Most of the devices in the Internet of Things (IoT) may be idle during any given time. Typically, only the IOT sensor is required to measure in an unfifty time interval, and a small amount of result data is sent to the signal collector, and then the lowest energy consumption is returned until the next measurement is performed. Some intelligent sensors can be used through small batteries, not need to charge or replace it.
If you can eliminate the need for a permanent connection power supply, the sensor can achieve an indefinite deployment and make smaller and lighter. This creates opportunities for new sensors, such as non-invasive medical sensors that can be worn comfortable. Wireless temperature sensing patch connected to the skin can perform rapid examination from time to time, while wearer can actually actually actively. Compared to reusable lead sensors, one-time patch also has a hygienic advantage.
Many other applications have benefited much after viscous sensor patch, such as monitoring temperature, humidity or pressure. They can also be used in personnel detection, industrial processes without connection monitoring, or intelligent agriculture, such as monitoring soil or greenhouse conditions, or checking livestock temperature.
A new smart sensor combined with ultra-low power sensors and RFID technology is rising. These sensors are powered by the RFID reader only when the RFID reader needs to record the readings. The battery sensor such as this is only acquired when needed, and then transmits the data to the reader without performing measurement or storage data separately.
Figure 1 shows a simplified overview of the function block of the passive patch sensor, including front-end interfaces, signal adjustment, data processing, wireless communication, and power management to analog or digital transmitter. In order to integrate various components, it is necessary to construct a system that works with a limited range of frequency field energy requires mature low-power design, and carefully considers the load and performs effective power management. Such sensors must be small and flexible, easy to mount, and must be comfortable, such as biosensor if wear equipment.
Chip and sensor label
Fortunately, there are a variety of integrated passive sensing and optimization options. There are TEXAS INSTRUMENTS RF430FRL 152H, which integrates all circuitry required to implement the functions shown in Figure 1, including 14-bit triangle integral ADCs for connecting to an analog sensor, and SPI / I2C ports that can be used to connect digital sensors. RF430FRL15XH with 2 kB non-volatile memory realized by ferroelectric RAM (FRAM), achieving low power, fast read / write speed, unlimited read / write durability, and high electromagnetic immunity. Further, since the FRAM operates at a low supply voltage, there is no need to charge the pump to generate an elevated programming voltage. Integrated radio complies with ISO 15693, allowing to read the sensor using a standard NFC / RFID reader or an NFC-enabled smartphone.
RF430FRL15XH also provides an evaluation kit that consists of a substrate and an integrated antenna with ambient light and temperature sensor. Support firmware includes RF stack, driver library, and boot code. Designing environmental support by Ti Code Composer Studio. It also provides a sensor hub enhancement package expansion plate containing MEMS motion sensors and pressure, humidity, temperature, and light sensors.
The supplied reference design encompasses everything you need to measure the biosensor patch for measuring temperature or tubular electrical response, including Android mobile phone applications that use NFC to ask sensors, and a PC GUI for configuring and display patch.
Integrated intelligent passive sensor
On Semiconductor has taken a different approach to develop a fully integrated intelligent passive sensor for monitoring temperature, humidity or pressure.
Ecosystems supporting these sensors include multi-combined development kits and portable batteries with their built-in GUI and IOT connections. The reader can collect data from the sensor tag. A variety of commercially immobilized or hand-held readers can also be used in conjunction with these labels.
As shown in Figure 2, the ON Semiconductor smart passive sensor adopts the incentive circuit, and the humidity or pressure monitoring can be achieved by measuring the impedance change, and a microcontroller is used, which contains adaptive RFID front end, sheet-loaded temperature. Sensor and integrated memory for unique identifiers. The label uses the industry standard 2nd generation UHF protocol to communicate. When the reader is initialized, the IC measures the temperature condition in this excitation circuit, and transmits measurement data containing digitized temperatures from the chip sensor to the reader. By monitoring the intensity of RF signal, the integrated RSSI can also proceed close to detection or action detection.
On Semiconductor developed a series of sensors that can be used in humidity measurements, immersion detection and temperature measurement, and summary is shown in Table 1. They are suitable for a variety of industrial and medical scenarios such as quality control and environmental monitoring.
Handheld readers that meet NFC and RFID standards can be used to read smart passive sensors and have been verified in use in supply chain management. Similarly, scanning the RFID tag is exactly the same as a record receipt or delivery, scanning the passive sensor can get a reading. In the supply chain application, upgrade the RFID tag to the sensor tag to bring additional functions, record the status of the goods in the supply chain in any position. For example, it is used to verify that it meets the predetermined storage conditions, or helps identifying a point in which damage in the supply chain may occur.
Scanning by mobile hand-held reader is not unique from passive sensors to collect data. The fixed reader can be placed in place to collect data from a sensor through its valid range. This supports accurate detection industrial equipment for maintenance. Multiple sensors can be placed in a predetermined location such as motor or bearing housing, electronic power module, and scheduled regularly. If there is no sensor tag, such analysis may require manual measurements using equipment such as infrared thermometers. The manual search will cause the position of the surface to be tested or slightly different or the time interval, so that the result is not accurate. Secure readers and permanently connected sensors can eliminate these errors, and the acquired data can be easily transferred to the host or cloud.
Summarize
The universal extreme power limits in the Internet of Things applications are pushing innovative solutions and the emergence of new devices. The smart passive sensor with existing RFID technology can be deployed for a long time, no battery or maintenance is required, and is powered only when the measurement is required. In addition to the simpleness of the battery, in a wide range of applications, they also have many advantages, such as higher security, repeatability, and user comfort.
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