It is important to understand what is happening in the greenhouse. Especially since we garden in the winter. We use Arduinos, temperature, humidity and waterproof sensors to learn what is happening in our greenhouse. The system for the pit greenhouse can be seen in action here.

We have had requests for more information on how to set up a system. As I am building the new system for the cattle panel greenhouse I will add information to this page (March 2022).

Cattle Panel Greenhouse

The cattle panel greenhouse has raised beds we will plant in. It will have the outer covering and at least one additional row covering through colder weather. The goal is to track the air temperature in the greenhouse, under the row coverings and outside. In addition we want to track the soil temperature in the growing beds, and maybe… one soil temp outside.

This system includes

  • Arduino Mega 2560
  • Ethernet Shield W5100 for Arduino R3 Mega 2560
    • Wired ethernet connection
  • Breadboard
  • Liquid Crystal Display (LCD) 
  • DHT11
    • Temperature and humidity sensor
  • DHT22
    • Temperature and humidity sensor
  • DS18b20 (3 of them)
    • Waterproof temperature sensor for soil and water
  • DS3231
    • Clock to hold time, requires a 2302 battery


For those who are new to programming, the best way to start is test the element and then add one element at a time to the main sketch. This page is not a tutorial on how to program to create a sensor system. It is the basic outline of what I used to create ours.

I used Arduino’s IDE (Independent Developers Environment) from Arduino. Each element has a recommended sketch – the code to makes that element work. I tested that each element worked independently of my system and that I had my wiring correct. Only then did I add the code to the main sketch. I made sure to have backups of my sketches along the way. The back up is wonderful for when something goes wrong.

For my build I set up the clock, LCD display and the Ethernet shield first. Then I added the sensors – checking each sensor through the serial port, then adding to the LCD display.

Posting my graph on line was accomplished once all the sensors were working. I created a database and table on my server to house the data. The last step was graphing the data with https://www.chartjs.org/ charts.

Here is the graph. Below is an image of the system. My wire management could be better.

  • Three Waterproof Sensors
    • Air – Outside air temp
    • Ground – Outside ground temp
    • Ground – Inside ground temp under row cover
  • DHT21
    • Air/humidity temp inside greenhouse
  • DHT11
    • Air/Humidity under row cover

Finished Sensor System

Below are links to the items I purchased to build my system. I am an Amazon Affiliate and do make a small amount on each item. If you go to their website and search – you can find the same items. These are just the ones I chose to use. After returning a few off brands I find that SunFounder components are reliable.

I do have a DHT11 in my system. It is an older sensor and not as good as the DHT21.

Mega 2560

Ethernet Shield

Waterproof Sensor

DHT 21 Sensor

LCD Display

Bread Boards