# Wireless Data Acquisition System with Feedback Function
## 2 Materials and Methods
### Improved DAS Design Concept for Low-Power GEPPs  
The concept of building a wireless DAS option, free from the gaps and weaknesses noted in Sections 1 and 2.1, is explained by the block diagram shown in Figure 2.  
The red rectangles in the upper left quadrant of the diagram indicate wireless smart sensors, each of which contains a primary measuring transducer PMT, a radio transmitter TX with an antenna, an infrared receiver IRR, and a microcontroller not shown in the diagram located in one housing. In the practical implementation of sensors, all of the listed modules are selected from among widely available products that have low-power consumption modes, which makes it possible to power them from small-capacity batteries. The sensors differ from each other only in the PMT module, which is selected depending on the type of physical parameter X being measured. Many modern digital sensors can convert two physical parameters simultaneously into a digital signal. In the diagram, they are indicated by the letters X and Y. For example, a BMP280-type sensor can output the measurement results of both atmospheric pressure and temperature to the microcontroller [35]. For the purpose of galvanic isolation, each sensor is powered by a separate GB. This gives us freedom to choose the placement of sensors and the ability to connect them to GEPP equipment at different potentials in relation to the common wire. In particular, this approach makes it possible to easily organize the measurement of the voltage of each individual battery in a chain of series-connected power batteries PA1...PA4. For this purpose, in the left column of the sensors shown in Figure 2 (VCS #1, VCS#2), it is enough to select specialized voltage and current sensors (VCSs) as the PMT. Since the current strength in batteries PA1...PA4 is the same, the current measurement pin is connected only to VCS #1, and for the remaining sensors VCS #2...VCS #4, it is not used. Choosing popular digital temperature sensors (for example, DS18B20) as the PMT makes it easy to perform the temperature measurement of each power battery and, in general, in any other places of the GEPP. In discrete value sensors of the \"0/1\" type, it is possible to forgo the purchase of a PMT by using microcontroller ports with level matching circuits and protection against overvoltage and impulse noise for its implementation. Most of the time, all wireless sensor modules, except the low-power IRR, are in energy-saving sleep mode. The waking up and polling of sensors are carried out by the DAS controller one by one via the infrared channel, so these processes cannot be disrupted by external influences via the radio channel. The sensors only transmit data using simple ESRMs, so the resistance of the sensors to external influences over the radio channel is higher than when ZigBee transceiver modules are used for this purpose, and the security of the entire system is higher than when using the Internet. The reception of data packets, verification of reliability, and decoding of sensor signals are carried out by the DAS controller from each sensor in turn using a simple RX receiving radio module, which does not have built-in functions for calculating the checksum and confirming reception. The software of the DAS controller ensures that information received from the sensors is displayed with time stamps on the laptop monitor screen and recorded on the hard drive. Unlike analogues, a significant part of the received information is also displayed on a 4-line LCD indicator, which makes it possible not to keep the laptop screen constantly on and thus save the resource of its battery, which is used to reserve power for the DAS receiving part during power outages. Unlike analogues, in the proposed DAS concept, the received data are not only recorded, but also analyzed in real time, and if their  
Figure 2: Wireless DAS block diagram for low-power GEPPs. values deviate from the norm, the DAS controller immediately issues a system response to these deviations in the form of IR commands.