Know-How

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.

Pop-pop Boat

In our complicated mind-set can we imagine a boat that is driven neither by an electric motor nor one of any IC engine... ???

But if you have ever been to any fair, you will surely come across one such boat(toy) which easily manuevers without implementing

any of such complex phenomenon.

No HIDDEN solid-state chips

JUST employ simple physics principles in ingenious ways

The toy is a jet-propelled boat. Heat from a small candle inside it makes it eject pulses of water from tubes at the rear just under

the water level, at five or more per second. That propels the boat at 10 cm/s or more, and it will go for as long as the candle burns.

These boats are usually been made out of material that floats( gnerally tinplate).

The boat's engine consists of just a boiler(chamber) and exhaust tubes.

The underlying steps would easily make you understand the mechanism within it :

Step:1 The boiler and the exhaust tubes have to be filled with water, and using two tubes allows water to be injected into one tube

while air inside the engine escapes through the other tube.

Step:2 When heat is applied to the boiler(by lighting a candle simply), water in the boiler flashes into steam. The expanding steam

pushes some of the water in the exhaust tube, propelling the boat forward.

Step:3 The steam bubble then condenses, creating a vacuum which draws water back in through the exhaust tube.

Step:4 The cooled water that is brought back into the boiler is then heated and flashed into steam, and the cycle repeats

　

This constant flashing and cooling cycle of the engine creates the distinctive noise for which the boat

is sometimes called "pop-pop" boat or "puff-puff" boat.

There is been an International Community in France working on this technique and improving this principle into various fields :

a. A wooden shoe powered by the similar technique

b. A nanotechnology device smaller than an ant that uses propulsion system similar to a pop pop engine,

but it uses audio waves instead of a flame as the power source.