12-03-2011, 10:06 AM
Submitted by
ASHVEN V GOPAL
RACHANA RADHAKRISHNAN
[attachment=10047]
INTRODUCTION
The project digital speedometer throws light on the concept of measuring speed in automobiles or other related equipment and displaying it suitably. The speed measurement is done with the help of a microcontroller and speed display is done on LCD. The microcontroller used in this project PIC 16F73. It is programmed so as to count interrupts. The interrupt is provided using a comparator. The output of comparator is controlled by LDR, which is illuminated by a high intensity LED. This arrangement of LED and LDR is placed on the side of wheel or the rotating part, of which speed is measured. The interrupt generated is counted by the microcontroller and speed is displayed in LCD. This is a simple method of speed measurement.
BLOCK DIAGRAM DESCRIPTION
ENCODER
Encoder is constituted by LED, LDR and comparator. As the disc rotates the illumination level of LED on LDR changes which change the resistance of LDR which in turn varies the voltage in the negative terminal of comparator. The comparator compares the variable voltage in its negative input with constant voltage on its positive terminal. The output of comparator will be low when LDR is not illuminated, i.e., when LED meets the dark portion of disc. The comparator used here is LM358.
LM358:
LM358 is a low power dual input operational amplifier. It consist of two independent high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. Application areas include transducer amplifiers, DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems.
For example, the LM358 can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional +15V or -15V power supplies.
PIC16F73
The microcontroller used here is PIC16F73. The entire function of this speedometer is controlled by this PIC.
FEATURES OF PIC16F73
• High performance RISC CPU.
• Only 35 single word instruction to learn.
• All single cycle instruction except for program branches which are two cycles.
• Operating speed: DC-20MHz clock input DC-200ns instruction cycle.
• Up to 8K x 14 words of FLASH Program Memory, upon 368 x 8 bytes of Data Memory (RAM).
• Interrupt capability (up to 12 sources).
• Eight level deep hardware stack.
• Direct, Indirect and Relative Addressing modes.
• Processor read access to program memory.
LIQUID CRYSTAL DISPLAY
A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals. It is the final output device that visualizes the calculated speed. LCD used in this project has 16 x 2 and it displays 4 bit data.
POWER SUPPLY
The whole circuit uses DC supply. A bridge circuit is included in the power supply section to rectify the AC in case 230V mains is used. A power regulator LM7805 is also used to provide a constant DC of +5V.
LM7805:
LM7805 is a switching regulator. Linear Technology manufactures a broad line of high performance switching regulator ICs with both synchronous and non synchronous internal switches. These regulators offer typical input voltage capability from 2.25V up to 60V, switching frequencies up to 4MHz and high efficiency operation up to 96%. Also burst mode operation, quiescent currents in the tens of micro-amps level can be attained. The combination of features allows very small, low profile circuit implementations with minimum external components. Other features include adjustable or synchronizable switching frequency, small in size, and more.
ASHVEN V GOPAL
RACHANA RADHAKRISHNAN
[attachment=10047]
INTRODUCTION
The project digital speedometer throws light on the concept of measuring speed in automobiles or other related equipment and displaying it suitably. The speed measurement is done with the help of a microcontroller and speed display is done on LCD. The microcontroller used in this project PIC 16F73. It is programmed so as to count interrupts. The interrupt is provided using a comparator. The output of comparator is controlled by LDR, which is illuminated by a high intensity LED. This arrangement of LED and LDR is placed on the side of wheel or the rotating part, of which speed is measured. The interrupt generated is counted by the microcontroller and speed is displayed in LCD. This is a simple method of speed measurement.
BLOCK DIAGRAM DESCRIPTION
ENCODER
Encoder is constituted by LED, LDR and comparator. As the disc rotates the illumination level of LED on LDR changes which change the resistance of LDR which in turn varies the voltage in the negative terminal of comparator. The comparator compares the variable voltage in its negative input with constant voltage on its positive terminal. The output of comparator will be low when LDR is not illuminated, i.e., when LED meets the dark portion of disc. The comparator used here is LM358.
LM358:
LM358 is a low power dual input operational amplifier. It consist of two independent high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. Application areas include transducer amplifiers, DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems.
For example, the LM358 can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional +15V or -15V power supplies.
PIC16F73
The microcontroller used here is PIC16F73. The entire function of this speedometer is controlled by this PIC.
FEATURES OF PIC16F73
• High performance RISC CPU.
• Only 35 single word instruction to learn.
• All single cycle instruction except for program branches which are two cycles.
• Operating speed: DC-20MHz clock input DC-200ns instruction cycle.
• Up to 8K x 14 words of FLASH Program Memory, upon 368 x 8 bytes of Data Memory (RAM).
• Interrupt capability (up to 12 sources).
• Eight level deep hardware stack.
• Direct, Indirect and Relative Addressing modes.
• Processor read access to program memory.
LIQUID CRYSTAL DISPLAY
A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals. It is the final output device that visualizes the calculated speed. LCD used in this project has 16 x 2 and it displays 4 bit data.
POWER SUPPLY
The whole circuit uses DC supply. A bridge circuit is included in the power supply section to rectify the AC in case 230V mains is used. A power regulator LM7805 is also used to provide a constant DC of +5V.
LM7805:
LM7805 is a switching regulator. Linear Technology manufactures a broad line of high performance switching regulator ICs with both synchronous and non synchronous internal switches. These regulators offer typical input voltage capability from 2.25V up to 60V, switching frequencies up to 4MHz and high efficiency operation up to 96%. Also burst mode operation, quiescent currents in the tens of micro-amps level can be attained. The combination of features allows very small, low profile circuit implementations with minimum external components. Other features include adjustable or synchronizable switching frequency, small in size, and more.
