What is an RFID Technology?
RFID stands for Radio Frequency Identification. Basically, RFID based components work on Radio-frequency or Radio-waves. It is used to track or identify a particular object, for instance, books in the library, inventory in the warehouse, tracking animals or birds or students or workers, etc.
Source: RFID Technology
Components
Generally, it is consists of two major components.
- RFID Reader
- RFID Tags/Cards
1. RFID Reader
There are many types of readers available in the market for RFID technology from which users can purchase as per the requirements and budget.
Block-diagram of RFID Reader
RFID Reader comprises three main elements, RF Signal Generator, Receiver or Feedback Signal Detector and lastly the Microcontroller.
- RF Signal Generator It continuously transmits Radio Frequency signals and creates a magnetic field around the Reader.
- Receiver or Feedback Signal Detector It receives a feedback signal from the object if the object is present in the magnetic field of the RFID Reader.
- Microcontroller It processes the data which is received as a feedback signal to track or identify the particular object.
2. RFID Tags/Cards
There are three kinds of RFID Tags, which are Active Tag, Passive Tag and Semi-passive Tag.
- Active Tag It has its own power supply as an energy source, which renders supply for sending feedback signal to Reader.
- Passive Tag Due to it does not consist of its own power supply, it relies on radio waves transmitting from Reader for the source of energy. Consequently, the range of these cards is small comparatively.
- Semi-passive Tag It has its own power supply as an energy source. However, to send the feedback signal it requires Radio frequency signals from RFID Reader.
Block Diagram of RFID Tag/Card
- Transponder Firstly Tag/Card receives Radio waves from RFID Reader and sends a feedback signal to the RFID Reader consecutively.
- Rectifier Circuit After that, the passive and semi-passive tags are rely on Reader RF Signal for power supply. Subsequently, energy is stored in the capacitors of rectifier circuit so that it can provide energy as an energy source.
- Controller At the end Controller processes the data similarly which is received from the transponder and uses a power supply from the rectifier circuit.
- Memory The unique ID or Tag serial number, location, manufacturer, photo, use history, a maintenance schedule, and much more are stored in the memory in the binary form (1 or 0). In addition, the server accesses the stored data from the memory to identify or track the object.
How does it work?
The working principle is based on Inductive coupling. The reader antenna and the tag/card antenna consist of a coil. When the reader is powered up it will start transmitting an RF signal using an RF signal generator and will generate a magnetic field using a coil. Meanwhile, if the Tag/Card is in the range of the reader then there will be a mutual induction between two coils. As a result, there will be an induced emf generated in the tag/card coil. Some portion of the emf will be used as a power supply for the controller and the memory element. This would take place after induced emf getting rectified through the rectifier circuit. The remaining portion of the emf is used for data transmission.
Subsequently, as the induced emf passes across the load, the current will be generated through the load. The data transmission takes place using Load Modulation. Switching On and Off of the load is known as a Load Modulation. Most importantly, the load will change the rate of the current as per the data stored in the memory element of the Tag. Consequently, changing the rate of the current will generate a feedback signal for the reader, and hence the data of the tag/card is shared.
Architecture of the RFID based an Access control system
Architecture is consists of three elements.
- RFID Reader and Tag/Card
- Controller
- Database
Circuit Diagram
To sum up, the admin can connect peripherals like a DC motor to open the door and give access to the authorized entry. In addition, as an alert Red LED and Buzzer can be connected too.
Source Code
<code>int count = 0; // count = 0
char input[12]; // character array of size 12
boolean flag = 0; // flag =0
void setup()
{
Serial.begin(9600); // begin serial port with baud rate 9600bps
pinMode(0,INPUT)
}
void loop()
{
if(Serial.available())
{
count = 0;
while(Serial.available() && count < 12) // Read 12 characters and store them in input array
{
input[count] = Serial.read();
count++;
delay(5);
}
Serial.print(input); // Print RFID tag number
if((input[0] ^ input[2] ^ input[4] ^ input[6] ^ input[8] == input[10]) &&
(input[1] ^ input[3] ^ input[5] ^ input[7] ^ input[9] == input[11]))
Serial.println("No Error");
else
Serial.println("Error");
}
}</code>
Source: ALL ABOUT ELECTRONICS, electroSome
Conclusion
Access control is a fundamental component of security compliance programs that ensures security technology. Most importantly, RFID technology gives contactless and appropriate results regarding access control. Above all, It is easy to install, quickly responsive, and less power consuming system.
Modern technology for access control includes fingerprint identification which is not the best solution for situations like the corona pandemic. Also, face identification which is not able to track the position of the person. In other words, RFID technology renders access control over unauthorized entries and tracks the location of the tag/card-holder simultaneously at the same time. Moreover, The applications of the convergence of the RFID technology and the Internet of Things is wide. For example, smart attendance system, access control system, Electronic toll tax collection, tracking of objects like cars, students, workers, books, etc.
