Ruler

Ruler

A KiCad PCB ruler that doubles as a desk reference for SMD footprints, drill sizes, and trace widths—and includes a small ATtiny85 circuit to light five LEDs. Designed by Philip McGaw.

The board is roughly 100 mm long and combines measurement scales with populated example parts you can touch, compare, and (optionally) program.

Features

Measurement & reference

• Metric and imperial ruler scales (including 1/8″ and 1/10″ subdivisions)
• Degree / protractor scale for rough angle checks
• Drill hole reference sizes
• Trace width and font size guides (mm and mil)
• SMD resistor footprints from 0201 through 2512, with separate hand-solder and machine-solder pad variants
• SMD LED examples (0201, 0402, 0603, 0805, 1206)
• Test points labelled for common pad/hole diameters (1.0–2.5 mm)

Electronics

The populated LEDs are driven by the ATtiny85. Firmware is not included in this repository—you will need to write and flash your own sketch (e.g. with Arduino IDE + ATTinyCore or avrdude via the ISP header).

Note: This ruler is intended as a reference and teaching aid, not a calibrated measuring instrument.

Repository layout

KiCAD/
├── ruler.kicad_pro      # KiCad project
├── ruler.kicad_sch      # Schematic
├── ruler.kicad_pcb      # Board layout
├── Common/              # Project symbols, footprints, design blocks
│   ├── Symbols.kicad_sym
│   ├── Footprints/      # Custom footprints (SquashedFly — https://squashedfly.eu/)
│   └── Design Blocks/
├── Libraries/           # Additional third-party symbol/footprint libraries
├── sym-lib-table
├── fp-lib-table
└── design-block-lib-table

Gerber output is configured to write to KiCAD/Gerber/ when you plot from Pcbnew.

Requirements

• KiCad 9 or 10 (project files were last saved with KiCad 10)
• PCBRulers footprint library — the board uses footprints such as PCBRulers:Metric_Ruler_96mm, PCBRulers:Inch_Ruler_3.5in_10, PCBRulers:Drills, and PCBRulers:Degree_Scale. Install the PCBruler library (or equivalent) and add it to your KiCad footprint library path if footprints appear missing.
• Standard KiCad libraries for passives, connectors, batteries, and the ATtiny symbol (project rescue lib ruler-rescue is embedded in the schematic)

Opening the project

1. Clone this repository.
2. Open KiCAD/ruler.kicad_pro in KiCad.
3. If prompted about missing libraries, confirm that Common/ paths resolve (they use ${KIPRJMOD}) and that PCBRulers is installed globally or added to fp-lib-table.

Project-local tables already point at bundled assets:

• Symbols: Common/Symbols.kicad_sym, Partsbox HTTP lib
• Footprints: Common/Footprints/

Building the board

1. Run Design Rules Check (DRC) in Pcbnew and resolve any issues for your fab’s capabilities.
2. Generate manufacturing files: File → Plot (Gerbers) and File → Fabrication Outputs → Drill Files.
3. Order from your preferred PCB fab. For best readability of the silkscreen scales and contact details, ENIG finish and a dark soldermask are commonly used on similar rulers.

Populate the optional electronics if you want the LED demo to work; the ruler scales and footprint references are useful even unpopulated.

Programming the ATtiny85

1. Connect an ISP programmer to J1 (6-pin, 2.54 mm pitch, 2×3).
2. Power the board from the CR2032 cell or according to your programmer’s requirements.
3. Flash firmware with your toolchain of choice.

Pin mapping and LED connections are defined in ruler.kicad_sch / ruler.kicad_pcb.

Credits

• Design: Philip McGaw — philipmcgaw.com · GitHub
• SquashedFly — title block worksheet (KiCAD/Common/Squashed Fly.kicad_wks) and optional PCB logo footprints (SquashedFlySilk, SquashedFlyCopper, etc.) in KiCAD/Common/Footprints/
• Ruler scale footprints from the PCBRulers / PCBruler ecosystem

License

Hardware design files in this repository are licensed under the CERN Open Hardware Licence v2 — Strongly Reciprocal (CERN-OHL-S-2.0), an open source hardware license recommended by the Open Source Hardware Association (OSHWA).

• SPDX identifier: CERN-OHL-S-2.0
• Copyright: Philip McGaw
• Full text: LICENSE

You may use, study, modify, and redistribute the schematic and PCB layout under those terms. Derivative designs must be released under the same license. If you share the design or boards built from it, include a copy of the license.