MQ-4 Natural Gas & CNG Sensor Module - High Sensitivity Methane Detector

Specifications

• Target Gas: Methane (CH4), Natural Gas (CNG)

• Secondary Sensitivity: Propane, Butane (Alcohol/Smoke interference is low but present).

• Operating Voltage: 5V DC ±0.1

• Heater Consumption: < 150mA (750mW)

• Detection Range: 200ppm – 10,000ppm (Methane)

• Output Format:

  • Analogue (A0): Voltage increases with gas concentration.

  • Digital (D0): Logic Low (0V) when threshold is exceeded (Active Low).

• Response Time: < 10s

• Dimensions: 32mm x 20mm x 22mm

Compatibility & Platform Support

• Arduino (Uno/Nano/Mega): Directly Compatible. The 5V supply and logic levels match perfectly.

• ESP32 / ESP8266:Caution Required. The Analog output can reach ~4.0V. You MUST use a voltage divider (e.g., 10kΩ/20kΩ resistors) to reduce the signal to 3.3V to protect your ESP32.

• Raspberry Pi : Requires ADC. The Pi has no analogue inputs. Use an external ADC (MCP3008) or an ADS1115 module to read the sensor data.

Key Applications & Projects

• Smart Kitchen Alarm: Trigger a buzzer and send a WiFi alert (via ESP32) if a stove leak is detected.

• Coal Mine Safety: Monitor methane build-up in enclosed underground environments.

• Biogas Plant Monitor: Measure the output quality and presence of methane in biogas digesters.

• Industrial Leak Sniffer: A handheld wand for checking pipe joints and valves.

Project Evolution

• Prerequisites: Familiarity with analogRead() and calibrating sensors in "clean air".

• The Upgrade: Moving from the general-purpose MQ-2 (Smoke/LPG) to the MQ-4 gives you Specific Selectivity for Natural Gas, reducing false alarms from cooking smoke.

• Effort Level: Intermediate. While wiring is easy, converting voltage to PPM requires deriving a mathematical curve based on the datasheet's logarithmic graph.

Virtual Technician: Wiring & Safety ⚠️

• VCC: Connect to 5V (Stable source required).

• GND: Connect to Common Ground.

• D0: Connect to Digital Pin (for alarm trigger).

• A0: Connect to Analogue Pin (for measurement).

• Power Warning: This sensor consumes ~150mA. Do not power it from a weak USB port or alongside servo motors, as voltage drops will cause erratic readings.

Accessories

• Included in the Package: 1 x MQ-4 Methane/CNG Gas Sensor Module

• Required Accessories (Not Included):

  • Main Board: Arduino Uno / Nano.

  • Indication: Active Buzzer (5V) for audio alarms.

  • Power: 5V 1A Adapter (Recommended over USB power).

  • Connectivity: Jumper Wires (Female-Male).

Frequently Asked Questions (FAQ)

• What is the difference between MQ-2, MQ-4, and MQ-5? MQ-2 is for Smoke/LPG (General). MQ-4 is tuned specifically for Methane (CNG). MQ-5 is tuned for LPG (Liquid Petroleum Gas).
• Can I test this with a lighter? Yes, but standard lighters use Butane. The sensor will react, but it is calibrated for Methane. It's good for a "function check" but not calibration.
• Why is the sensor hot? The internal heater must reach ~40°C to activate the chemical sensing layer. This is normal.
• How do I calibrate it for 0ppm? Power it in clean air for 24 hours. Measure the voltage (Ro). Use this baseline in your code.
• Does it detect Carbon Monoxide (CO)? It has very low sensitivity to CO. Do not use it as a safety monitor for CO. Use MQ-7 instead.
• Can I use a 9V battery? No. 9V will destroy the heater. You must regulate it to 5V.
• Why is the digital LED always on? The sensitivity potentiometer might be set too low. Turn the blue knob counter-clockwise until the LED turns off.
• Is it waterproof? No. Moisture damages the sensor. Use a weatherproof enclosure with airflow holes for outdoor use.
• What is the lifespan? Approx 4-5 years if not exposed to corrosive gases or water.
• Can it detect "Town Gas"? Yes, if the town gas is Methane-based (Natural Gas).
• Why does the reading spike when I turn it on? The sensor needs 30-60 seconds to stabilize chemically on startup. Ignore the first minute of data.
• Can Raspberry Pi power this directly? The 5V pin on the Pi can power it, but do not connect the output pins directly to the Pi's GPIO.
• Does humidity affect readings? Yes, high humidity can slightly lower the resistance. Datasheets provide compensation graphs.
• What is the "Preheat" time? For a quick test: 5 minutes. For a reliable safety device: 24 hours.
• Can I extend the sensor with long wires? Analog signals degrade over long wires. Keep wires under 50cm or use the Digital output for long runs.
• How do I convert voltage to PPM? You need to use the Rs/Ro ratio and the log-log formula found in the datasheet.
• Is this sensor UL/CE certified for home installation? No, this is a component for development/prototyping, not a certified consumer appliance.
• Can I use it to detect sewer gas? Sewer gas contains Methane, so yes, it will detect it.
• What happens if I reverse VCC and GND? The module typically has no reverse protection and may be damaged permanently.
• Can it control a solenoid valve directly? No, the output current is tiny. You need a Relay Module to switch a valve or heavy load.