06-01-2011, 04:58 PM
[attachment=7982]
SUBMITTED BY,
JOMESH JOSEPH
JOSE TOM K
VINUPRASAD O M
DHANESH PRAKASAN
GUIDED BY,
SHAMLA B
SENIOR LECTURER
DEPT. OF ECE
GEC THRISSUR
ABSTRACT
The aim of our project is to develop prototype of a product “Digital Speedometer”. It's used to measure speed up to 999 kmph with a resolution of 1 kmph. It's a hardware project done in the field of Digital Electronics and Instrumentation. It can replace ordinary analog speedometer which has low range and resolution. It's rather inexpensive and can be used in almost all vehicles. It can also be used for measuring speed on industrial machinery and modified version of circuitry can be used as an rpm counter.
This Digital Speedometer is provided for use in an automotive vehicle and includes a transducer for connection to a conventional speedometer cable driver. Transducer is equipped with an IR LED and a photo transistor,that produces pulses in response to the rotational motion of the speedometer cable driver. Pulses are transmitted to a counting circuit which is reset by multivibrator circuits. The number of pulses from the transducer is indicative of speed of the vehicle. It is tabulated by the counting circuits during intervals between reset pulses. The number of counts tabulated during each period is passed to a visual display.
INTRODUCTION
AIM
The present invention relates to a Digital Speedometer for use with vehicles having internal electrical power supply. In particular, the invention relates to a digital speedometer for automotive vehicles such as auto mobiles, trucks and motor cycles. The Digital Speedometer designed is highly efficient , low cost and can measure speed up to 999 kmph with a resolution of 1kmph.
AREA OF PROJECT
It‟s dealing with Digital Electronics Circuits and Instrumentation. The main sections of the circuitry are IR section, Comparator, Timer, Counter, Latching section and LED display.
MOTIVATION
The aim of our experiment is to create an efficient low cost Digital Speedometer. It was inspired by the fact that most of the modern-day vehicles use analog speedometers which have resolution of about 5kmph and the range is also limited.
Historically auto motive vehicles have been provided with mechanical speedometers in which rotation of wheel of the vehicle or of a drive component of the transmission is transmitted as a torsional impulse the torsional force applied to the cable is typically transmitted to needle in the instrument panel which is deflected across a scale to indicate speed at which vehicle is travelling. The Principal dis advantage with such systems has been the requirement for a signal generating system independent of the conventional mechanical speedometer system associated with the auto mobile. It increases the cost of the vehicle.
The Digital Speedometer we have designed can measure up to a speed of 999kmph with a resolution of 1kmph. It‟s rather inexpensive and can be used in almost all vehicles.
INPUT SECTION
Input Section consists of IR LED, photo transistor, a comparator and a mechanical section. An opaque disc is mounted on the spindle attached to the front wheel of the vehicle. This disk has ten equidistant holes on its periphery. On one side of the disc an Infrared LED is fixed and on opposite side of the disc, in line with the IR LED, a phototransistor is mounted. IC LM324 is wired as a comparator.
TIMER SECTION
Timer section consists of astable and monostable multivibrator circuits. So we use IC 556 for this purpose. Astable section is used to trigger the monostable multivibrator. IC 7400(AND gate) is used to set the gating period.
OUTPUT SECTION
Output section consists of counter and latching sections along with LED display. IC 7490 is used to implement the counter section. The number of pulses counted during the gating period is the speed N in kmph. IC 74175(Quad D flip-flop) is used as the latching circuit. It helps in keeping the LED display constant for a particular period of time so that displayed value could be read. IC 7447 is used as BCD to seven segment decoder. Common anode LEDs are used in the output section to view the speed measured.
CONCLUSION
An efficient low cost digital speedometer which can measure speed up to 999kmph with a resolution of 1kmph has been designed.
Resolution can be improved by using additional displays.
Circuit can be modified using microcontroller and LCD display
