RFID is a technology to identify and track any kind of objects. As the name already indicates the technology makes use of radio waves. The two main features of radio waves as an identification technology are that the communication can operate without any contact (wireless) and it can be used as a power source. This is possible because radio waves are a type of electromagnetic radiation hence it can be used to emit current.

The idea to detect objects with radio waves came up with the development of the Radar in 1935. The basic problem they realized after being able to detect airplanes is that they could not distinguish between enemy planes or their own planes. The Germans solved the problem first as they discovered, that if they rolled their planes, on their way back to the base, the reflected radio signal also chances. The British solved the problem a bit later more advanced as they installed transmitter in the planes that could receive signals from the radar stations and sending the signal again back, to identify themselves as a friendly plane.¹⁾

After the World War RFID found usage in civil applications like in anti-theft systems for articles in stores. The tags could save 1bit which represented an on/off state. More or less the same concept is still used in most electronic article surveillance systems.

The most important step to a leading identification technology happened in 1999 with the establishment of an “AUTO-ID Center” at the Massachusetts Institute of Technology (MIT). The project got founded by the Uniform Code Council, EAN International, Procter & Gamble and Gillette. The research goal was to find a way to put low-cost RFID tags on products to keep track of them in the full supply chain. The final solution used a small unique number stored on each RFID tag. These numbers where linked to a database which was accessible over the internet. Inside the database the actual desired data was stored. The main benefit of this solution was that they had to store only a real small amount of data on the tag itself, whereby the main data was stored on a database accessible via the internet.

The RFID Technology has always two roles a transponder which is in most cases a RFID-tag and a RFID reader. The RFID transponder is a device which can store a variable size of data and can transmit it to the reader via radio waves. The RFID reader can read and write data from RFID tags.

All RFID tags are built with the same concept. They have an antenna and a microchip. The microchip typically has the size of a grain of sand. Inside the chip is a logic unit, the memory, a modulation unit for modulation received or to be transferred data and a power control unit. The design of an antenna can be very unique, but the length is defined by the microchip used frequency and has the same proportion as the used radio wavelength.

RFID tags can differ in many aspects. The size, the frequency and even the way they use power. In size the tags differ from a length not more than a grain of rice to a size of more than 10-15 centimeters. The size of a RFID tag is highly correlated to the way to power the RFID-Tags and is the most distinguishing feature. There are tags with no attached power source called passive tags and some tag which comes with an included power source called active tags.

As already mentioned the passive RFID tags have no on-board power source. This has the benefit that the tags can be built very small. Another benefit of no attached power source is that the tags can be built very resistant against environmental influences. For example there are tags which can resist temperatures from minus 45°C till 220°C²⁾ also there are tags which can resist corrosive chemicals like acid. ³⁾ Typical reading distances are 1 till 10 cm, but under laboratory conditions are distances up to 9 meter possible.⁴⁾ Even when the tag has no build in power source, the RFIDchip still needs energy to operate. Therefor the antenna uses the frequency of the radio signal and works like an inductor. This energy is then used to load a capacitor. If enough energy is available, the RFIDchip starts sending his stored data to the RFID reading device. To make a full transmission the reader is committed to send a continuous flow of radio signals to energize the RFID tag.

Active RFID tags have a source of power available, like a battery or a solar-panel. These power sources energize the RFID-tags to let them operate all the time. The main benefit of an active RFID tag is that the recognition process is much faster because the tags antenna has not to emit the energy from the reader. Instead the RFID tag can directly be detected by the reader and therefor read the RFID tag without any delay. Another benefit of an integrated power source is that the tag can send a much stronger radio signal. Therefore possible reading distances starts at 1 centimeter till 100 meter. Drawbacks of an integrated power source are higher costs and the bigger sizes of a single tag compared to a passive RFID tag.

RFID uses several radio frequency bands which are designed to be used by Industrial, Scientific and Medical purposes (ISM-Band). In general higher frequencies means higher data-speed and higher communication distances.

But higher frequencies can also have disadvantages if some specific materials in the environment are present. The following table shows a list of materials which behaves different if lower or higher frequencies are used. Radio frequency lucent (RF-lucent) means the presence of this specific material has no influence on signal transmissions, whereas RF-opaque materials can block, reflect or scatter radio signal. RF-absorbent materials can drain the signal and the passive tags can't load up current from the signal.

