# Applications of the Open-Source Hardware Arduino Platform in the Mining Industry: A Review
## 2 Arduino in Field Monitoring Systems
### Atmospheric Monitoring  
[PERSON] et al. [33] developed a system for measuring hazardous gases and temperatures in underground mines and providing warning messages using light fidelity (Li-Fi) technology. Li-Fi uses light from the infrared to the near-ultraviolet spectrum. An LM35 sensor was used to measure the temperature in the underground environment, and an MQ2 sensor was used to detect combustible gases such as liquefied petroleum gas (LPG), propane, hydrogen (H\({}_{2}\)), and methane (CH\({}_{4}\)). A system using the Arduino UNO as a microcontroller was built in each of the mining and control rooms. The system in the mining area transmitted information to the control room through Li-Fi after measuring the gas and temperature, and the control room served to collect information from multiple mining areas. As Li-Fi was used as the communication technology, this study had the advantage of being secure; there was no interference with radio frequencies. However, there were limitations; only laboratory tests were conducted, without application to actual mines. [PERSON] and [PERSON] [34] established a monitoring system based on ZigBee communication for safety in coal mines. The temperature was measured using the LM35 sensor, and the gas was detected using an MQ6 sensor. The MQ6 sensor is used to detect gases such as propane, butane, LPG, and natural gas. In addition, a fire sensor that could detect fires within 1 m was used to prevent fires. The measured value could be checked through a liquid crystal display (LCD), and an alarm could be triggered through a buzzer. The fire could be extinguished using a motor and fan, but the effectiveness of this approach was not verified, as it was not applied to an actual mine site. Using Arduino UNO as a microcontroller, it involved connecting sensors and actuators and building a ZigBee-based WSN. The monitoring system consisted of an underground section and ground section. The underground section acquired and transmitted information, and the ground section received information. In a similar way, a real-time monitoring system for underground mines [35] was constructed using Arduino UNO and ZigBee modules. In this study, an MQ7 sensor for carbon monoxide (CO) detection, an MQ4 sensor for CH\({}_{4}\) detection, an MG811 sensor for carbon dioxide (CO\({}_{2}\)) detection, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sensor Name** & **Sensor Type** & **Detect** \\ \hline MQ2 & Gas sensor & Methane, butane, LPG \({}^{1}\), smoke \\ \hline MQ3 & Gas sensor & Alcohol, ethanol, smoke \\ \hline MQ4 & Gas sensor & Methane, natural gas \\ \hline MQ6 & Gas sensor & LPG, butane gas \\ \hline MQ7 & Gas sensor & Carbon monoxide \\ \hline MQ8 & Gas sensor & Hydrogen gas \\ \hline MQ9 & Gas sensor & Carbon monoxide, flammable gases. \\ \hline MQ135 & Gas sensor & Air quality (benzene, alcohol, smoke) \\ \hline MQ136 & Gas sensor & Hydrogen sulfide gas \\ \hline MG811 & Gas sensor & Carbon dioxide \\ \hline MiCs2714 & Gas sensor & Nitrogen dioxide \\ \hline DHT11 & Temperature and Humidity sensor & Temperature range: 0-50 \({}^{\circ}\)C (\(\pm\)2 \({}^{\circ}\)C) \\  & Humidity range: 20–80\({}^{\circ}\)RH (\(\pm\)5\({}^{\circ}\)RH \({}^{2}\)) \\ \hline DHT22 & Temperature and Humidity sensor & Temperature range: \(-\)40–80\({}^{\circ}\)C (\(\pm\)0.5 \({}^{\circ}\)C) \\  & Humidity range: 0–100\({}^{\circ}\)RH (\(\pm\)2\({}^{\circ}\)RH) \\ \hline LM35 & Temperature sensor & Temperature range: \(-\)55 \({}^{\circ}\)C to 150\({}^{\circ}\)C (\(\pm\)0.5 \({}^{\circ}\)C) \\ \hline ADXL335 & Accelerometer & 3-axis sensing (\(\pm\)3 g measurement range) \\ \hline ADXL345 & Accelerometer & 3-axis sensing (\(\pm\)16 g measurement range) \\ \hline \hline \end{tabular} \({}^{1}\) LPG: liquefied petroleum gas. \({}^{2}\) RH: relative humidity.  
\end{table} 
Table 3: Sensors used in the reviewed articles for field monitoring. and a DHT11 sensor for temperature and humidity were used. When a value above a threshold was measured, it was possible to provide an alert through a buzzer and LCD.