Collection Station

The Collection Stations are small battery powered wireless devices outfitted with environmental sensors. They collect and publish the data to the Hub for processing. This project is built with the esp32 micro-controller, C++ and embedded realtime operating system.

Publishing Sensor Data

The idea is pretty simple really: build a network of wireless battery powered devices to gather environmental data such as temprature, moisture, light levels, etc. The collected data will then be published via MQTT wirelessly to the Hub.

Types of Published Data

The planned data types to be published by the system are concerned with the following types of sensors.

  • Temprature
  • Humidity
  • Moisture
  • Light
  • Barometric Pressure

Technically any type of data could be published and collected however we are focused on the type of data our OG application will use. Data will be transmitted as either integer or floating point, depending on the sensor and how it collects the data.

Data Storage

Due to the limited nature of the sensor stations storage space, relatively little historic data will be saved on the station itself. The expectation that data published by the station will have been consumed and aggregated by the Hub or a similar subscriber.

Long term storage of the data is the job of the Hub or other data aggregator. The CS is an embedded system expected to run with very little resources.

The esp32 Chip of Choice

We are going to the esp32 as the chip of choice for building the Collection / Control Station.

Some features that make this chip very attractive for building the Collection / Control Station. In addition to it’s availability and the wonderfully mature esp-idf DevKit, the esp32 has the following features we will be taking advantage of:

  • Wireless support for Wifi & BLE
  • Sophisticated low power modes
  • Support for batteries
  • Non Volatile Memory
  • Over The Air Updates
  • Digital GPIO
  • Analog GPIO

We’ll discuss all of these items and how they benefit the development of our projects hardware.

The esp32 is CHEAP

An esp32 and a handful of sensors can easily be assebled for less than $20 (if you have a solering iron or breadboard) on your kitchen table.

This is chip is no toy, it is an industrial stalwart!

Network Connectivity

The most attractive part of the esp32 in my opinion are the networking capabilities for wireless networking. Bluetooth Lightweight Edition (BLE) and ubiquitos Wifi are built right on the esp32 itself.

Mesh Networks

During the 2nd phase of development, the Sensor Station will be enhanced with Mesh Network capabilities. That is the ability for an esp32 to build a self forming network, eliminating the need to pre-configure devices.

Mesh Networks also provides the capability of running a network where no previous network infrastructure exists or is accessible.

Batteries and Low Power Modes

Battery options in stereo with smart programming of sleep and low power network protocols provide the potential of building sensors that can truely be “set it and forget it” dutifuly running for years with a single watch battery.

This will become a primary area of research and development for this project in the near future.


Options for solar power and rechargeble batteries give us the hope of building something that could last into perpituity. In other words, the hardware should fail before one of these devices ever run out of power.

OTA Updates

The downside of little wireless, battery operated devices scattered about to and fro becomes very real when it is time to upgrade all these devices.

That is where Over-The-Air (OTA) updates becomes a life saver! When new versions of software become available, they can be either pushed down to the devices, or pulled by the device from a server.

The updates happen in a matter of seconds, reboot and the station will resume it’s previous duties, most likely with out missing a single published datapoint.


If this project sounds interesting to you at all, please drop me a line and say hello. Also consider signing up for the project email list, where you will get only good stuff about the project, no SPAM, never.