ESP32 MiCS-4514 Dual Gas Sensor
Overview
The MiCS-4514 is a dual gas sensor capable of detecting oxidizing gases (e.g., NO₂) and reducing gases (e.g., CO, NH₃). It provides analog outputs for gas concentration, making it ideal for air quality monitoring, HVAC systems, and industrial safety applications.
About MiCS-4514 Dual Gas Sensor
The MiCS-4514 is a dual-sensor gas detection module designed for air quality monitoring and industrial applications. It can simultaneously detect oxidizing gases (NO₂) and reducing gases (CO, NH₃, CH₄, ethanol, hydrogen), making it ideal for smart air quality systems and environmental monitoring.
⚡ Key Features
- Dual-Sensor Design – Detects both oxidizing and reducing gases.
- Independent Sensing Elements – Each with its own heater and sensitive layer for enhanced accuracy.
- Analog Voltage Output – Provides a signal proportional to gas concentration, readable via ADC.
- Ideal for Air Quality & Industrial Applications – Used in pollution monitoring, HVAC, and safety systems.
For additional air quality monitoring solutions, consider the CCS811, which detects TVOCs and eCO₂. 🚀
The MiCS-4514 offers a compact design with low power consumption and fast response time, making it suitable for portable devices, HVAC systems, and IoT applications. Its dual-element architecture provides flexibility for multi-gas detection in a single device.
Where to Buy
Starting from
25$ per piece
Prices are subject to change. We earn from qualifying purchases as an Amazon Associate.
Technical Specifications
Pinout Configuration
The VCC pin is used to supply power to the sensor, and it typically requires 3.3V or 5V (refer to the datasheet for specific voltage requirements). The GND pin is the ground connection and must be connected to the ground of your ESP32.
The MiCS-4514 pinout is as follows:
- Pin 1 (Vcc): Power supply input (5V).
- Pin 2 (GND): Ground connection.
- Pin 3 (Reducing Gas Output): Analog voltage output for reducing gases.
- Pin 4 (Oxidizing Gas Output): Analog voltage output for oxidizing gases.
- Pin 5 (Heater Control): Heater control input (PWM).
- Pin 6 (Heater Ground): Heater ground connection.
Wiring with ESP32
Vcc to a 5V power supply, GND to ground, and the Reducing Gas Output and Oxidizing Gas Output to analog input pins on the microcontroller. For heater control, connect the Heater Control pin to a PWM-enabled digital output pin. Ensure that appropriate current-limiting resistors are used for heater operation.Troubleshooting Guide
Common Issues
❌ Sensor Not Detected on I2C Bus
Issue: The MiCS-4514 sensor is not recognized on the I2C bus, leading to initialization failures.
Possible causes include incorrect I2C address configuration, improper wiring connections, or faulty sensor hardware.
Solution: Verify the sensor's I2C address using an I2C scanner and ensure it matches the address defined in your code. The default I2C address is 0x75. Check all wiring connections to ensure they are secure and correctly aligned with the microcontroller's I2C pins. If the sensor is still not detected, consider testing with a different sensor to rule out hardware defects.
🚫 Zero PPM Readings for All Gases
Issue: The sensor outputs 0.00 ppm for all gas parameters (e.g., CO, NO2, NH3, C2H5OH) despite proper connections.
Possible causes include insufficient warm-up time, incorrect sensor initialization, or faulty sensor hardware.
Solution: Allow the sensor to warm up for at least 3 minutes after powering on, as it requires this time to stabilize. Ensure that the sensor is properly initialized in your code and that the correct I2C address is specified. If the issue persists, the sensor may be defective and require replacement.
⚠️ Inaccurate Gas Concentration Readings
Issue: The sensor provides gas concentration readings that are significantly off from expected values.
Possible causes include improper calibration, environmental factors affecting sensor performance, or incorrect data interpretation in the code.
Solution: Calibrate the sensor in a controlled environment to establish accurate baseline readings. Ensure the sensor is placed in an environment free from contaminants that could affect its performance. Review your code to confirm that the data from the sensor is being interpreted correctly, considering any necessary conversion factors.
🔄 Sensor Readings Fluctuate Significantly
Issue: The sensor outputs gas concentration readings that fluctuate wildly, making it difficult to obtain stable measurements.
Possible causes include an unstable power supply, external electromagnetic interference, or faulty sensor hardware.
Solution: Use a stable and regulated power supply to power the sensor. Ensure that the sensor and its connections are shielded from sources of electromagnetic interference. If the problem persists, consider replacing the sensor, as it may be defective.
Debugging Tips
🔍 Serial Monitor
Use the Serial Monitor to check for error messages and verify the sensor's output. Add debug prints in your code to track the sensor's state.
⚡ Voltage Checks
Use a multimeter to verify voltage levels and check for continuity in your connections. Ensure the power supply is stable and within the sensor's requirements.
