Compost Sensor


This is a tutorial on building a Compost Temperature monitoring system. It details how to build a web connected wireless sensor network and shows one possible way it could be constructed.
A Medium level of knowledge and skills are required. Basic knowledge of soldering and bread boarding will be very useful. I will assume that you know enough Arduino code to understand what a Function is, how a Library is useful, and why Serial Communication is important. And you will need to know enough electronics to understand what I mean with terms like Voltage, Current, Resistance, etc. A (very) basic knowledge of how radio works would also be useful for understanding the concepts, but not essential for following along. This is not advanced by any means and I will attempt to always reference materials that will cover these concepts in greater detail.
This tutorial is not about building a polished final product. I am going to assume that you are accompanied by some basic fabrication skills and are capable of doing some problem solving in this area. I will show an example of my project at the end, but I will not be talking extensively on housing design or fabrication. This will be purely about the code and electronics to get up and running with the various communication types, sensors, and data storage. That being said, by the end of this tutorial you will have a web connected sensor network working on your breadboard. Putting it into a housing will be easy after that.

Why Measure the Temperature of Compost?

“Composting is the biological decomposition of organic matter under aerobic conditions.” Micro-organisms consume organic material and oxygen and create heat as a waste product. By measuring this heat you can predict decomposition rate, oxygen content (loosely), and the overall health and efficiency of your composting operation. It helps to predict when the pile needs to be turned to introduce more oxygen, when the pile is finished with its hot cook cycle, and if you have effectively killed any pathogens or weed seeds that might be present in the feed stocks. Monitoring is an important aspect to streamlining and creating a stable process and workflow to get a predictable and consistent result through each cook, improving the overall efficiency in the operation.


This project uses short range Radio and Cellular communication to get sensor data from individual probes in the compost to an online database. The hardware will be built on the Arduino platform using the Moteino wireless boards. We will be using thermistors for our temperature sensing, an Ad fruit FONA cellular module for our cellular communication and the Spark fun Data Service for our online database.

Parts List

Note: You will need an ftdi board to upload code to the Moteino’s.

Sensor Node (per node):

Cellular Gateway

  • Moteino w/RFM69HW
    • This should be the same part as the Sensor nodes.
  • FONA GSM Board
    • You will also need an antennae, depending on which type of FONA board you get, either will work. I like the low profile antennae. Just make sure the Antenna you get matches the connector on the FONA you have.
  • Lithium Ion Battery
    • This can be a big or small battery depending on your design. Also might be worth considering solar charging. Voltaic Systems makes nice stuff. I used one of their products in my system.
  • SIM Card
  • Breadboard

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