# The Use of Wireless Networks and Mobile Applications in the Control of Electric Machines
## 5 The Use of Wireless Transmission and Mobile Application in Control  
The developed mobile application in a form of a user interface for controlling the electric motor via a wireless network has been used to modernize the research stand in the power electronics laboratory located at the Gdynia Maritime University. This stand has a set of modules with Myristors controlled from a three-phase phase angle controller, which allows the control of rectifier output manually by using a traditional knob. The range of control voltage is \(0\div 10\) V. It corresponds to the scope of firing angle \(0\div 180^{\circ}\). The relation between the control voltage and the firing angle is linear. The higher value of the control voltage, the higher value of the firing angle and the lower the rotational speed of the DC motor. The control is performed in an open-loop and does not include the feedback from the value of the motor rotational speed. The methods described earlier in the text  
Figure 5: Main circuit structure. Figure 6: Simulation results for the firing angle of the rectifier’s Myristors equal to \(60^{\circ}\). Figure 7: Simulation results for the firing angle of the rectifier’s Myristors equal to \(60^{\circ}\). enable PMDC machine rotational speed control from the level of mobile application with the use of wireless communication. In this case, a constant numerical value is sent from the application to the microcontroller in order to generate PWM signal. Its average value is passed to the controller which defines the firing angle. Then, based on the value of the firing angle, thyristor switching pulses are generated. The values of the reference voltages and the firing angles of the thyristors are presented in Table 3 and Figure 9. The LCT-167 PWM system is responsible for converting the PWM voltage to its average value (Figures 2 and 3). The designed system is meant to enable the remote control of such a system and permit a comparison of traditional control with a remote one. The view of research stand with both types of control strategies is depicted in Figure 8.  
Verification of the proper operation of the application and wireless transmission was performed in the power electronics laboratory. The developed control application was used to control the rotational speed of a PMDC motor supplied by a three-phase thyristor rectifier, whose communication with a mobile device was via a Bluetooth or Wi-Fi module. The rectifier supply line-to-line voltage was 3 \(\times\) 110 V, while its frequency was equal to 50 Hz. The test results for control using both the Bluetooth and Wi-Fi technology are shown in Table 3.  
Figure 8: Laboratory stand. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & **(Bluetooth) PWM** & **(Wi-Fi) PWM** & **Thyristors Firing** & **Rotational** & **Motor Supply** \\  & **Value [\%]** & **Value [\%]** & **Angle [\(\lx@math@degree\)]** & **Speed [RPM]** & **Voltage [V]** \\ \hline
1 & 54 & 54 & 90 & 100 & 8 \\
2 & 48 & 49 & 85 & 533 & 31 \\
3 & 38 & 39 & 70 & 1075 & 70 \\
4 & 32 & 34 & 60 & 1365 & 87 \\
5 & 30 & 32 & 55 & 1490 & 95 \\
6 & 26 & 28 & 40 & 1850 & 115 \\
7 & 25 & 27 & 30 & 1987 & 122 \\
8 & 21 & 23 & 15 & 2100 & 130 \\
9 & 19 & 21 & 0 & 2190 & 135 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Measurements for both control systems with wireless communication. Figure 9 shows the characteristics of the dependence of the supply voltage on the motor potential idling speed and the dependence of the PWM value of both the Bluetooth and Wi-Fi technologies on the thyristors firing angle. A PWM signal between 0% and 100% duty cycle corresponds to Bluetooth and Wi-Fi PWM values between 0-255 and 0-1024, respectively.