Smellamatic
An open-source stink score machine you can build yourself.
Smellamatic stuffs an ESP32, a tiny fan, and a handful of gas sensors into a friendly box that estimates how funky the air around it really is — then prints a playful Stink Score on a little OLED. All the code, CAD, and wiring is free.
* Not for sale. Open-source files only.
The assembled Smellamatic v0.1 on a workbench.
A relative odor experiment, in a box.
Smellamatic is a DIY ESP32-based odor experiment. It measures relative smell intensity using common maker components and gives you a playful stink score instead of a lab-grade odor measurement.
Under the hood it’s a Seeed XIAO ESP32C3 talking to a BME688 environmental sensor, an MQ-136 for sulfur-flavored funk, and an MQ-137 for ammonia/amine vibes. A tiny 5V fan keeps fresh air flowing across everything so you’re sampling the room, not just the box.
The ESP32 mashes those readings together into a single 0–100 Stink Score and shows it on a 0.96" OLED with a little verdict like “Slight Funk” or “Criminal.” That’s the whole gag.
Translation: it’s a vibes-based gas detector you built yourself.
Front view: OLED, buttons, and the tiny fan.
Sniff. Sense. Score.
Sniff
A small 5V fan pulls room air across the sensor array so you sample what you actually want to measure, not stale gas trapped in the case.
Sense
The BME688 watches VOCs, the MQ-136 watches sulfur-like compounds, and the MQ-137 watches ammonia and amine-family funk.
Score
The ESP32 fuses the readings into a single playful 0–100 Stink Score and paints it on the OLED with a verdict word.
Important: Smellamatic is not a certified gas detector, medical device, or safety instrument. It’s a maker toy. Treat the score as a vibe, not a measurement.
The shopping list.
A pile of common maker parts. Nothing exotic, nothing soldered to the moon. Substitute freely — the firmware is designed to be poked at.
- 1Seeed XIAO ESP32C3BrainWi-Fi MCU, USB-C onboard
- 1BME688Environmental + VOCI²C, the smart-ish nose
- 1MQ-136Sulfur-like gasesAnalog, needs warmup
- 1MQ-137Ammonia / aminesAnalog, needs warmup
- 10.96" I²C OLEDScore displaySSD1306, 128×64
- 15V 30×30×10 fanAirflowSwitched via MOSFET
- 1USB-C 5V breakoutPower inOr use the XIAO USB-C
- 1Logic-level N-MOSFETFan switche.g. AO3400 / 2N7000
- —Buttons, rocker switchUI + power2× momentary, 1× SPST
- —Resistors + hookup wireMisc10k pull-ups, 220Ω, etc.
- 13D-printed enclosureContainmentSTL/STEP in the CAD files
What it actually looks like.
Photos of the device, its internals, and the build process.
Front view
The guts
Build in progress
Everything you need. All free.
Smellamatic is free to build, remix, and improve. Links below will go live as files are published — placeholders for now.
Source Code
ESP32 firmware (Arduino-flavored C++). Sensor drivers, scoring logic, OLED UI.
CAD Files
STEP + STL for the 3D-printed enclosure. Tweak it, remix it, make it bigger.
Wiring Diagram
PDF schematic and a friendly hand-drawn pin map for the soldering-averse.
Bill of Materials
Spreadsheet with part numbers, suggested suppliers, and rough hobby pricing.
Assembly Guide
Step-by-step photos walking from a bag of parts to a working Stink Score.
License: do whatever
Released under a permissive open-source license. Build one, give one to a friend, sell t-shirts about it. Just don’t pretend it’s a real gas detector.
The Stink Score, defined.
A totally vibes-based five-tier scale. It is calibrated against the rigorous scientific standard of “how mad is the person sitting next to you?”
Like a pine forest after rain.
Someone took off their shoes.
Open a window, casually.
Open ALL the windows.
Evacuate. Apologize. Reflect.
Safety disclaimer.
Smellamatic is a fun DIY relative odor meter. It is not a certified gas detector, medical device, industrial safety monitor, or air quality compliance tool. Do not rely on it for detecting dangerous gases or making safety decisions.
If you smell gas, call a professional. If Smellamatic agrees with you, that’s a fun coincidence — not a substitute.
Built in a garage, for the love of dumb hardware.
Smellamatic was created by Jaron King as a playful open-source hardware experiment combining electronics, sensors, code, and questionable smells. The goal: prove you can ship a real circuit board and a real joke at the same time.