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The limitations of developing high-tech communication systems cause the area of people who can use this service to be uneven. One technology that can be used for areas not yet reached by this high-tech communication service is to use radio communication technology. Today radio communication technology continues to develop and produce an increasingly limited frequency spectrum. One way to improve the efficient use of available frequency spectrums is the transition from analog technology to digital technology. A very significant benefit in the use of digital technology is to save the use of radio frequency spectrum bandwidth with signal compression techniques. One device that still uses analog technology is a handy talky (HT). In addition to the lack of frequency spectrum efficiency, HT technology still requires a radio station license (ISR) for its use. This experiment designed a two-way digital audio communication system that was transmitted using the NRF24L01 radio frequency transceiver module on the 2.4Ghz frequency. Analog input data from the microphone will be converted into digital data through the ADC (Analog to Digital Converter) process using a microcontroller and the digital data that will be sent is first digitally modulated using GFSK modulation then transmitted digitally. On the other hand data that already contains voice information received again by another NRF24L01 transceiver is received by the Arduino microcontroller and then formed into a PWM signal (pulse width modulation) and then released to the speaker. So the method of using digital transmission can produce efficiencies in the frequency spectrum.

Wireless technology is one of the most common technologies used in our day to day life. As wireless technology is very much easier to implement rather than wired, day by day its application is increasing. Through the continuous development of wireless communication technology it is now highly used in wireless equipment controlling. That is we can control our electronics and electrical equipments from a certain distant part. In this paper a multipurpose radio controlled car is designed with nRF24L01 wireless transceiver module, Arduino Uno R3 and DC motors to monitor risky areas. The RC vehicle is controlled by a distant controller or transmitter unit to move the vehicle to the risky location for monitoring.

Electrical energy can not be separated from the name kWh Meter, a tool used to measure and record the amount of electrical energy usage has a shortage of kWh meters can not be monitored remotely how much energy is used, so it is rather inconvenient for PLN officials to check the use of electricity for postpaid customers. This research was conducted to design a prototype of a wireless electrical energy transmission system and design a wireless electrical energy recording system using the NRF24L01 wireless transmitter module and the PZEM004T kWh meter module. The design in this study uses the principle of electromagnetic induction to transfer electrical energy at close range, while to transmit data, the authors use the NRF24L01 module. Besides, the authors use the PZEM004T module to measure various magnitudes. Based on the results of observations and measurements of the design of the tool, the authors found that the transmission of electrical energy using electromagnetic induction is not effective for longer distances because the energy lost in the air is getting bigger. So this technology needs to be further investigated. Besides, the measurement of electrical quantities using the PZEM module has a small difference (under 2%) with measurements using a multimeter, so it can be said that the measurement with the PZEM004T module is effective.

Most wearable intelligent biomedical sensors are battery-powered. The batteries are large and relatively heavy, adding to the volume of wearable sensors, especially when implanted. In addition, the batteries have limited capacity, requiring periodic charging, as well as a limited life, requiring potentially invasive replacement. This paper aims to design and implement a prototype energy harvesting technique based on wireless power transfer/magnetic resonator coupling (WPT/MRC) to overcome the battery power problem by supplying adequate power for a heart rate sensor. We optimized transfer power and efficiency at different distances between transmitter and receiver coils. The proposed MRC consists of three units: power, measurement, and monitoring. The power unit included transmitter and receiver coils. The measurement unit consisted of an Arduino Nano microcontroller, a heart rate sensor, and used the nRF24L01 wireless protocol. The experimental monitoring unit was supported by a laptop to monitor the heart rate measurement in real-time. Three coil topologies: spiral&ndash, spiral, spider&ndash, spider, and spiral&ndash, spider were implemented for testing. These topologies were examined to explore which would be the best for the application by providing the highest transfer power and efficiency. The spiral&ndash, spider topology achieved the highest transfer power and efficiency with 10 W at 87%, respectively over a 5 cm air gap between transmitter and receiver coils when a 200 Ω resistive load was considered. Whereas, the spider&ndash, spider topology accomplished 7 W and 93% transfer power and efficiency at the same airgap and resistive load. The proposed topologies were superior to previous studies in terms of transfer power, efficiency and distance.

Ultrasonic power transfer (UPT) is a promising method for wireless power transfer technology for low-power medical applications. Most portable or wearable medical devices are battery-powered. Batteries cannot be used for a long time and require periodic charging or replacement. UPT is a candidate technology for solving this problem. In this work, a 40-KHz ultrasound transducer was used to design a new prototype for supplying power to a wearable heart rate sensor for medical application. The implemented system consists of a power unit and heart rate measurement unit. The power unit includes an ultrasonic transmitter and receiver, rectifier, boost converter and super-capacitors. The heart rate measurement unit comprises measurement and monitoring circuits. UPT-based transfer power and efficiency were achieved using 1-, 4- and 8-Farad (F) super-capacitors. At 4 F, the system achieved 69.4% transfer efficiency and 0.318 mW power at 4 cm. In addition, 97% heart rate measurement accuracy was achieved relative to the benchmark device. The heart rate measurements were validated with statistical analysis. Our results show that this work outperforms previous works in terms of transfer power and efficiency with a 4-cm gap between the ultrasound transmitter and receiver.