Bedroom Aeroponic Tomatoes

grow-tent

A few months ago, I learned of a method for growing plants called aeroponics. Having a bit of an addictive personality, and knowing such a project would involve a fun mix of agriculture, plumbing, electronics, and coding, I decided to jump in and construct a high-pressure aeroponic system in my bedroom.

My goal was four-fold:

  1. Gain practical experience with electronics. My only knowledge up until this point was an Electricity & Magnetism physics course at university.
  2. Automate as much of the process as reasonable.
  3. Complete the project. I have issues with not finishing projects I start.
  4. Eat tasty bedroom tomatoes.

This post is only meant to give a high-level overview of what I made. I’ll go into more details of how everything works in a later post.

What is Aeroponics?

Many people are aware of a technique for growing plants called hydroponics, wherein plants are grown in a nutrient solution instead of soil. A subset of hydroponics, called aeroponics, takes this principle further by suspending the plant roots in thin air and only occasionally spraying the roots with nutrient solution via misters. The roots are exposed to air over 99% of the time. NASA has been experimenting with aeroponics since the late 1990’s, finding it to be the most efficient method of growing plants in outer space.

Aeroponics systems can reduce water usage by 98 percent, fertilizer usage by 60 percent, and pesticide usage by 100 percent, all while maximizing crop yields. — NASA

Although aeroponic systems can be extremely efficient at growing plants, my project was NOT to study how to optimize plant yields using this technique. The variables involved in plant growth are too numerous to attempt to study for a first-time bedroom grower with a single system. Variables include light & dark cycles, dry & wet cycles, droplet size, temperature, humidity, CO2 levels, nutrient mix, etc. Instead, I looked at various blogs and forums to see what seemed to work best for most people and just went with it.

Fun fact: Marijuana growers are the most vocal community on the internet when it comes to researching hydroponic and aeroponic growing techniques. Given that I’m from Pennsylvania where growing marijuana is illegal, I must be on a list somewhere.

What Exactly Did I Build?

Let me present the completed project that took me a couple months of work:

inside-grow-tent

The tote on the left contains the main plumbing parts (pump, accumulator tank, pressure relief valve, etc) along with the controller box. Sitting on top of that is the computer-controlled humidifier.

The plants themselves are suspended from net cups in black 5 gallon buckets. On the left are two cherry tomato plants, and in the right bucket are three basil plants. Although they’re stacked two buckets high each, the bottom buckets are completely closed off and just used as stands so the root chambers will drain properly.

My decision behind choosing cherry tomatoes and basil as my first grow was simple: it was late November and those were quite literally the last two packets of seeds at Home Depot.

The bucket to the right is the reservoir into which the root chambers collectively drain, and from which the pump pulls more nutrient solution, creating a closed-loop system.

inside-the-tote-1

Please pardon the mess of wires. I forgot to tidy up before you came.

inside-the-tote-2

inside-the-controller-box

roots

grow-tent-intake-fan

grow-tent-ventilation-duct

My grow light and ventilation (intake) fan, both of which are now computer controlled, hang above my plants. As you can see from the image above, yes, this thing is really in my bedroom. The entire project is contained within something called a grow tent. Grow tents are typically used by marijuana enthusiasts who want to discreetly grow their crop in a controlled environment; I’m using it to grow tomatoes. To each their own.

It was actually quite a hassle to get the environment systems working properly because the conditions in my grow tent were dry and hot. The original ventilation fan I was using, a much more powerful exhaust fan, would cycle the air in the room so quickly that the humidifier couldn’t keep up if its life depended on it. I ended up settling on a janky solution where I taped a smaller circulating fan to the ventilation duct so that it could pump in cold air from outside. Clearly, this solution won’t work during the warmer months, so I’ll probably end up buying a swamp cooler to deal with this dry & hot predicament.

Did I Accomplish My Goals?

Short answer, yes. It is complete, highly automated, I gained some practical experience with electronics, and I ate tasty bedroom tomatoes!

Automation

I was able to automate the entire system and make it reliable enough such that I only have to intervene for a few routine tasks.

What I’ve automated:

  • Misters in the root chambers turn on & off at regular intervals.
  • The pump re-pressurizes the system when the line pressure drops too low. I have a two-gallon accumulator tank (the big blue cylinder in the tote) so the pump only needs to turn on about six times a day.
  • The humidifier turns on/off based on humidity levels in the grow room.
  • The ventilation fan turns on at regular intervals to provide fresh air, but is also controlled by a temperature sensor, so it’ll stay on when the temperature in the grow room gets too hot.

What I was not able to automate:

  • Refilling the humidifier. This occurs once per day.
  • Replenishing the nutrient solution. This occurs once per week.
  • Pruning the plants. I usually do this every few days, and it’s necessary to keep the plants away from the light and to cull undesirable branches.

The first two manual interventions could easily be solved with automation. I could buy a humidifier that ties into a water line, but my current living arrangement precludes that option. Likewise, I could buy pH sensors, EC sensors, and dosing pumps to handle nutrient monitoring and replenishment. However, I’d run into a similar issue as with the humidifier in that I can’t tie this project into a water line at my current locale. Also, I don’t have enough plants to warrant the additional cost of that kind of setup.

Unfortunately, pruning the plants, hanging the plants, and harvesting the fruit are tasks that will exclusively belong to humans for the foreseeable future. While companies are currently working on technology to help ease the burden of farmers, the dexterous nature of these tasks make them extremely difficult for robots to do.

Hands-On Electronics Experience

I think this project was the right level of difficulty for an electronics beginner. It required learning to solder, design circuits, lay out and mount circuit boards, read a multimeter, and crimp connectors.

The electronics portion also contained the biggest headache for me, which was a result of naiveté with real-world electronics: delivering power to all of the devices from a single 120V AC power cord. My devices run the gamut of voltages, from 120V AC, to 24V AC, to 12V DC, to 5V DC. I drastically underestimated the work required to build my own voltage converters. Building a black box that could handle these inputs/outputs is something I could do with more time, but I didn’t want to risk getting bogged down in the weeds and not finishing the project. As a result, I ended up using a series of consumer converters. They’re the ugly silver things sitting on top of the accumulator tank.

Along with the biggest challenge, I also had the most fun wiring up the electronics. As a programmer by trade, I’m used to working in an entirely digital environment. The first time I was able to get some python code to interact with the real world was incredibly satisfying! Crimping connectors was also fun because it gave my project a professional feel where the end assembly just involved plugging everything together.

Tasty Bedroom Tomatoes

tomatoes-for-days ‘Nuff said.

Conclusion

Overall, I’m happy with the way the entire project turned out. I feel it wasn’t too massive in scope for a person who never finishes anything, but provided enough of a bite that kept me busy for a while. I learned a ton, and if I end up moving into a larger place I’ll definitely create a 2.0 version that’s more automated and can accommodate more plants. There’s so much more I wanted to discuss in this post, such as how exactly the system works, lighting choices, the monitoring system, etc., but I ended up cutting much of it out as I needed to give an overview before diving into anything. Look out for a future post where I’ll dive into these topics!