17-12-2012, 06:26 PM
traffic lights using VHDL
traffic lights using VHDL.docx (Size: 356.49 KB / Downloads: 41)
INTRODUCTION
Traditionally traffic lights are controlled by microcontroller 89C51. The primitive mechanical traffic lights have no way of having a versatile delay. But using CPLD as a 16-bit µP and use it in the domestic application to improve the primitive mechanical traffic light.
This project attempts to control the traffic lights using VHDL. Being an electronic system it is reliable, compact and maintenance free. VHDL makes the system versatile as the ON-OFF times can be easily varied by changing the delay loops through software. Even the sequence of lights i.e. whether the yellow light has to glow or not can be programmed easily by modifying the software. This project is practically implemented and tested. Since Programmable Integrated Circuits provides repeatability and flexibility, we can program it more than 10000 times. And this is not possible for fixed logic IC.
The best part of using CPLD is we can easily reprogram it. We don’t have remove the CPLD from the hardware. We can program it by placing it into the same board
DESIGN MODEL
Functional block includes the following things
• CPLD XC9572
• Clock Generator
• ULN2803 Driver
• Traffic lights
• Power supply(+5V.+12V)
SPECIFICATION
CPLD
CPLD XC9572 is the world of digital electronics systems, there are three basic kinds of devices memory, mocroprocessors and logic devices. Memory devices store random information such as tha contents of a spreadsheet or database. Microprocessors execute software instructions to perform a wide variety of tasks such as running a word processing program or video game. Logic devices provide specific funtions, including device-to-device interfacing, data communication, signal processing, data display, timing and control operaations, and almost every other functions a system must perform. In case of CPLD it has wiring among the logic in the IC. So the wiring on the printed circuit board can be made little.