droneiotclient

Overview

This is the client end of a system designed to measure sensor data from a set of "Data Loggers" deployed in the field, retrieve the sensor data from a "Data Collector" device, and then process and use the data. The system contains 4 main items:

1. esp32_sleep: This code is for the Data Logger. The device is meant to include an ESP32 microcontroller, an SSD1306 display screen, a BME280 temperature/pressure/humidity sensor, and an IR receiver. The device consumes very low power so that it can last for weeks on battery power alone. It wakes up on a configurable interval to collect data, stores that data, and goes back to sleep. When the Data Collector device sends an IR signal to the device, it wakes up, sends its data using point-to-point WiFi (ESP-Now), and goes back to sleep. The device also has a second Wifi mode, which can be toggled using a push button. In this mode, the device wakes up, connects to a WiFi network, and posts its data to a server.

2. esp32_receiver. This code is for the Data Receiver. It is also meant to be used with an ESP32 device. The receiver uses a 38kHz-modulated infrared signal to wake the Data Logger when one button is pressed. It receives the Logger's data using ESP-Now point-to-point WiFi. It stores data from many sensors, and when it is in range of a WiFi network, you can push another button to make it upload its data.

3. You'll need a server to collect and store data from the sensors. An open-source server that is compatible with this project available here: https://github.com/oyetkin/droneiotserver

4. Demo notebook. There are myriad ways to use and store the data, but we've created one sample project. It displays the locations of some sensors, and also creates a heatmap of some other sensors. Depending on what data is currently on the server, this demo script may fail to display data, but it should be easy to edit it to display whatever data is on the server.

Quick start

1. Build the Data Logger and Data Receiver, following the schematic diagrams in the repository. There's also a tutorial article with more details on components and wiring.
2. Clone this repo. In both esp32_receiver and esp32_sleep, edit the lines of code for your server URL and your WiFI ssid and password. In esp32_sleep, edit the lines of code for your latitude, longitude, and device name.
3. Clone and run the server repo here: https://github.com/oyetkin/droneiotserver
4. Upload the esp32_receiver and esp32_sleep code to their respective devices. Set the Data Logger to Wifi Mode using one of the two buttons if you want it to upload data directly, or set it to Trigger Mode if you want to collect data through the receiver.
5. Run the Demo ipy notebook to visualize your data.

Read the tutorial for a more detailed introduction. See the server repo for more details on how to retrieve data.

File guide

1. Tutorial article, schematic
2. PCB Bill of materials for PCB
3. code

Ideas for future developers...

There are a lot of things that can be done to make this device work better. Here are some ideas:

1. Currently, the Data Logger tells the Data Collector the time interval between its data, and the time since the last measurement. The Data Collector can use this to figure out what time each of the data points were recorded. However, this only works if you never miss a measurement. If the Logger fails to record a measurement today, it will record tomorrow's measurement in the spot meant for today, which messes up the timing. To fix this, you could record a "gap" or "blank" whenever you miss a measurement. To do this, you'd have to edit the data protocol to reserve a specific byte pattern as NaN. For instance, you could write 0xFFFF (which is currently the maximum value of a measurement) whenever you want to write a "blank," and make sure the Data Collector knows that 0xFFFF means "blank," not the max value.
2. If the device loses power, it'll lose all its memory. This is a weakness for applications where the sensor needs to log data in harsh conditions (such as low temperature or being moved around or dropped). You could write to PROGMEM instead of the RTC memory.
3. The device currently works on an ESP-32 Dev Board. The board has a voltage regulator for 5V --> 3V3, and an LED that's always on. That takes a whole lot of power! To achieve the low-power modes this design is meant for, you can redesign the device to work on the bare ESP32 chip instead of the Dev module.
4. In this vein, you could use a transistor, controlled by the ESP32, to control power to other devices. Before putting the ESP32 to sleep, you'd switch the transistor off so that the other devices don't consume any power when not needed. You'd want to pull the base low and use a bigger resistor to limit the current drain associated with the transistor itself.
5. Also, the OLED and the Serial Monitor are slow and power-inefficient. You could remove the print statements and delay()s associated with using these displays in order to spend less time and power awake.