⁵⁾ Radio frequency (RF) properties of Example Material Types

RFID can be categorized mostly as an enabling technology that allows companies to build up applications with great value for a high diversity of fields, considering that its own value is rather small. In very general words, RFID is mostly used for identification and tracking purposes. A great feature of RFID technology is that it requires minimal human intervention once an application has been deployed, and this is mostly because the tags can usually be read even when they are not facing a reader´s antenna.

The range application field of RFID technology is potentially limitless. Even though it is quite usual for RFID to be associated only with supply-chain management or consumer packaged goods industries, its current application can go far beyond those areas. Some of the most common application types will be outlined in this section, and by “application types” it is meant to be understand as several different application members that share the same characteristics ⁶⁾.

This application class type can be characterized by the two following steps:

• The first one consist on attaching a tag containing a unique identifier on an item to be tracked, and thus identified.
• The second one consist on reading this tag information at specific fixed locations while the item moves.

The tag identifier together with the associated reading time and the location information, can provide near real-time information about the whereabouts of this item at a particular point in time, which implies that selecting appropriate locations to install the readers is crucial on defining the level of traceability. A list of such location´s information can be used to track the object's movement during its life cycle. Additional information can also be captured, such as which personnel moved the object from one location to another. For example, this information has been proved useful to determine the personnel responsible for shrinkage, if any. You can also associate various actions with this tracking activity, such as triggering an alarm if an object is not spotted at a location at a certain time.

Example: Supply-chain management ⁷⁾

Basically, most of the benefits of using RFID in the supply chain issue from the better traceability, identification and automation level that this technology offers. The potential of RFID to facilitate and automate the tracking of movements at different supply chain levels and at minor costs makes it possible to trace the product in the different steps of its transformation, to immediately access information in case of crisis, to facilitate product withdrawal, to better control shipping and receiving, to optimize flows and to immediately locate every tagged item. Better identification means much more accuracy, which allows manufacturers and retailers to operate and collaborate more efficiently, so that both can be more responsive to the needs of customers, thus reducing product shortage in the store. But the key to realize maximum return on investment and to reap substantial business benefits consists in strategically incorporating RFID and other sensor-based into the information architecture and business processes. For instance, RFID and wireless network systems could be integrated to provide full-time, wide-scale monitoring. The success of RFID also depends on the relevance of its use .

The inventory monitoring and control application class type is characterized by the following:

• Attaching a tag containing a unique identifier on an inventory item to be monitored
• Detecting the presence or absence of this item in the inventory by attempting to read the tag data on a periodic basis

When an item is placed in inventory, the tag data is read by a stationary reader, which then transmits the tag data and its location (based on this reader's location) to the back-end inventory system. The back-end inventory system registers the item in the inventory database. While physically in inventory, the reader (which has this tag in its read zone) periodically transmits all read tags in its read zone to the inventory system. If the back end does not receive a registered item's tag data corresponding to this reader, the back end assumes that the item is absent from the inventory. If this item's absence results in an out-of-stock situation for this item type, the inventory system can take the following actions:

• Automatically notify personnel and other associated systems
• Post an order for this item to its supplier(s)

Example : Smart Shelves ⁸⁾

A smart shelf is a shelf in a store that has been equipped with an RFID reader. The RFID reader can be built-in the shelf itself or be installed behind/under/above normal shelves. By continuously scanning the RFID tagged items on the shelf, the RFID reader consistently notifies the back-end system about the existing items and their movement. It will also identify items that do not belong on a certain shelf as „misplaced items“. By tracking items, their movements and whereabouts, the system provides retailers with information that can be analyzed and translated into customer preferences. Thereby RFID-equipped smart shelves provide retailers with various ways of improving their customer service and increasing sales .

The asset monitoring and management application class type is characterized by the following:

• Attaching a tag that contains a unique identifier on an asset item to be monitored
• Detecting the location and other properties and states of this item in real time by attempting to read the tag data on a periodic as well as on an on-demand basis

The basis of this class of application is the determination of the location of an item in real-time using RFID tags. The entire frequency range of RFID has asset-related products. You can use both passive and active tags for asset monitoring. In this context, note that an ANSI standard already exists. The ANS INCITS 371 standard developed by the International Committee for Information Technology Standards enables users to locate, manage, and optimize mobile assets throughout the supply chain. Generally, stationary readers read the asset tags when they pass through a certain facility. This data and the readers' location information are then transferred to the back end and fed into an asset-monitoring system. Both local and global/wide-area monitoring is possible. You can use satellite communication networks to link RFID systems for global asset monitoring; the major vendors that offer asset-monitoring solutions have either bought or partnered with at least one satellite communications company. Note that today, no such (active) tag exists that can perform satellite communication directly. However, a reader or a network of readers can be connected to a base station that, in turn, can use satellite communication. You can also use wireless 802.11x networks for local monitoring. This application class type has a large overlap with item tracking and tracing. Indeed, an item to be tracked can be viewed as an asset that can be monitored. However, one distinguishing aspect of this type of application is collection of asset properties in real time, together with its unique ID, to aid in management of this asset.

