An Overview about MQ135 Sensor
MQ135 is an air quality sensor that can detect a wide range of gases, comprising NH3, alcohol, smoke, carbon dioxide, and benzene. And, hence ideal for offices, industries or factories, or workplaces. MQ135 gas sensor has an acute sensitivity to Ammonia, Sulfide, smoke, and other toxic gases. Because of its low cost and, it is suitable for air quality monitoring applications.
Internal structure
The MQ135 alcohol sensor comprises a tin dioxide (SnO2), a perspective layer inside aluminum oxide micro-tubes (measuring electrodes), and a heating element inside a tubular casing. There is an enclosed stainless steel net at the end face of the sensor and the backside holds the connection terminals.
Working Principle
When the ethyl alcohol, smoke appears at the sensitive layer of the tin dioxide, the resistance decreases. By using the external load resistance we convert the resistance variation into a suitable voltage variation.
Features and Specifications of MQ135 Sensor
There are many prominent features and specification of MQ135 which makes it more extraordinary
Features
- Good sensitivity to harmful gases in a wide range.
- It has a long life and low cost.
- Possesses high sensitivity to ammonia, benzene, sulfide gases.
- It is a simple drive circuit
- Wide detecting scope
- Fast response and High sensitivity
- Stable and long life
Specifications
- Operating Voltage is +5V
- Detect/Measure NH3, NOx, alcohol, Benzene, smoke, CO2, etc.
- Detection Range: 10 – 300 ppm NH3, 10 – 1000 ppm Benzene, 10 – 300 Alcohol
- Heater Voltage: 5.0V
Pinout of MQ135
| Pin Number | Pin Name | Description |
| 1 | Vcc | The [in is there to power the module, requires 5V |
| 2 | Ground | To connect the module to the system’s common ground |
| 3 | Digital Out | Digital output pin, the Threshold value can be set by using the potentiometer |
| 4 | Analog Out | Analog output pin. Analog voltage based on the concentration of the gas |
Applications of MQ135 Sensor
Air Pollution Detecting Systems
Through this one can monitor the Air Quality over a web server using the internet and will generate an alarm when the air quality gets lower than a certain level. It means it warns a user when there are intolerable amounts of harmful gases are present in the air like carbon dioxide, ammonia, benzene, etc.
Detection of Harmful Gases
A sufficient amount of harmful gases like CO2, alcohol, smoke, benzene, and ammonia can be detected through MQ135.
Breathalyzers
A breathalyzer is a device used for detecting blood alcohol content from a breath sample. This means the device can estimate the volume or amount of alcohol from your breath. Since MQ135 detects alcohol gas, therefore can be used in the breathalyzer.
