Electronic Design

RFID: Another Wireless Technology Perfect For Industrial Apps

RFID is one of a number of automatic identification (auto-ID) systems that are in use today. Bar codes and smart cards are other well-known methods. The whole idea behind auto-ID is to eliminate the need for employees to enter data, reduce data entry errors, and improve efficiency overall. RFID uses wireless techniques to provide a quick identification of almost any object or person.

Two main parts make up an RFID system: the tags and the reader. A tag or transponder is a small, usually flat component that's glued to the product. It has a coil antenna connected to a memory chip. The chip stores a unique electronic product code (EPC) identifying that particular type of item. When the tag is interrogated by the reader, the tag transmits the code to the reader.

The reader contains a transmitter to signal the tag and a receiver to pick up the code and send it to a computer. The transmitted signal is strong enough to induce a signal into the tag antenna, which can be rectified and filtered into dc to power the memory and the simple ASK-modulated transmitter. The tag is fully passive, and no battery is required because it takes its power from the transmitter in the reader. Reading range usually spans about one meter to almost 20 feet, depending on the frequency of operation.

Tags operate at several standard frequencies. The low band uses 125 kHz or 134.2 kHz; the high band uses 13.56 MHz; and the UHF frequency is usually 915 MHz. Sometimes, a 2.4-GHz microwave system is employed. The higher-frequency systems have the longer range and often implement more expensive active tags that contain a small battery. The readers usually have an RS-232/422/485 interface to a PC, and available software automates the code entry, storage, and management.

The mind boggles over the myriad of possible RFID applications. However, many uses are just not practical due to cost. While technology now gives us a tag cost in the 10- to 25-cent range for very high volume, that's still too high for general product use (like razor blades or soap). Thus, the older and cheaper optically read bar codes are safe.

Active tags usually run about one dollar but have a longer range. They're used on high-ticket products like cars, trucks, trailers, train cars, and other capital equipment items. Once the tag price drops to the five-cent level, applications are expected to really explode. We're almost there.

RFID tags have been utilized for years in automatic toll collection and for tracking truck trailers and train cars. Other applications include animal tracking, security badges, and parking access. As tag prices drop, look for their use in supply-chain management in warehouses, shipping and handling, asset management, and inventory control. Airline baggage handling is a coming target. Big retailers like Walmart are testing RFID, and the U.S. Department of Defense is adopting the technology to manage and track military equipment and supplies.

As for industrial uses, look for it to land in factories to track materials flow, subassemblies, and finished goods. Several RFID systems could tie into other industrial networks to further automate the process and improve efficiency. Now that standards are being established (e.g., ISO), look for continued development and lower tag prices.

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