mq135

🚀 Overview

mq135 is a minimal, #![no_std] Rust driver for the MQ135 air quality sensor.
It’s designed for embedded systems using the embedded-hal ADC traits.

The MQ135 sensor detects air quality by measuring gases like CO₂, NH₃, Benzene, and Smoke via analog voltage readings. This driver converts those readings into gas concentration (PPM).

✨ Features

• ✅ Calibration support in clean air
• ✅ Measures PPM values for multiple gases (CO₂, NH₃, Benzene, Smoke)
• ✅ Uses generic embedded-hal traits for wide MCU compatibility
• ✅ No standard library (#![no_std]), perfect for microcontrollers
• ✅ Easy-to-use API for quick integration

📦 Usage

First, add the crate to your dependencies:

[dependencies]
mq135 = "0.1"  # replace with latest version
embedded-hal = "0.2"  # or your compatible version
libm = "0.2"  # for math in no_std environment

Example code snippet:

use mq135::{Mq135, GasType};

// `adc` must implement `embedded_hal::adc::OneShot`
// `pin` is the ADC input pin connected to MQ135 sensor output

let mut sensor = Mq135::new(adc, pin, 10_000.0); // RL load resistance in Ohms

// Calibrate the sensor in clean air before readings
sensor.calibrate_in_clean_air().unwrap();

// Get gas concentration in PPM
let co2_ppm = sensor.read_gas_ppm(GasType::CO2).unwrap();

println!("CO2 Concentration: {:.2} ppm", co2_ppm);

🧪 Calibration

Calibration is necessary to set the baseline sensor resistance (R0) in clean air. This ensures accurate gas concentration measurements.

🌬️ Supported Gases

⚙️ Dependencies

• embedded-hal — Hardware abstraction layer for embedded devices
• libm — Math functions compatible with no_std environments

📄 License

This project is licensed under the MIT License © 2025 Prabesh Shrestha.

🤝 Contributions

Contributions, issues, and feature requests are welcome! Feel free to check the issues page.

Thank you for using mq135! Happy coding and clean air monitoring! 🌿