# Wireless Data Acquisition System with Feedback Function
## 2 Materials and Methods
### Improved DAS Design Concept for Low-Power GEPPs
Commands are decrypted on the power equipment side using an infrared command decoder (DC IRC), powered from the main battery through a step-down DC/DC converter. After decoding, the commands act on the GEPP power equipment through executive units (EUs). Let us consider the behavior of the proposed system in various situations. At a normal voltage of each battery, switch S3 of the main battery charging circuit is closed, and the standard Load1 is connected to the output of the GEPP inverter at the right time. If there is a dangerous excess voltage of at least one battery, two options for automatic system response are possible. In the most straightforward version, the system's reaction could be to issue the command Cmd3 to turn off the main battery charging circuit with switch S3. However, this solution is not the most optimal, as it leads to the underutilization of natural energy. The best option in this case is to issue commands to switch the additional AC Load #2 from utility power to GEPP power. A load of this nature (or even several of them) can always be found and connected to low-power GEPPs, located, as a rule, close to inhabited buildings. This could be, for example, ventilation and lighting installations, advertising structures, etc. An increase in the GEPP load current will cause a decrease in the voltage of each battery, but due to the presence of hysteresis in the subroutine for responding to voltage changes, issuing commands to turn off the loads will not occur until the voltage of at least one of the power batteries PA1...PA4 reaches the lower permissible threshold. Therefore, all \"extra\" natural energy will be effectively used. To prevent flicker operation of switches S1 and S2, the DAS controller must be set to the correct lower and upper thresholds for issuing and removing commands Cmd1-Cmd3 and the corresponding time delays. If there is a dangerous drop in voltage of at least one battery, the DAS controller switches the loads to power from the utility network with a time delay, preventing battery failure. The ability to transmit a large number of feedback commands provides great opportunities not only to prevent the failure of GEPP equipment, but also to implement various promising options for optimizing the process of converting natural energy into electrical energy. The proprietary software for the sensors and DAS controller developed by the authors made it possible to ensure that there are no disruptions to the monitoring process of the remaining sensors when any sensors are turned off during operation, as well as \"hot\" automatic activation of the sensors registered in the system. The number of sensors in the system is limited almost only by the maximum permissible increase in the sensor polling cycle time. For example, with an interval between polling pulses of 0.5 s and a number of sensors of 32, the cycle time will be 16 s. The minimum interval limitation of 0.5 s is due to the finite amount of time it takes for the wireless sensor components to wake up from sleep mode. Unlike most DAS construction concepts analyzed in Section 1, the proposed concept allows one to connect a large number of sensors to the system and place them in any convenient GEPP locations without increasing the number and length of connecting wires, that is, to implement a truly wireless DAS. The proposed system also implements the function of online remote diagnostics of sensor status, which is not available in analogues, without connecting additional wires using requests submitted from a hand-held IR remote control in pauses between polling pulses, as shown in Figure 2. Diagnostic requests are received by the infrared receivers (IRRs) included in each smart sensor. The diagnostic process is described in detail in Appendix B and, in part, in Section 2.3. The team of authors designed, manufactured, and tested a full-scale model of the proposed DAS, containing part of its components, the minimum required to begin the practical use of DAS.