My experience building the MVP food computer


#1

My experience building the MVP food computer

Hello all,

I finished build the building the MVP food computer and wanted to share my experience building it. Hopefully others can find it useful in the future and I know real-world experiences is good feedback to the maintainers of the project.

Overall, it was a really positive experience, a big thanks to the open agriculture staff for having such accessible plans, an open forum, and creating an affordable way for the community to build food computers. All my interactions with you all have been really positive and I was able to get my questions answered quickly. Keep it up!

Pre-build

My background

I am fortunate that I am a software engineer, which came in handy when installing the software (more on that later). I don’t have very much hardware and electric experience, this was my first time soldering things on my own (more on how I messed that up to come). I also have almost zero experience with growing plants. I grew basil on my apartment balcony once, and it wound up overgrowing since I didn’t maintain it.

So I am pretty green (ha! because plants, get it?) in all areas except the software. I mention this because I think its good to note you really don’t need much electrical, botanical, or software experience to build a MVP food computer.

The parts

I stuck mostly to the Bill of Materials when buying parts. Some of the parts were out of date or out of stock so I had to get alternatives. I’m pretty sure I got everything from home depot, lowes, and amazon.

If I get time I’ll dig up my order history and receipts and come up with my BOM, but really the BOM should be hosted in github or a place that the community can suggest edits to keep up with out-of-date materials. If anyone is stuck on getting a part just reply to this post and I can tell you what I bought.

The cost wound up being a bit more than $300, probably close to $400 when all was said and done. I think this is because I splurged on things like a better webcam and ended up buying two raspberry pis since I thought I fried one.

The build

I stuck to the slideshows and videos in the forum post when I was building the food computer. I went out of order in a couple areas, but went in the suggested order of building the enclosure, then brain, then operational/plant parts.

I won’t go into the step-by-step build process here, that is what the documentation is for, but more share my experience and some photos. Photos were definitely worth 1000 words when I was assembling everything!

The enclosure

I cut the PVC pipes using a table top wood saw.

Then I assembled the enclosure. Easy enough once everything is cut to the proper length.

Taped the walls of the mylar exterior. Laying down the tape in a long straight line is hard! Wound up doing two strips to make sure there were no open areas.

Top and bottom mylar pieces

Secured the bottom of the enclosure with the zip ties to the frame.

Cut a hole for the exhaust fan and poked holes for the zip ties. I figured out after securing it, you have to poke two holes for each zip tie so it can loop around. I didn’t do this, the fan still stayed in place, but I taped the sides with the metallic tape to ensure its more secure. I think you are supposed to do this step later, but I did it at this stage :man_shrugging:

Walls are secured to the frame with zip ties. I used three on top per secured side. The bottom edge of the walls were left without zip ties since they are taped on.

Enclosure is done! (wood board placed on top temporarily)

This process was very straightforward, no problems here.

The brain

The brain was definitely a little challenging than the enclosure. I don’t have much electric experience so it was a learning experience.

Drilled holes in the board after marking around all of the parts on the board. Don’t forget (like I did) a larger hole in the middle for the light fixture and 2 holes in each corner to zip tie the mylar to the bottom

I cut the extension cord on the side and the end

Cut one of the DC adapter wires to connect to the relay board

Connected the extension cord according to the specs to the relay board!

Connected the DC adapter to the relay board

Taped this up

I put both the relay board and later the raspberry pi on screws upside down with nuts to keep the screws from falling though and keep the board elevated off the wood. Do not use metal nuts for this. I learned this the hard way and smoke came from my raspberry pi when I plugged it in later. I wound up getting a new one because I thought I fried it, but it turns out I wired it backwards… It still worked fine.

I would up replacing the nuts with plastic ones and that is the current setup. Pictures to come later in the post on that.

Mounted the raspberry pi as well. (Don’t do this with metal nuts for the reasons I mention above)

Next up was setting up the light fixture, I cut the ends off of the light bulbs with a finer-toothed hand saw, it wasn’t perfect, but it worked

I pushed the lamp cord through the mylar

Connected the lamp. I wasn’t sure which side was positive and negative. Someone who is more experienced with electrical helped me figure it out and I marked it on the case.

Screwed it on using the holes drilled and secured with a nut on the back.

Lights all screwed in!

Wired up the relay board and rasberry pi… this may be when its wired backwards so take it with a grain of salt :salt:

Hooked up the circulation fan. LEDs make for some good pics! :camera:

It is suspended by zip ties that are fastened with another zip tie end piece (pic is before trimming).

Secured the webcam

I soldered the humidity sensor. This is the second soldering… I actually completely messed up the first one because I soldered everything in a row together and if I remember correctly, it prevented the raspberry pi starting up correctly, which is what made me think I fried mine due to the metal nuts.

This was then attached to the wires and hung on the inside of the food computer

Added the power cord. This is everything hooked up (minus the air pump)

I attached the air pump to the inside

So here is the final raspberry pi mounting setup I went with. After the smoke incident, I put down electrical tape under the pi and the relay board. Something about exposed plywood and my wiring makes me nervous… Notice I’m now using plastic nuts. This set up works well to keep the raspberry pi elevated and good access to the SD card

Drilled holes in the tubs. I used a two inch drill boring bit (I think thats the name?) to drill the holes. That worked very well.

