# Circuit Diagram Generator > Generate clear, beginner-friendly circuit and wiring diagrams for microcontroller projects (Raspberry Pi Pico + NeoPixels, push buttons, rotary encoders, sensors, switches, batteries) using the schemdraw Python library, in the Moving Rainbow house style — red power rail across the top, black ground rail across the bottom, amber signal wires, light component blocks, white background, and PNG + SVG output. Use this skill whenever the user wants to create, draw, generate, redraw, or update a circuit diagram, wiring diagram, schematic, hookup figure, "how the parts connect" illustration, or breadboard wiring picture for a kit or microcontroller project — even if they don't mention schemdraw by name. Also use it when adding a wiring figure to a kit's documentation page. - Skill: `dmccreary/circuit-diagram-generator` (Agent Skill, multi-file: 3 files) - Install (CLI): `npx skillmds@latest add dmccreary/circuit-diagram-generator` - Raw SKILL.md: https://api.skillmd.com/api/skills/dmccreary/circuit-diagram-generator/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Design & Media - Author: dmccreary (https://skillmd.com/u/dmccreary) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/dmccreary/circuit-diagram-generator --- # Circuit Diagram Generator Generate consistent, classroom-friendly wiring diagrams as code so they are reproducible, version-controlled, and easy to tweak. Every diagram is a small Python program that uses [schemdraw](https://schemdraw.readthedocs.io) to emit a PNG and an SVG. The goal is a picture a beginner can *follow with their finger*: power comes in at the top, ground sits at the bottom, and each wire is color-coded by what it carries. Prioritize readability over schematic formality. ## When to use this Use it for any request like "draw the circuit for the X kit", "make a wiring diagram", "show how the parts connect", "update the schematic", or "add a hookup figure to the kit page". It targets microcontroller + peripheral projects (Pico, NeoPixel strips/rings, buttons, encoders, potentiometers, sensors, battery packs), but the house style works for any small DC circuit. ## Prerequisites `schemdraw` must be importable. Check it, and stop to ask the user to install it if missing (don't silently pip-install): ```bash python3 -c "import schemdraw; print(schemdraw.__version__)" # expect 0.20+ ``` ## Workflow ### 1. Get the pin map and the electrical details — don't guess The diagram must match the code that will actually run. Read the kit's `config.py` and the lab/example source under `src/kits//` to learn: - **Which GPIO pin each part uses** (e.g. `NEOPIXEL_PIN = 0`, `ROTARY_ENCODER_PIN_A = 12`). The shared `config.py` is the source of truth — prefer it over comments. - **How switches are wired electrically.** If the code calls `machine.Pin(..., Pin.PULL_UP)`, the button/encoder uses the Pico's *internal* pull-up, so its other leg goes straight to **GND** — no external resistor and no VCC pin. This is the common case in these kits. Only show a `+`/VCC pin and pull-up resistor if the code/hardware actually needs one (e.g. a KY-040 module with onboard resistors). - **Where power comes from.** Power an addressable LED strip from **VSYS** so it runs on battery (~4.5 V from 3×AA) *and* on USB (~5 V). A battery pack feeds VSYS through the power switch. If the pin map is genuinely unavailable, ask the user rather than inventing pins — a wrong pin number in a "helpful" diagram is worse than none. ### 2. Hold the house-style layout in mind This layout is what makes the diagrams feel calm and legible. Follow it unless the user asks otherwise. - **White background.** - **Red power rail across the TOP**, **black ground rail across the BOTTOM** — this mirrors a breadboard's `+`/`–` rails and physical intuition (power up high, ground down low). It is the signature of the house style. - **Microcontroller** as a light-blue block, center-left. Put **signal/GPIO pins on its right** (facing the peripherals) and **power pins (VSYS, GND) on its left**. - **Peripherals** (LED strip, encoder, sensor, potentiometer) as light-fill blocks to the **right**, pins on their left facing the MCU. **Align each peripheral's signal pin to its MCU GPIO pin** (use the same `pinspacing`) so the wires are straight horizontal runs — slanted or jogging signal wires are the number-one thing that makes these diagrams look messy. - **Watch for the adjacent-pin overlap trap.