Low Power I2C Methane Sensor Module

by Pratik (A PCBArtist)

A low power I2C methane sensor module that can be easily interfaced with any microcontroller is not easy to find in the market. Sensor modules like MQ-4 work fine but suffer from low selectivity, high power consumption and rather long warm-up time.

Considering all of the above, we decided to come up with a range of sensors that are low power, work off of 5V power supply and produce gas concentration readings in ppm (parts per million). These new gas sensors are powered by an STM32 ARM Cortex-M0+ MCU to add data processing on analog sensor signals. The host can simply read the gas concentration value in ppm and control the module mode if required.

pcbartists i2c methane sensor module
PCB Artists I2C Methane Sensor Module

Methane Sensor Module Hardware

The PCB Artists I2C methane sensor modules uses Figaro’s TGS2611-E00 analog methane sensing element. The TGS2611 series measures methane in the range of 300 ppm to 50,000 ppm with good accuracy and repeatability. It is not sensitive to stray gases other than hydrogen and methane, thanks to the integrated gas filter.

The TGS2611 is a catalytic sensor in a metal can package. The internal sensing element is simply a sense resistor that changes its resistance based on the concentration of methane around it. The sensor is also influenced by a variety of other factors that need to be taken into account to calculate a usable ppm methane concentration value.

Here is a block diagram of the PCB Artists I2C methane sensor module.

pcb artists tgs2611 i2c methane sensor block diagram
Block Diagram, TGS2611 I2C Methane Sensor Module

How the I2C Methane Sensor Works

To make things easier for you, the methane sensor module controls the sensor element to fetch analog data and processes it.

Here are some functions that the TGS2611 methane sensor module performs and produces methane concentration readings:

  • Methane sensing element health check
  • Sensor heater health check
  • Temperature compensation
  • Humidity compensation (optional)
  • Averaging readings to reduce noise
  • Power management of sensor to save power
The methane sensor I2C register map provides documentation on accessing the sensor and its functions.

Measurement Modes

The sensor module supports three measurement modes.

Idle/low power mode

In this mode, the sensor module is in its lowest power state. The sensing element is turned off and only the MCU is running to allow for I2C communication.
All I2C registers are accessible in this mode.

Single measurement mode

This is a low power measurement mode designed to save system power. The host MCU can simply start a single measurement run and go to sleep. The I2C methane sensor module will power up the sensor, calculate reading as per the set sampling duration and go back to idle mode.
The host MCU can then wake up and fetch the methane reading in ppm. This mode is suited for battery powered monitors that need to sample once in a while only.

Continuous measurement mode

During continuous measurement mode, the methane sensor module keeps the TGS2611 powered up and constantly samples the sensor for acquiring methane concentration. This mode consumes the most power and is recommended for applications that have mains power or are used for continuous monitoring (alarm systems).

Change Log
  • Initial Release: 8 December 2022

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