Green Detect

Wireless Sensor Network Platform (WSN) , for enviromental monitoring

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Green Detect project was created with the aim of providing the community with a tool to monitor and control the environment.
The Green Detect network is independent of the Internet, so it can work even in geographic areas where the Internet is not present.
In the Green Detect local network it is possible to connect from 1 to 60 sensors that transmit their data via wireless through the ESP-NOW protocol to a computer where through the Green Detect application it is possible to monitor each individual sensor, detect alarm conditions, locate the sensors in an animated geographic map and record all acquisitions in order to collect all data for preventive and statistical purposes.
Each individual sensor module is powered by a supercapacitor (or Nimh batteries) charged by a solar panel.
Green Detect is Opensource: anyone can modify and improve the project, for example by adding new types of sensors.

The Network

Each individual sensor module has a specific address that can be programmed by the user using the buttons on the module's electronic board.

The first sensor module transmits its data via 4 bytes to the second module every 30 seconds.

Each module receives the data of the previous modules and retransmits them to the next module adding its own 4 bytes.

The network can include from a minimum of 1 to a maximum of 60 sensors.

This maximum limit is to stay within the transmission limit of the ESP-NOW protocol which is 250 bytes (60x4 = 240).

The maximum suggested distance between one sensor and the next is 100 meters

Therefore the network can develop linearly for a total length of 6 km, for example along a river.

Or you can arrange the sensors in a grid covering for example an area of 1 km x 600 m, such as a field or a portion of a forest.

The last module of the network communicates with the gateway module connected via USB serial to the supervisor computer.

The network is completely independent from the Internet, so it can work even in remote and connectionless areas.

However, if the supervision PC is connected to the internet, the collected data can be shared in IOT applications together with the data of other Green Detect local networks, in order to create a global monitoring!

Sensor Module failure

What happens in the event of a module failure?

In the event of a module failure, communication is interrupted and the acquisition of all sensors is momentarily lost.

After a delay time of 2 minutes, the module following the faulty one begins to transmit data to the following modules, informing the supervisory system of the fault to the previous module.

This condition generates a specific alarm and it is therefore possible to go promptly to replace or repair the faulty module and restore the network in a very short time.

Sensor Module description

The sensor module is based on the Wemos Mini PRO board, containing the ESP8266 microcontroller.

The Microcontroller programming software was developed with Arduino IDE.

The power supply to the microcontroller and the sensors connected to it is provided by a 400F supercapacitor, whose output between 1.5v and 2.7v is raised to 5V by a step-up converter.

The supercapacitor is charged during the day by a 6v 3.5W solar panel.

The supercapacitor is not soldered to the board, but is fixed by a clip and connected by a connector, in order to make its possible replacement quick and easy.

In critical geographic areas (low light, rainy areas) or in case of high consumption sensors, where the supercapacitor may not be able to meet the energy needs, it can be replaced with 2 Nimh batteries in series, without modifying the board, just plug into the same connector.

The module works according to the following steps:

1. sensor signal acquisition

2. receiving data from the previous form

3. data transmission to the next module

4. Deep sleep mode (30 seconds)

All modules connected to the network are synchronized with each other.

Using the buttons and leds on the board, it is possible to program the module by defining the address and the type of sensor used.

The settings are stored in the flash memory of the microcontroller.

The Sensors 

The module can accept digital, analog (10 bit), Onewire and I2C sensors.

Two or more sensors can be combined and connected to the same module, the limit is represented by the fact that we can transmit a maximum of 3 bytes.

Each type of sensor (single or combined) is associated with a unique number, up to a maximum of 99 sensor types.

The addition of new sensors involves updating both the microcontroller software and the supervision application: everyone can do it because the project is Opensource!

If you set sensor type = 0, the module is used just as repeater.

Here are some examples of sensors that can be connected:

Sensor type 1: SR01 Ultrasonic...

