BlueSensor

Arduino based device for temperature, air humidity and gas concentration measurment.

Hardware

PCB dimension is 70mm x 55mm. Schematics is available in two PDF files (BlueSensor_v1.1_PCB_top.pdf and BlueSensor_v1.1_PCB_top_miror.pdf). PCB can be manufactured with chemo transfer method invented by Volk Darko. In that case mirror image should be used. Schematics have been developed by Darko Volk.

Needed materials:

• 1 x Arduino Nano
• 2 x MQ2-x gas sensors*
• 1 x DHT-22 (AM2302) humidity and temperature sensor
• 2 x (max 4 x) DS12B20 temperature sensor (on a cable)
• 1 x buzzer
• 1 x LED diode
• 1 x 4.7k Ohm resistor
• 1 x 270 Ohm resistor
• 1 x 100 Ohm resistor
• 1 x battery case (for 4 x AAA batteries)

PCB is designed to additionally connect:

• 1 x HC-05 Bluetooth module
• 1 x 2k Ohm resistor
• 1 x 4.6k Ohm resistor

However, in future versions Bluetooth will not be supported.

MQ-x gas sensor are cheap sensors for detecting leakage of various gases:

• MQ-2: combustible gases
• MQ-3: alcohol
• MQ-4: CH4， natural gas
• MQ-5: LPG, natural gas, coal gas
• MQ-6: LPG
• MQ-7: carbon monoxide
• MQ-8: hydrogen
• MQ-9: carbon monoxide and combustible gases
• MQ-135: air quality sensor

They have analog output and are not calibrated.

Software

Python application bluesensor-server.py is used for displaying data from BlueSensor or SDS dust sensor in a web application. Appication runs web server on a localhost and calls data reader.

Currently there are two data readers available:

• read-serial (in read-serial.py), which reads JSON data from BlueSensor connected to USB port;
• read-dust (in read-dust.py), which reads data from SDS011, SDS018 or SDS021 dust sensor connected to USB port, and formats it to JSON;
• read-raw-serial (in read-raw-serial.py), which reads raw (tab-delimited) data from device connected to USB port, and formats them to JSON (you can use this for any sensor device which does not support our JSON format);

First you need to install Tornado Python web server. Od Ubuntu/Debian based systems you can do it with: sudo pip install tornado

Then you connect BlueSensor or SDS dust reader to USB port and run:

• for reading data from BlueSensor connected to ttyUSB0: python3 bluesensor-server.py read-serial 0
• for reading data from SDS dust reader (dust reader should always be connected to ttyUSB0): python3 bluesensor-server.py read-dust

When application is started, you can open URL which is printed in console:

• for BlueSensor data from ttyUSB0: http://localhost:8080/
• for BlueSensor data from ttyUSB1: http://localhost:8081/, etc...
• for SDS dust sensor data: http://localhost:8089/

Arduino firmware for BlueSensor is available in a file BlueSensor_JSON.ino. Output data from BlueSensor are printed in JSON format. Dust reader already uses JSON formatting.

Note on running the software on Ubuntu 23.04

In Ubuntu 23.04 the Python application is reporting an error:

Got JSON: "<module>(63): serial.serialutil.SerialException: [Errno 2] could not open port /dev/ttyUSB0: [Errno 2] No such file or directory: '/dev/ttyUSB0'"

However, if you check with lsusb, you will see that the device is connected:

Bus 005 Device 059: ID 1a86:7523 QinHeng Electronics CH340 serial converter

... and also attached to ttyUSB0:

sudo dmesg | grep ttyUSB*
[299102.079653] usb 5-2: ch341-uart converter now attached to ttyUSB0

The solution: sudo apt remove brltty (this removes Braille display support).

Our JSON format

Data from sensor devices are presented in JSON format, which self-describes sensor device and connected sensors. Here is the example of it:

{
	"metadata": {
		"device_name": "BlueSensor",
		"device_id": "BlueSensor1",
		"device_location": "Slovenia",
		"sensors": {
			"temperature1": ["Room temperature", "DHT-22", "°C", "orange", "not ready"],
			"humidity": ["Humidity", "DHT-22", "%", "blue", "not ready"],
			"temperature2": ["Liquid 1 temperature", "DS18B20", "°C", "red", "ready"],
			"temperature3": ["Liquid 2 temperature", "DS18B20", "°C", "yellow", "ready"],
			"gas1": ["Alcohol", "MQ-3", "raw value", "green", "ready"],
			"gas2": ["Combustible gases", "MQ-2", "raw value", "violet", "ready"]
		}
	},
	"time": 0,
	"data": {
		"temperature1": "none",
		"humidity": "none",
		"temperature2": "none",
		"temperature3": 25.0625,
		"gas1": 296,
		"gas2": 282
	}
}

Installation

First, clone this GIT repository to your local machine:

git clone https://github.com/MatejKovacic/BlueSensor

Then install dependencies:

sudo apt install python-tornado python-tz python-serial

If you want to get the latest vesrion:

cd BlueSensor
git pull

Now you are ready to run the application, for example, gathering data from BlueSensor connected to ttyUSB0:

cd BlueSensor
python bluesensor-server.py read-serial 0