LamaPLC: SGP Sensirion Gas-sensors with I²C communication

The Sensirion SGP sensor family includes high-performance, multi-pixel gas sensors tailored for indoor air quality monitoring. Using metal-oxide (MOx) technology on a single chip, these sensors detect multiple pollutants and remain stable against contamination.

Core Sensor Models

• SGP30 (Legacy standard): The first of its kind to offer multiple sensing elements on one chip. It provides calibrated signals for Total Volatile Organic Compounds (TVOC) in parts per billion (ppb) and a calculated CO₂ equivalent (eCO₂) based on hydrogen concentrations.
• SGP40 (VOC optimized): Designed specifically for VOC detection in indoor environments. It replaced the SGP30's raw ppb output with a more robust VOC Index (1–500) that automatically adapts to the surrounding environment.
• SGP41 (VOC + NOx): The current flagship for air treatment devices like purifiers. It includes all the VOC capabilities of the SGP40 but adds a dedicated sensor for Nitrogen Oxides (NOx), a common combustion byproduct from stoves and vehicle exhaust.
• SGPC3 (Ultra-low power): A variant optimized for mobile and battery-operated devices, offering reliable gas sensing with minimal power drain.

Key Comparisons

Feature	Sensirion SGP30	Sensirion SGP40	Sensirion SGP41
Primary Output	TVOC (ppb) & eCO₂ (ppm)	VOC Index (1-500)	VOC & NOx Index
Detection Focus	Broad VOCs & H₂	Volatile Organic Compounds	VOCs + Nitrogen Oxides
Power Consumption	~48 mA (active)	~2.6 mA (at 3.3V)	~3.2 mA (at 3.3V)
Stability	Excellent (siloxane resistant)	Enhanced long-term stability	Enhanced long-term stability
I²C Address	0x58	0x59	0x59
Supply Voltage (VDD)	1.62V – 1.98V (1.8V typ)	1.7V – 3.6V (3.3V typ)	1.7V – 3.6V (3.3V typ)
TVOC / VOC Output	0 – 60,000 ppb	1 – 500 Index	1 – 500 Index
eCO₂ Output	400 – 60,000 ppm	N/A	N/A
NOx Output	N/A	N/A	1 – 500 Index
Max Sampling Frequency	1 Hz	Up to 10 Hz (raw data)	Up to 10 Hz (raw data)
Moduls
	GY-SGP30	GY-SGP40	GY-SGP41

The SGP sensors can be integrated with the Tasmota system. For more information, see here.

The GY-SGP41 module operates on a flexible 3.3V to 5V DC power supply. The core SGP41 sensor chip, however, has a narrower supply voltage range of 1.7V to 3.6V.

• SCL: A5
• GND: GND
• SDA: A4
• Vdd: 5V

Arduino code

When interfacing the SGP41 VOC and NOx sensor with an Arduino, the most reliable approach is to use the official Sensirion I2C SGP41 library or the Adafruit SGP41 library.

This basic example initializes the sensor and retrieves raw VOC and NOx signals.

#include <Arduino.h>
#include <SensirionI2CSgp41.h>
#include <Wire.h>
 
SensirionI2CSgp41 sgp41;
 
void setup() {
    Serial.begin(115200);
    while (!Serial) { delay(100); }
 
    Wire.begin();
    sgp41.begin(Wire);
 
    // Initial self-test
    uint16_t testResult;
    if (sgp41.executeSelfTest(testResult) || testResult != 0xD400) {
        Serial.println("SGP41 Self-test failed!");
    }
}
 
void loop() {
    uint16_t error;
    uint16_t srawVoc = 0;
    uint16_t srawNox = 0;
 
    // Use default compensation (25°C, 50% RH)
    // For better accuracy, feed real T/RH from another sensor here
    error = sgp41.measureRawSignals(0x8000, 0x6666, srawVoc, srawNox);
 
    if (!error) {
        Serial.print("Raw VOC: "); Serial.print(srawVoc);
        Serial.print("\tRaw NOx: "); Serial.println(srawNox);
    } else {
        Serial.println("Measurement error!");
    }
 
    delay(1000); // Wait 1 second
}

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