Tubs are in the food computer and drilled

Shot of the inside. The one thing that I forgot is to drill holes for the air pumps in the tubs, I do this later.


You are supposed to tape the plywood to the food computer, but I still have yet to do so. I really want to be sure everything is working fine before I tape it!

I used some tape with velcro on the back to secure the door. I used metallic tape at first, but that rips easier, so I would up reinforcing with duct tape.

The software install

The software install was straightforward, but hit some issues which I had to work past. I also tried to some different things, like set up headless ssh access and being a software engineer, poked around with the software, so I can’t say it was a typical install.

I have some suggestions, hopefully I don’t come off as overly critical. The software works great when installed and working and is currently running maintenance-free.

I ran into some of the issues detailed in this thread, myself and another user were able to work out everything though.

My biggest suggestion for the software is to keep the software documentation with the software in Github. I mention this in a thread already started on the documentation and detail the reasons why there. I think this would be a big improvement to the open source MVP project. Hopefully, I can find some time to make a pull request to do just this.

A few things I recall doing differently than the docs specified: I had to run the setup script with sudo, some of the scripts and commands were not capitalized in the slides and are capitalized in the repo.

I think many of the steps could be skipped by using a one-liner setup install similar to how you install homebrew. A script is kept in the github repo and you curl it and pipe to a command to run it. Copying and pasting code on a linux machine can be daunting for the non-technical (god help them if they get stuck in vim). I can submit a pull request with this way of doing things, but since I can’t update the docs along with the change, so ideally the docs move to github first.

I had some strange issue where the light would turn off a minute or two after I started up the food computer. I have no idea if its just my setup or an actual bug. I am able to work around it by adding the StartUp.py script to crontab to run every 3 minutes.

I was able to submit a fix to get rid of the caching the charts on the browser which I found really helpful, especially running the pi headless. Happy to contribute back!

I also had to tweak the webcam command in scripts/Webcam.sh to fswebcam -S 100 -r 1280x720 --no-banner /home/pi/MVP/pictures/$DATE.jpg, but I’m using a different webcam than the one in the BOM so that is probably why.

Hopefully one day I can go through a fresh install and report any issues I find.

I am running the rasberry pi “headless”, meaning I access it from another computer. Maybe I can do a post more on that later. It is nice to access the dashboard on another computer.

The dashboard is really great! I love that I can see all this info

Thanks

I am happy to say I have some seeds growing in the computer now. Hopefully this helps people who are building the MVP or deciding to build it and is good feedback for the team. If you have any questions, feel free ask in this post.

Big thanks to the openag team and everyone involved in the MVP computer. I really love that a community like this exists and the decision to keep all of this information open. :seedling: :computer:


#2

@jmitsch Thanks for documenting your build and taking lots of pictures. That was a good post.

One suggestion… If you want to want to make your build a bit safer, you could add two plastic junction boxes: one to enclose the relay board and one to enclose the wiring underneath the light bulb socket.

@Webb.Peter What do you think about the idea of modifying your build instructions to add junction boxes around all the 120 VAC wiring for the lights? Every time I see pictures posted here on the forum of bare lamp cord wiring or junctions wrapped in electrical tape, it makes me really nervous that somebody’s gonna burn down their house, electrocute their kids, or otherwise have something very bad happen. Likewise for descriptions of smoke or loud popping noises after applying power to a new build–this post has the second build report along those lines.

As a starting point, you could look at the standards that apply to household electrical wiring (e.g. National Electrical Code (NEC)). It’s a good bet that you could pick up a copy of the NEC standard in the electrical section of Lowe’s or Home Depot–or at least some kind of simplified guide for electricians. Libraries and bookstores would probably also be a good source of books on complying with building codes that apply to electrical wiring for home improvement projects.


#3

@wsnook Thanks for the suggestion, I think the junction boxes or a similar solution would be a worthwhile addition to MVP. It is good to know I am not the only one concerned about amateur electrical work and exposed plywood. If/when I make these enhancements, I’ll be sure to document it and share


#4

Yeah, wall power is worthy of respect and caution because it can kill, injure, or start fires. My current attitude is the result of a couple close calls in the days before I wised up and got a lot more careful.

One thing that’s really nice to have in your toolkit is a non-contact voltage tester. I’ve got a Fluke 2AC VoltAlert that I use any time I’m working on wiring for lights, outlets, or switches. It’s very good for making 100% sure that things that aren’t supposed to have voltage on them really are not powered.


#5

Thank you Mr. Mitsch for that detailed journal with explicit pictures. At Stockbridge High School we have just purchased all the materials and have it ready to start after thanksgiving break. Our students will be building it with our computer science teacher who is willing and cheerful to help us in this project. Your report will be an additional reference as we get to those contexts. This is the best part of being a part of this committed group. Thank you again.