FINAL YEAR PROJECT 1 (WEEK 11): Alcohol Sensor

Objectives:

1) To know the operation theory of alcohol sensor

2) To find suitable alcohol sensor

Method:

1) By making research in the internet

There are a number of alcohol sensors on the market. Police use them to estimate blood alcohol concentration (BAC) although this is more accurately determined through a blood test. Alcohol gas sensor detects the concentration of alcohol gas in the air and output its reading as an analog voltage. On the market there are different types of sensors to detect gas alcohol such as ethanol. There are five common families to detect the alcohol which are:

1) Catalytic combustion sensors

2) Sensors semiconductor flat surfaced (advanced flat surfaced alcohol sensor)

3) Sensors semiconductor specific

4) Electrochemical sensors(fuel sensor)

5) Infrared sensors

For this project, semiconductor sensor is chosen to detect the alcohol gas and the type that had be chosen is MQ-3 semiconductor sensor. Sensitive material of MQ-3 gas sensor is thin oxide (SnO₂)

which with lower conductivity in clean air. When the target alcohol gas exist, the sensor's conductivity is more higher along with the gas concentration rising. The change of conductivity is converted to correspond output signal of gas concentration. MQ-3 gas sensor has high sensitivity to alcohol and has good resistance to disturb of gasoline, smoke and vapor. The sensor could be used to detect alcohol with different combustion, it is with low cost and suitable for different application.

Configuration 

Features

• Good sensitivity to alcohol gas
• Long life and low cost
• Simple drive circuit

Application

• Vehicle alcohol detector
• Portable alcohol detector

The alcohol sensor MQ-3 suitable for detecting alcohol concentration in breath like a common breathalyzer such as portable alcohol detection. It provides an analog resistive output based on alcohol concentration. The resistance of the sensor reduces when alcohol concentration increases. The sensor gives output as per the condition of the breath through the logic circuit which is sent to microporcessor. This power supply needs for this sensor is 5V. 

MQ-3 ALCOHOL SENSOR CIRCUIT

PIN CONNECTION

MQ-3 ALCOHOL SENSOR

There are conditions that we need to follow so that the this alcohol function as we need. The conditions are:

1. Organic silicon steam cause invalid, sensors must be avoid exposing to silicon bond, silicon latex, putty or plastic contain silicon environment.
2. If the sensors exposed to high concentration corrosive gas, it will not only result in corrosion of sensors structure but also it cause sincere sensitivity attenuation.
3. The sensor performance will be change badly if sensors be sprayed polluted by alkali metals salt especially brine or be exposed to halogen such as fluorin.
4. Sensitivity of the sensors will be reduced when spattered or dipped in water.
5. Do avoid icing on sensor's surface otherwise sensor will lose sensitivity.
6. Applied voltage on sensor should not be higher than stipulated value otherwise it cause down-line or heater damaged and bring on sensors' sensitivity characteristic change badly.
7. In indoor conditions, slightly water condensation will effect sensors performance lightly. however, if water condensation on sensors surface and keep a certaion period, sensor sensitivity will be decreased.
8. The sensor resistance produce reversible drift if it's stored for long time without eectrify which drift related with storage conditions. sensors should be stored in airproof without silicon gel bag with clean air. for the sensors with long time storage but no electrify, they eed long aging time for stability before using.
9. Continual vibration will result in sensors down-lead response then repture. 
10. If sensors meet strong concussion, it may lead its lead wire disconnected. 

First test with MQ-3 Alcohol sensor

Conclusion:

This week I am going to learned about the alcohol sensor as it is the one of the component which is used in my project. The type of alcohol sensor and the application of of it need to take note so that it is suitable to use in this project. This project will used the MQ-3 alcohol sensor. The alcohol sensor sense the alcoholic content if the rider is drunken. If the driver is drunken, the LCD display will displayed to give information that the rider is drunken and the motorcycle cannot start. This will ensure safety of the rider because he or she cannot ride the motorcycle if he or she is drunken which will decrease the potential of the accident happens.