Introduction: Gas Detector

By Electronic Circuits
About: We are a group of people that design amateur electronic circuits.

This article describes implementing a basic gas detector with a gas detector sensor circuit and a voltmeter. Both circuits can be ordered on eBay, Amazon, or Aliexpress. You can see how the circuit in the video detects the presence of the gas that is used in gas stoves. You can watch the second video with music to see a summary of this article.


The voltmeter circuit can work with voltages between 3 V and 9 V. The gas sensor circuit needs 5 V. I used a 6 V battery holder that holds four 1.5 V AA batteries. Because I used rechargeable batteries that have a voltage of 1.2 V instead of 1.5 V, the total voltage was 1.2 V * 4 = 4.8 V (not 6 V). If I used lithium 1.5 V batteries then I would have needed to connect a 0.7 V general purpose diode in series with the power supply to reduce the voltage from 6 V to 5.3 V. I can use an additional 0.3 V Schottky diode in series with general purpose diode to further reduce the voltage to 5 V.


Nowadays, you can buy a 6 V battery holder with 5 V USB output. However, you will need the USB plug for that device.


The circuit can be connected to a comparator with a buzzer to make a gas leak alarm.

Supplies

Components: small matrix board, gas detector circuit, voltmeter circuit, 6 V AA/AAA quad battery holder, four AA/AAA rechargeable batteries, 0.9 mm metal wire.

Tools: wire stripper, pliers, screw driver.

Optional components: lead-free solder, general-purpose diode.

Optional tools: 60 W soldering iron (for the lead-free solder).

Step 1: Connect the Gas Sensor

Connect the gas sensor circuit to the socket jumper leads. The gas sensor circuit has four pins. One pin for positive Vcc (5 V), one pin for negative ground (0 V), one for analogue output (AO), and one for digital output (DO). There is also a potentiometer to adjust the offset voltage when no gas is detected. I connected the jumper leads to all pins except for digital.

Step 2: Make the Circuit

I connected the gas detector to the voltmeter and power supply. I did not connect a diode in series because I used 1.2 V rechargeable batteries instead of 1.5 V batteries. I did not use a soldering iron. I twisted the wires with my fingers and pliers.

Step 3: Testing for CO2 Gas

Testing on CO2 from my breath shows a very small change in voltage.