Additional Resources
Code Examples
Arduino Example
#include <Wire.h>
const int reducingGasPin = 19; // Analog input for reducing gas
const int oxidizingGasPin = 18; // Analog input for oxidizing gas
const int heaterPin = 5; // Digital output for heater control
void setup() {
Serial.begin(9600);
// Configure heater pin
pinMode(heaterPin, OUTPUT);
digitalWrite(heaterPin, HIGH); // Turn on the heater
}
void loop() {
int reducingGasValue = analogRead(reducingGasPin);
int oxidizingGasValue = analogRead(oxidizingGasPin);
// Convert analog values to voltage
float reducingGasVoltage = reducingGasValue (5.0 / 1023.0);
float oxidizingGasVoltage = oxidizingGasValue (5.0 / 1023.0);
Serial.print("Reducing Gas Voltage: ");
Serial.print(reducingGasVoltage);
Serial.println(" V");
Serial.print("Oxidizing Gas Voltage: ");
Serial.print(oxidizingGasVoltage);
Serial.println(" V");
delay(1000);
}ESP-IDF Example
#include <stdio.h>
#include "driver/adc.h"
#include "esp_adc_cal.h"
#include "driver/gpio.h"
#define REDUCING_GAS_CHANNEL ADC1_CHANNEL_7 // GPIO19
#define OXIDIZING_GAS_CHANNEL ADC1_CHANNEL_6 // GPIO18
#define HEATER_PIN GPIO_NUM_5
#define DEFAULT_VREF 1100
void app_main(void) {
// Configure heater pin
gpio_pad_select_gpio(HEATER_PIN);
gpio_set_direction(HEATER_PIN, GPIO_MODE_OUTPUT);
gpio_set_level(HEATER_PIN, 1); // Turn on the heater
// Configure ADC
adc1_config_width(ADC_WIDTH_BIT_12);
adc1_config_channel_atten(REDUCING_GAS_CHANNEL, ADC_ATTEN_DB_11);
adc1_config_channel_atten(OXIDIZING_GAS_CHANNEL, ADC_ATTEN_DB_11);
esp_adc_cal_characteristics_t *adc_chars = calloc(1, sizeof(esp_adc_cal_characteristics_t));
esp_adc_cal_characterize(ADC_UNIT_1, ADC_ATTEN_DB_11, ADC_WIDTH_BIT_12, DEFAULT_VREF, adc_chars);
while (1) {
uint32_t reducing_raw = adc1_get_raw(REDUCING_GAS_CHANNEL);
uint32_t oxidizing_raw = adc1_get_raw(OXIDIZING_GAS_CHANNEL);
uint32_t reducing_voltage = esp_adc_cal_raw_to_voltage(reducing_raw, adc_chars);
uint32_t oxidizing_voltage = esp_adc_cal_raw_to_voltage(oxidizing_raw, adc_chars);
printf("Reducing Gas Voltage: %d mV\n", reducing_voltage);
printf("Oxidizing Gas Voltage: %d mV\n", oxidizing_voltage);
vTaskDelay(pdMS_TO_TICKS(1000));
}
}ESPHome Example
sensor:
- platform: adc
pin: GPIO19
name: "Reducing Gas Voltage"
update_interval: 1s
- platform: adc
pin: GPIO18
name: "Oxidizing Gas Voltage"
update_interval: 1s
gpio:
- platform: output
pin: GPIO5
id: heater_control
interval:
- interval: 1s
then:
- output.turn_on: heater_controlPlatformIO Example
platformio.ini
[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200PlatformIO Example Code
#include <Arduino.h>
const int reducingGasPin = 19; // Analog input for reducing gas
const int oxidizingGasPin = 18; // Analog input for oxidizing gas
const int heaterPin = 5; // Digital output for heater control
void setup() {
Serial.begin(115200);
// Configure heater pin
pinMode(heaterPin, OUTPUT);
digitalWrite(heaterPin, HIGH); // Turn on the heater
}
void loop() {
int reducingGasValue = analogRead(reducingGasPin);
int oxidizingGasValue = analogRead(oxidizingGasPin);
float reducingGasVoltage = reducingGasValue (3.3 / 4095.0);
float oxidizingGasVoltage = oxidizingGasValue (3.3 / 4095.0);
Serial.print("Reducing Gas Voltage: ");
Serial.print(reducingGasVoltage);
Serial.println(" V");
Serial.print("Oxidizing Gas Voltage: ");
Serial.print(oxidizingGasVoltage);
Serial.println(" V");
delay(1000);
}MicroPython Example
from machine import ADC, Pin
import time
# Pin definitions
reducing_adc = ADC(Pin(19)) # Analog input for reducing gas
oxidizing_adc = ADC(Pin(18)) # Analog input for oxidizing gas
heater_pin = Pin(5, Pin.OUT) # Digital output for heater control
# Configure ADC
reducing_adc.atten(ADC.ATTN_11DB)
oxidizing_adc.atten(ADC.ATTN_11DB)
# Turn on the heater
heater_pin.on()
while True:
reducing_voltage = reducing_adc.read() (3.3 / 4095)
oxidizing_voltage = oxidizing_adc.read() (3.3 / 4095)
print(f"Reducing Gas Voltage: {reducing_voltage:.2f} V")
print(f"Oxidizing Gas Voltage: {oxidizing_voltage:.2f} V")
time.sleep(1)Conclusion
The ESP32 MiCS-4514 Dual Gas Sensor is a powerful Air Quality sensor that offers excellent performance and reliability. With support for multiple development platforms including Arduino, ESP-IDF, ESPHome, PlatformIO, and MicroPython, it's a versatile choice for your IoT projects.
For optimal performance, ensure proper wiring and follow the recommended configuration for your chosen development platform.
Always verify power supply requirements and pin connections before powering up your project to avoid potential damage.
