An open-source fermenter

A device to promote plant-based protein and open-source tools so that everyone can make them at home for the benefit of our planet

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At a citizen level, eating plant-based food is the best solution we've found to tackle the climate crisis. Tempeh is a natural source of plant protein obtained by fermenting legumes with fungi, it has been discovered in Indonesia several hundred years ago. It was initially an economic invention to cope with meat consumption, but it can be deployed as an innovative and regenerative solution.

We need technological help to grow tempeh in places where the climate is not suitable for its growth. The idea of our fermenter is to replicate the Indonesian climate, to cooperate with nature and help it to help us. It doesn't need to be intrusive, connected to the internet, track our habits or consume more energy than it actually needs. It just needs to produce heat according to what the growth of the mycelium requires. Only a few components are needed. Components that we can understand, repair and improve and that reconcile open-source technology with citizens and food production.

Fermenter Electronics

How does it work?

The fermenter is composed of a small fan, a heating pad, an electronic board with a micro-controller, a screen and a button, and a temperature sensor. The sensor measures the temperature in the fermenter, the heating pad produces heat in exchange for electricity and the fan spreads it evenly. The interface (screen, button) allows the selection of the ideal temperature for the desired fermentation and the programming of a timer.

The printed circuit board (PCB)

After several prototypes were made in Fab Lab Barcelona using a Roland SRM-20 mini milling machine and a single-sided PCB, we finally decided to go one step further and reduce the size of our PCB by designing a two-sided PCB to better fit the design of our fermenter. The PCB is now designed in Fusion360 and produced by a PCB manufacturer. Below are the schematic and manufacturing files.


PCB design

The PCB was designed with the following constraints in mind:

  • The display, rotary encoder and RGB LED on the top side, all other components on the other side. This is to facilitate assembly, which can be done later by a pick and place machine.
  • The USB port of the Raspberry Pico is oriented to the right. This allows easy access once assembled in the cabinet for any updates.
  • Connectors for the power supply, fan, heating pad and sensor at the front. This allows easy access to connect and disconnect inputs/outputs as required, even when fully assembled.

Fermenter cabinet

Cabinet design

The Fermenter has been designed to be placed in the kitchen as well as in the living room, or any other inspiring room, be it on a worktop or a coffee table. On the upper part is the interface, through which you can program a fermentation cycle in a simple way. To open the door, simply slide it upwards and it will naturally stop at the right height thanks to magnets. Inside, the shelves are arranged at regular intervals to ensure good air circulation between the ferments. Behind the technical panel, the fan blows the warm air generated by the heating pad downwards, and to the sides, again ensuring uniformity of heat within the cabinet. The heat rises naturally, following the shape of the Petri dishes, making fermentation a success.


The fermenter is manufactured using digital fabrication techniques which are CNC milling, laser cutting and 3D printing. The design is harmonious, unique, compact and clear with particular attention paid to the choice of materials for a sustainable product. The external enclosure is made of natural wood fibre panel dyed in the mass with organic colouring agent, very satisfying to mill with great finish and texture. The shelves and the inner technical panel are lasercut from stainless steel sheet for easy maintenance and durability. And fastening systems are complemented by 3D printed parts made of PLA, a compostable polymer obtained from corn starch.


The whole is 355mm high, 169mm wide and 169mm deep. With the door open, the maximum height is 545 mm.


Our designs use an open source licence (CC BY-NC-SA 4.0) so anyone can download, improve, and change them to fit their particular needs. The only rule is that you share these new designs under the same open licence so anyone can use and improve them. You can download a fermenter and build it yourself, or buy one from us.


This open-source fermenter would cost you about €80 per unit to produce. This is in line with the average price of small kitchen appliances such as a rice cooker for example. As far as we know, there are no domestic tempeh fermenters on the market. Only professional incubators from 300€ onwards which are bigger because they are meant to be used in professional kitchens.

In Europe, you will pay between 2 and 4 € for 100g of tempeh. If you make your own tempeh with the fermenter, it will cost you less than 1€ for 100g of tempeh. The fermenter...

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Zip Archive - 177.78 kB - 10/22/2022 at 04:24


Gerber files, Assembly, Drill files

Zip Archive - 137.90 kB - 08/18/2022 at 13:56


Adobe Portable Document Format - 39.12 kB - 08/18/2022 at 13:56


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View all 32 components

  • 2022 Hackaday Prize

    Maud Bausier10/23/2022 at 13:28 0 comments

    Okay, we have completed the final steps of the Official Rules to be eligible for the Final Round Judging of the 2022 Hackaday Prize! Everything is in the hands of the Jury now. Looking forward to hearing the results on November 5th. In any case, we are glad that our project has won the Challenge 04 Climate Resilient Communities and proud to be among the 50 finalists competing for the top prizes.

  • Our video is online

    Maud Bausier10/23/2022 at 13:26 0 comments

    We have just uploaded a 3 minute video of our open source fermenter on youtube! We had fun recording it in our home town of Barcelona, Spain and then editing it while staying in Bali, Indonesia. We are very happy with the result. We hope you like it!

