$300 Food Computer - MVP


I am troubleshooting over at @drewthomas89’s right now on his MVP. We are running into the same problem @DanB and I’m going to have a call with @webbhm to try and resolve this and will get you the fix by tomorrow. I’ll get back with you ASAP.


@DanB @Webb.Peter @webbhm

I’m linking a build guide I’ve made for the current software version. Starting from an empty SD card and following these instructions I was successful; Please let me know if you run into any problems or if any of the instructions are unclear.


Have you looked into using beneficial microbes to help with microbial antagonism? I noticed in the strawberry thread that other guy is “flushing” his strawberry water every few days. I know little in the area of hydroponics / aeroponics , but even my experience with growing random plants in jars of water seemed like they needed the water changed frequently to do well. I just assumed that this was because the water got “stale” mostly from being a anaerobic environment where bacteria could grow but also that the plant roots were dying from lack of CO2 / Oxygen. I suspected that adding a pump with a aerostone or whatever they are called might fix this, but i never got around to trying it. I just bought some [airstones] though the other day.

I’ve seen airstones used in lots of DIY window growing and diy algae bioreactors.

Check out this PDF i copied from Maximum Yield Magazine, May 2016, page 86.
output.pdf (469.3 KB)


@BioLumo I could talk about this for hours!

What you are referring to is the lack of oxygen in the root zone, we measure this as Dissolved Oxygen (DO), which is directly related to the temperature in the root zone as well. Warmer temperatures = lower DO saturation point. There’s all sorts of cutting edge techniques to increasing oxygen (nanobubbles, high-pressure aeroponics, liquid ozone, etc) but I prefer to just lower the root zone temperature if possible.

“Temperature controls the rate of plant growth. Generally, as temperatures increase, chemical
processes proceed at faster rates. Most chemical processes in plants are regulated by enzymes
which, in turn, perform at their best within narrow temperature ranges. Above and below these
temperature ranges, enzyme activity starts to deteriorate and as a result chemical processes slow
down or are stopped. At this point, plants are stressed, growth is reduced, and, eventually, the
plant may die. The temperature of the plant environment should be kept at optimum levels for
fast and successful maturation. Both the air and the nutrient solution temperature must be
monitored and controlled. A chiller must be purchased to maintain the water temperature at a
sufficiently cool level. Water temperature should be maintained at 50-68 F (15-20 C).
Temperature control of the nutrient solution is critical to controlling the pathogen population so
that the entire crop is not lost to disease”



@Webb.Peter, cool. Are you saying just controlling temperature alone can create a specific amount of DO in the water? I find that hard to believe that controlling temperature just on its own would have such a dramatic effect, but i acknowledge my ignorance in this area. Though i can see it helping.

So it sounds like you indeed are controlling root temperature (water) separate from air temp. That’s good. I had read awhile back that most plants prefer their roots to be slightly cooler than their leaves. Sounds like you are keeping the roots at 20 C while your leaves are at about room temp (22-23 C). Most human pathogenic microorganisms grow at 37C (body temp), but this is not true for all and i would think certainly not true for many plant pathogens.

Controlling temp will help with many, but i imagine many others are adapted to cooler temps and will thrive in those temps quite well (i.e. 20 C), so i think investigating other pathogen reduction techniques to be worth the effort. Hence my mentioning of Microbial Antagonism. This is a technique that works well in humans, so why not in plants. Besides i know in soil plants often grow better when grown in non-sterile non-mono environments like with beneficial fungi as the fungal networks help plants gain more nutrients. Paul Stamets work also mentions crazy cool interesting things like how fungal networks can transmit pathogen data to other plants. For example when one tree is attacked by a certain bug the fungal networks can transmit that data over miles away and the other plants that have not been attacked show a response to the bug attack by emitting certain stress chemicals. But this is in soil, not water. Still cool though.

Though not pathogenic, a good example of this adaption to different temperatures can be seen in domesticated strains of Oyster Mushrooms. The white ones grow at 55–75 °F. The blue ones grow at 45–65 °F. . And the pink ones grow at 70–85 °F.

EDIT: i forgot to add that with aeroponic piezo-based misters that if you leave them on all the time they heat up the water quite a bit from all the vibration going on. So i imagine controlling water/root temps with those could be quite the challenge.


I’m weak on the pathogen area, but I do know there is a correlation between temperature and DO. I have yet to experiment with how well air stones completely saturate water, and where exactly the line is drawn.

image (16)

This is a good thread on the topic, also Caleb drops some knowledge that’s relevant:

If you’re looking into piezo’s you should read up on the discussions about fogponics on these forums:

@BioLumo Edit: if nothing else just read this:


Hi @Webb.Peter, I am about to order from the BOM based on your 12/17 updates. Having read through this entire thread when I have found time over the last month, I noticed that you had asked if someone could create an amazon shopping list for “one click” shopping. Do you know if anyone has done this yet? I can try to make the shopping process even more seamless (you guys have done a great job already!) for the next person if there isn’t already a ready-made list. Looking forward to getting started with my wife!


@wolverine1018 I actually did go ahead and put together an Amazon shopping list for this. The reason I didn’t make it more public was because I ran into the annoying problem that it won’t let me add duplicate parts to the list. The BOM requires two 12V DC power supplies, and 2 packs of the GE bulbs. This list is complete, except for the fact that you have to order duplicates of both of those parts. If you have an idea on how to fix this let me know, I keep getting an error about having the same item twice!

Goodluck with your build, please let us know how it goes and don’t hesitate to ask any questions.