** If two *multi-pin* peripherals (say two potentiometers, or an encoder + a sensor) attach to GPIO pins that sit next to each other, aligning each block to its single pin forces the blocks to overlap vertically. The fix: give the MCU **extra empty GPIO slots as spacers** (e.g. lay out 7 slots and leave gaps) so consecutive peripherals land on rows far enough apart for their full height. Decide the vertical budget before placing blocks. - **Power input** (battery pack + power switch) as a vertical column on the **far left**: it taps the top rail, runs down through the switch and battery, and its negative terminal drops into the bottom ground rail. - **Common ground:** every ground returns to the single bottom rail. Place one `Ground` symbol on it. - **Color = meaning.** Red = power, amber/orange = data & signal (including button lines), black = ground. Put a small **wire-color legend in the top-left**, above the power rail, and a **title** at the very top. - **Light pastel fills with dark text** so pin names stay readable; give each component class its own hue. - **Dots mark real connections.** Wires that merely cross with no dot read as not connected — lean on this instead of forcing every wire to avoid every other. ### 3. Write the generator script Copy [`scripts/circuit_diagram_template.py`](scripts/circuit_diagram_template.py) to live next to the kit's source — the repo convention is `src/kits//circuit-diagram.py` — and adapt the three marked sections: the component blocks, the signal wiring, and the power/ground wiring. The template already encodes the house style (rails, colors, legend, battery column, PNG+SVG export) and runs as-is so you have a working starting point. Set `OUT_DIR` to the kit's docs image folder (`docs/kits//img/`) so the figure lands where the page can reference it. Keep each diagram a **standalone script** (no shared import) so it stays independently editable and copy-pasteable — matching how code is stored per-kit in this repo. For the schemdraw API specifics you'll need while editing — the `Ic`/`IcPin` parameters, orthogonal `Wire` routing, the `.linewidth()` vs `.lw()` gotcha, labeling vertical elements, and white-background export — read [`references/schemdraw-cookbook.md`](references/schemdraw-cookbook.md). ### 4. Render, then LOOK at the result and iterate Run the script, then **Read the generated PNG** and inspect it like a student would. This visual check is not optional — schemdraw places things exactly where you tell it, so the first render almost always has an overlap or a slanted wire to fix. ```bash cd src/kits/ && python3 circuit-diagram.py ``` Check for: blocks overlapping each other, pin labels colliding with the block title, signal wires that aren't perfectly horizontal, labels clipped at the canvas edge, and wires crossing *through* a block. Nudge coordinates, widen a block (`edgepadW`), or reroute, then re-render. Repeat until it's clean. ### 5. Embed it in the kit page Reference the PNG from the kit's markdown with descriptive alt text, restate the color key in words, and list the connections. Pattern: ```markdown ![Wiring diagram for the showing the Pico connected to ...](img/circuit-diagram.png) Follow the colors: **red** wires carry *power*, **amber** wires carry *data and button signals*, and **black** wires are *ground*. - The strip's **DIN** (data-in) goes to **GP0**. - ... ``` For student-facing pages, add a short "how to read it" note (a dot = connected; crossing wires without a dot are not) and follow `CONTENT-GENERATION-GUIDE.md` (reading level, and the Pixel mascot voice for tips). Teacher-facing pages use the professional register with no mascot. ## Checklist before you call it done - [ ] Pin numbers match `config.py` / the lab code exactly. - [ ] Power rail is red and on top; ground rail is black and on the bottom. - [ ] Signal wires are straight and amber; power is red; ground is black. - [ ] Background is white (`d.save(..., transparent=False)`). - [ ] Both `circuit-diagram.png` and `circuit-diagram.svg` were written. - [ ] You actually opened the PNG and confirmed nothing overlaps or clips. - [ ] The figure is embedded with alt text and a color key on the kit page.