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This paper describes a novel low-cost tire pressure monitoring system (TPMS) for bicycles. The system is based on a battery-less near field communication (NFC) tag that integrates a pressure sensor, which is placed between the tire and the inner tube. The system uses no battery since the energy is obtained from the magnetic field induced by the reader in order to establish the communication. The pressure can be read by any NFC-enabled reader such as a smartphone. The pressure sensor is a force-sensing resistor (FSR) that controls the oscillation frequency of a 555 timer-based oscillator. The frequency is read and computed by a microcontroller, and the result is written via $\text{I}^{2}\text{C}$ bus to the memory of a near-field communication integrated circuit (IC), which is read by a commercial smartphone or NFC reader. A prototype is designed on an FR4 substrate which integrates a $12 \times 16$ mm antenna connected to the NFC IC (NT3H211 from NXP). The proposed prototype has a 3D-printed enclosure to protect the components mounted on the surface of the PCB and to protect the tire from punctures. A system for characterizing the read range is presented. The tag requires a minimum magnetic field of $2.9~A_{RMS}/m$ to operate up to a distance of 8 mm between reader and the tire, providing enough power to supply energy to the whole circuitry and to receive the information stored at the NFC IC. The system has been tested with a 59 mm-width mountain bike tire. The sensor has been characterized using a simple polynomial fitting to obtain the pressure from the measurement of the oscillation frequency. An accuracy of 0.1 has been accomplished in the range of 0.5 to 2.2 bar. To test the system, several inflation cycles have been performed and showed that the system presents good repeatability.

The tire pressure sensor is a wireless sensor that has been used in automobiles for many years, but the power supply has always been a bottleneck restricting the service life of the sensor. The article proposes a method for collecting heat energy in the environment, designs an energy harvesting circuit and achieves self-power supply of the tire pressure sensor. The thermoelectric generation(TEG) is used to convert the thermal energy accumulated inside the tire into electric energy. An ultra-low voltage electric energy collecting circuit is designed based on the LTC3108 power management chip. Experiments have shown that the designed circuit can collect energy as low as 100 mV, 10 mA, 1 mW, and successfully drive the tire pressure sensor after a period of accumulation.

This topic is derived from the practical problems of L Company. Aiming at the problem of high scrap rate and direct cost loss of tire pressure sensor from L Company, a process optimization scheme was designed. It analyzed the three processes which can lead to ion contamination in the manufacture of tire pressure sensor. The process includes PCB bare board manufacturing and cleaning process, reflow solder process on assembly circuit board as well as finished assembly process. Through the analysis of the sources and hazards of various pollutants and the detection methods, the process optimization scheme was confirmed. In this paper, deionized water was used to clean PCB bare board. Through experimental verification, the experimental results showed that the content of chloride ions in the process was reduced from 4.2μg/in2 to 0.95μg/in2, and the content of sulfate ion decreased from 4.2μg/in2 to 2.4μg/in2. After the optimization for reflow furnace temperature curve and the finished product assembly process, the contents of weak organic acids decreased from 37.8μg/in2 to 3.57μg/in2. In addition, the contents of sodium and ammonium ions decreased from 6μg/in2 to 1μg/in2, and the chloride ion content in the finished product also declined. Through the optimization of the manufacturing process, the problem of high failure rate in the aftermarket is solved, the product quality level and service life are improved. Meanwhile, the failure rate and scrap of product process are reduced, and the competitiveness of the company is improved. [ABSTRACT FROM AUTHOR]