# Ohmforge

> Draw a circuit, switch it on, and measure it with real-feeling bench instruments. Ohmforge is a free electronics lab in your browser: a schematic editor with 40+ parts, its own SPICE-style simulator (DC operating point, DC sweep, AC/Bode and transient analysis) and virtual instruments – multimeter, 4-channel oscilloscope, function generator, current-limited bench supply, Bode plotter and logic probe. Current flow is animated, voltages are colour-coded and overloaded parts burn out, so you see what a circuit does before you build it. Everything runs locally; projects stay on your device.

Ohmforge (Virtual electronics workbench) is a premium app of usefulweb.site (https://usefulweb.site/): a full program that runs in the browser. Its engine is deterministic and the same functions are exposed as tools, so an agent can compute exactly what the app shows.

## Use it
- Landing page: https://ohmforge.usefulweb.site/
- Workspace (browser app): https://ohmforge.usefulweb.site/app - open a project with https://ohmforge.usefulweb.site/app#project=<base64url-encoded project JSON> or a template with https://ohmforge.usefulweb.site/app#template=<id>
- Project file format (JSON Schema): https://ohmforge.usefulweb.site/project.schema.json
- Tutorials: https://ohmforge.usefulweb.site/tutorials
- JSON API: POST https://ohmforge.usefulweb.site/api/v1/tools/<toolId>/calculate (catalog: https://ohmforge.usefulweb.site/api/v1/tools)
- OpenAPI: https://ohmforge.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://ohmforge.usefulweb.site/mcp

## Engine tools
- [Ohmforge DC Operating Point](https://ohmforgedcoperatingpoint.usefulweb.site/): SPICE netlist in, node voltages, branch currents, power and overload warnings out. API: POST https://ohmforge.usefulweb.site/api/v1/tools/ohmforge-dc-operating-point/calculate · MCP tool `ohmforge_dc_operating_point`
- [Ohmforge Transient Simulation](https://ohmforgetransient.usefulweb.site/): Simulate a circuit over time: waveforms, Vpp/RMS/frequency, CSV and a chart. API: POST https://ohmforge.usefulweb.site/api/v1/tools/ohmforge-transient/calculate · MCP tool `ohmforge_transient`
- [Ohmforge AC Sweep (Bode plot)](https://ohmforgeacsweep.usefulweb.site/): Frequency response of a circuit: Bode magnitude/phase, −3 dB corner and unity gain. API: POST https://ohmforge.usefulweb.site/api/v1/tools/ohmforge-ac-sweep/calculate · MCP tool `ohmforge_ac_sweep`
- [Ohmforge LED Resistor Calculator](https://ohmforgeledresistor.usefulweb.site/): Series resistor for LEDs, rounded to a standard value and checked with a real diode model. API: POST https://ohmforge.usefulweb.site/api/v1/tools/ohmforge-led-resistor/calculate · MCP tool `ohmforge_led_resistor`

## Formats
- Import: Ohmforge project (.ohmforge.json), SPICE netlist (.cir, .sp, .net, .txt)
- Export: Ohmforge project (.ohmforge.json), SPICE netlist (.cir), Schematic SVG, Schematic PNG, Bill of materials (CSV), Measurements / waveforms (CSV), Print sheet (PDF via the browser)

## Limits
- Device models are simplified: no temperature effects, no charge storage beyond constant junction capacitances, no breakdown in transistors.
- Op-amps have one dominant pole and symmetric slew-free outputs; the 555 and logic gates are behavioural models.
- No subcircuits (.subckt), no .param/.step/.meas, no noise or distortion analysis.
- Dense matrix solver: comfortable up to a few hundred nodes, not for very large netlists.
- Live mode runs as fast as your device allows; fast circuits (MHz) are slowed down automatically.
- Phones get a read-only view; editing needs a tablet or larger screen.