Vermiculture Project Part 1

Keywords: #raspi #hobby #gardening

I have a project that’s been in my head for a while: vermiculture. But it sounds like a lot of work. So of course, I want to automate it.

Right now this is a sketch of a plan, but I figured I’d share.

My interest in vermiculture is twofold

  1. Amazing soil supplement for vegetable gardening
  2. My girls like fishing with worms, they’re everywhere and it feels dumb buying them.

So my goals here are to both to get that sweet composty-stuff as well as basically breed worms.

Basic Needs

So my understanding so far from reading is that I need:

  • a good container, or tiered containers for rotation.
  • a stable temperature range so they don’t cook or freeze
  • good substrate for them to go through (nom nom nom)
  • the right amount of water, damp but not soaked

Automation opportunities

I stink at maintaining moisture levels for sensitive stuff. So it would be really nice to make it “just work”.

I live in 7c for gardening nerds. That means it gets pretty hot in the summer and cold in the winter.

My plan is to do this in my utility room in my garage. It’s pretty poorly insulated from my house, so my Heat and AC leak into it and buffer the temperature from the outside.

But I’m not 100% comfortable that it won’t walk outside of the acceptable temperature range and these wormies can’t just dig deeper. So I should get alerted about that.

I have no running water in the room and have 0 plan to run a hose in there. So I will need to keep some sort of water container as a buffer prior to a valve controlling the output. I should get alerted when that gets low to remind me to fill it.

Good news is that there’s no rain, so I don’t have to worry as much about waterproofing as with building a normal irrigation system. Also I have power readily available. So no need to run extension cords, protect power adapters, or figure out elaborate setups with batteries and/or solar panels.

I love metrics. So I want to feed telemetry into my InfluxDB/Grafana setup I use to monitor my home network.

Things I need so far

For the automation

  1. A Raspberry Pi or similar system. I need GPIO and probably i2c and/or SPI, and I’d like to write this in Go or Python if I have to.
  2. Moisture sensors. I need one that can be dumb for the water buffer storage. But the one(s) for the trays may need to be more sophisticated.
  3. Temperature/humidity sensor(s) 4. A solenoid valve to control water flow.
  4. A mechanism for push notifications. I hate just using SMS or email.
  5. A metrics store/dashboarding.

So I think I have an RPi 2 or 3 I can shift to this. If not I may end up buying something RPi-like, due to availability these days.

I do have the dumb moisture sensor covered. I need to see if I can use this for more than just wet/dry and get a decent gradient of moisture out of it or if I need to get something more sophisticated.

I do own a couple i2c temperature/humidity sensors already and a Dallas 1-wire waterproof temperature-only sensor. I accidentally bought the second i2c sensor because I forgot I already had one.

I’m going to steal the solenoid valve from a Orbit watering timer similar to this one. I have it from when I was using a rain barrel to water my garden. I gave up on that for a lot of reasons I won’t go in to here.

I’d look at doing a 24VAC one with a relay, but that’s a pain, and I already have this one. I also found a helpful teardown of a similar model. Basically, it means I have to flip the polarity to operate this thing. Also, you can see how crappy the dial is on this thing.

I’m using Pushover for push notifications because it’s so easy that it’s worth the $5.

For metrics and dashboarding I already have an InfluxDB/Grafana setup running on a RockPro64 that I use for monitoring my home network gear. I couldn’t get a RPi 4 w/ 4GB RAM, so went with the RockPro64 for it, and am so happy I did. Much better suited for that task.

Physical Stuff

I’ll need a container for the water buffer. I’m thinking a 5 gallon bucket. I may have parts left over from my old rain barrel setup to reuse here, or can just get another kit. It’s an easy way to get the water out to normal hose diameter for the solenoid valve. I’ll also need a short host, probably just one of those flex adapters folks use from an outdoor tap to their garden hose will be great.

I’ll need something to go from the hose-sized output from the valve to probably 3/16ths tubing. Don’t know if I’ll do pinholes in aquarium tubing or actual soaker hose. I may have some of the latter left from my previous irrigation project. I’m not sure I can get enough water pressure for the real soaker hose to work.

I need the tiered tray contraption. I’m thinking of checking out the dollar store or Walmart for something I can use or punch holes in to work.

Substrate: I need something for these worms to live in and eat. My plan is to use a mixture of organic garden soil, actual from-the-ground soil, and shredded cardboard. I have a shredder that chews through it and I get plenty of plain brown boxes these days.

Worms! I don’t want to buy worms for this. It may not be a real issue, but I don’t want to be unnecessarily introducing foreign worms here. I have known places in my and my mom’s back yard to be able to get enough to seed this project with.

What’s Next?

I really need to figure out the exact circuitry I’m going to need, especially to drive the valve.

I need to know what I want to measure at what points so that I can ensure I can actually connect all of these things at the same time. As is, I have 2 different digital sensor types (i2c and Dallas 1-wire) and the solenoid and moisture sensor that would have to be banged on by raw GPIO.