Simulating #
Breadpad runs your circuit through ngspice, the standard open-source SPICE engine — the same numerical models used in professional EDA tools.
Probes #
Arm the Oscilloscope tool (P) and tap tie points to drop measurement probes; tap a probed hole again to remove it. Probes record the voltage at their node.
The free tier plots signals from up to 2 probes; Premium plots them all.
The oscilloscope pill #
The pill in the toolbar shows your probe count and — once at least one probe is placed — a live sparkline: a continuously running background simulation of your circuit, updating as you edit. A warning badge on the pill means the live run hit a simulation error.
Tap the pill to open the analysis menu.
Analyses #
| Analysis | What it does |
|---|---|
| Transient Analysis | Plot how voltages change over time. |
| Realtime | Watch signals live in a full-screen scope with adjustable time window, voltage range, and speed. |
| Operating Point | Read the steady-state DC voltages now. |
| SPICE Shell | Edit and run the raw SPICE netlist (see SPICE Netlists). |
The first three need at least one probe; the SPICE Shell is always available. Other SPICE analyses (AC sweeps, DC sweeps, noise, …) can be run from the SPICE Shell with standard dot-commands.
Transient analysis (the Analyzer) #
The Analyzer chart plots every selected signal over time. Controls:
- Chart domain — start/end time, a zoom slider, and the number of data samples.
- Temperature (Premium) — set the nominal and operating temperature; parts with temperature coefficients react accordingly.
- Data export (Premium) — Export CSV writes the plotted data; Export WAV Audio renders a dedicated 44.1 kHz run of the signal as an audio file.
- Simulator Logs — the raw ngspice output for the last run, useful when a simulation fails.
The free tier plots up to 2 signals at once on results charts; Premium is unlimited.
Tolerances, Monte Carlo, and sweeps #
- Setting a tolerance % on a part (Premium) makes each simulation run sample that part’s value from a Gaussian distribution — run repeatedly to see Monte Carlo spread. Values without an explicit tolerance use an implied tolerance from their significant figures.
- Temperature coefficients (TC1/TC2, Premium) shift part values with the simulation temperature.
- Component editors offer a one-tap sweep of their own value (e.g. “Sweep Resistor”) that runs a DC sweep across the value ± tolerance and charts the result.
When a simulation fails #
Every netlist failure is surfaced with the offending ngspice message. The most common causes: a node with no DC path to ground, a short across a source, or an unconnected lead. See Troubleshooting.