Firebeetle 2 Gas Sensor

About the project

I recently won a FireBeetle 2 ESP32E on the ElectroMaker Show and thought it would be a great opportunity to build a portable gas sensor.

Project info

Difficulty: Easy

Platforms: ArduinoDFRobotSeeed StudioEspressifNode-RED

Estimated time: 1 week

License: MIT license (MIT)

Items used in this project

Hardware components

Firebeetle 2 Board ESP32-E Firebeetle 2 Board ESP32-E x 1
Fermion: 1.8" 128x160 IPS TFT LCD Display with MicroSD Card Slot (Breakout) Fermion: 1.8" 128x160 IPS TFT LCD Display with MicroSD Card Slot (Breakout) x 1
Grove - Multichannel Gas Sensor v2 Grove - Multichannel Gas Sensor v2 x 1
GROVE MS8607 GROVE MS8607 x 1
Lithium Ion Polymer Battery Ideal For Feathers - 3.7V 400mAh Lithium Ion Polymer Battery Ideal For Feathers - 3.7V 400mAh x 1

Software apps and online services

Arduino IDE Arduino IDE
Node-Red Node-Red

Hand tools and fabrication machines

AnyCubic Kobra 2 AnyCubic Kobra 2 x 1


Robin Mitchell did a Product of the Week video on the  FireBeetle 2 ESP32-E board from DFRobot about a month ago.  And I won the giveaway on Ian's  show.   I had mentioned that I would use it to build a portable gas sensor since I had just gotten a Multichannel Gas Sensor board from Seeed Studio.  So, here is that project.

The FireBeetle 2 ESP32-E board has some great features that make it ideal for building a portable IoT sensor - ESP32 processor with WiFi/Bluetooth, battery interface, GDI display port, and female GPIO headers.


Here are the parts that I am using for my project (front and back):

Top: Fermion 1.8" 128x160 TFT Displaywith GDI cable

Middle: FireBeetle2 ESP32E

Bottom: Seeed MultiGas Sensor V2

LiPo battery

Arduino IDE

I normally use the Arduino IDE to program ESP32 boards and the DFRobot Beetle boards are included in the Board Manager esp32 boards.  I am using Arduino IDE 2.2.1.  I included the following Additional Boards Manager URL under Preferences:  "".

Then selected the FireBeetle 2 ESP32-E:

And used the default settings for my programs:

Hardware Connections

GDI Display - 18 pin FPC cable

MultiGas Sensor - GPIO Header 3.3V, GND, SCL(22), SDA(21) to Grove 4 pin connector

Battery -  2 pin JST-PH connector VBat, GND; Voltage Monitor on A2(34) - divide by 2 

Optional momentary push button on D7(13) to GND


3D Printed Case

For flexibility I decided to mount all the parts except for the sensor in a 3D printed case.  The sensor connects via a Grove connector.  That way it is easy to swap sensors.

Top - TFT Display with slot for SD card

Bottom - FireBeetle2, LiPo battery, Grove connector(I2C), hole for Reset button access, Push Button, cutout for USB-C connector access

Display Test

The first thing I wanted to verify was the operation of the TFT display.

Install display library DFRobot_GDL from github into Arduino IDE.

Upload the TFT sample code from FireBeetle_2_Board_ESP32_S3_Advanced_Tutorial.  The code also runs on the FireBeetle2 ESP32E.

Picture below shows code running on TFT with case open before battery and cover were installed. 

MS8607 Test

Since I had not used the MultiGas sensor I wanted to try an I2C sensor that I have used before as a functional test.  I decide to use the MS8607 PHT (Pressure/Humidity/Temperature) sensor.

I installed the Adafruit MS8607 and Sensor libraries.  I wanted to publish the sensor values using MQTT so that I could display them on a Node-Red UI.  I run a local MQTT server and Node-Red using a RPi4.  

Here are the libraries that I am using:

#include <Wire.h>
#include <WiFi.h>
#include <PubSubClient.h>
#include <Adafruit_MS8607.h>
#include <Adafruit_Sensor.h>
#include "DFRobot_GDL.h"

The picture below shows the readings on the TFT.  Case is complete but still running on USB power.

Results on Serial Monitor:

The Node-Red Flow

Very simple flow receives PHT data on the topic published by the FireBeetle2 using an MQTT input node and displays it on the dashboard using a chart node.

The Node-Red Dashboard

MultiGas Sensor V2

Now to get with the actual project - the gas sensor.

The Seeed MultiGas Sensor V2 board uses four individual gas sensors for each gas type:

  1. GM102B NO2 sensor
  2. GM302B C2H5OH sensor
  3. GM502B VOC sensor
  4. GM702B CO sensor

The wiki is here: Grove-Multichannel-Gas-Sensor-V2.

The library on github is here: Seeed_Multichannel_Gas_Sensor.

Here is a picture of the gas sensor operating on battery power:

Results on Serial Monitor:

The Node-Red Flow

The Node-Red Dashboard


The gas sensor interface and display is working as I had planned, but there is still some work to be done.  I am somewhat confused by the results that I am getting from the Seeed MultiGas Sensor library.  The results that I get are not gas readings in PPM but just conversion of raw sensor voltages, so I will need to figure out how to "calibrate" or adjust them.

Here are the library sensor values along with the sensor voltages:

I guess I was confused by a Hackster project that I saw that used the same gas sensor and library: Air Quality Monitoring Station.  

That project called the same library functions to read the sensors but somehow returned "sensible?" values in PPM (except the NO2).  

Something that I will need to figure out.  For now at least I can get a qualitative measure of gas readings, i.e. detect changes.

Test with Isopropyl Alcohol

A quick test using isopropyl alcohol surprised me.  I don't have any active air movement but the time it took for the sensor to clear after exposure to a small amount of spilled alcohol was much longer than I expected (hours).  And the CO sensor is somewhat noisier than before the test.  I'll need to do a lot more experimenting with the sensor responses to different stimuli...

Schematics, diagrams and documents

FireBeetle2 ESP32E Schematic

CAD, enclosures and custom parts

FireBeetle2 Case Back (bottom)

Back of case to holf FireBeetle2, Battery, and Grove connector. I added a hole in the side to access the Reset button on the FireBeetle2 -use a paperclip or other pin. I also included a cutout for a momentary pushbutton.

FireBeetle2 Case Front (top)

Front of case to hold 1.8" TFT Display. There is a slot in the side to allow access to the SD card on the Display PCB.



Interface Seeed MultiGas Sensor V2 with FireBeetle2 ESP32E and publish data using MQTT


Interface MS8607 Pressure, Humidity, Temperature sensor and publish reading using MQTT

TFT Basic Test

Test 128x160 GDI Display with FireBeetle2 ESP32E


Photo of ralphjy


Retired EE, maker, electronics hobbyist. Current interests include AI enhanced video applications and cellular IoT.


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