Hydroponics: Progress Report 25-Feb-2023

We now have an operationally testable system. Yay!!

Current Status

Here’s where we are now:

  • All the major components have been bought, or built, unit tested, and integrated into the system, except for the lights
  • I don’t have the lights for the system yet. Just a few days ago, the container ship from China docked in Long Beach, CA, so I expect the lights to arrive shortly
  • The system will ultimately have 3 plant towers, but towers 2 and 3 won’t be 3D printed and installed until tower 1 proves itself
  • The lettuce factory has been moved from the workshop into its permanent home in the basement
  • The plumbing and electrical systems tests were passed; only one tiny water leak had to be addressed.
  • Temporary lights were installed so we can get started with operational testing

What’s Next

The next steps will be:

  • Connect robot controller hardware to the relays in the wiring cabinet
  • Write the Lettuce Factory robot software, install it on the hardware, and test it
  • Load the factory with nutrient solution and turn it on, and start the Factory control robot
  • Move all the plants from the germination tank to their respective sockets on Factory Tower 1
  • Install the new lights when they arrive

The Story in Pictures

Here are a few pix that tell the story of construction and installation. Then there’s a few pix about how the system actually works, with extra detail about the key components. Finally we take a look at what it’ll take to begin operations, and how the system will be connected to the robot that will control it.



Side view of the system. It’s about 6′ long, 3′ wide, and 9′ tall. Nutrients flow from the nutrient tank bottom right, up to the gravity tank at the top, down through the supply manifold to each of the towers (only tower 1 installed now), out the bottom of the tower through the return manifold and back to the nutrient tank.
Bottom tier of the system shows the carriage, the tower support, the return manifold that collects nutrient solution from the bottom of the towers and conveys it back to the nutrient tank, and the nutrient tank itself
Perspective view. Wiring cabinet and controls in the front, tower 1 next, gravity tank on the bottom, pipe conveying nutrient up to the gravity tank, and gravity tank at the top.

Initial Testing

The control panel. Main power switch is at the bottom, then comes the ammeter that shows power consumption, then the aerator pump switch, the open slot for the circulation fan switch, the nutrient pump switch, and finally the open slot for the light switch.
Inside view of nutrient reservoir tank. Power cord, air supply, and return manifold enter on the left, the pump and the aerator stones on the bottom, and supply line from pump to gravity tank exits on the right

Useful Operations Data

The aerator pump only uses 8 watts, but runs constantly. You can barely hear it run.

The nutrient pump is a half horsepower pump. It uses about 400 watts when running, and it takes about 30 seconds to move the 6 gallons of nutrient solution from the reservoir tank up to the gravity tank

With just one tower operational, it takes about 18.5 minutes to drain the gravity tank through the tower and back to the nutrient tank.

When I write the control robot, I’ll use this operational data. The design of the robot has to address:

  • number of operational towers
  • flow rate of nutrient through each tower
  • target time interval between nutrient solution applications
  • how long it will take to drain the gravity tank based on the number of operational towers

What’s Next?

As I mentioned above, the next major tasks are to connect the controlling computer to the lettuce factory, then write the software that will control the factory, and then load up the tower with new plants, and start operations. I’ll use temporary lights until the new ones arrive, whereupon they’ll get installed. That will be very exciting!

Here’s the little computer that will control the relays in the wiring cabinet. The board on the left is where the wires to the relays will connect
And here are the relays in the wiring cabinet. A relay enables a tiny signal from the computer to turn on a high-powered device. The tiny wires from the computer connect on the left, and the high power lines to the aerator, circulation fan, nutrient pump and lights connect on the right. The big black components are the switches (the actual “relay”) the computer turns on and off.
Germination tank where we’re starting lettuce plants before they go into the towers. The germination tank … ah, shall we say, is in need of some upgrades.
A romaine lettuce plant, in its special cup, ready for insertion into the tower
This is how the cup is loaded into the tower. The roots of the plant penetrate the slots on the cup, and grow down into the tower’s main cylinder, where they are regularly bathed in a nutrient- and oxygen-rich solution

Next Progress Report

I’ll produce another progress report as soon as sufficient tasks are accomplished to warrant it. I expect that’ll be in late March 2023.

Author: Tom Pfotzer
I'm a retired I.T. worker who runs a farm. Like many of us, I'm trying to figure out how to respond to the slow-motion environmental and economic collapse we're engulfed in. I want to work with people who understand what's going on and are ready to do something about it.

3 thoughts on “Hydroponics: Progress Report 25-Feb-2023

  1. This is a wonderful project; thank you for these reports!

    A thought re: lighting:

    reproducing the fluence of sunlight with electricity is kind of expensive. Over time, the cost might justify setting up an outdoor illumination arrangement for use on days with no risk of rain. Provided that the plants can tolerate it, you could increase the effective light intensity by placing a flat reflective surface horizontally to the south of the setup, and a vertical reflective surface to the north. This would provide some (depending on how reflective the surfaces are) back-side illumination and would increase the front-side illumination. OTOH, the light exposure might degrade the polymer components over time, and it would be necessary to acclimate the plants to the increased exposure.

    Consider incorporating red lettuce in your plants mix; I’m especially fond of the variety “Merlot”, which gets a deep burgundy (under sunlight; my LED-lit indoor starts are much paler). Red lettuces have loads of antioxidant phytonutrients.

    I’ll continue to follow this project with great interest.

    1. Samuel:

      Artificial light is indeed expensive. I expect the lights I’ve bought to use around 400 watts collectively, and they’ll be on 12+ hours a day (not sure what the optimum daylength for lettuce is yet).

      As you know from the report, I have a greenhouse, and I expect to adapt and extend this system for use in the gh. I thought I’d use the basement/household scale system to do some learning before I scale it up. Gh ops have some issues, too, and the gh will have to get some improvements – ventilation and heat management in particular – before it’s ready for prime-time. This has been the subject of considerable thinking and component development over the past few years, and I’m nearly ready to commence construction.

      That said, my expected design is a bit complex, and uses some expensive (for me) inputs, so it’ll take me a few months to wind into that work. But this design I have in mind addresses a lot of the key issues of greenhouses (bleed energy, big variances in temp and rel humidity, etc.).

      And all your suggestions about light management (reflectors, etc.) are right on-point. Hopefully, we’ll get a chance to discuss those ideas, as I think my designs will benefit from a 2nd pair of eyes.

      I’ll see if I can’t find Merlot seeds and get some started right now. Pls provide a link to a source if you get a sec.

      As I mentioned over @ NC, the next big thing is to get the germination system up to snuff; what I have is really bad right now, and all of a sudden, I need a lot of new seedlings, pronto.

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