Then it labeled every pin, color-coded the wires by net, produced a professional bill of materials, and added a fuse and indicator LED when I asked for them. Zero prompt engineering. A single paragraph, three follow-ups, twelve real components, one working schematic. This is Circuitcaster with an AI in the driver's seat.
Pasted verbatim into the Claude side panel next to app.circuitcaster.com. No custom system message, no examples, no schema hints. Just this:
Opus navigated to app.circuitcaster.com on its own, read the site's /llms.txt AI manual, discovered the window.CIRCUITCASTER driving surface, and built the whole thing. It saved the project as "recharge" and told me how it wired everything.
Prompt: "label all the pins and use wire colors that make sense, label each component also for easy placement". Opus took 100 more actions to apply a net-based color palette (each net = a distinct color) and label every single pin by function. Saved as a new project so the original stayed untouched.
Pin labels applied automatically per Opus's design:
Opus produced the BOM with practical notes on values, footprint variants, and current-rating trade-offs — the kind of context a good engineer includes. When I asked to add fuse + bypass cap + indicator LED, it added four more parts to both the schematic AND the BOM in one turn.
| Ref | Component | Suggested value / part | Qty | Notes |
|---|---|---|---|---|
| U1 | Buck regulator (step-down) | LM2596S-5.0 | 1 | TO-263-5 / TO-220-5. Fixed 5V so FB ties direct to output. |
| L1 | Power inductor | 33 µH, ≥2 A | 1 | Shielded preferred. |
| D1 | Schottky diode — reverse-blocking | SS34 / 1N5822 | 1 | Blocks night-time back-drain through the panel. |
| D2 | Schottky diode — flyback | SS34 / 1N5822 | 1 | Fast recovery, low Vf. |
| C1 | Input bulk cap | 470 µF, 25 V electrolytic | 1 | Rated above 12V panel voltage. |
| C2 | Output smoothing cap | 220 µF, 16 V electrolytic | 1 | Low-ESR recommended. |
| C3 | Input bypass cap | 0.1 µF ceramic, 50 V | 1 | Across U1 VIN–GND, placed close to the regulator. |
| F1 | Fuse + holder | ~2 A slow-blow | 1 | In series on the panel + line, before D1. |
| R1 | LED series resistor | 1 kΩ, 1/4 W | 1 | ~3 mA at 5V. |
| LED1 | Power/charge indicator | 3 mm LED (any color) | 1 | 5V → R1 → LED → GND. |
| J1 | Panel input connector | 2-pin screw terminal, 5 mm pitch | 1 | +12V and GND from solar panel. |
| J2 | USB-A output connector | USB-A female, 4-pin | 1 | VBUS, D−, D+, GND. D+ ↔ D− shorted so phones draw full DCP current. |
Rows tinted amber are the four parts Opus added when I asked for optional protection + indicator: bypass cap, fuse, current-limit resistor, indicator LED.
Every one of these is a genuine engineering deliverable. None of them required prompt engineering, worked examples, chain-of-thought scaffolding, or agent frameworks. Circuitcaster exposes a machine-readable manual at /llms.txt and a JavaScript surface at window.CIRCUITCASTER. Opus reads them and drives the app the same way an engineer would — just faster.
Point any AI browser at Circuitcaster and give it a naked prompt. See what comes out.
⚡ Open Circuitcaster