Example: Animal tracking

Today, use of RFID is becoming common to track livestock. A tag attached to an animal can be used to monitor its health, movement, and so on. Animal tracking can also be used to track wildlife and fish to monitor their characteristics (such as migration and breeding patterns). ISO 11784 /11785, the international standard for radio frequency identification of animals based on 134.2 KHz technology, is the prominent standard for animal tracking. Some criticize this standard being susceptible to duplicate identification numbers that can be introduced by different manufacturers due to lack of proper enforcement of the identification numbers by the standard bodies. The International Committee for Animal Recording (ICAR) is a Paris-based international body that is responsible for worldwide standardization of animal recording and productivity evaluation. ICAR, in agreement with the ISO, has been developing compliance procedures for testing and validation of RFID systems with this ISO standard .

RFID can provide an effective deterrent against theft. A solution of this type is characterized by the following:

• Attaching a tag to an item to be monitored for theft
• Reading the tag ID at the vulnerable points
• Alternative or additional features such as the ability to remove an attached tag from the item only after the correct payment has been made, the ability to detect movement of the attached item and reporting it to a nearby reader

You can use both passive and active tags for this purpose. For a high-value item such as a laptop, an active tag with a built-in motion detector can be attached to the item. Whenever this laptop is moved, the built-in motion detector in the tag can sense the motion and transmit this information to its surroundings. An appropriate reader can receive and relay this information to a back-end system. The back end can then initiate various actions. For example, it can either lock the exit(s) through which the item can be taken out of the building, it can trigger an alarm, or it can initiate a video recording of the place where the item is currently located. If a passive tag is used, its tag ID can be read at an exit point, or the absence of this tag can be detected by the back-end system using stationary readers (attached to the ceilings in the storage area, for instance). This, in turn, can trigger multiple actions by a back-end system. The cost of implementing an anti-theft RFID solution needs to be carefully weighed against the benefits. Retail is a very important area for anti-theft applications.

Example: Automotive anti-theft immobilization

Automotive anti-theft immobilization. In this commercially deployed solution, an embedded reader located inside the car (for example, in the steering wheel) becomes activated when a driver turns the ignition key. This reader then attempts to read the valid unique code from a tag in its vicinity. Generally, the tags are small and can be embedded in an ignition key (for example, in the key head). If the reader detects a valid tag, the ignition starts. In general, passive 134.2 KHz LF tags are used. However, today's car thieves can breach these systems in various ways (for instance, by locating and overriding the embedded RFID unit, or by using a device that can imitate the code transmitted by such a key). To counter these methods, new-generation RFID anti-theft applications use a combination of active and passive tags that involve multiple authentication steps. The automobile cannot be started until all authentication steps have succeeded. Therefore, even if a potential car thief overrides one or a few of these steps, the other steps will prohibit the thief from starting the car and driving it away.

This electronic payment application class type is characterized by the following:

• A tag that contains a unique customer number
• Reading this customer tag data at the Point of Sale Center (POS)

At the time of transaction, the customer identification data on the tag is associated with the actual customer account number at the back end. This level of indirection protects customer account numbers in case the tag is missing or stolen. When a reader at the POS reads the customer identification data from the tag and the associated customer account number is located, the transaction then proceeds normally like any other regular transaction.

Example: Electronic toll payment

Toll agencies allow drivers to pay for tolls electronically at toll booths. A customer opens an account with a predefined amount of money with an agency that is responsible for toll collection. The customer then receives a tag with a unique ID. This tag is mounted, generally on the vehicle's windshield so that it can be read properly by readers at toll booths. When this customer drives through a toll booth that accepts electronic payment, the tag ID is read, the associated prepaid account is accessed, and the toll amount is subtracted from the account balance automatically. The tag can display the account status by turning on its different-colored indicators. For example, green means toll paid, yellow means toll paid but account balance is low, and so on. A customer can fund his prepaid account with a credit card that automatically gets charged when the account balance is insufficient. Alternatively, a customer can also replenish his account online, via phone, or can mail a check.

