DIY Modified Bread Machine Incubator

I hereby present: “The Breadman Incubator”… TaDa!

I will admit that i never truly got into the DIYbio movement, but to say it didn’t leave an impact on me also wouldn’t be truthful. So what is this machine? And what is it for? Well, I’m glad you asked…

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In short this is a modified bread machine. Only modified to the extent that the native electronics have been replaced with an arduino (in this case an old low-cost diavolino), an arduino screw-shield, the native thermistor replaced with my own 10k ntc thermistor, and a 7 segment display from sparkfun electronics. Oh, and my own custom orange plexiglass cover! I’m quite proud of that cover! It’s main design is to regulate specific temperatures. In the case of DIYbio, in theory it can be used to regulate a temperature to be an incubator. Mainly bacteria, but it could also be used as an egg incubator, or a “hyper germination chamber” for squash seeds!. This last one is the only one i have actually tested, and i was able to see a squash seedling emerge in only one day! All of these potential uses still fall within the category of do-it-yourself biology.

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Currently the programming is limited to a pre-set temperature at 37 degrees Celsius. This is often the optimal temperature to cultivate bacteria. Or so i’m told by Wikipedia. It is also the max temperature listed as being able to germinate squash seeds. huh, who knew?

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Now, a lot of people out there might say: “why on earth would would you want to cultivate bacteria!” and one step further: “why on earth would you make a machine to grow bacteria!; Isn’t that dangerous?!” Well, umm.. I never said i actually would grow bacteria in this thing, more i created it just because i like the “i could” factor. In reality this is more of a proof-of-concept design built only to impress myself. But to answer the second question/statement.. Yes, growing bacteria is potentially dangerous.. unless you know what you are doing, what kind of bacteria is safe to work with, and proper safety protocols. Those who are familiar with the DIYbio movement will know that such safety concerns have been discussed before and that the general consensus is basically “use common sense” and “know what you are doing”. If these two principles are followed everything will be fine.

Besides, the great thing about this is that in theory this could be programmed to be it’s own sterilizer too! That’s a great plus for safety. Wikipedia say’s this:

Eventually, the entire item reaches the proper temperature needed to achieve sterilization. The proper time and temperature for Dry-Heat sterilization is 160 °C (320 °F) for 2 hours. Instruments should be dry before sterilization since water will interfere with the process. Dry-heat destroys microorganisms by causing coagulation of proteins.

I did a basic programming test to see if this machine could reach 160 degrees Celsius. It seemed like it could. The only thing needed would be a way to accurately keep track of time (like the unused chronodot i have lying around) and a button or something to initiate a programmed sterilization routine.

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In this design i have not implemented use of the motor. One because i really couldn’t think of a good use for it. But two because in my initial testing phase i accidentally destroyed both an arduino mega and my computer (i assume by not properly protecting them from the kickback electricity from the motor). Yeah, it was “my bad”! Quite literally. Yeah, so a caution to anyone who decided to build a similar project, i recommend not programming your arduino while it is plugged into the electronics of your bread machine. Program it first, and then hook it up to test it. It was only when the usb cable of my arduino were plugged into my computer (with the motor running (i think)) that bad things happened. 😦

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I found this old piece of scrap aluminum that handily fits at the bottom to cover the motor thingy. It gives it a nice flat surface. Petri dishes or anything that needs a flat surface will need something like this.

So.. Does it work?.. Yup. At least in a basic sense. It definitely could use some improvement. The programming is very basic in terms of turning the relay on if it is under a preset temperature (in this case 37°C) and turning it off it is above. While this works, it is not efficient nor really all that accurate. A PID loop would probably improve it much. Also adding a chronodot would help to have a temperature compensated accurate time clock in case i wanted to incubate something for a specific amount of time. I probably will add the chronodot at some point. A fan to help regulate temperature might also be a good fix, but if the autoclave feature were implemented it would have to be autoclavable (or removable). The fan could unintentionally introduce mold spores, but if proper sterilizing techniques were used this could be avoided. And perhaps a magnet switch to turn things off when the cover is opened.

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The arduino code for this project can be found here.

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3 thoughts on “DIY Modified Bread Machine Incubator

  1. A few years ago I picked up a lab-surplus incubator. After a few minor repairs, it was made functional again. Like you, I’ve mostly used the incubator for quick-starting seed germination. I’m currently thinking about how to install lighting inside it, to support sprouting seeds while others in the batch are still waking up.

    • Nice! glad to hear i wasn’t the only one with the idea. And thanks for visiting my blog! Speaking of lab surplus, my local university has a surplus “store” that i like to visit once in awhile. The really good stuff is rare, but comes from the science and medical departments. I few years ago i got a nice electrophoresis power supply and just the other day i finally got myself an adjustable pipette. Funny you mention thinking about adding LED’s to your incubator as i was thinking about that the other day for mine as well. Also maybe a micro fan for air circulation. Since plants absorb light in blue and red spectrum frequencies the most, many premium plant grow lights have red & blue LEDs. I have an old open source diybio blue led transilluminator (http://pearlbiotech.com/pages/blue-transilluminator-factsheet), which i got for free as a gift, but i now see they are being sold for a very high price. But they are basically made of $30 worth of parts (a 8×8 blue led matrix (https://www.adafruit.com/products/956), a pcb with resistors, and some blue Plexiglass used as a further blue light filter). I was thinking of using it, but it only has blue light and you want to have both blue light and red light, so i will have to think about a different solution for seedlings.

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