4. OBJECTIVE:
The aim of the project is to display the speed and
distance covered by a vehicle per hour in digital. So that even a
normal person can easily understand the readings.
5. SYNOPSIS:
In this project we make use of a speed transducer.
The rotation of the wheel is sensed by the combined action of a
reed switch and a magnet fixed on the wheel. The sensor sends a
pulse to the microcontroller each time a revolution is made using
optocoupler and it is counted by the counter present in
microcontroller. This count value is used to measure the speed and
distance using the standard readings present in the memory. The
speed and distance are displayed in LCD. The circuit uses a
microcontroller AT89C2051, an LCD display, sensor, serial
EEPROM and some commonly available components. It is very
accurate when compared to analog meter. It is reliable due to use
of microcontroller. It reset to zero after completion of
99,999.9km.. It is easy to build and fix on any vehicles.
9. The Reed Switch described above is a 1 Form A
(normally open (N.O.)or Single Pole Single Throw (SPST))
Reed Switch
10. Many reed switches and reed sensors are
used for proximity sensing and are activated by a magnet.
As the magnet is brought into the proximity of the reed
sensor/switch, the device activates. As the magnet is
removed from the proximity of the reed sensor/switch, the
device deactivates. However, the magnetic interaction
involved in activating the reed switch contacts is not
necessarily obvious. One way of thinking about the
interaction is that the magnet induces magnetic poles into
the metal parts of the reed switch and the resulting
attraction between the electrical contacts causes the reed
switch to activate.
WORKING OF REED SWITCH
12. Features - AT89C2051
Compatible with MCS-51 Products
2K Bytes of Reprogrammable Flash Memory
2.7 to 6V Operating Range
Fully Static Operation: 0 Hz to 24 MHz
Two-level Program Memory Lock
128 x 8-bit Internal RAM
15 Programmable I/O Lines
Two 16-bit Timer/Counters
Six Interrupt Sources
Programmable Serial UART Channel
Direct LED Drive Outputs
On-chip Analog Comparator
Low-power Idle and Power-down Modes
20-pin DIP
13. EEPROM
AT24C02 is an electrically erasable and programmable
ROM. It has a 2Kbits of memory size arranged in 32
pages of 8 byte each. There are 256 (32 x 8) words each
of one byte. The data is transferred and received serially
through serial data (SDA) pin.
15. Calculations
You first need to know the radius of the bike’s front wheel.
The calculations here are based on Hero Honda’s Splendor
model. The radius of the front wheel is 30 cm. (This can
vary with the brand or model.)
Circumference of the wheel= 2πr
(where ‘r’ is in cm)
= 2 3.14 30
= 188.4 cm or 1.884 meters
16. Speed. Let’s assume that in 1 second the wheel completes one
revolution. In other words, in one second, the bike has covered 1.88
meters. Therefore the speed in km/hour:
N 1.88 3600/1000
=N 6.784 or N 6.8
where ‘N’ is the number of revolutions per second. ‘6.8’ is a constant
and only ‘N’ varies; for example, if ‘N’ is 5, the speed equals 5x6.8=
34 km/hour.
Distance. The odometer is updated every 100 meters. To cover 100
meters, the wheel is required to make approximately 53 revolutions
(100/1.88). The microcontroller takes care of the tasks of revolutions
counting, speed calculation, conversion and display of results.
17.
18.
19. APPLICATION:
It is used in motorbikes to display the speed in
digital
It is used in cars to display the speed in km/hour
ADVANTAGE:
1. Digital readout
2. Speed displayed in km/hour
3. Distance traveled displayed in Kilometers
4. Readings saved in non-volatile memory (EEPROM)
5. Reliability due to use of the microcontroller
6. No mechanical wear and tear
