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This is a design for a Auto Fare Meter capable of communicating with a smart card. This particular
project was the subject of an article in a newspaper. The circuit diagram and photographs. The programs
inside the meter and smart cards.

Working:

An 18-pin PIC and a 16 character two line liquid crystal display make up the measuring instrument.
A clock program together with a quartz clock crystal enable an accurate clock to be running. This
clock is used for (1) calculation of waiting charge and (2) for the switch over to enhanced rate for
night time fare. This is currently fixed at 150% of the day fare, for fares called between 10pm and 5am.

Fare computation:

The running fare is a simple scaling of the distance covered. A photo-interrupter fitted to the speedometer
cable delivers pulses proportional to the distance to the meter. These are counted (ie, devided) to obtain
the pulses to increment the fare. Initially the minimum charge is loaded and the fare does not increase for
for the corresponding distance.

Waiting Charge:

If the auto stops for more than three minutes while on a fare the waiting charge gets added to the total.
This is a simple scaling of the time and is implemented by resetting a seconds counter every time
a distance pulse is received. If the counter reaches three minutes the waiting charge gets clocked in.

Payment by smart card:

At the end of the ride, the fare has to be paid by the remaining credit inside a smart card, or by cash,
or both. If a smart card of the proper format is inserted the fare amount is deducted from the card.
The card gets updated by the reduced amount. A register inside the meter gets enhanced by the same
amount. In case the card does not have sufficient funds, a different card may be inserted or the amount
paid by cash.

Crediting the driver's card:

At the end of the day, the driver inserts his card and all the amount stored inside the meter gets transferred
into his card. This may then be redeemed for cash at a central location which also handles the issue and
recharging of these smart cards.

Advantages

Since the amount of fare and credit are all stored inside the smart cards and the fare meter, the meter does not
have to communicate with a central server in order to carry out a transaction. The smart card reader is just a set
of contacts and a switch and so much simpler than a magnetic card reader. The reprogrammable microcontroller
inside the meter permits tariff changes to be implemented by a simple firmware update.

Limitations

Since the card carries cash inside it access to it has to be limited by strong encryption and cryptography. Somebody
with the necessary resources might crack the encryption and fraudulently reprogram the fare cards to higher credit,
thus obtaining free rides at the expense of the system.

Enhancements

The cash transactions recorded in the cards may be replaced by a record of card number and fare amount, which are
then reconciled at a central location at the end of the day. Thus the potential for cheating the system may be reduced
but at the expense of requiring much more storage in the meter. In this case the card would just serve to identify a
particular customer, much the same as magnetic swipe cards are used as credit cards by the banking industry.

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