Introducing a cost-effective solution requiring no maintenance costs through a video

Battery-free wireless sensors can be used to verify temperature, pressure, proximity, and humidity data in various applications where size and accessibility are critical. This latest technology, which operates without batteries, integrates the key features and functions of various types of sensors into a single chip.

In addition to the fact that stimulus detectors are not used, what is more important is that sensing is possible even without a separate MCU designed for each sensing node. The detected data is sent to a remote central processing hub called an 'interrogator,' where the next stage of post-processing takes place. Unlike conventional sensor solutions, a single processing unit can handle many sensors at once.

Battery-free wireless sensors are a highly cost-effective solution, and once installed in a product, they effectively eliminate the need for maintenance. Due to the low cost of battery-free wireless sensors, systems adopting this technology are highly suitable for disposable products such as automotive tire pressure monitoring solutions (TPMS).


ON Semiconductor is making headlines by showing a video (http://www.onsemi.com/community/blog/post/auto-tire-pressure-monitoring) demonstrating how its smart passive sensor products are used in tire pressure monitoring solutions.

This demo used a standard-sized passenger car tire suitable for ON Semiconductor's smart passive sensor tag. The sensor tag consists of an inductive tune loop used as a sensing element, a printable antenna, and a smart sensor IC.

First, a flexible metal piece is mounted inside the tire to induce a change in loop inductance due to the rise and fall of pressure. Then, an adaptive RF front-end configured in the smart sensor IC is used to detect the impedance change in this environment and modify the change value to maintain maximum antenna gain.

Changes in impedance are transmitted to the microwave RFID reader as a 5-bit sensor code. ON Semiconductor used a handheld reader in the demo, but in actual applications, this can be changed to a fixed reader built into the vehicle. When the sensor code obtained at this time is transmitted to the reader, the back-end microcontroller can be configured to process the detected information and transmit that information as a specific tire pressure to the instrument panel or electronic control unit inside the vehicle.

In this demo, pressure was measured three times. First, a tire inflated to 42 PSI was measured using a standard analog pressure gauge, and the result was compared with the value from a smart passive sensor positioned inside the tire. If the demo operates correctly, a value within a margin of error of 2 PSI should be read from the sensor tag. In the actual demo, the value read by the analog pressure gauge was 41.9 PSI, while the value read by the smart passive sensor was 41 PSI. This demonstrates a result within a margin of error of +/-2 PSI.

The second measurement was taken after lowering the air pressure to 38 PSI (the analog pressure gauge displayed 38.2 PSI), at which point the smart passive sensor tag read 39 PSI, which is within the margin of error.

The third and final measurement was taken with the tire pressure lowered to 35 PSI (the analog pressure gauge showed 35.2 PSI), at which point the value of the smart passive sensor was 36 PSI.

Through this demo, we explored how a tire pressure monitoring solution can be implemented using ON Semiconductor's smart passive sensors. A passive tag created by combining a printable antenna and a single smart sensor IC enables the implementation of a very low-cost tire pressure sensing solution.