Toby's Build Diary


I’m going to go for it. I had originally wanted to build a high pressure aeroponic system, but I found the community that exists around the food computer very compelling.

I’m located in Canada, but only 45 minutes north of the border, so I’m going to be trying to stick as close as possible to the BOM. As it stands, I’ve found most of the pieces for the motherboard, and they’re shipping their way from various corners of the world. I’m also going to make a concerted effort to avoid “hacking” as much as possible. For a first pass, I’d like to keep it as similar as possible to everyone else’s.

I’ve got nothing really exciting to say at this point, but figured I’d formally declare my intentions. No motivation like being held accountable by a bunch of internet folks.

Wish me luck, and let me know any handy tips you have.


Stuff I’ve purchased so far (prices in CAD unless stated otherwise):



Voltage Control

  • 4-Channel Relay - $16.99 x 2 = $33.98
  • AC Relay Box Back Receptacle - Haven’t purchased this yet
  • AC Relay Box Front Panel - Haven’t purchased this yet
  • AC Plug - Already had a few of these lying around
  • AC Extension Cable - $4.80


Air Conditioning

  • Heater - Haven’t purchased this yet
  • Humidifier - $13.76
  • USB Wall Adapter - $15.99 - I hate the tiny little cubes that are listed on the BOM (well, not those exactly). I’ve purchased plenty of similar products and the quality all over the map - mostly not great.
  • Circulation/Vent Fans - $11.99 * 2 = 23.98
  • Fan Guards - $3.09 * 2 = $6.18
  • Fan Louvres - Haven’t purchased this yet

Environmental Sensing

Enclosure Sensing

Water conditioning

Water sensing

  • Water Temperature and EC Sensor - Haven’t purchased this yet
  • pH Sensor - Haven’t purchased this yet


Additional Components

  • Sacrificial AC Extension Cable for high gauge wire - Have some regular cable lying around
  • Wago Lever Nut Assortment - $39.99 (USD)
  • Heat Shrink Tubing - Already have an assortment around
  • Grove Cables - Haven’t purchased this yet
  • Foam mounting tape - Haven’t purchased this yet
  • Electrical Tape - Already have a bunch
  • Air Exchange Box - Haven’t purchased this yet
  • Short Screws - Haven’t purchased this yet
  • Long Screws - Haven’t purchased this yet


Glad you went for it Toby. I’m also glad you went with a Pi2. I’m working on trying to get the disk image to work on a pi3 as we speak, and its been an absolute nightmare. Best of luck!


For unrelated endeavors I have both a Pi Model A and a Pi Model B, and I recently purchased the Pi 3 Model B, but figured I’d probably run into trouble if I tried to switch out a piece like that. Seems that for the time being it’s much easier to use the Pi 2. I mentioned it here, but the image on Google Drive worked for me.


  1. Be completely confused as to how anything is supposed to work
  2. Ask for help
  3. Get directed to the Pi 2 Model B image on Google Drive (down at the bottom of the commit message)
  4. Download the 2 GB image with my relatively slow rural internet connection
  5. Go do something else while it downloads
  6. Extract it with WinRAR 5.40 beta 2 on Windows 10 - turns into a 7.6 GB image
  7. Write it to a new MicroSD card with Win32DiskImager version 0.9.5
  8. Boot the Pi, connecting it to an external HDMI monitor
  9. Get the following messages: ```
    0x25: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt
    Automatically removing dirty bit.
    Performing changes.
    /dev/mmcblk0p1: 73 files, 3706/7161 clusters
    mountall: fsck /boot [353] terminated with status 1
    fsck from u til-linux 2.20.1
1. Optimistically turn it off and back on again (and again, for good luck)  
1. Unplug it from the monitor  
1. Plug in the touchscreen display
1. It boots first shot!
1. Connect it to Wi-Fi, `apt-get update && apt-get upgrade`
1. Become extremely annoyed with the screensaver that's constantly popping up, and the entire UX on such a tiny display
1. Try and SSH in without luck
1. Give up for the night and come here to write stuff instead of doing things.


SSH should work fine. Did you use -u pi? If not, it tries to log in with your current user.


Upon booting it today, I can see the Pi no problem. Took a minute to figure out the password - mentioned in the commit message that also links the image (openag). It’s possible I had mistyped the IP address last night and then gave up immediately.

I’m super used to running Raspberry Pis headless, so it took a while to get frustrated trying to use the tiny, tiny touchscreen (and the incredibly irksome screensaver) and realize that I could VNC into it.

I installed TightVNC on my Windows machine and my Raspberry Pi using these instructions. That worked well, and the screensaver didn’t affect the VNC session. Poking around the image is interesting. There’s a lot there that seems to just have been on the machine when it was imaged, as opposed to being a blank provisioned machine. A whole bunch of images from someone’s grow - appears to have gone well!


