$300 Food Computer - MVP


Thanks a lot for the huge amount of work you put into this. I would like to build one of my own. Now I have a question (might be a stupid question): Is there any reason not to keep it in the bedroom, like is the fan loud or does it smell or anything like that? I don’t really have any other space to keep it.


@Dimitri Nope - that’s another benefit of having the enclosure. Otherwise, the lights can be pretty obnoxious at night - but other than a slight hum from the fan (and air pump) there isn’t really any noise. There shouldn’t be any concerns about smell (assuming you aren’t growing anything…smelly) :slight_smile:

Very interesting adaptation - I’d be interested to see your GitHub when you’re finished. It sounds like you’ve got a bit of experience with software, looking forward to seeing your build. I’d suggest starting your own thread, as you mentioned, things get complicated quick!


I like the simplicity of the reservoir filler. Do I assume it is a mechanical float valve? That is great for KISS, but down the road it may be difficult to raise or lower the fill level (if the plumbing is drilled through the reservoir wall), and you don’t have any records of how much/when it was filled (though could mark the volume level on the bottle and manually record).
I currently have a similar gravity set-up, but with a solenoid valve. If I do it over again, I would switch to a pond pump in a bucket (using the same control code); lifting a 5 gal bucket to the top of my plant rack is a disaster waiting to happen.
Let me know if you would like the control code.


HI there, I have a question.

Can I use plywood box instead of mylar ?


Yes and No. The physical box can be anything (mine is a cardboard moving box). The purpose of the mylar is not for physical support, but the need for a light reflective surface that will increase the effectiveness of the lights.
If you want to use plywood, I suggest you line the inside of the box with mylar. I used a spray adhesive to glue mylar gift wrap to the inside of my cardboard box.
The physical design of the MVP box was in part decided by what would be minimal cost, and the minimal need for tools and building skills. Plywood tends to require more tools and skills.


Thanks :slight_smile:


can I use these fans ?


Likely they would work. Do you plan to use them as they are, or take this assembly apart and wire them separately?
As long as you have a power supply that matches their voltage (12v?) you should be able to wire one of them up to the relay, and the fan/thermostat logic will work.


I am planning to use these fans separately.

Thanks for the reply.


What is the use of Air pump in this Project?


Air pumps are necessary to add Dissolved Oxygen to the water. Without them, the roots will begin to rot in a deep water culture solution.

See the earlier discussion about DO on this thread for more details: $300 Food Computer.


In hydroponics, the plant roots need a lot of oxygen. The air pump (and airstone) oxygenate the water in the reservoir, assuring the roots get plenty of oxygen.


Food Computer Update
Our Food computer is out on the main floor for our patrons to view. We have had a few questions about what it is, what is hydroponics, and comments about using the food computer as an incubator for starting spring plants.
The lettuce is doing great and we plan to leave it in there up until Monday when we would like to harvest and start a fresh batch for patrons to watch grow. We made little pulped paper pods to try and start the fresh batch with instead of the Rockwool. I see from the source you provided why it was originally chosen, but I think we might try a few different types of sprouting mediums. I see from your last response you mentioned a product called pop rooter, someone else mentioned horticubes made from peat moss. I think many of our patrons would want to use the unit to start their seedling and eventually plant outside. Peat moss would be more environmentally friendly for a transplant. I couldn’t find what the pop rooter was made from.

Thank you for the resources. Do you have any other support materials available to supply for the public? We found a brochure on hydroponic and have that set out for patrons, but if you have your own we would be happy to switch or add-on. Also, we have a passive program question of, “Would you ever grow hydroponic vegetables in your Home? Why? We will let you know the responses once we have a collection.


@DanB, @house, @Webb.Peter
MVP Startup on reboot - rc.local

I spent some time looking into this problem and discovered it was a bug I created (actually two: 1) the execution permissions were turned off, 2) If the file ran, it would exit before getting to the commands). I would give you a file to replace the current rc.local, but I cannot attach the file to this forum; so you will have to edit the file yourself. From a command prompt, open the file in an editor with:
sudo leafpad /etc/rc.local

There should be comments at the top (lines starting with #), It should look like:

This script is executed at the end of each multiuser runlevel.

Make sure that the script will “exit 0” on success or any other

value on error.

But you will likely notice that the line with “exit 0” got messed up, so the line starts with:
exit 0"
Put a # at the front of this line and don’t worry about the messy text. All the top half of the file should be comments.
Save the file and exit, then run the following command to make sure the file is executable.

sudo chmod +x /etc/rc.local

This should now run properly on the next reboot.
I changed releaseScript_Final.sh, so it now copies rc.local over to /etc, rather than editing it. And modified scripts/startup.sh so it creates log/startup.log to give you some confirmation of the boot. These new files are in github.
This has been a real nuisance, sorry for missing this.

Libraries & Food Computers: PLIX Build (Public Library Innovation Exchange at MIT Media Lab)

Ran this and confirmed the fix works. Rebooted and localhost:8000 populated immediately (no refresh needed).

I’ll run a fresh install from scratch over the weekend and update the documentation accordingly. Thanks again @webbhm for all of your hard work and troubleshooting.


Our Food Computer is flourishing and many patrons have come by to look at it and ask questions. We have been keeping a record as questions are asked. Here are some updated photos.

In the photo with the three people, from left to right we have Alford and Cynthia from the Detroit Regional Patent Office (they were here doing a program and dropped by the Science & Technology department to see what we have been working on) then myself, Stephanie, on the far right.

Here are a couple of source we have used when reading about Rockwool safety, usage, pros and cons etc.



The link for the prepared parts documentation doesn’t work. Is the file still there or is there a newer version?


I fixed this - not sure why the link stopped working. Should be good now!


Thanks a lot Peter! Works fine now.



It’s so great to see other people successfully growing and using our design as a way to showcase & start discussions about food/agriculture in your region. I know there are several urban farms (successful) around Detroit, I’d be interested to know what your plans are for the food computer going forward (personal & through work) and how we can help support you. I’m always extremely curious to learn more about the “user” especially when I know the job wasn’t easy (Sorry)!


Wow! Consider me “Schooled”. I just learned quite a lot about Rockwool (and its history), it seems like many of those referred to Rockwool as it was used for insulation. I’m curious if it still has the same negatives effects in such small quantities. I’d be interested to hear @wsnook thoughts on this, if you haven’t checked out this thread of his it’s a great source of knowledge about hydroponics / CEA:

I’ll be interested to hear how your paper experiment goes. I’ve been experimenting with Coco Coir and agree that Rockwool is far from ideal (cost, sustainability) but for right now it seems to be very common in the industry of hydroponics. All of that being said, the Rockwool I get in bulk always comes with a pair of rubber gloves. @sjolliff My suggestion: start a forum topic (similar to Will’s) to start the discussion. From my experience, a lot can go missed inside of threads but if you post a thread you’ll likely find all sorts of “experts” on growing mediums are on the forums.