MQ4 Gas Leak Detection System using ESP32 and MicroPython
MQ4 Gas Leak Detection System using ESP32 and MicroPython is a runnable microcontroller simulation example on SensBench — open the wired circuit, inspect the code, and compile real firmware in your browser, no install needed. Last updated Aug 14, 2026.
FREE SIMULATOR EXAMPLE · BEGINNER
MQ4 Gas Leak Detection System using ESP32 and MicroPython
This example runs a gas leak detector on the ESP32 — the MQ4 methane sensor, a warm-up delay, and a threshold alert loop. The kitchen gas-alarm pattern in MicroPython.
| Board | ESP32 DevKit (Xtensa LX6, 240 MHz) |
|---|---|
| Difficulty | beginner |
| Category | basics |
| Libraries | None — just the Arduino core |
| Runs in | Sensbench browser simulator — free, no account |
The exact circuit you get when you open this example — already wired, ready to run.
The sketch
# main.py
from machine import ADC, Pin
import time
# MQ4 gas sensor setup
mq4 = ADC(Pin(34)) # Analog input pin
mq4.atten(ADC.ATTN_11DB) # Full voltage range
mq4.width(ADC.WIDTH_10BIT) # 10-bit resolution
# Buzzer setup
buzzer = Pin(15, Pin.OUT)
# Threshold for gas alert (tune this based on testing)
GAS_THRESHOLD = 240
while True:
gas_value = mq4.read()
voltage = gas_value * 3.3 / 1023
print("Gas reading (raw):", gas_value)
print("Voltage:", round(voltage, 2), "V")
# Alert condition
if gas_value > GAS_THRESHOLD:
buzzer.on()
print("⚠️ Gas leak detected! Buzzer ON")
else:
buzzer.off()
print("----------------------------")
time.sleep(2)How it works
The firmware reads the MQ4’s analog output after a warm-up delay and compares it to a threshold. Above it, the alert path triggers — an LED and serial message, with the buzzer or relay being the real-world actuator. The loop samples continuously so a leak is caught within one sample period.
The threshold is the calibration point: the MQ4’s baseline varies with clean-air conditions, so the code’s threshold must be set against the sensor’s actual baseline, not a datasheet number. The serial output logs the raw reading, which is how the threshold gets tuned.
Before you build it for real
The MQ4’s warm-up is mandatory — 20-30 seconds on real hardware, and readings taken early are garbage; the simulator’s instant readiness hides a real deployment’s startup window. The threshold drifts with humidity and temperature — the sensor’s baseline shifts with the weather, so a threshold set in winter alarms falsely in summer; real designs use a self-calibrating baseline. And the sensor alone is not a safety system — gas detectors need redundancy, alarm persistence and placement near the ceiling (methane rises), none of which the firmware can provide.
Get the parts
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FAQ
What does the MQ4 detect?
Methane and natural gas (CNG/LNG) — the MQ4’s tin-oxide element changes resistance in the presence of combustible gas. It is the classic kitchen gas-leak sensor, and the firmware’s job is the threshold-and-alert loop around it.
Why does the sensor need warm-up?
The MQ4’s heater element must reach operating temperature before the sensing surface stabilizes — typically 20-30 seconds on real hardware. Readings taken during warm-up are meaningless, which the firmware’s startup delay accounts for.