Heather the Cow SAO

a hardware talisman for OHS 2025 in Scotland

What is Heather? Why is Heather?

Heather is a 3D printed Highland cow (plural: Heathers). She’s also a SAO (Shitty Add-On)—a tiny hardware trinket designed to plug into compatible badge headers at conferences like the Open Hardware Summit 2025 in Edinburgh, Scotland. She is open source. She is adorable. She is questionably constructed. She is held together by Emotional Support & Stability Pins (ESSPs). Do not ask her to do more.

Heather exists because:

• Scotland has cows and they are glorious
• I went SAO-less on day one of OHS and nearly cried in a club on St. Laurent. We are healing.
• Electronics are crafts.

If you received a Heather from me...

There are many reasons you might be holding a Heather. Perhaps:

• I am repaying a debt
• I want to be your friend
• I want to bring you joy, whimsy, and at least one LED

Whatever the reason, handle her with care and reverence (and maybe a little hot glue). 🔥 DO NOT LOOK AT THE BACKSIDE.

If one of the pins falls out... it's okay. It was likely just an Emotional Support Support & Stability Pin (ESSP) and not critical to the glow. Probably. ; w ;

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HOW TO HEATHER

Materials

You will need:

• Filament (PLA) to print Heather and the header
• Two (2) humble components:
  • A 5mm LED
  • A 100–220Ω resistor
• Hot glue
• A dream

Downloads:

• Main .3mf file or .stl file for 3D printing
• Fake header .stl file

Assembly Guide (ish)

• 3D print the main STL with up to 4 colour changes (grid supports), and one of the DIY headers

• Use a 5mm LED + 100–220Ω resistor
• Wire it to the SAO 3.3V and GND pins
• Add pokey wires for the ESSPs (Emotional Support & Stability Pins)
• Hot glue like your badge depends on it (because it does)
• Optional: Solder to secure. Try not to melt Heather.

Assembly Guide (actually)

Step 1: Print your Heather

• Layer height: 0.2 mm
• Supports: Build plate only
• Infill: 15%
• Colour changes: Up to 4 (for maximum fashion)
• Also print a DIY header (if desired - it’s janky)

Step 2: Insert the LED

• Insert the LED into the back of Heather: anode (long leg) on the right, cathode (short leg) on the left

Step 3: Add the resistor

• Twist the resistor leg to connect to the LED anode
• Clip the extra wire after twisting

Step 4: Bend into position

• Bend the leads at right angles so they aim toward the header pins
• Don’t let the legs touch

Step 5: Add the Emotional Support & Stability Pins (ESSPs)

• Insert a pokey wire (ESSP) into the leftmost top and/or bottom header holes
• These don’t connect to anything! They’re for structure

Step 6: Power test

• Plug Heather into a 3.3V power source: a CPX, Arduino, or your badge’s SAO header
• 3.3V goes to the top row, GND to the bottom row
• If she glows: PASSED QC!! If not... check your connections, maybe moo encouragingly

PASSED QC!!!! KINDA!

QC Stickers

Heather is proudly ratchet, but she works. She's passed QC if she glows. And since I can't stop you from looking at the back, here are some recommended sticker labels to slap on:

• QC passed (kinda)
• QC passed-ish
• QC (BY)PASSED

(far right: a Heather with her own power source!)

[Coming soon: the QC sticker files]

Credits and Thanks

• Thank you Nanik for giving me my first SAO at OHS 2024! The Analog Bird SAO
• Inspired by jmarler's ShittiestSAO
• 2x3 header made using Mofosyne's Parametric Spacer for Male Headers