Breadboard Simulator

Placing parts

Components on the left: drag a part onto the board, or click it to drop it mid-view.

• Every chip is drawn as its DIP top view with the datasheet pinout: pin 1 by the notch.
• R turns the selection a quarter turn, Shift+R the other way.
• Remove a part by dragging it back onto the Components panel, or select it and press Delete.

Wiring

Wiring works the way it does in KiCad.

1. Start — click a pin, or press W to start at the pointer. The Wire button keeps the wire tool on.
2. Draw — the wire follows the pointer with one square corner; each click fixes a corner. / turns the corner the other way and Backspace takes the last one back.
3. End — click a pin, or click along another wire to make a junction (a dot). Double-click, Enter or Esc ends it where it is.

• Only a wire's ends connect. Corners join nothing, and wires that only cross do not connect. An end that reaches nothing is marked with a small square and listed in Checks.
• Click a wire's open end, or press W over it, to carry on drawing it.
• Drag a part and its wires follow; drag a single segment to slide it; select a segment and press Delete to remove just that segment.
• Colour over the canvas chooses what wire colours mean: Signal (red +5 V, dark ground, blue inputs, violet gate signals, amber lamps) or Level (green HIGH, grey LOW). A floating net is grey dashed, a net in contention red dashed.

Breadboards

• Each numbered column has a five-hole strip a–e above the centre channel and f–j below. A pin in a hole joins that strip — the only way a breadboard connects anything.
• A chip or DIP switch dropped on the board turns and straddles the channel, pin 1 bottom left. Resistors, LEDs and displays drop into the nearest holes.
• Jumpers: press on a hole to start one, click another hole to end it.
• The rails carry nothing until you wire them, as on a real bench: run the supply's + to a + rail and − to a − rail. The top and bottom rails are separate.
• Dragging the board carries everything plugged into it. Load breadboard example in Saved shows a 74LS00 driving an LED, built this way.

Power and the supply

The VCC and ground symbols name the two rails. With no bench supply on the board they are fed an ideal 5 V, so a chip with pin 14 on VCC and pin 7 on ground simply works.

Add a bench supply for what a real one gives you: an output from 0 to 15 V (slider, typed value, presets or ▲ ▼ on its face), a current limit from 10 mA to 3 A (the face shows CC when it limits), and a power button. 74LS parts want 4.75–5.25 V: outside that you get a warning, below 3 V the chips stop, and above 7 V they are reported destroyed.

Building from an expression

Type any expression into BUILD above the board — letters, an apostrophe for NOT, · or nothing for AND, + for OR, brackets as deep as you like — and press Build. Breadboard Simulator uses spare gates in packages already on the board first, seats a new chip where there is room, and wires it all up. A term that turns up twice is built once. Find gate instead looks for the gate on the board that already works that expression out.

Probes, inputs and notes

• A logic probe reads the net under its tip: H, L, Z or X, and the voltage.
• Name your inputs: select a DIP switch and type its input names (A B C D), or press A, B, C…. Its − and + (or the − + keys while it is selected) count through every combination.
• An expression probe on an output shows its smallest sum of products and minterms, and the expression as wired; hover any part of it to light the wires that carry it.
• A truth-table probe tabulates the same function, marking the row the board sits on; a K-map probe draws it as a map.
• A pin note is a note with a tip: attach it to a pin and type in the inspector. It changes nothing electrically.
• Hover a pin to see its signal and where it comes from. Ctrl-click a pin to light the path feeding it; Shift-click to light its whole net.

Checks

The Checks tab lists every finding as an error, a warning or a note, each with the fix and a Show button that selects the parts involved. Among them:

• the supply off, shorted, set outside 4.75–5.25 V, or over its current limit;
• a chip not powered (which pin is missing) or powered backwards;
• two outputs driving one net against each other;
• a net stuck between 0.8 V and 2.0 V — typically a 10 kΩ pull-down on an LS input, which needs under 2 kΩ;
• open inputs, wire ends that reach nothing, and leads not in a hole;
• an LED with no series resistor, run too hard, or lit too faintly;
• an output asked for more than it is rated for, and resistors over a quarter watt.

Below them: the supply budget, and every package with its power state and outputs.

Parts list and library

Parts is the bill of materials counted off the board — chips, resistors by value, LEDs by colour, displays, switches, one 0.1 µF capacitor per package, jumpers and breadboards — with a to-scale breadboard plan and a rough cost to buy it all. The Library tab gives each part's pinout, pin functions, supply current and output drive, with a button to put one on the board.

Saving

Saving is automatic. The Saved tab lists your boards: click one to open it, edit the name to rename the open one, New board and Duplicate start another, and × moves one to the deleted folder. Load example board and Load breadboard example open as boards of their own.