I haven’t done much CAD beyond SketchUp, so I don’t have the software to open most of the files in the repo. I downloaded SolidWorks eDrawings software, and that appears to work for me.

Is the intention that these pieces are milled?


I managed to set the hardware up without milling. Drilling, sawing and cutting can take you a long way…


Same thing as @Peperoni… No access to a mill or CNC or any of the fancy stuff. Jigsaw costs 50$ and does most of the work just fine :slight_smile:


As @silversson mentioned a jigsaw is incredibly useful, but be sure to pick up a few holesaws for your drill. They come in handy.


Alright, I’ve picked up a Rubbermaid Bus Box for $23.66. It appears to be exactly the same dimensions as the one mentioned in the BOM (although the Amazon listing is a bit misleading, the correct dimensions are in the detail section down below).

I did my first Home Depot trip, spent about an hour and a half looking around the store and ended up leaving with about 150$ worth of stuff that wasn’t quite right… I think I’ve become spoiled by online shopping. I’m going to try and go a different route this weekend and see what I can do to get started on the mainframe, likely end up returning everything to Home Depot. PVC sheets are insanely expensive, and nobody appears to carry the style of punched steel referenced in the BOM.

At this point, I think I’m going to try going for some lighter gauge aluminum. My hope is that it will be equivalently able to meet the strength requirements, weigh less, and be far easier to work than steel. As a side perk, it should last better than steel in a humid environment. If I were at all a competent welder, I think I would try and weld the frame and save on some of the hardware costs - unfortunately I’m terrible, so I’ll stick to the original instructions. Maybe for my second food computer…


So I looked at PVC, and the Home Depots in my area don’t carry any 4’x8’ PVC sheets. What they did have available was something like this 1" x 10" x 8’ for $41. That would be a small fortune extrapolated to 4’ wide, so I got a 4’ x 8’ sheet of spruce plywood. I also got some sheet vinyl flooring, so my plan right now is to cover the plywood with vinyl, and then mount everything on top of that. I was getting vinyl flooring anyways as a cheep option to protect the floor of a new chicken coop, so I just got a little bit more. It comes 12’ wide and the salesman said they sell a minimum of 8’ long sections, so I figured this was a decent opportunity. Maybe I’ll caulk the seams or something to try and keep the water form wrecking the wood… I haven’t gotten that far.

I’m excited to have finally gotten some time to really do something. I roughly cut the plywood into sections with a worm saw, then cut it to the proper dimensions on the table saw, and it seems to have gone well. I’m lucky enough to have gotten an old table saw out of the garbage that just needed a scrub and new wiring, (Don’t mind the mess…)


I cut the base board (21 3/8" x 33"), the motherboard panel (21 3/8" x 31 7/8") , and the motherboard dock panel (15 3/4" x 20 3/4"). I decided to start here because I wanted to get a feel for how big everything was going to be.

Holding pieces together with the bus bin reservoir in place, I can finally say I’ve actually started this project:

Next step will likely be cutting all the metal to make the frame, as well as cutting out the hole in the motherboard panel where the dock panel sits. Plenty of work left.

Spruce plywood: $19.55
Sheet vinyl: 2 2/3 square yards (arbitrary amount, room for error) @ $8.82 per yard = $23.52
Small bucket of vinyl adhesive: $10.97


I mentioned that I went to Home Depot and spent a bunch of money and didn’t get anything useful. Specifically, while still trying to get a 4’ x 8’ x 1/2" PVC sheet, I picked up a 4’ x 8’ x very thin PVC sheet. I was thinking this would be workable, but not really ideal. It was also expensive.

$57.67 for the sheet.

It seemed flexible enough, but just didn’t provide any benefits that I could tell compared to the vinyl flooring. My understanding is that they’re very similar materials, the vinyl flooring is just a little bit thinner and has a print on top. You can probably see in the picture, but one side of the sheet was textured - I think this is undesirable because it either makes it more difficult to adhere to the plywood, or it causes unevenness when attaching the other hardware.

After looking through the Home Depot selection of angle metal I found nothing that was exactly the piece listed on the BOM. There were a selection of 4’ pieces, but nothing particularly usable. I ended up getting 1 1/2" inch punched steel, but it’s not uniformly punched. I’m not sure who had it in their diary, but someone warned against this as it makes things more problematic. Either way, as I noted before, it was more expensive than anticipated and not ideal.

