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

Similar projects worth following
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.

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


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


fbrd - 35.60 kB - 08/18/2022 at 13:56


fsch - 27.63 kB - 08/18/2022 at 13:56



Enclosure fabrication file for CNC milling

AutoCAD DXF - 165.89 kB - 08/18/2022 at 11:18


View all 7 files

View all 32 components

View all 2 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?



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

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates