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In this study, a gear shifting mechanism was designed and applied on an auto clutch featured
bike to make the gear transmission process faster and less destructible for the diver using
Embedded System design. The present automatic transmission is fully mechanically controlled
and costs very high and it is not suitable for small displacement engines. But the gear
transmission mechanism designed makes driving easier and to achieve efficient driving. This
new device must be reliable, has small dimensions, economical and low maintenance cost. This
project aims to improve the gear shifting process with a suitable control mechanism to
implement in clutch featured bikes. According to the suggested gear shifting method, the
microcontroller selects the transmission gear as per the speed of the vehicle without any human
interference. The head light control is designed which dims and dips if any vehicles comes
opposite with high beam. This is a safety feature installed to avoid accidents caused due to high
beam lights having blinding effect on drivers coming from the opposite direction.
Keywords: Automatic gear transmission, automatic headlight control, Digital speedometer,
Inductive proximity sensor, Microcontroller AT89s51.
1.1 Overview
The topic of current interest in the area of controller development for automatic
transmissions with a finite number of gearshifts which transmits the gears automatically with
respect to speed. Gearshifts in automatic transmissions involve a change in the power flow path
through the transmission. Advantages of these automatic transmissions include simplicity of mechanical design and savings in transmission weight and size, which are beneficial in terms of
fuel economy and production costs. This enables gain in fuel economy while meeting drivability
and performance goals, these savings become more significant.
The designed automatic transmission is done in an auto-clutch featured bike which can be
applied effectively and efficiently in a clutch featured bikes with suitable control techniques. The
ultimate goal of our project is to transmit the gears without the human interference and to attain
efficient, safe and easy driving in cost effective way. Microcontroller is the heart of the system
which handles all the sub devices connected across it. We have used Atmel 89s52
1.2 Automation
Automation is the use of control system to control a process replacing the human
operators. It is a step beyond mechanization, where human operators are provided with the
physical requirements of work.
Automation is now often applied primarily to reduce the human effort thereby to attain
desired operation. Another major shift in automation is the increased emphasis on flexibility and
convertibility in different process.
One safety issue with automation is that it is often viewed as a way to minimize human
error in the system, increasing the degree and the levels of automation also increase the sequence
of error that accidently created in automated systems. Different types of automation tools that
exist in today’s environment are Programmable logic controller, Microcontroller, SCADA, etc.
1.3 Types of Transmission
 Manual transmission
 Automatic transmission
1.3.1 Manual Transmission
A manual transmission or sequential type is a type of transmission used on motorcycles
and cars, where gears are selected in order, and direct access to specific gears is not possible.
With traditional manual transmissions, the driver can move from gear to gear, by moving
the shifter to the appropriate position. A clutch must be disengaged before the new gear is
selected, to disengage the running engine from the transmission, thus stopping all torque transfer.
1.3.2 Automatic Transmission
An automatic transmission is one type of motor vehicle transmission that can
automatically change gear ratios as the vehicle moves, freeing the driver from having to shift
gears manually and to achieve efficient driving.
1.3.3 Advantages of Automatic Transmission
• Easier to drive in stop-and-go traffic and available in most cars, an automatic
transmission has definite benefits
• The main benefit of automatic transmissions is that they are simply easier to use.
• Fuel efficient.
1.4 Embedded System
All embedded system uses either a microprocessor (or) microcontroller. The software for
the embedded system is called firmware. The firmware will be written in assembly language (or)
using higher level languages life ‘C’ (or) ‘Embedded C’. The software will be simulated using
micro code simulation for the target processor. Since they are supposed to perform only specific
tasks, the programs are stored in ROM.

An embedded system is some combination of computer hardware and software, either
fixed in capability or programmable, that is specifically designed for a particular function.
Industrial machines, automobiles, medical equipment, cameras, household appliances, airplanes,
vending machines and toys (as well as the more obvious cellular phone and PDA) are among the
myriad possible hosts of an embedded system. Embedded systems that are programmable are
provided with programming interfaces, and embedded system programming is a specialized
An Embedded system is a special-purpose computer system, which is completely
encapsulated by the device controls. It has specific requirements and performs pre-defined tasks,
unlike a general purpose personal computer.
 Avoids lots of Electronic components.
 Build in with rich features.
 Probability of failure is reduced.
 Easy interface.
1.5 Block Diagram Description
The presented project is aimed to perform operations such as automatic gear
transmission, automatic headlight control, and digital speedometer. Here the speed is the inputs
to the microcontroller unit.
The inductive speed sensor senses the speed of the vehicle from the front wheel and
sends train of pulses as output to the microcontroller unit. The microcontroller unit checks the
pulses for sample time period and calculates the speed of the vehicle.
As programmed, the microcontroller actuates the Relay 1 and Relay 2 through the driver
unit depending on the speed of the vehicle. The DC motor function is to transmit the gear lever
by pole reversal technique which is performed using the relays.
Since it requires slowing down the engine at the time of gear transmission, the supply to
the ignition coil is grounded so as to slow the engine.

2.1 Inductive Speed Sensor
Inductive proximity sensors are designed to operate by generating an electromagnetic
field and detecting the eddy current losses when a ferrous metal target enters the field. The
sensor consists of a ferrite core, an oscillator, a trigger-signal level detector and an output circuit.
The oscillator creates a high frequency field radiating from the coil in front of the sensor
centered on the axis of the coil. When a metal object enters the high-frequency field, eddy
currents are induced on the surface of the target. As a metal object advances into the field, eddy
currents are induced in the target. This results in a loss of energy in the oscillator circuit and
consequently smaller amplitude of oscillation.

The detector circuit recognizes a specific change in amplitude and generates a signal
which will turn the solid state-output “ON” or “OFF”. When the metal object leaves the sensing
area, the oscillator regenerates allowing the sensor to return to its normal state.
The inductive speed sensor has a built-in hysteresis to avoid unwanted switching of the
sensor due to,
• Mechanical vibration of the sensor or the gear wheel
• Electrical interference
• Circuit oscillation at very low rotational speed

A larger hysteresis provides a better immunity to disturbances but, on the other hand,
reduces the maximum sensing distance d, as the sensor signal must exceed the hysteresis levels
to be recognized.
2.2 Microcontroller
Microcontrollers are microprocessors with peripheral devices and memory embedded in a
single chip. They are used in almost all modern day appliances controllers and so it is produced
in millions. The most popular microcontroller architecture is Atmel 89s52. There are many number of IC manufacturers offering microcontrollers based on this architecture. Atmel is one of
them. The microcontroller 89s52 from Atmel is chosen for this project.
2.2.1 AT89S52
The AT89s52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K
bytes of Flash programmable and erasable read only memory (PEROM). The device is
manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with
the industry standard 80C51 and 80C52 instruction set and pin out. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a conventional nonvolatile memory
programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel
AT89s52 is a powerful microcomputer which provides a highly-flexible and cost-effective
solution to many embedded control applications.
• 8K Bytes of In-System Reprogrammable Flash Memory
• 256 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Sources
• Programmable Serial Channel
• Low-power Idle and Power-down Modes
2.2.2 Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that
can be configured for use as an on-chip oscillator, as shown in Fig.4. Either a quartz crystal or
ceramic resonator may be used. To drive the device from an external clock source, XTAL2
should be left unconnected while XTAL1 is driven, as shown in the figure. There are no
requirements on the duty cycle of the external clock signal, since the input to the internal
clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high
and low time specifications must be observed.

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