1. What is a Taxi Meter? A Taxi Meter is an electronic instrument (Fig-13.4) which is fitted with a rented Taxicab to record: Distance traveled, Waiting time, and Fare. These are the minimum features that a Taxi Meter should have.
2. Features of a Taxi Meter: Apart from the above mentioned three features, the Taxi Meter can have many other features of which the two most important are: Real Time Clock to know the time of the day, and a Printer to get the hard copy of the journey details. The other optional features that can be added with the meter are:
Radio link for dispatching trip information to supervisor.
Interaction with GPS systems to receive security assistance during danger/accident.
Seat sensors that detect the presence of passengers.
Credit or prepaid card support.
Extra charge for luggage.
Speed of the Taxicab.
Diagnostics support like determining the ageing of the wheel/tire and LED test.
3. Authorized Tariffs in Bangladesh:
Flat Fare for the 1st 2 Km journey : Tk 40.00
Fare for next each Km distance traveled after 1st 2 Km : Tk 12.00
Distance Update (Designer's option): 10m
Waiting Time fare for each 1-min (60-sec) waiting: Tk 2.00
Fare Update for each 200m distance traveled after 1st 2 Km (Tk 12.00/5): Tk 2.40
Advance Fare (fare Update) for 200m after 1st 2Km crossing (1/5th of 1 Km): Tk 2.40
Calculation Reference: Distance
4. Conceptual Pictorial view of 3-window Taxi Meter (with diagnostic support)
Fig-13.1 is a line sketch that reflects the idea of the "to be Taxi Meter" perceived at conceptual level looking at the functioning of the real Taxi Meters in the CNGcabs, talking with the people who repair these meters, and standard design specs.
For the development and testing of the Taxi Meter, I have used Arduino NANO Learning Kit and C/C++/Arduino Language in my own style of creativity The physical implementation of this conceptual level is given in Fig-13.3.
Figure-13.1: Conceptual pictorial view of 3-window Taxi Meter (with diagnostic support)
(1) The transducer is attached with the gearbox of the Taxicab. The "real transducer" (Fig-13.4) that is being used in this project is from a particular company, and it produces about 16 pulses (known as WTP for Wheel Turning Pulse) when the taxicab moves 10 m distance.
(2) The meter has three windows:
DDM Meter (Digital Distance Meter) to record distance traveled by the taxicab at every 10 m.
DFM Meter (Digital Fare Meter) to record total fare including the flat fare of Tk 40.00 for the 1st 2 Km, and
DWM Meter (Digital Waiting time Meter) to record waiting time in the trip (max: 99 Min 99 Sec).
(3) For development and testing of the Taxi Meter, we will be using 555-based (Fig-13.2) 1 Hz oscillator instead of "real transducer" to simulate WTP pulses.
Figure-13.2: 555-based low frequency oscillator to simulate WTPs
(4) When the taxicab has not yet been hired and the driver has pressed down the RST button, the DDM Digital Distance Meter), DFM (Digital Fare Meter), and DWF (Digital Waiting Time Meter) will show 0s. That is:
DFM : 0.00 Km
DFM : 0.00 Tk
DWM : 0.00 Mn //(0 minute and 00 second)
(5) After the taxicab has been hired and the driver has pressed the "HRD (Hired)" button, the digital meters will show:
DFM : 0.00 Km
DFM : 40.00 Tk //Flat fare for the 1st 2 Km or 20 min waiting time or of combination
DWM : 0.00 Mn //(0 minute and 00 second)
(6) The taxicab has started moving, the DDM advances by 10 m. There will be no change in DFM meter until the taxicab has just crossed 2 Km distance. It is assumed that the taxicab has not encountered any waiting state in the trip. When the taxicab has just crossed the 2 Km distance, DFM is augmented by Tk 2.40 which is an advance payment to the driver for the cost of 200 m distance given the fare rate is Tk 12.00/Km. The meter readings are:
DFM : 2.00 Km
DFM : 42.40 Tk //40.00 + 2.40
DWM : 0.00 Mn (0 minute and 00 second)
5. Physical Pictorial view of 3-window Prototype Taxi Meter (with diagnostic support)
Figure-13.3: Physical pictorial view of 3-window prototype Taxi Meter (with diagnostic support)
6. Physical Pictorial view of 3-window Simplified Prototype Taxi Meter (no diagnostic support)
Figure-13.4: Physical Pictorial view of 3-window simplified prototype Taxi Meter (no diagnostic support)
Working Principle: (1) The green color gadget of Fig-13.4 is the transducer which is fitted with the gearbox of the Taxicab, and it generates about 16 pulses when the Taxicab moves by 10 m distance. These pulses are called WTP (wheel turning pulses), and they are accumulated by TC0 Module of the MCU to update DDM Meter (Digital Distance Meter) by 10 m.
(2) The flat fare for the first 2 km is Tk 40.00 and then the fare is Tk 12.00 for each km covered. The DFM Meter (Digital Fare Meter) accumulates/updates fare for each 200 m traveled which is Tk 2.40. When the Taxicab just crosses initial 2 km distance, the DFM shows a reading of Tk 42.40 (40.00 + 2.40) which means that the Taxi driver is paid an advance payment for the fare of 200 m; as a result, there is no chance for the driver to lose fare even the passenger gets down at any place.
(3) There is a fare for waiting time which is Tk 2.00 for each minute waiting. As the practical journey/trip is a combination of distance traveled and waiting time, the fare is always computed based on the combined effect of distance and waiting time; where distance is the reference. The DWM Meter (Digital Wait Meter) records the total waiting time happened in the trip (0.00 to 99.99 = 0 Min 0 Sec to 99 Min 99 Sec).
(4) There are three buttons on the face plate of the Taximeter of Fig-13.4 and these are:RESET, TOPAY, and HIRED. The functions of these buttons are:
a) RESET: The driver pushes this button to bring 0.00 into DDM, 0.00 into DFM, and 0.00 into DWM.
b) HIRED: The driver pushes this button when the Taxicab is hired. As a result, o.00 comes into DDM, 40.00 (as Flat Fare) on DFM, and 0.00 into DWM. This button will work only for once during the whole journey and after the rest button that brings Tk 0.00 in DFM.
c) TOPAY: the driver pushes this button at the end of journey. As a result, all activities of the Taxi Meter gets frozen. The display reading do not change. The passenger records the distance traveled, fare charged, and the waiting time. This button will work only when the taxicab is in "waiting state".
7. There could be three types of journey/trip for the taxicab and these are:
(1) Distance-drive (D-drive): There is no waiting in the trip. The whole fare is due to distance traveled and the flat fare.
(2) Time-drive (T-drive): There is no distance traveled. The whole fare is due to waiting time and the flat fare.
(3) Combined-drive (C-drive): This is the practical journey. The whole fare is due to the combined effect of distance traveled, waiting time, and flat fare.
8. Physical Pictorial view of 2-window Simplified Prototype Taxi Meter
In this meter, the Distance and the Waiting Time are shown on a single display unit (the Top one in Fig-13.5) on multiplexed basis. Thus, there is a saving of four display units and reduces the cost of the meter a little bit.
Figure-13.5: Physical pictorial view of 2-window simplified prototype Taxi Meter
9. Schematic Diagram of an Arduino NANO based 3-window Taxi Meter
Figure-13.6: Schematic Diagram of an Arduino NANO based 3-window simplified Taxi Meter of Fig-13.4
10. Pictorial view of the development Process of Arduino NANO based Taxi Meter
Figure-13.7: Pictorial view of the development process of Arduino NANO based Taxi Meter l