Fluxa

Fluxa is a browser-based workspace for drawing, arranging and exploring simple electronic circuits.

• Version: 1.5
• Repository: github.com/Arvanta/Fluxa

What is included

• A component library with passive components, sources, ground, diodes, bridge rectifiers, LEDs, BJTs, MOSFETs, transformers, 555 timers and 741 op-amps.
• A small selectable catalog of example market models such as 2N2222, 1N4007, 1N4148, IRFZ44N, NE555P and LM741CN.
• SVG circuit editor with drag/drop, move, snap, pan, zoom, Undo/Redo, component rotation, duplication, deletion and nearby-terminal auto-connect.
• Wiring by clicking two terminals or dragging between terminals. Existing wires can be selected, reconnected or removed.
• Schematic and Breadboard views. Breadboard view can use either a simple light background or a perforated-board background.
• Dark and light application themes.
• Seven guided Learn Mode builds: LED + resistor, voltage divider, RC filter, push-button LED, NPN switch, 555 timer and basic op-amp concepts.
• Beginner hints that highlight the next relevant library part or circuit component without locking the editor.
• A real circuit solver (solver.js): modified nodal analysis for the DC operating point (parallel branches, loaded dividers, switches, diodes, LEDs, Zeners, bridges, BJTs, MOSFETs, op-amps) and a time-domain transient engine for capacitors, inductors and AC sources.
• Measurement panels backed by that solver: a virtual meter whose probes read the nodes you choose, Quick Measure, an oscilloscope and spectrum computed from the simulated waveforms, a thermal view and the Smart Circuit Inspector.
• Simulation-only visual feedback for active wires (branch currents and directions from the solver), node voltage labels, LED brightness, optional thermal heatmap and amber open-path previews.
• Short glossary cards in Properties for common component terms and units.
• PNG and SVG output based on the active canvas view.
• Fluxa JSON export and confirmation-based JSON import.
• Local project storage, share-link generation, and a standalone Fluxa.html build.

Run

Standalone version

For normal use, no server, backend or package installation is required. Open this file directly in a modern browser:

Fluxa.html

Modular source version

index.html references separate local CSS, JavaScript and asset files. A small static server is recommended while developing or modifying the modular source:

cd fluxa
python3 -m http.server 4173 --bind 0.0.0.0

Then open http://localhost:4173.

Basic use

1. Drag a part from Library onto the canvas, or click its + button.
2. Use the combined Select & Wire tool (shortcut V or W).
3. Click two terminals, or drag from one terminal to another.
4. Select a part or wire to reveal its small contextual action bar.
5. Keep Quick Measure enabled to show the lower-right readout; click a wire or component to inspect it. Turn Wiring off to click terminal nodes instead of starting wires.
6. Open Learn to start a guided build; Beginner hints remain optional and do not restrict the editor.
7. Use Export to create PNG, SVG or JSON output, or choose Import Fluxa JSON to reopen a saved circuit.

Themes and views

• Use the Light / Dark button in the top bar to switch the application theme.
• Use Schematic / Breadboard in the editor toolbar to switch the circuit view.
• In Breadboard view, turn on Real board to get a solderless breadboard: parts plugged into the same 5-hole column strip or power rail are connected. Arrange on board places two-leg parts automatically (series neighbours share a column strip); switching views restores each view's own layout.
• ERC tab: floating pins, missing ground, parallel/shorted sources, single-use net labels; click an item to jump to it.
• Export → Bill of materials (CSV), SPICE netlist (.cir); Import netlist reads SPICE (.cir) and KiCad (.net).

Project files

fluxa/
├── index.html                     # Main modular entry point
├── styles.css                     # Application styles
├── app.js                         # Editor state, rendering and interactions
├── solver.js                      # DOM-free MNA circuit solver (DC + transient)
├── Fluxa.html                     # Generated standalone single-file build
├── assets/
│   ├── fluxa-logo.png             # Application logo
│   ├── social-preview.png          # GitHub social preview image
│   ├── screenshots/
│   │   ├── fluxa-schematic.png    # Dark-theme README screenshot
│   │   └── fluxa-light.png        # Light-theme Breadboard README screenshot
│   └── fritzing/                  # Selected reference SVG assets and attribution
├── vendor/
│   └── konva.min.js               # Local Konva bundle for the mini-map
├── tests/
│   └── solver.test.js             # Solver unit tests (node tests/solver.test.js)
└── scripts/
    ├── build_standalone.py        # Rebuilds Fluxa.html
    ├── test_regression.py         # Browser regression tests (Playwright)
    └── test_verify.py             # Measurements-tab / About smoke test

Standalone build

Fluxa.html is a portable version with the application CSS, JavaScript, Konva bundle and logo embedded in one file.

After changing index.html, styles.css, app.js, solver.js, the logo or Konva bundle, regenerate it with:

python3 scripts/build_standalone.py

Current limitations

Fluxa solves circuits with its own compact nodal-analysis engine and simplified, piece-wise-linear part models (constant-threshold diodes, an LED lookup curve, switch-style MOSFETs, a three-state BJT, a finite-gain op-amp with rail clipping). With AC sources the readouts are steady-state RMS values from the transient engine and the oscilloscope shows the real waveform. 555 timers are not simulated yet and transformers only couple AC. It is a learning tool and not a replacement for SPICE. There is no backend, authentication or real-time collaboration layer.

Credits

Selected local reference assets under assets/fritzing/ originate from the Fritzing Parts Library. See assets/fritzing/ATTRIBUTION.md for the included attribution note.

Tests

node tests/solver.test.js                                   # solver unit tests, no dependencies
python3 -m http.server 4173 &                               # then, with Playwright installed:
python3 scripts/test_regression.py http://127.0.0.1:4173/index.html
python3 scripts/test_regression.py http://127.0.0.1:4173/Fluxa.html

Learning, projects and offline use (v1.5)

• Learn: seven guided lessons that check your circuit's result, plus nine "broken circuit" challenges.
• Examples: 15 ready-made circuits.
• Projects: several circuits saved in your browser (IndexedDB).
• Offline / install: serve the folder over http(s) (or run node server/server.js) and install Fluxa from your browser; it then works offline.
• Short links: run node server/server.js; the Share dialog then offers short links stored on that server. See HANDOFF.md for limits.