Soldering the DIY Gas Detector

Written By: Marcus Schappi

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Difficulty
Easy
Steps icon
Steps
8
In this tutorial, you’ll guide users through soldering the components of a DIY gas detector module. The kit likely includes a gas sensor MQ2, headers, resistors, and a PCB. The end goal is a functional sensor board that can detect gases such as CO, methane, or LPG

Step 1 Tools and Materials

Step 2 Kit Components


Component -
MQ2 Gas Sensor -  Main sensor (large metal can)
PCB with Silkscreened with component layout
Buzzer for Sound alert
Potentiometer (Trimpot) - Sensitivity adjust
IC Socket + IC socket -  NE555 comparator
Resistors x4 
Rectifier Diode - Polarity protection
Green + Red LEDs - Status indicators
Orange Relay - For triggering external loads
Barrel Jack- Power input 6V Required
Switch - Power Control

Step 3 Add Resistors

 Insert Resistors (R1–R4)
Bend leads to fit the holes.

Match resistor values according to the silkscreen.

R1 and R2 are 1K resistors - 
  • 1kΩ resistor colour code (4-band):
  • Brown
  • Black 
  • Red 
  • Gold

R3 is 130R
  • Brown
  • Orange
  • Brown
  • Gold

R4 is 5.1R
  • Green
  • Brown
  • Gold
  • Gold

Insert, flip the board, solder, and trim.

Step 4 Add Trimpot (VR1), Buzzer and Power Jack


Add Trimpot (VR1)
  • Used for threshold adjustment.
  • Push in as far as it will go and solder.

Add the Buzzer (BZ1)
  • Match polarity if marked (+ or –).
  • Peel off the sticker and you will see a + on top.
  • Push through, solder, and trim.

Add Power Jack (J1) 
  • These parts take more heat—use flux if needed.
  • Solder carefully so joints are solid.

Step 5 Add Red and Green LED

 Solder the LEDs (D2 = Green, D3 = Red)
  • Match the flat side (cathode) with the flat line on the PCB.
  • The longer leg should be near the edge of the board.
  • Test with a coin cell before soldering if unsure.

Step 6

Insert the Relay (RL1)
  • Align pin layout carefully (may only fit one way).
  • It should sit flat against the board.

Mount the Gas Sensor

Solder the 3-pin Switch

Step 7 Install the IC Socket

 Install the IC Socket (U1)
  • Align the notch in the socket with the notch on the PCB marking.
  • Solder all 8 pins.

Insert the IC into the Socket
  • Ensure orientation notch matches socket and silkscreen.

Step 8 Power and Test

Power & Test

Supply 5V–9V via barrel jack
Sensor warms up (1–2 min)
Adjust the potentiometer until:
Green LED = baseline OK.
Red LED or buzzer = gas detected.
Test with a source of gas (e.g., lighter held near sensor—not lit!).