Hey readers! I hope you are having a good day. Today, we are learning the basics of another MQ sensor family, the MQ-3. This sensor is designed for the detection of alcoholic gases in the air surrounding it. Gas sensors are widely used in multiple applications, and they provide information to the other components of the circuit. In the air, it can detect the 25-500ppm alcohol gas concentration and is a highly sensitive detector. We are going to study it thoroughly from scratch.
In this article, we are going to start the discussion with the basic introduction of this sensor. We’ll understand its datasheet and will know the basic details about its internal and external structure. After that, we’ll move towards the features, specifications, and best platform to buy these sensors. Then, we’ll see the circuit diagram and working principles, and in the end, we’ll go through the applications of this sensor. All of this is going to be very simple, and we will try to make it useful and uncomplicated. Let’s move on to the first topic:
The MQ-3 is an alcohol gas sensor that belongs to the MQ gas sensor family and is particularly designed using SnO2 to detect the gas using lower electrical conductivity in the air. When fresh air enters the sensor’s structure, this semiconductor gas sensor can detect the presence or absence of alcohol gases. If the target gas is present in the air, the resistance of the semiconductor material is enhanced with the rise in gas concentration. The structure is designed in such a way that it has a high sensitivity to alcohol. Moreover, it has good resistance to gasoline, smoke, and vapors.
The following gases are possible to detect using an MQ-3 alcohol sensor:
The MQ-3 alcohol sensor is studied in different ways. Here are the three tables that will define the specifications of this sensor depending on different sets of parameters:
In the standard work condition, the characteristics given in the table below are considered:
Parameter |
Value |
Units |
Technical Condition |
Remarks |
Symbol |
Vc |
VH |
RL |
RH |
Parameter name |
Circuit voltage |
Heating voltage |
Load resistance |
Heater resistance |
Technical condition |
5V±0.1 AC OR DC |
5V±0.1 ACOR DC |
200KΩ |
33Ω±5% Room Tem |
The following parameters are considered when checking the environmental characteristics of the MQ-3 alcohol sensor:
Symbol |
Parameter Name |
Technical Condition |
Tao |
Operating Temperature |
-10℃-50℃ |
Tas |
Storage Temperature |
-20℃-70℃ |
RH |
Related Humidity |
less than 95%Rh |
O2 |
Oxygen Concentration |
21%(standard condition) |
Moreover, here is the table related to the sensitivity characteristics of the MQ-3 alcohol sensor:
Symbol |
Rs |
α |
Vc |
Vh |
Parameter name |
Sensing Resistance |
Concentration slope rate |
Circuit voltage |
Heating voltage |
Value |
1MΩ- 8 MΩ (0.4mg/L alcohol ) |
≤0.6 |
5V±0.1 |
5V±0.1 |
Technical Condition |
0.4mg/L alcohol |
Standard detecting condition |
N/A |
N/A |
Before learning the structure diagram, it is important to understand the configuration of the sensor. It contains three sets of pins (collectively six pins):
The above images show the 2D configurations of the MQ-3 alcohol gas sensor. The details of these pins will be discussed in the table below:
Pin Name |
Function |
H1 |
Heater power supply (5volts DC) |
H2 |
Ground |
A1 |
Sensor supply voltage (5 volts DC) |
A2 |
Output voltage (analog, proportional to alcohol concentration) |
B1 |
Ground |
B2 |
Not used (can be left floating) |
The core material in these gas detectors is highly sensitive to heat which plays an important role in gas detection. Before using any sensor, it is crucial to check its sensitivity graph. Here is the graph for the MQ-3 alcohol sensor:
In the figure above, the parameters used are understood by the following explanation:
So it was the information about the datasheet, and if you require more details, then you visit the following link:
The MQ-3 alcohol sensor has four external pins, and its pin diagram is given here:
A brief description of each of them is given in the table:
Pin Name |
Function |
VCC |
Sensor power supply (typically 5 volts DC). It provides the main operating voltage for the sensor. |
GND |
It is the ground pin. This is the reference point for electrical connections and ensures proper circuit operation. |
Heater |
