Happy Fall! Use promo code GROW1000 to save 5$ on board only orders. Contact us for quotes on international orders.
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Boards and Kits by OpenSensor.io:
Intelligent Grow Automation!

Unlock the full potential of your indoor garden with our cutting-edge Boards and Kits, utilizing either a Raspberry Pi Pico or ESP32S3 in the Pico form-factor. Effortlessly monitor your plants and automate watering to ensure they are perfectly cared for!

  • Smart watering: Set customized moisture threshold per plant and provide the optimal hydration needs.
  • Easy-to-install: Our board and parts seamlessly integrate into your existing indoor gardening setup.
  • Real-time monitoring and visualization: Stay up-to-date with environment and moisture levels by reporting data to OpenSensor API.
  • Pico form-factor: Harnesses the power of modern, cost-effective microcontrollers and marketplace sensors for ultimate control.

Optimize your indoor garden with GrowMax Boards by OpenSensor.io and experience the difference!

GrowMax v1.0 board

Intelligent Grow Automation

Take the hassle out of plant watering with OpenSensor GrowMax boards, your one-stop solution for effortless automation. Our advanced system supports up to 8 individual plant moisture sensors and 8 micro submersible pumps, ensuring precise hydration for each of your plants.

Leveraging the power of Raspberry Pi Pico or Pico W, along with the open-source MicroPython package GrowMax, our plug-and-play automation is perfect for beginners and experienced gardeners alike. Plus, with both I2C channels available for expansion, you can unlock limitless possibilities for your indoor garden.

Board Only


Fully assembled Growmax board only, entirely DIY for sourcing other components.



Sale: $110

Growmax board and enough parts to get started with 3 plants; provide your own pico.



Sale: $180

Growmax board and enough parts to automate 6 plants, Pico W included and pre-installed.



Sale: $200

Growmax board and enough parts to automate 8 plants, Pico W included and pre-installed.


Board Only




GrowMax Board

Pico W Pre-installed

OpenSensor.io 3D Printed Case

Pimoroni Moisture Sensors w/ custom 2 meter cables

3 of each

6 of each

9 sensors, 8 cables

Mini submersible pumps w/ 2 meter cables and connectors




Optomax Liquid Sensor w/ 1 meter cable and connector attached




Qwiic stemma QT cables 2.5 meters




Silicone Tube 5mm ID x 8mm OD meter

8 meters

10 meters

Primerus Pot-Dripper Rings w/ adapters

Four 10" & Two 6"

Six 10" & Two 6"

2A USB wall charger and 2 meter MicroUSB cable

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Growmax is Open Source!

Easy installation using our packages published on PyPI and open-source code on GitHub: OpenSensor growmax is designed for the grow community and plant hobbyists alike! Our kits bring together the best custom-made and aftermarket components, enabling quick deployment of intelligent plant automation systems at the point of use.

Data Reporting and Device Controls

Growmax boards can be configured to report sensor data into the OpenSensor.io API layer. Visualize your data in our grafana dashboards and manage your devices on the OpenSensor.io website. Recent feature release allows issuing manual watering commands from the website in near real time.

To protect the operation of your pumps, it's important to install an Optomax liquid level sensor or alternative water switch approximately 3 inches from the bottom of the reservoir. The most effective way to install an Optomax sensor in your bucket is by using a step bit with a drill, carefully crafting a hole just large enough to accommodate the liquid level sensor. With a step bit and careful handling, installation is straightforward and precise.

OpenSensor Data Graphing Service
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Technical Details

  • Eight discrete plants: 8 Moisture sensor ports paired with 8 Pump ports.
  • Moisture sensor ports intended for use with Pimoroni moisture sensors (3 pin JST-SH 3.3V).
  • Pump port is mosfet powered by 5V VBUS with kickback voltage buffer (2 pin pico-blade).
  • Two dedicated optomax liquid level sensor ports; 5V power with 4V to 3.3V voltage divider of the input (3 pin pico blade).
  • Two dedicated I2C channels with Qwiic connectors on board connecting external devices and sensor arrays to the board.
  • Control higher power applications by adding an external I2C relay board, and auto refill your water reservoir!
  • Three ADC channels are exposed an additional GPIO pin as 3 pin pico-blade connectors powered by 3.3V.

Minimal DIY Required

Our board and software offers a wide range of configurations. Our kits range from fully DIY to inclusive packages with custom sourced parts. You will require a 5 or 7 gallon bucket dedicated for the pump reservoir. For larger reservoirs: consider maximum lift of your selected pumps in relation to container height, and consider the affects of gravity siphoning when water level is much higher than output point.

Buckets with Optomax liquid sensors installed

Frequently asked questions

Things you may be wondering about the GrowMax boards by OpenSensor.io


Absolutely! The package price covers USPS first-class shipping with tracking.

GrowMax Board

The GrowMax board is a custom-developed plant automation board, powered by a Raspberry Pi Pico form factor microcontroller unit (MCU).

Yes, the boards are double-sided and assembled by JLC.

Simply plug a Pico compatible device with headers into the GrowMax board to provide the CPU and software instructions. Install the GrowMax package from PyPI to get started.

Microcontroller Support

The Pico is an affordable, versatile microcontroller board with a wireless variant for IoT devices. Other MCU variants that follow the Pico form factor and pin-outs are generally compatible with GrowMax.

Connect the board to your computer's USB port and run the program from the Thonny IDE to see program outputs. More information is available on the GrowMax GitHub page.

Data Displays

Certainly! You can use one of the two available Qwiic connect I2C channels with I2C displays. GrowMax version 1.1.5 supports SSD1327 and SH1107 chipsets for displays.

Moisture Sensors

The GrowMax board features 8 moisture sensor ports designed for capacitive moisture sensors, which are measured by a single pin reading pulses per second. Note that these differ from ADC and I2C moisture sensors.

We recommend Pimoroni Grow moisture sensors as the best on the market. They are directly compatible with the ports on the GrowMax board.

Yes, the digital chips on moisture sensors can corrode and provide inaccurate readings over time due to dirt and moisture. Avoid directly watering them and consider applying a conformal coating to protect the sensor chips from the environment.

Drip Rings

The default drip-limiting holes may not provide sufficient flow for an effective watering cycle. Widening select holes with a small drill bit is recommended.

The default water inlet on the state for the Primerus Pot-Dripper Rings minimizes water inlet flow, so we supply T-adapters and separate stakes to hold up the rings.

Contact Opensensor.io

Interested in our products and learning more? We would love to hear from you.

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GrowMax flower test Oct 11th to Nov 19th

GrowMax test board in action; growth shown from Oct 11th to Nov 19th.