Food Computer Amazon Shopping List


Hey Peter,
Ya it seems that the list can be created but you can’t add the list to the cart in one fell swoop and you also have to update the quantity once you add the items to the shopping cart.

Also, is there a difference between the si7024 and si7021 temperature sensors? I assume that the link is correct, and the title was just fat fingered bc I am not seeing an si7024 sensor by adafruit.

For the 10’ sections of PVC, it doesn’t look like Lowe’s sells those online anymore. I had to go get those in store. No biggie, just thought I’d mention it if it should be mentioned in the BOM.


@wolverine1018 I appreciate you letting me know about problems! “SI7024” was 100% a typo, I fixed the BOM accordingly. Hows your build coming so far? Please post pics/start a thread and let me know if you have any other problems/questions.

Seriously, if anyone out there reading this has some other issue they’ve noticed with our documentation PLEASE tell us. Errors with software compilation, inconsistencies, all of it. That’s why we open-sourced it, to make it better!

That’s obnoxious - I’m tempted not to give people the link even because I worry they won’t correct the quantities and get confused. Let me know if you disagree.

Well, shoot, I’m worried they’ll stop selling them in the stores as well and that was just leftover stock. We may have to go to a smaller/larger PVC (1/2" to 1") or switch materials @drewthomas89.

Does anyone have ideas for substitutes to the PVC? Keep in mind the MVP is about price and ease of assembly. We chose PVC for a few reasons:

  1. It can be cut easily (not metal), in theory with just one tool (keyhole saw - $9 on BOM).
  2. It is standardized/easy to find locally (I’m hesitant to say internationally, but I think so?)
  3. It has connectors that do not require any power tools or extra purchases.
  4. The entire frame costs less than $20.


The build hasn’t really begun yet. I am doing some of the prep work right now, but my wife and I will be moving out to Japan in the coming weeks. I figured I’d get everything purchased and partially assembled before the movers come, and I didn’t want to have it built and up and running then have to tear it down. Will update as we make progress out there!


thanks a lot for the detailed documentation. I am student working on building a food computer, and i am just a beginner. Is it possible to find out where and how to connect the relays and sensors on the food computer ? Like some document. Sorry if this is a basic question, but I was unable to locate anything so far


@Narahari Slides 13-16 “Brain Subassembly Documentation” in the first post should contain what you need. This is the main pic we have right now of the MVP wiring, I agree it’s difficult to read, it looks like there’s an extra line in there that needs to be deleted. I’ll talk to the team about fixing this.

This is the pinout:

‘3 - SDA to si7021’
‘5 - SCL to si7021’
‘29 - light relay (relay #4)’
‘31 - (reserved for relay #3)’
‘33 - (reserved for relay #2)’
‘35 - GPIO13 fan control (relay #1)’

If you aren’t familiar with a Pi Diagram, here is that as well:


@Webb.Peter Thanks a lot for the connection diagram. I will try this out tomorrow, and figure out the wiring hopefully.

Great Job Peter.

Thanks again, Regards,


@Webb.Peter I was able to connect sensors today. Thanks a lot. I used some reference from the code.

Did you try to run any tests on the sensors you connected ? Or do you have any link where there are instructions to test the sensor ?


/home/pi/MVP/setup/Validate.sh is a script to run tests on the entire system (or read the file to see the individual tests). You can run it from a command line.
Also, running individual Python applications usually have a test function. So to test the SI7021 temperature sensor, you can run the python file /home/pi/MVP/python/si7021.py.
You can run this from the Python IDE, or from the command line:
python /home/pi/MVP/python/si7021.py


I got the sotware working thanks guys! CouchDB was finally working. It took me three tries but I made it work following the slideshow you posted @Webb.Peter. I am trying to figure out how to start reading and displaying the data, i need to work a bit on that. When I click in the data entry bottom and plug in values to test it, an error appears, is that normal?


Great to hear @Juan1! What was the reason you couldn’t get your CouchDB to work? We’ve run into problems previously as well, but we can consistently replicate and diagnose.

@webbhm added the data entry button to test some features we have in development. Unfortunately, the two-way communication requires a different type of server, which we decided to not include on this last release (security isn’t finished), for now just ignore the button.

The end of the slide deck should show you how to access the CouchDB GUI as well as how to access the charting via localhost. Keep in mind, chromium (Pi browser) sometimes requires you to “clear history” in order to have the most recent data show up. This is something we hope to solve in our next release with a remote DB/UI rather than a locally hosted server.

There is also a data.txt file inside of the MVP folder that shows you the raw sensor readings if you want to go around CouchDB.


I got that, I have the openag_ui working and I can access the UI using the URL: http://{IP Address of Food Computer}:5984/app/_design/app/_rewrite.

I see this below. My question is I dont see any reading on the sensors at Water Temperature, Air CO2 or Humidity. Is this how is it supposed to be ? Is there a way to know if the sensors are monitoring the CO2 levels and other things properly for testing purposes


Woah - @Narahari it looks like you’ve got the V2 Food Computer UI running on MVP hardware?

I’m a little confused as to what you have physically built. The $300 Food Computer/MVP has only temperature/humidity capabilities in the original build. There is code written (not thoroughly tested) for water temperature, water level, and co2 as well.

If you’ve got the V2 UI running on the MVP codebase - you’re already one step ahead of us. We started to go in this direction but so far have stayed with the more simplistic UI.
Is your code on GitHub? If so please post as well as a picture of your physical build so I have a bit more context.