Read more »

04 Win

Installation files for Green Detect Windows application

Zip Archive - 29.64 MB - 06/27/2022 at 22:05


03 Solar

Solar Panel electrical drawings and 3d file to print the solar panel case

Zip Archive - 171.55 kB - 06/27/2022 at 22:03



Sensors electrical drawings and 3d file to print the sensors case

Zip Archive - 534.52 kB - 06/27/2022 at 22:02


01 Module software Arduino

Arduino IDE ESP8266 code

Zip Archive - 8.55 kB - 06/27/2022 at 21:59


00 Module PCB Kicad

Module PCB Kicad files + gerber files and BOM

Zip Archive - 2.18 MB - 06/27/2022 at 21:58


View all 18 components

  • Module failure test

    Sergio Ghirardelli07/12/2022 at 20:38 0 comments

    What happens when one of the sensor modules fails?
    The answer is in the following video ...

  • 60 modules communication test

    Sergio Ghirardelli07/07/2022 at 14:46 0 comments

    We all know that theory is often not reflected in practice.

    Could I submit a sensor network project, claiming a network of 60 sensors without being sure it worked?

    No! I had to be sure, so I decided to test if my theoretical calculation was correct.

    The following video shows the tests carried out.

    Why 60 modules limit?

    Green detect wireless sensor network uses ESP-NOW protocol.

    The first ESP-NOW technology limitation is that the total number of peer devices should be less than 20.

    How did I exceed this limit?

    I simply created a chain network, where each device communicates with 2 other devices the one from which it receives the packets and the one to which to send the processed packets.

    Basically I created many small networks, exceeding the limit of 20 devices.

    Why can Green Detect network include a maximum of 60 devices?

    Because the ESP-NOW technology has another limitation: up to 250-byte payload can be carried.

    And since I have foreseen 4 bytes of transmission per sensor, I can use a maximum of 60 sensors (60x4 = 240 bytes)

  • Solar charger circuit

    Sergio Ghirardelli06/30/2022 at 12:41 0 comments

     When I thought about the Green Detect project, I immediately had in mind the outdoor use and the total energy autonomy of the sensors, with solar panel charging and energy storage,

    The challenge I immediately thought about was to make the project significantly more eco-compatible by using a supercapacitor.

    I made the first tests with low cost supercapacitors, with poor results.

    So I tried with a quality product at a reasonable price: Eaton cod.XV3560-2R7407-R

     For the choice of the supercap, I used the Eaton calculation tool:

    I was clearly aware that it would be the practical test to tell me if the choice was right!

    The first breadboard tests were encouraging, so I started working on the solar charging circuit.

    I needed a simple, inexpensive circuit able to get even a few mA to the supercap (for example on cloudy days).

    The charge of the supercap must follow a fundamental rule: the charge voltage must not bring the supercap to a voltage higher than 2.75 V.

    The end-of-charge voltage of the supercapacitor is the same as that of 2 Ni-Mh batteries in series: this analogy led me to think of a solution that would leave a door open for “plan B”: use 2 NiMh batteries instead of the supercap in case this fails to power the sensor.

    After a series of tests I thought about using a current shunt regulator circuit.

    I simulated the circuit with online Falstad simulator:

    This circuit keeps the voltage constant by draining the current to GND.

    The voltage is established by appropriately dimensioning the voltage divider resistances at the base of the NPN transistor.

    With a few additions and improvements, the charging circuit is this:

    I added schottky diodes to block reverse currents and the possibility to charge from USB.

    The only effect to consider is the temperature on the body of the power transistor Q2 at the end of the charge, when all the current supplied by the 3.5W solar panel (max 520 mA) is drained to GND by Q2.

    To dissipate the heat, I designed a large GND plane at the bottom side of the PCB, also I added a heatsink on transistor Q2.

    The result is good: the temperature on the transistor body does not exceed 60 °!!!

    I love simplicity!

View all 3 project logs

  • 1
    Definition of quantity and type of sensors, order material

    Define the number of sensors that will make up the network and the type, considering that some modules can be used as signal repeaters without connected sensors (sensor type = 0).

    Then proceed with ordering all the necessary material, following the list in the "components" section. 

    Don't forget to order the additional Wemos D1 mini for Gateway.

  • 2
    Component assembly

    For each sensor carry out assembly of:

    • Sensor Module.
    • Solar Panel.
    • Sensors
    • Unit assembly according to sensor electrical drawing
  • 3
    Load software into the microcontroller and set Network address

    Download latest Green Detect sw version from Github repository.

    With Arduino IDE, open the file .ino and set set your unique network address.

    Save, compile and Install last software version on each module Wemos Mini pro microcontroller by Arduino IDE.

View all 9 instructions

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