# Applications of the Open-Source Hardware Arduino Platform in the Mining Industry: A Review
## 3 Arduino in Wearable Systems  
### Overview  
Numerous accidents in underground mines (mainly coal mines) are caused by gas leakages, roof collapses, collisions with equipment, low oxygen concentrations, and other operating conditions. Thus, the mining industry has attempted to monitor positions of equipment, environmental quality, and ground vulnerability and to inform mine workers of this information to secure their safety and health. Toward this aim, in addition to field monitoring methods, various wearable devices and technologies for mine workers have recently been developed [58], particularly since Google Inc. launched head-mounted displays. The purpose of wearable device-based monitoring is similar to that of the aforementioned field monitoring. However, there are differences between the two systems, in that the measured value from the wearable system is more realistic to miners; an alarm can be activated immediately. A wearable safety management system in a mine environment can play a vital role in reducing the risk of accidents and in ensuring the safety and health of each miner. In this process, the Arduino has been applied in the mining industry as a controller for connecting sensing to an actuator, to develop wearable safety management systems such as a (smart or intelligent) helmet or belt. Most wearable systems using Arduino in the mining industry consist of four parts: sensor, microcontroller (Arduino board), communication, and actuator elements (Figure 7). * The sensor in wearable systems is closely related to the purpose of the system being developed. Various types of sensors are available on the market and are usually found on consumer wearable devices according to the intended application, such as environmental sensors, biosensors, and position tracking sensors. These sensors are embedded in wearable devices for observing or measuring real-time underground parameters, such as the gas concentration, temperature, humidity, atmospheric pressure, oxygen concentration (for air quality or air density monitoring purposes), piezoelectric characteristics (for device wearing status monitoring purposes), vibrations (for destructive event or collision detection purpose), human heart rates or pulse rates (for human biocharacteristics monitoring purposes), and positions of machines or workers (for location monitoring purposes). * The microcontroller serves as a platform for receiving the data measured by sensors (sensor output) and for transmitting the data to monitoring stations through wireless communication or actuating a device (e.g., providing alarms such as a buzzer) under specific conditions (called threshold limit values or critical safety values) using the measured data, based on coding or programming an Arduino IDE or Python. Arduino is a widely used hardware with low power usage and an easy-to-use open-source software platform for most electronics projects. Thus, the Arduino Mega, Arduino Nano, and Arduino UNO board (models) are frequently used to control microcontroller boards in systems. * A wireless communication function is necessary to transmit data to a remote office or web server at a control station, as a communication network is generally not installed in underground mines. To establish a wireless communication network, various wireless communication technologies for data transmission and receiving have been utilized in the reviewed published literature, such as ZigBee, Bluetooth, and radio frequency identification. * An actuator refers to something (e.g., wearable device) that actuates something else (e.g., a sound, message, display, or vibration). In particular, an actuator is usually an electric device that causes a mechanical device to switch in some fashion. Various wearable devices have been developed, such as smartwatches, smart eyewear, fitness trackers, smart clothing, and wearable cameras, according to their functional properties and capabilities (Figure 8) [58]. However, most of the studies reviewed in this section employed a (smart) helmet as an actuator.