GrowMax by OpenSensor. io

I developed the Growmax board and software routines because I wanted a practical way to manage growing more than a couple indoor plants. I set out to meet my own use cases as an indoor grower while maximizing the available features of the Raspberry Pi Pico form factor.

The GrowMax v1.1 board gives the ability to control 8 discrete micro submersible 5v pumps and read from corresponding moisture sensors. Intentionally built to pair with using Pimoroni Grow sensors, which are plug and play with the 8 moisture sensor ports on the board board.

The growmax board has two ports specifically intended for use with Optomax liquid level sensors for setting the low and high water level marks of the automation reservoir. The low water mark is important to prevent pump burn out by signifying to the growmax software that the water level is too low to run the pumps. A high water sensor can be used when automating the re-filling of the reservoir.

Recent software version 1.1.3 added support for the Adafruit SSD1327 128x128 monochrome display to be paired with a switch for enabling/displaying the display using an interrupt on the pico.

I also use the board to report data from the Adafruit scd-4x CO2/Temp/Humidity I2C sensor to opensenor-api powered by FastAPI and MongoDB Timeseries database. The opensensor-api and growmax board software are separate software packages, both open source. However the growmax board does not require to report data in order to automate plant growing, growmax is configurable and data collection is disabled by default.

NextSteps

I need to do some plumbing work to run an RO water line over to my reservoir, and then I can work on selecting the right water solenoid valve and power source to control the refilling of my reservoir.

Additionally I've ordered an I2C pH meter that is designed to be perpetually submersed in the reservoir, so I can begin to measure pH readings periodically, which could be tied into auto feeding schedules. I personally prefer growing with dry amendments and feeding clean water, so I am not sure how far I'll explore the liquid nutrient auto dosing for my own needs, but I may consider it for the sake of science!

GrowMaxBoardTechnical Details

• 8 Moisture sensor ports (3 pin JST-SH)
• 8 Pump controls (2 pin pico-blade)
• Note: The growmax open source software never operates more than one pump at a time due to power limitation of 300mA from a standard pico.
• Moisture sensor ports intended for use with a Pimoroni moisture sensor and is fed from 3.3V
• Pump ports are mosfet powered by 5V VBUS (2 pin pico-blade) with kickback voltage buffer.
• Two dedicated ports (3 pin pico blade) powered by 5v VBUS with 4V to 3.3V voltage divider of the input intended for pairing with Optomax liquid level sensors (for detecting low and high water marks on a reservoir).
• Both dedicated I2C channels exposed with Qwiic Stemma/QT connectors on board.
• Common use case for I2C is connecting external sensor arrays to the board for data collection, adding a display, or driving higher power applications with an I2C relay board.
• The three ADC channels of the Pico are exposed as well as the last GPIO pin of the pico as 3 pin pico-blade connectors powered by 3.3V

NOTE: This device should always be powered by 5V USB as it was not designed to run off a 3.7V battery, for example.