Heater element power supply, which is typically 5 volts DC. This powers the internal heater element and plays a crucial role in the sensor's response to alcohol. |
AO |
It is an analog output voltage level proportional to alcohol concentration. This pin provides an analog voltage signal that varies based on the amount of alcohol detected by the sensor. Here, the specific voltage range and sensitivity will depend on the specific sensor model and surrounding conditions. |
Package Format |
Description |
Applications |
DIP (4-pin) |
Standard through-hole, easy prototyping |
|
DIP (6-pin) |
Standard through-hole, with additional pins for features |
|
SMD |
Compact surface mount for PCBs |
|
TO-220 |
Larger package with heat dissipation tab |
|
Custom Module (Basic) |
Encapsulated with basic circuitry |
|
Custom Module (Advanced) |
Encapsulated with additional features & communication |
|
The MQ gas sensor family works on the detection of different gases. In some cases, these can be used alternatively. But if we talk about the other classes of gas sensors, some other detectors can be used in place of the MQ-3 sensor, and these are listed below:
There are different ways to buy electronic components like MQ-3 but the most promising platforms to buy these products online are:
The working principle of the MQ-3 alcohol sensor can easily be understood by learning its internal structure. It is a heat-driven sensor and, therefore, is covered under the mesh known as the anti-explosion network. This network is the double layer of the stainless steel material that ensures the heat-sensitive material inside the sensor remains safe from the outside’s flammable gases. The special feature of its structure is the presence of a plastic cover that we don't see in models like MQ-2. This cover not only protects the sensor but is also responsible for filtering unwanted materials.
Inside this mesh, there is a simple star-like structure of the sensing material surrounded by the size elements. These are called the connecting legs and consist of three pairs of leads. The two H leads are connected to the Nickel-Chromium coil. It is a popular conductive alloy that helps to maintain the connection between the star-structured elements.
The remaining leads (A and B) are connected with the sensing element. All of these are connected together with the help of platinum wires that make the structure more protected and provide conductance as well.
In the case of the MQ-3 alcohol sensor, aluminum oxide (AL2O3) ceramic with a tin dioxide coating (SnO2). is used in the form of a tubular structure and is known as the sensing element. It is important to notice that tin oxide is the most important element here because it is sensitive to alcohol, which is the basic purpose of this sensor. The role of aluminum oxide is to improve efficiency and heat sensitivity. It maintains the continuous heating of the system and, as a result, helps in efficient results.
Now, that you know the basic structure, you can understand the flow of the MQ-3 sensor:
The physical dimension of the MQ-3 alcohol sensor is similar to that of its other companion sensors. These are mentioned in the table below:
Dimension |
Value |
Units |
Notes |
Diameter |
20 |
mm |
N/A |
Height |
30 |
mm |
N/A |
Pin Length |
4-5 |
mm |
Can vary slightly depending on the manufacturer |
Weight |
~8 |
grams |
N/A |
Mounting Hole Distance |
18 |
mm |
Centre-to-centre distance between holes |
Pin Pitch |
2.54 |
mm |
Distance between pin centers |
The MQ-3 is designed to test the presence of alcohol-related gases. It is usually the part of the project that is designed for safety purposes. Here are some common applications for which MQ-3 is a popular choice:
One must keep in mind before using this sensor that it is not an accurate sensor and certain limitations are tied to it. Therefore, it is not suitable for critical applications that require precise measurements.
Hence, today we have learned a lot about the MQ-3 alcohol sensor. It is a sensitive alcohol detector that is used to detect multiple gases. We have seen the data sheet of this sensor, where we have seen the pin configuration, working conditions, and internal structure of the MQ-3 alcohol sensor. After that, we saw the working principle in detail, and after knowing the physical dimensions, we saw the applications of this sensor. I hope I have conveyed all the points, but still, if you want to know more, you can ask in the comment section.
