Formatting PLC Ladder Logic for Forums and Documentation

Why Ladder Logic Breaks in Web Editors

Ladder logic represented as ASCII art depends entirely on fixed-width (monospace) character rendering. Every character must occupy identical horizontal space so contacts, coils, branch lines, and rail symbols align column-by-column. Web WYSIWYG editors almost universally default to proportional fonts (Arial, Verdana, Helvetica), where an | pipe character is narrower than an M, collapsing carefully spaced rungs into unreadable noise the moment you paste.

Secondary failure modes include:

• Editor HTML sanitizers collapsing consecutive spaces to a single   or stripping them entirely
• Auto-formatting engines removing leading whitespace on paste
• Line-feed normalization converting \r\n to <br>, shifting vertical spacing
• Clipboard-to-HTML conversion embedding invisible span tags that break column alignment

ASCII Ladder Diagram Conventions

No universal standard exists, but the following character set has the widest cross-platform fidelity using only 7-bit ASCII (CP437/UTF-8 compatible):

Minimal Two-Rung Example

|----[I:0/0]----[/I:0/1]--------------(O:0/0)----|  Rung 0000
|
|----[I:0/2]----+----[I:0/3]----+----(O:0/1)----|  Rung 0001
|               |               |
|               +----[I:0/4]----+
|

Render this in Courier New 10 pt or Consolas 10 pt. Both fonts are available on Windows, macOS, and most Linux desktops, ensuring the recipient sees identical column widths.

Recommended Authoring Workflow

1. Open a plain-text editor — Notepad++ (notepad-plus-plus.org), VS Code, or even Windows Notepad. Set font to Courier New or Consolas, size 10.
2. Set encoding to UTF-8 (no BOM). Avoid Windows-1252; the curly-quote substitutions it produces corrupt pipe characters on Linux readers.
3. Draw rungs using only standard ASCII characters (codes 32–126). Avoid box-drawing Unicode (U+2500 range); they render correctly in some terminals but fail in most web forms.
4. Verify alignment by toggling the editor's word-wrap OFF and scanning column positions visually.
5. Copy the text block (Ctrl+A, Ctrl+C).
6. In the target forum or documentation system, insert a code/preformatted block first (BBCode: [code]...[/code]; Markdown: fence with triple backticks; HTML: <pre><code>...</code></pre>), then paste inside it using Ctrl+Shift+V (paste without formatting).
7. Preview before submitting. Check that pipe characters are vertically aligned and spacing matches the source.

Font and Encoding Specifications

For internal documentation (Word, PDF), set the code style to Courier New 9 pt, no kerning, character spacing = 0 pt. In Microsoft Word: Format → Font → Advanced → Kerning for fonts: uncheck. This prevents Word's automatic kerning from shifting column alignment at print time.

Exporting Ladder from the PLC IDE

The cleanest way to share ladder logic is to export a screenshot or PDF from the native IDE. This eliminates all ASCII formatting problems.

For image uploads to forums, target PNG format, ≤ 1200 px wide, ≤ 150 KB. Use IrfanView or ImageMagick to batch-resize: magick ladder_rung.png -resize 1200x> -quality 85 ladder_rung_web.png.

Workarounds for Forum Image Size Limits

Many PLC forums enforce pixel-dimension limits that are narrower than typical screen captures (commonly 800 px wide, occasionally as low as 550 px). Strategies:

• Crop to the specific rung: Select only the ladder rung area in the IDE before screenshotting. Eliminates toolbar chrome and whitespace.
• Scale the IDE zoom to 75% before capturing: reduces pixel dimensions while keeping text legible.
• Use a free image host (imgur.com, postimages.org) and embed the direct-link URL in the forum post using [img]URL[/img] BBCode. Bypasses the forum's upload pixel limit entirely.
• Attach as PDF: Most forums allow PDF attachments with higher size ceilings than images. A full-page rung printout as PDF is universally readable.