  • New pictures

    Maud Bausier10/23/2022 at 10:35 0 comments

    We have added new pictures of our fermenter in the details section but also in the instructions section with some details of the assembly and the interior of our fermenter for a better understanding of how it works.

  • Put the Indonesian Climate in a box

    Maud Bausier10/23/2022 at 09:46 0 comments

    Hey! Just a nod to Indonesia with our new background photo. Being in Bali at the moment, we can confirm that the hot and humid climate here makes us feel like fermenting tempeh. We literally put the Indonesian climate in a box with our open-source fermenter.

  • Benchmark

    Maud Bausier10/23/2022 at 07:15 0 comments

    We have added a benchmark section to our details, please have a look! 

  • Code updated on Githud

    Maud Bausier10/23/2022 at 05:47 0 comments

    Find the latest execution code of the Fermenter on Github. There are new features in the interface such as an introduction, a timer, some icons, and an improved menu for a better user experience. Don't hesitate to give us feedback! We have also improved the heating system.

  • From Vimeo to Youtube

    Maud Bausier10/22/2022 at 10:28 0 comments

    Here is a quick note to say that we have moved our instructional videos from Vimeo to Youtube as we discovered that they were not watchable in some Asian countries. I hope most of you can now play them!

  • Production and fabrication files are updated

    Maud Bausier10/22/2022 at 08:17 0 comments

    We have just uploaded the production files for the board (ODB++ files, Gerber files, assembly and drilling files).

    We also uploaded the latest version of the CNC and laser cut files for the cabinets, technical panels, and shelves as well as the 3D printing file for the fasteners.

    No big changes, just to make sure that the small modifications we've made are updated here for a better manufacturing and assembly experience.

  • Fermenter electronics

    Antoine Jaunard10/20/2022 at 05:47 0 comments

    In order to make the manufacture and assembly of the fermenter easier, we have made the PCB with or without the electronic components available for sale on our website. This will allow you to get to your first tempeh faster, without having to worry about the compatibility of the different components.

    We hope this will be useful to you! Don't hesitate if you have any feebacks, we are listening.

    Electronic kit →
    PCB only →

  • Files updated

    Antoine Jaunard08/18/2022 at 14:01 0 comments

    We have uploaded the latest versions of the fabrication files. There is now everything needed to make the cabinet and the electronics. Let us know what you think about it!

View all 11 project logs

  • 1
    The printed circuit board (PCB)

    To obtain the PCB, you have three options. The first is to mill the PCB yourself using a mini-milling machine. This is what we did at the beginning of the project, but as the size of the PCB gets smaller and the number of via's increases, it becomes more and more complex, although still possible. The second option would be to send the "DOMINGO_FERMENTER_BOARD_PRODUCTION" folder to a PCB manufacturer, they would then take care of the production. The third and easiest option is to buy the PCB directly from us. You can buy it with or without components, already assembled or to solder yourself. Contact us for more details.

  • 2

    Solder the components by following the instructions printed on the PCB, or by referring to the board design or schematic file. Below is a legend of the components that could lead to confusion.

    • Q1, Q2: Mosfets
    • IC1: Voltage regulator
    • R4, R5, R6, R7: 10K resistors
    • Z1: Diode
    • R1, R2, R3: 220R resistors
    • C1, C2: Capacitors

    Soldering tips and tricks

    • We find it easiest to start soldering the small components on the back side (where the Domingo logo is) so you can keep the PCB flat on your work surface.
    • The diode has a direction and therefore a line painted on its packaging. It indicates the ground. It goes to the side of the longest line seen on the PCB.
    • The connectors have legs on both sides that must be soldered as well to strengthen the components in place. Especially because they will receive forces when connecting and disconnecting cables.
    • The direction of the Raspberry Pico can be seen from the small rectangle on the PCB indicating the Pico’s USB port. Solder it accordingly.
    • The RGB LED ground leg can be identified by the white dot printed on the PCB.
  • 3
    Connecting i/o
    • The JST-2Pin connectors are placed so that the 12V line is on the right pin and the GND line on the left pin. Make your cable accordingly. 
    • The sensor cable comes ready to use, so no potential mistakes here.

View all 8 instructions

Enjoy this project?



lhatch1 wrote 10/28/2022 at 09:19 point

I'm in if hot sauce is involved.  Also, is a Pi needed?  Off to read more.

  Are you sure? yes | no

Antoine Jaunard wrote 10/28/2022 at 09:35 point

Yes! we recommend a sriracha sauce! We wrote a recipe on our website >

A Pi is not needed, only a Raspberry Pico as the microcontroller.

  Are you sure? yes | no

Gabor wrote 08/04/2022 at 20:05 point

I am disappointed the display doesn't say "Tempehrature"...

  Are you sure? yes | no

Antoine Jaunard wrote 08/18/2022 at 14:03 point

Hehe, that's the name of an event we're planning with a friend who ferments hot sauce!

  Are you sure? yes | no

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