In this publication we thought to unravel to you one of the common piece of technology which we all have used whenever we have traveled in metro railway; though small but technically beautiful. Its the travel coin or the travel-pass card that we use as a token for our journey. Came across so many times, but did you imagine any time what they are composed of ? Here we will explain it in as simple as possible.
In our +2 we have learnt the theory on which this technology is based, it is, Faraday’s principle of magnetic induction. These tags are technically called passive Radio-Frequency-Identification [RFID] tags. Going term by term, 'passive' tags power themselves from the energy they collect from high gain antennas, i.e. they don't have an inbuilt power source.
'Radio-frequency' implies that they use low frequency [120- 140 kilohertz] or short range systems (< 40cm). So, due to these two reasons they must be in close proximity to the RFID reader’s antenna in order to
collect enough energy to function.
Working Principle :
A current flowing through the coil of a reader produces a magnetic field around it. This field induces the tag’s coil in the vicinity to generate a small current. The tag switches on and off the loaded resistor by its information stored in an inbuilt circuitry to change the impedance of the reader antenna coil. This brings about variation of the current in the tag’s coil, which in-turn causes a small current variation in a reader’s coil due to the mutual inductance between the two, and the variation is detected by reader. This is how, the reader obtains the tag information by variation of reader antenna voltage. This form of communication between a reader and a tag is called 'load modulation'.
RFID tags transmit many different pieces of data, which in this case is the tag’s unique identifier. The unique identifier stored in the database at the back-end is used as the key that identifies information about the users
journey.
In our +2 we have learnt the theory on which this technology is based, it is, Faraday’s principle of magnetic induction. These tags are technically called passive Radio-Frequency-Identification [RFID] tags. Going term by term, 'passive' tags power themselves from the energy they collect from high gain antennas, i.e. they don't have an inbuilt power source.
'Radio-frequency' implies that they use low frequency [120- 140 kilohertz] or short range systems (< 40cm). So, due to these two reasons they must be in close proximity to the RFID reader’s antenna in order to
collect enough energy to function.
A current flowing through the coil of a reader produces a magnetic field around it. This field induces the tag’s coil in the vicinity to generate a small current. The tag switches on and off the loaded resistor by its information stored in an inbuilt circuitry to change the impedance of the reader antenna coil. This brings about variation of the current in the tag’s coil, which in-turn causes a small current variation in a reader’s coil due to the mutual inductance between the two, and the variation is detected by reader. This is how, the reader obtains the tag information by variation of reader antenna voltage. This form of communication between a reader and a tag is called 'load modulation'.
RFID tags transmit many different pieces of data, which in this case is the tag’s unique identifier. The unique identifier stored in the database at the back-end is used as the key that identifies information about the users
journey.
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