Hackergrant II Project Report – SaladBar

Image result for tower gardenBy Skip Xtian

63% of employees eat two or less daily servings of fruits/vegetables, the lack of which contributes to gastro­intestinal problems according to medical experts. Being able to have readily available fresh fruit and veg throughout an office building that staff can pick and eat when they walk by would greatly improve all employee’s diet. The issue with using standard Hydroponic Grow Towers is that somebody has to learn all about the subject.What nutrients are needed? What pH is best for these plants? Will I get nutrient lock out? And the list goes on…

Enter Salad Bar.

A complete stand alone tower that does most of the work for you. When it needs help, it will let you know.You simply select the produce you are going to grow and it will adjust the waters nutrients to match and keep the pH balanced for the entire grow cycle. You will get notifications when it’s time to:

  • Place the plants in the tower.
  • Top up any of the Solutions.
  • Remove wastewater (Great to put onto other office plants)
  • You will also be able to monitor the data and fine tune the settings accordingly to produce the best results

The initial plan was to automate the dosing of a tower garden like above. However as the project went on it evolved to a much more complete solution.

Consisting of 6 x Micro Controller (4 x Atmel, 1 ESP8266 & 1 STM32), SaladBar became a fully integrated system with Touch screen display. You place your plants in rock wool and expanded clay in the vertical sections, On the screen select your main crop. It will suggest other plants that are suitable for that Nutrient/Ph level and away it goes.


It controls, monitors and logs the mains water intake, adds nutrient and adjust ph according to your plant selection. Each of the nutrient tanks have a float switch to alert when levels are low.

The pumps were salvaged from ex medical equipment and have very fine grained control.

The most expensive part of this system is the 3 submerged probes, I monitor Dissolved Oxygen, Ph and Electrical Conductivity (nutrient level).

We also monitor the Reservoir water temp, Air temp and Humidity.

It drives 6 x 240V (3 x 5A, 3 x 10A) solid state relays that control the main pump, a circulation pump, an air Pump, a dump pump with spares for lighting, heating/cooling.

I separated the Brain PCB from the Control PCB, which will allow me to easily swap from a mains powered system to a 12/24v Solar Powered system at a later date.

The system was design to accommodate an aquaponics garden too, with connectors for a rain gauge and 6 more DS18B20 temp sensors as well as a fish feeder motor driver.

It has enough smarts to calculate the Nutrient to Fresh water ratio on a daily bases and when this gets close to flat lining it triggers the Reservoir dump and clean process.

All data is logged via wifi to an AWS RDS instance with lambda triggers set for any alerts that get SMS’d to the user.

The touch screen also has overrides so you can drive the pumps yourself and monitor the sensors locally.

This is a completely custom system, All parts (The Tower, PCB’s, Touch Screen UI, Cloud DB & Lambda, etc) were designed and build by myself with the help of Robert for some gluing and fixing.