser, and you can try it without an account; an account keeps your projects. The Arduino IDE is only needed to compile a sketch, and it can upload it straight to a board on the bench.
Yes: the editor, the simulation and the schematic all work by touch on a phone, in a layout made for it.
211 of them: the 74LS, 74HC and 74HCT logic listed above, 43 CD4000 CMOS chips, the 555 timer, the 28C16 and AT28C256 EEPROMs, the 62256 RAM, and Ben Eater's 6502 computer (W65C02S, VIA, ACIA). Each chip links its datasheet, and a right-click shows the simulator source that runs it.
Yes: the compiled sketch runs on an emulated ATmega328P (Nano and Uno) or ATmega2560 (Mega) at 16 MHz, uploaded from the Arduino IDE or loaded as a .hex.
Its netlist, yes: from KiCad, EasyEDA (classic and Pro), Digital, Logisim-evolution or SPICE. The parts can be placed automatically, each net shows whether it's complete and Auto-route wires what's missing. The Schematic view then draws the circuit in KiCad's style, to edit with KiCad's keys and export as SVG or PDF.
The boards' tie points connect like the real thing, wires lie hole to hole as they'll be cut and bent, and the build sheet lists every part by its pin-1 hole and every wire by its holes, colour, gauge and length. While it runs, Warnings lists what a real build gets wrong (a missing resistor, decoupling capacitor or debounce, an input left floating), and shorted and floating lines are ringed on the board.
Share copies a read-only link for anyone, with the notes and the running circuit; Stop sharing ends every link to the project.
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