Hello learners! I hope you are doing good. Today, we are learning about an important member of the gas sensor family, which is the MQ-2. When it comes to detecting or measuring smoke or gas, the MQ series gas sensors are widely used components in circuits. These sensors come with an operational amplitude comparator and a digital output pin therefore, they have applications in multiple fields of life. Mostly, it is used in Arduino projects where it senses the gas and the information is fed into the Arduino to allow the circuit to work according to its digital output.
In this article, we are going to discuss the basic introduction of this sensor in detail, along with the datasheet. Moreover, we’ll know its pinouts in detail and will see some important circuit diagrams. Moreover, we’ll try to figure out the workings and applications of this sensor in different domains to understand the core concept. This is going to be a detailed article on the MQ-2 sensor, so let’s get started.
The MQ-2 is a metal oxide semiconductor (MOS) gas sensor and one of the most widely used sensors in the MQ series. We know that MOS sensors are known as Chemiresistors because there is a sensing material in them that works based on the change in its resistance when it is exposed to the reactive gas. Hence, when using the MQ-2 in the circuit, it can detect multiple gases and provide the digital values of change in the gases at its output pin. The list of gases this sensor can detect is given next:
This sensor is particularly suitable to detect combustible gases, smoke, and other pollutants. Basically, it consists of the tin dioxide (SnO2) semiconductor gas sensor, a comparator (using the op-amp), and necessary supporting components.
Before using any electrical component, it is important to study its datasheet. The datasheet has multiple characteristics, and some of these are mentioned below:
Here is a table that provides the basic details of the MQ-2 smoke/gas sensor:
Parameter |
Value |
Units |
Model Number |
MQ-2 |
N/A |
Sensor Type |
Semiconductor |
N/A |
Standard Encapsulation |
Bakelite (Black) |
N/A |
Detection Gas |
Combustible Gas & Smoke |
N/A |
Concentration Range |
300-10000 ppm (Combustible Gas) |
ppm |
Loop Voltage (Vc) |
≤ 24 V DC |
N/A |
Heater Voltage (VH) |
5.0 V ± 0.2 V |
DC/AC |
Circuit Load Resistance (RL) |
Adjustable |
Ω |
Heater Resistance (RH) |
31 Ω ± 3 Ω |
Ω (Room Temp.) |
Heater Consumption (PH) |
≤ 900 mW |
N/A |
Sensing Resistance (Rs) |
2 KΩ - 20 KΩ (in 2000 ppm C3H8) |
Ω |
Sensitivity (S) |
Rs(in air)/Rs(1000 ppm isobutane) ≥ 5 |
N/A |
Character Slope (α) |
≤ 0.6 (R5000 ppm/R3000 ppm CH4) |
N/A |
Temperature & Humidity |
20°C ± 2°C; 65% ± 5% RH |
N/A |
Standard Test Circuit (Vc) |
5.0 V ± 0.1 V |
DC |
Standard Test Circuit (VH) |
5.0 V ± 0.1 V |
DC/AC |
Preheat Time |
Over 48 hours |
N/A |
The sensors can detect multiple gases, and the sensitivity of the resistive material is different for all of them. Based on the multiple experiments and the specification, here is the sensitivity graph for the MQ-2 smoke/gas sensor:
The sensitivity material is affected not only by the type of gas but also by other parameters such as humidity and temperature. Here is the graph that shows the details:
If you want to know more details about the datasheet, then here is the link to it:
The MQ-2 smoke/gas sensor has four pins, as shown below in the image:
The pin arrangement may vary depending on the model. Here, one must know that the DOUT pin is not always present, but some models do not have it, and in such cases, the analogue pin AO is the output pin. The details of each pin are given next:
Pin Number |
Pin Name |
Function |
1 |
VCC |
Supplies power to the sensor (typically 5 volts DC) |
2 |
GND |
Ground connection |
3 |
DOUT (optional) |
Digital output pin (usually pulled high when no gas detected, goes low when gas detected) |
4 |
AOUT |
Analog output pin (voltage level varies depending on gas concentration) |
The internal structure is shown below to add more detail in this discussion:
Package Type |
Description |
Pros |
Cons |
Applications |
Breakout Board |
Sensor mounted on a board with labelled pins and components. |
