The archive · Product Ideas · Product decision · 2014
Matthew Arbesfeld's ~$100 DIY sous-vide cooker earns a 194-point HN thread
For an MIT fab-lab final project, Matthew Arbesfeld built a sous-vide immersion cooker from ~$100 of off-the-shelf parts with Bluetooth control.
Matthew Arbesfeld
What it had to solve
For his final project in MIT's fab-lab class (course 863.14), Matthew Arbesfeld wanted a sous-vide immersion cooker — a device that keeps water at an exact temperature for long, even cooking, a technique long reserved for high-end restaurants and only recently moving into home kitchens. Commercial units cost around $300 at the low end and $2,000 on average, and he also wanted Bluetooth control so he could run the cooker from anywhere on his floor.
How it works
Sous-vide cooking — sealing food in bags and holding it in water at a precisely controlled temperature for far longer than normal cooking times — was a technique of high-end restaurant kitchens that was only beginning to reach home cooks in 2014. The equipment was the obstacle: an average sous-vide cooker cost about $2,000 and even low-end units ran around $300. Matthew Arbesfeld, an MIT student finishing the fab-lab course 863.14, set himself the final-project task of building his own, cheaper version — and one he could control over Bluetooth from anywhere on his floor.
The electronics were almost absurdly simple. A waterproof DS18B20 one-wire temperature sensor read the water; a 25-amp solid-state relay switched AC current to cheap immersion heaters; and a BLE Mini module carried Bluetooth serial traffic to the microcontroller. A Dallas Temperature library turned sensor data into readable commands on an ATMega328, chosen because the libraries exceeded 8KB. Around that core he designed a parametric enclosure in SolidWorks and printed the two halves in PLA on a MakerBot Replicator 2, joined by a friction-fit sliding mechanism.
The finished device cooked real food: eggs at 76°C for 45 minutes with yolks that tasted like butter, a burger at 57°C seared on the grill, and a boneless ribeye held at 56°C for 90 minutes that came out medium-rare throughout — the result conventional cooking cannot reliably produce. Because the relay could switch any AC device, the unit doubled as a general temperature-controlled switch, able in principle to smoke meat or refrigerate beer. The complete parts bill was about $100, with the Bluetooth module the single most expensive item at $32.
He published the full recipe — schematic, board layout, SolidWorks file, mobile app and all code on GitHub — and posted it to Hacker News, where it drew 194 points and 137 comments. Much of the discussion focused on the AC wiring, and the page itself records the lesson: there were safety issues in the original design, and commenters prompted fixes such as crimped terminal connectors, terminal blocks instead of screw caps, a physical barrier between the high-voltage and low-voltage sides, and GFCI-protected outlets around water.
Why it lands
- The cost gap was concrete and public: roughly $100 of parts versus $300–$2,000 for commercial units gave the build an obvious value claim from the first sentence.
- Every component was off the shelf — microcontroller, waterproof one-wire sensor, solid-state relay, BLE module — so the invention lay in assembly and control software, not custom silicon or tooling.
- Bluetooth control was the feature that made the homemade unit competitive with commercial cookers rather than merely cheap, and it drove the app design around recipes and notifications.
- Publishing the schematic, CAD file and GitHub code turned a one-off student build into a recipe other makers could copy, extend or argue with.
- Inviting Hacker News to critique it turned a real safety flaw in the AC design into documented improvements, closing the loop between maker and community.
What it did
The finished cooker produced food that made the case for it: eggs cooked at 76°C for 45 minutes with butter-like yolks, a burger held at 57°C, and a boneless ribeye at 56°C for 90 minutes that came out medium-rare all the way through. Because any appliance could be plugged into the relay, the device also worked as a general temperature-controlled AC switch — the same rig could smoke meats or refrigerate beer. Posted to Hacker News, the project drew 194 points and 137 comments, where electrical-safety feedback led Arbesfeld to acknowledge and document fixes for the AC side of his original design.
What you can take
When a tool costs far more than its components, the opportunity is in the assembly: commodity parts plus published build notes can undercut an appliance by an order of magnitude.
Since then
The project page stayed live on MIT's fab-lab site, with the code on GitHub under arbesfeld/Sous-Vide. The Hacker News thread became a public design review: commenters flagged the dangers of running mains electricity near water, and the page was updated to acknowledge the original design's safety issues — crimped connectors, terminal blocks, a high/low-voltage barrier, GFCI protection. No commercial follow-up is documented in the material; what survived was the build, its food results, and a worked example of a sous-vide cooker from commodity parts at a third of the cheapest commercial price.
Sources
- Final Project: sous-vide immersion cooker
- For my final project I built a sous-vide immersion cooker (Hacker News discussion)
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