5 x $24.80 per 8 foot section = $124.00

I visited a local metal shop - Loucon Metal Ltd - and they have an awesome selection. They don’t have anything punched at all, and it would be 84/hour to have anything done. It was very neat visiting the shop - all the different widths and thicknesses and geometries of a whole bunch of different materials. I talked to the guy there about what I was trying to do with it, and as with everyone I talk to I'm sure he's positive I'm going to grow pot. Regardless, he was very helpful, and lead me towards architectural aluminum. It's lightweight, it's attractive, it's easy to work, and it's more suitable for the humid environment than steel. Structural aluminum would be quite a bit more expensive, and for the spans the food computer is dealing with the architectural will hopefully do. I confused myself while ordering, and ended up getting an extra 10', so that wasn't ideal, but at least I have some room for error now. I had them do up a quote for the same product but in steel, and it was about 2/3 the price - for the ease of working, I figured it was worth the extra 30

5 x $17.44 per 10’ 6063 T5 aluminum angle, 1-1/4" x 1-1/4" x 1/8" = $87.20 (should have been 69.76 if I had ordered the correct number).
1 x $11.31 per 7’ 6061 T6511 aluminum flat bar 1-1/2" x 1/8" = $11.31

I’m hoping the aluminum and the vinyl will serve me better than the steel and PVC.


So I tried a first pass at 120VAC Control Module. Started with a box with one of the permanent knock-outs.

Had to smack it with a hamemr to get it started:

Went easily enough from there:

Fast forward a bit, and I was just trying to put the finishing touches on the box. About to call it a night when this happened:

I didn’t look too closely while I was at the store, I was in a bit of a rush. I guess it’s a box for a dryer receptacle, not a regular 3-prong plug. The holes are about a half inch short of reaching the mounts on the outside. Lucky everything comes apart, I guess?


I’m jammed up waiting for Grove cables (why does everything use Grove cables?), so I figured I’d start as much of the mainframe as possible. If I’m being honest, I was a bit intimidated by this section. I’ve never worked with metal before, so I was pretty unsure how it would go. The good news - holy cow aluminum cuts easily! I’m fairly certain I’ve cut wood that seemed more difficult. I used a regular 7 1/4" miter saw. It had a blade that was a couple years old, regular carbide tipped wood ripping blade.

Rigged up my extremely fancy jig:

And tried it out. It went excellently! Even being extremely over-cautious and meticulous about cutting, it only took about 20 minutes to cut everything. Next step is picking up some fasteners and drilling some holes!

Thanks to @JamesO for a clarification on one of the measurements that was inconsistent. Always a bit stressful when cutting things that cost money.


I thought it would make sense to use GFCI receptacles, given the likelihood of exposure to moisture.

Unfortunately, they are roughly 22$ each, but safety is a good thing, right?

I opened up the box:

And it doesn’t appear to have 2 contacts, so I don’t know how to separate the two receptacles. Back I go to the documented parts I guess.


120VAC Control Module

Alright. Attempt number 2 at the AC control module - this time using an electrical box that actually fits the receptacles…

Cut up an old extension cord (stranded wire) and some regular Romex

Harvest it for parts

Grab a receptacle

Figure out how to cut the tab

Snip the tab on each side with a pair of wire cutters:

Label the outlets:

Wire up the leads:

Attach everything with the Wago connectors. This is the first time I’ve used them, they seem handy but a little expensive. It’s nice that they’re so reusable.

Looking at the exposed contacts on the back of the relay block, I figured it’d be a good idea to cover them with some electrical tape:

I guess I should have read through the instructions all the way, it’s mentioned in one of the last steps to cover with electrical tape, then with duct tape. It’s all wrapped up right now, but when I eventually have to take it apart again, I’ll use the opportunity to put on some more tape.

Hook up the relay block:

First pass at AC control module:

It’s a bit messy, but at least it’s all connected.


##120VAC Control Module: Take 2

Following @JamesO’s post here, I realized the relay board is supposed to be inside the electrical box. That was not going to happen with 6 inch leads everywhere (or at least not easily for me)

Back to the drawing board! I pulled it all apart, and started fresh. To get an idea what kind of space I’d be dealing with, I oriented the relay board in a direction that would be convenient:

I cut all the wires much shorter, and made an effort to cut off any bits of the stripped parts that would be concerning if left as they were. I flipped the outlets over so that I could wire everything up in a straight line, with my idea being I could fold it over like a sandwich after the fact:

That seemed to work reasonably well:

With a little muscle, I managed to squeeze everything in nice and snug:

I still don’t have Grove cables, but Amazon prime helped me out with some ribbon cables:

Pulling 6 of them off:

Putting it all together (ooooohh, together-y!):

Immediately taking it apart to make sure I haven’t messed anything up. Note: my relay block, which is not exactly the same as the one on in the BOM, is active low. Ground -> ground, Vcc -> +5v, IN[1-4] -> ground = everything on.

Great success!

Stranded vs. Solid Wire

Looks great to me! I don’t think that the active low relay boards will be an issue- I’m using the BOM ones and they do the same thing (It took me a little bit to figure out, I got zapped once in the process, but only once I grounded the control wires in frustration did I realize their behavior haha).