Robotics – Automation Projects

Autonomous Basil Farm With Robot Arm!

Growing basil is great, but do you know what’s even better? Having an autonomous basil farm!

As the saying goes: “never spend ten minutes doing something by hand, when you could spend 10 hours failing to automate it”.

Although I may be bad at gardening, something I am good at is enthusiastically trying to solve problems through the medium of hot glue and sketchy electronics. I have written this Instructable in the hope that it might provide some inspiration and useful information about the process of creating your own autonomous basil farm!

Just as a quick disclaimer, I put this project together this week so have not had time to test it with growing yet. Hopefully In 50-60 days I will be able to report back with tales of an epic basil harvest.

Supplies:

  • PVC piping
  • MG996R servos
  • Aluminum extrusion
  • Stepper motor & driver board
  • Arduino
  • Wall power supply / battery with voltage regulator
  • Nutrient solution
  • Rockwool cubes
  • Basil seeds
  • 5v pumps and tubing
  • LED lights
  • 3d printing facility
  • Pulley belt

Step 1: PVC Pipe System

This farm does not use any soil, this is for a few reasons:

  1. Growing things in soil is less efficient in terms of water usage
  2. Soil is less space efficient.
  3. The nutrient composition in soil is harder to tune.

Therefore the basil is to be grown hydroponically. This means that a pipe system has to be made to carry the nutrient solution around the basils.

I used PVC box section from Wickes. This was big enough for me and the shape meant that it was easy to drill holes using a hole saw bit.

I’m sure there are connector parts that you can buy to fit these parts together however I didn’t really want to have to buy them and hot glue seemed to work well-ish.

The PVC can be easily cut with a hacksaw.

In terms of the spacing of the basils, I followed the guidance of the seed packets and just used a^2+b^2=c^2 to ensure they weren’t to close together.

Step 2: Basil Deep Frying

Obviously, you can’t just drop the basil seeds into the pipe system and let them swim around. This is why you need to use rock-wool cubes (yes, it is literal wool made from rocks!). This keeps the basil seeds in place and provides an initial medium for them to grow in.

I 3d printed little baskets that fit the rock-wool and go into the pipe system holes. They also have a cylindrical section cut out for 2p coins (the only things I could really find that worked). This allows the electromagnet on the robotic arm to attach on them and move them about.

Step 3: The Water System

This system uses three pumps:

  1. The first pump runs from the nutrient-water reservoir into the main pipe system. This pumps turns on at specific intervals in time, in order to keep the nutrients topped up.
  2. The second pump runs inside of the main pipe system to circulate the water around the plants, to ensure the plants get an even amount of nutrients.
  3. The third pump is used to remove water from the system after its nutrients have been depleted.

These pumps run off 5 volts. Transistors are used in combination with an Arduino to control them.

Link to the pumps I used

The nutrient water has been made using Formulex 1 mixed with standard tap water in a ratio of 5ml for each litre of water.

The reservoirs have been made out of large Tupperware boxes.

Step 4: Step 3: Lighting

Basil is able to be grown with light 24/7. This means that I will be using a light at night to increase the yield.

Link to an article which explains the effect of light wavelength on growth – picture comes from here.

I am using a 12v LED light strip as this is something I had left over from a previous project. Unfortunately, I do not have one of the mini voltage-boost circuits, so they have to be run at a different voltage to the main system (5v).

I am using an LDR to sense when it is getting dark, which turns on the light.

https://www.instructables.com/Using-an-LDR-Sensor-With-Arduino/

The strip is mounted on top of the basils using some left-over dowels.

Step 5: Powering the System

This system runs at 5 volts and draws a significant amount of amps when the robot arm is moving. This means that a decent power supply is required.

There are two options:

1. Use a wall based power supply. This has the benefit of not needing to be recharged. Just make sure it can supply a decent amount of amps (2+) at 5v. Be careful.

2. Use a battery (lipo’s are the best in terms of current capability however a lead acid one could also work if you had one of them). This has the benefit of it being portable. A voltage regulator needs to be used, to smooth out the sag as the battery runs out of charge.

Step 6: Stepper Motor Linear Actuator

The robot arm needs to move along in a linear fashion in order to reach each of the basils.

I used a stepper motor that came with my Arduino and designed the slider in Fusion 360, I think the general rule is just add as many fidget spinner bearings as possible to try and make it stable.

I designed mine to slide along a left-over green house aluminium extrusion. A 3d printer belt can then be used in conjunction with the Arduino stepper motor library to slide the robotic arm up and down.

https://www.instructables.com/BYJ48-Stepper-Motor/

Step 7: Robot Arm

I decided to build a robot arm for this project as I thought it would be a fun challenge and it has the benefit of it moving the basil plants around for me.

The MG996R servos for the robot arm were the best choice for me as they give a good balance of power whilst relatively not being too expensive.

They have 3 wires. The 5 volts and ground wires were connect to the breadboard. Each of the signal pins can then be connected to digital pins on the Arduino. Be careful with the wiring as I have already managed to damage one of mine.

I have attached the Fusion 360 file with the parts I used, however, if you want to build your own one I would highly suggest that you design your own as you will probably require different reach lengths. I also had to tinker with the sizes a lot to get the parts to fit so if you want to copy them you will probably need to adjust them.

Instructables has lots of great resources to learn these skills

In terms of controlling the arm; you can use trigonometry do this but with mine it just didn’t seem worth it as the tolerances are a bit lacking. Instead I am just creating functions with trial and error that move the arm to specific locations. This works and is easier to fine tune.

How robots use maths to move – James Bruton

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