DIY Incubator Cooks Bacteria… Or Yogurt!

Ever wonder what kind of fecal content is in your drinking water? Do you also like yogurt? If so, this DIY Bacteria Incubator is just for you!

[Robin] is part of the BioDesign team for the Real-World project which is an interdisciplinary project featuring biology, electronics, and environmental sciences to bring together solutions for real world water problems. Since it’s a community oriented project they strive to keep it open-source and well-documented in order to share with everyone.

The DIY Incubator is a rather simple tool that can be used to help analyze water for fecal contamination, which is a problem in many third world countries. It consists of a styrofoam box, a light bulb and a home-brew Arduino which provides the PID control of the heat. For bacterial analysis, regular coliform bacteria live at 35C, while fecal coliform prefer about 44C — if incubated at these temperatures the bacteria will make itself known very quickly (within about 24 hours).

Oh and if you don’t want to find out how dirty your water is, you can also make yogurt instead. Check out a short demonstration of the incubator after the break.

14 thoughts on “DIY Incubator Cooks Bacteria… Or Yogurt!

  1. Nifty, almost the exact opposite of what I’ll be building in a couple of weeks.
    I ordered two polystyrene foam boxes like that last week, plan to stack them and add a peltier to use as a universal 5L kegerator and single-batch fermenter.
    Just have to wait for the peltier to come in from China..

    1. You severely overestimate the heat-moving capacity of a peltier chip and/or are severely underestimating the heat capacity of a keg.

      You’ll be lucky if the peltier can barely keep up with thermal leak through from the insulation.

  2. I am very pleased to see more biology related posts on hackaday! This is a refreshing change from the usual arduino/raspberry-controlled blinking things. And let’s not forget about the 3d printed things with servos attached as well :D

  3. I was under the impression that you only need to boil the milk for a short period of time before letting it cool enough to add the culture to make yogurt; they suggest 20-30 minutes boiling time.

  4. In general this type of equipment is very interesting because in compact form you can produce food, fuel, polymers and recycle different types of materials, because the microorganisms are small biochemical factories.

  5. While it’s cool to see a biology hack on here, I wonder if this is another where the financial benefit is dubious. A reptile egg incubator is under £100, and does heating and cooling with peltier units to 1 degree C accuracy, and with a larger volume. I wonder if the total cost of their project beats that, when they work out the value of their time per hour working on it. Might be better to just leap ahead and start some interesting biology experiments.

    1. Hi John, this is a very good point to raise.

      The part cost for the electronics is $17 in small quantities and the PCB (including shipping) was $20 for 7 boards (<$3/board). So the control board amounts to roughly $20. Everything else can be salvaged (1 old reading lamp for bulb and wiring, food container for Styrofoam box, old mobile phone charger for wallwart). You can probably buy everything for <$10 at a junk part store or flea market.

      As for time, it is free if you are a volunteer citizen scientist ;) It wouldn't be fair to factor in an industry-standard engineer salary.

  6. For home use, I recommend a short chain of the small variety of “blink” incandescent indoor/outdoor fairy/Christmas lights and a “powerswitch tail” or other enclosed relay.

    The fairy lights are the big advantage: already more or less water proof, even more efficient at producing heat (less energy wasted producing light), is less likely to melt the foam, more robust against breakage, and remarkably cheap this time of year. Since an incandescent blink light spends more time off as it warms up, the blinky part is a convenient backup if your primary temperature controller fails, and otherwise an approximation to “PID” for those of us who find “bang-bang” a better fit to an on-off relay.

    Mine got only little use for yoghurt, a bit more for ricotta, and a lot more as a proofing oven for bread.

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