October 27, 2017 by Robin Mitchell
This PIC gas alarm system displays detection levels and fires an alarm when a dangerous level of gas is detected.
| 4 | 1K Resistor | ||
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| 3 | 100nF Capacitor | ||
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| 1 | 10uF Capacitor | ||
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| 2 | 1N5817 Diode | ||
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| 1 | LED | ||
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| 1 | 2N3904 | ||
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| 1 | 10K Potentiometer | ||
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| 1 | Buzzer | ||
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| 1 | 16 X 2 LCD | ||
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| 1 | LM7805 | ||
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| 1 | PIC16F1516 | ||
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| 1 | MQ-2 Sensor | ||
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Gases such as natural gas can be incredibly dangerous, and can even lead to death if not kept in check. In this DIY Hacking project, we will look at the MQ-2 Gas Sensor, understand how it works, and learn how to make a simple PIC alarm system that both displays the current detection levels and fires an alarm when a dangerous level of gas is detected.
View the full-size schematic.
The two main components of this project are the MQ-2 sensor and the PIC16F1516. The MQ-2 gas sensor is capable of detecting multiple kinds of explosive gases, such as alcohol, and has high sensitivity to gases including LPG, propane, and hydrogen. At the heart of the sensor is SnO2 (tin oxide), which has a large resistance when in clean air. When the sensor comes into contact with an explosive gas, the sensor's resistance decreases. This sensor is mounted on a PCB that has a comparator circuit, so when the detection level goes beyond a limit, a signal is produced that can be read directly by a PIC (the output pin of the sensor is either 1 or 0). However, the sensor module also has an analogue output, which allows us to make measurements. So the MQ-2 sensor is connected to two pins on port A of the PIC16F1516: RA0 and RA1. RA0 handles the digital signal, which informs the PIC that the gas levels are at a dangerous level, while RA1 handles the ADC conversion, which allows us to display the detected value on an LCD.
The PIC itself runs firmware, which...
You can build this project using most circuit construction techniques, including breadboard, stripboard, matrixboard, and PCB. All the components in this project are available in through-hole packages, and due to some unforeseen circumstances, I could not get a PCB made. Therefore, I opted to use stripboard, which resulted in a rather neat-looking project!
Even though this project can detect explosive gases, it is in no way reliable enough or proven to work in all situations. This is a fun project that aims to explore sensors, so do NOT use this in an industrial environment where people's lives are dependent on the project. If you need a gas alarm, purchase a commercial one that is proven to work!
Graduated from the University Of Warwick in Electronics with a BEng 2:1 and currently runs MitchElectronics.