RFID has been successfully used in providing access control solutions. A solution of this type is characterized by the following:

• A tag that contains unique identification data and that is carried by the object or the person to gain access.
• Reading the tag ID data at the access control points (with the ID then being forwarded to a security system that decides the actual access permission)

RFID tags are widely used in identification badges, replacing earlier magnetic stripe cards. These badges need only be held within a certain distance of the reader to authenticate the holder. Tags can also be placed on vehicles, which can be read at a distance, to allow entrance to controlled areas without having to stop the vehicle and present a card or enter an access code [3]. This application type is relatively mature compared to some other prevalent application types in terms of the RFID technology and systems that go with it. One of the characteristics of a mature technology is the existence of standards. The ISO 15693 (ISO SC17/WG8) vicinity cards standard is widely accepted by 13.56 MHz access control products.

Example: Perimeter and Building Security System

The permissions associated with a particular ID for a particular facility can be granted or revoked dynamically based on a central control system. Such an ID is first forwarded (via an RFID reader connected to a network) to this central security system. This system then uses a variety of factors, such as the number of access times to this facility by this ID, to decide whether permission should be granted.

Our own patch uses the Clock project by vvvv contributor westbam and enhances it with RFID functionality to show the time of selected countries (Brazil, Germany and Portugal). To make this path work a prototyping Interfaces RFID Kit is necessary. Any other RFID Reader which is connectable to a serial port is also working. After that you have to change the list „accepted RFID ID’s“ inside the file „RFID.v4p“ to the RFID tag id’s you are using.

Download: rfid_clock.zip

RFID patch from the book Prototyping Interfaces. The patch shows a world spining automatically, which can react on rfid tags and shows specific countries which are linked to the RFID tag id.

Download: world_map.zip

The easiest way to work with the RFID reader is to use my simplified RFID patch which returns the RFID index as an integer instead of a spread.

Download: Simplified RFID reader

In this section you can find external links to projects involving RFID technology and Arduino microcontoller with details of the implementations, including used materials, circuit diagrams and videos.

Using the Parallax RFID Reader with an Arduino		This project is a quick introduction to using this RFID reader with the Arduino system.
Arduino RFID Card Reading		How to setup an RFID reader (like this one) with your arduino, read some numbers, and use that data to make a secure entrance database.
RFID Access Control System using Arduino		This project uses a pre-built RFID reader module to interrogate commonly-available passive tags, looks up the tag ID in an internal database, and release a lock using an electric strike plate if the tag is authorised.
Build an RFID time-clock system using Arduino		With this project you can build an RFID time-clock system to keep track of employees, children and more.
Simple RFID access system using Arduino		In this tutorial you can make an RFID access system. It’s very simple and can be used with a wide variety of end-uses
Arduino RFID Lock		The Arduino RFID lock is a lock that can be opened easily, but is secure. The lock works with a server database that can register card codes. On the door there is a RFID reader connected to the lock. If the RFID reader reads a registered card the door will open.
RFID cat door using Arduino		This is a cat door/flap that can only be opened by the animal that wears the appropriate RFID tag. Arduino controls the process. It features a custom made antenna large enough to function as a gate, which makes it easy for the animal to activate and quite reliable.
RFID pet feeder using Arduino		If you have two cats and one of them is on a diet but the other needs free food, you can build a feeder with RFID capability that only opens for the cat that needs free access. The free-food cat wears a collar with an RFID tag.
Arduino RFID Door Lock		I a simple circuit with a basic ATMega 168 arduino chip and a ID-20 RFID reader to control an electronic door lock.
Arduino RFID car starter		The purpose of this project is to use an Arduino UNO to start your car.

In this section you can find some links to several short videos showing RFID with Arduino implementations, so you can get inspired with simple ideas and do your own project or try to replicated the ones shown here.

• RFID Cat entrance

• RFID kit log

• Cat feeder

• Car engine start

• door opener

RFID is a powerful technology to identify physical objects. For hardware hacking RFID has the advantage that the complete communication process is wireless and through the size of a tag they can be easily hidden. Also the tags are affordable and costs around 20ct and 4€ for private persons. (Passive tags) Similar solutions for object identification like the QR-Code or the barcode have the drawback that these solutions needs a tag which has to be in sight of the reading device, whereas RFID can operate even if the tag is out of sight e.g. in a coffee-machine. Drawbacks of the RFID technology are that the tags are more expensive than a printed QR-Code or barcode. Within vvvv RFID is a perfect solution to enhance daily physical objects with new interactive functionality.

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