- Easy to use. - Provides stable operation. |
- May not have advanced features. |
Hobbyist projects, educational use, gas detection. |
Integrated Module |
Sensor with additional circuitry like a microcontroller. |
- Advanced features (calibration, digital output). |
- Higher cost. - May be less customizable. |
Industrial applications, gas detection systems. |
Sensor Type |
Examples |
Electrochemical Sensors |
Figaro TGS series, Sensirion SGP series, Amphenol NovaSens SC series |
Improved MOS Sensors |
Sensirion SPS30, Shinyei Figaro TGS822, and Amphenol NovaSens SCS series |
Optical Sensors |
Laser-based gas detectors, Infrared (IR) gas sensors, and photoionization detectors (PIDs) |
Other Alternatives |
MEMS-based gas sensors |
Biomimetic sensors |
In addition to all these, the MQ series has multiple members that are widely used in place of MQ-2. These may include
Along with millions of other products, sensors like MQ-2 smoke/gas sensors are available at the following platforms:
eBay
Amazon
AliExpress
The working principle and characteristics of the MQ-2 are easily understood by studying the internal structure in detail. Here is the detail of each part, and we’ll discuss the working principal using the following structure:
As mentioned before, the MQ-2 smoke/gas detector works on the principle of chemisorption. It is defined as:
"Chemisorption is the process by which the molecules of the material adhere to the solid surface because of the chemical bonding."
In the case of MQ-2, chemisorption is the process in which the gas molecules surrounding the sensor interact with its surface material and cause a change in the electrical resistance.
It is a heat-driven sensor, therefore it is covered with two layers of steel mesh. These layers are referred to as the anti-explosion network. This sensor is designed to detect combustible gases; therefore, the anti-explosion network is responsible for the protection of the heater element from the surrounding gases.
This network is in the form of a mesh so that it filters the suspended articles and allows only gases to reach the internal sensitive circuit. A copper plating is used to secure the mesh at its place.
When the mesh is removed, the following structure is seen:
This star-shaped structure is responsible for the detection of the gas. Here is the explanation of each element:
Once the gas enters this internal chamber, it reacts with the depletion region of the sensing element. As a result, the amount of oxygen decreases depending on the amount of the external gas, and as a result, there is a change in the resistance. The magnitude of this change determines the amount of combustible gas surrounding the gas sensor.
The sensor has a voltage divider circuit that converts the change in resistance into the output voltage, which is then sent as an output through the pin.
Most features of this sensor have been discussed so far in this article, but here is a quick revision of these features:
This is a simple-to-use sensor that is compatible with multiple circuits. Another feature that supports its importance is its low cost and high-quality performance.
The following table shows the dimensions of this sensor:
Dimension |
Value |
Units |
Diameter |
20 |
mm |
Height |
30 |
mm |
Pin Length |
4-5 |
mm |
Weight |
~8 |
grams |
The smoke and gas detector sensors are used in different ways in the project and are one of the most important parts of such circuits. Here are some basic examples of MQ-2 smoke/gas sensor applications:
Residential gas leak detection (homes)
Industrial gas leak detection (factories)
Basic fire alarm systems (buildings)
General air quality monitoring (sensor network)
Portable gas detectors (personal safety)
Educational electronics projects
Hence, today we have learned the basic information and its detailed specifications. We started with the basic introduction of the MQ-2 sensor and how it works. We understood its features, and workings and read the datasheets. In the end, we see some simple applications in different domains of life. I hope this was an informative guide for you, and if you want to add more information in it, you can comment to us.
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