# The Use of Wireless Networks and Mobile Applications in the Control of Electric Machines
## 2 Selected Wireless Transmission Technologies  
There are two main wireless transmission technologies used in remote control strategies: Wi-Fi and Bluetooth. They are easy and cheap to implement, they have been tested under various conditions and each smartphone is equipped with such a standard. Another advantage is a relatively simple implementation of these technologies on currently accessible digital platforms such as Arduino, Raspberry PI and NodeMCU v3. In addition, their range and data rates meet the requirements with an excess. Bluetooth belongs to the open specification of computer and telecommunication technology IEEE 802.15.1, which enables wireless communication over short distances within a range of about 10 m [15; 16]. Due to the fact that the Bluetooth communication range is small, it is most often used in order to replace cable connections of ICT (information and communication technology) and computer devices in close vicinity of the computer. Bluetooth wireless communication creates a WPAN (IEE 802.15) Personal Area Network (WPAN), in which devices change their location in accordance with the users' movement. These types of devices include mostly mobile phones, smartphones, digital cameras, audio sets, cameras, printers, scanners, and other devices in which wired communication is of little use [16; 17; 18]. Wi-Fi network constitutes the most popular wireless communication technology used by devices nowadays and belongs to the 802.11x standard, which describes WLAN local networks. It uses radio waves for communication and data transfer. Using a Wi-Fi module is notably suitable for bandwidth, high speed and large distance coverage as well [19; 20]. The frequency bands used by Wi-Fi network are 2.4 GHz and 5 GHz, however, there are several varieties of this technology as it has been evolving since 1997. The typical ranges of Wi-Fi transmission in an open area and inside buildings are about 100 m and 30-50 m, respectively [21; 22]. The list of selected standards of 802.11 transmission is presented in Table 1.  
Presented list summarizes selected parameters and features of both described wireless transmissions. Paper [10] presents a broad comparison of protocols used in Internet of \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Standard**} & **Theoretical** & \multirow{2}{*}{**Frequency**} & **Date of** & **Modulation** \\  & **Throughput** & & **Introduction** & **Technique** \\ \hline
802.11n & 600 Mb/s & 2.4 GHz and 5 GHz & 02-2006 & OFDM \\
802.11 ac & 1 Gb/s & 2.4 GHz and 5 GHz & 2013 & OFDM \\
802.11 ax & 10 Gb/s & 2.4 GHz and 5 GHz & 2017 & OFDM \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of selected standards of the 802.11 transmission. Figure 1: Schematic diagram of an open-loop remote control system of a DC electric drive. Things (IoT) technologies, for example, LoRaWAN, NB-IoT, ZigBee, 6 LoWPAN, etc. In typical IoT applications, wireless transmission technologies characterized by very low energy consumption are the ones which are most often used (e.g., devices supporting them can operate on a battery for a year or two). However, these are mostly low-speed solutions and they require specialized and dedicated devices to build the transmission infrastructure. A comparison of selected parameters of the applied wireless transmission technologies with the technologies used in IoT solutions is presented in Table 2[23]. Figures 2 and 3 show the diagrams of systems that constitute controllers realizing described methods of wireless transmissions. They also give the possibility of the measurements of consumed current and the value of temperature on the machine housing, which is an important function due to the safety aspect since the presented system operates in the open loop control. These measurements, except their major function which is the monitoring of machine operation status, constitute checking signals. They confirm the correct operation of wireless communication. In case of a lack of it, the controller switches to the automatic engine shutdown mode.