This project implements the concept of wireless technology and LED scrolling display to construct an energy efficient and versatile electronic notice board for institutional purpose. The system uses dot matrix LED panels to construct a horizontal display module in which any kind of messages can be displayed and scrolled. The message to be displayed can be send wirelessly from a remote computer with the help of wireless RF transmitter and receiver. This system is also equipped with the RFID technology for institutional applications in which any student can be logged in using his unique ID to view his academic status like percentage of attendance, exam results sectional marks etc. for this application an RFID reader is included in this display board. For effectively implementing this RFID based display board each and every student should have their own unique electronic ID card.
FUNCTIONAL BLOCK DIAGRAM
DISPLAY BOARD SECTION
LED DOT MATRIX ARRAY
RS232 – TTL Converter
Power supply section power the whole circuitry. Different section of this system requires different voltage levels. This requirement cannot be achieved using a single power adapter or battery. So a power supply consist of dc-dc converter is used in our project. The DC-DC converted dc power supply can provide 12v dc, 9v dc and 5 v dc simultaneously for display, discrete IC and micro controller respectively. The power supply section is also included with short circuit protection to prevent system being damaged due to the careless usage or electrical malfunctions.
The controller used here is PIC 16f877a, which is an 8 bit micro controller used for general purpose medium scale applications. In our project this device retrieves signals from the RF receiver as serial data through its URAT port on a baud rate of 2400 bps and stores in its internal data memory. From there it sends the data one by one to display section to display it. The scrolling algorithm is also done through the program written in the controller. This controller also communicate with the RFID reader to fetch the ID of RFID card brought to its proximity and then retrieves the corresponding registry entry to display it in the display board. The scrolling message mode and personal message mode is switched with help of two way switch attached in the display board end. When the switch is in its normal position the message from the PC is displayed and when the switch is in other position the board will display the personal information of the student whose card is in the proximity of the RFID reader.
The display used here are dot matrix LED. The whole panel consist of 32 displays each one of 5x7 dot matrix LED. Each character in this display is formed using four such display units. That means the whole display can show a total of 8 characters at a time. The display is drived and controlled using a ring counter IC 4017. By this IC we select each display independently and their column.
It uses persistence of vision to let you drive the 32 led matrixes with only 10 microcontroller outputs! Normally you would need 32outputs for 32 LEDs but by using multiplexing and a helper chip you can get away with 10. LED Display multiplexing simply means turning on one led for a short period of time and doing this repeatedly for each LED. If you do this fast enough then your eye will not notice any flicker.The LEDs are no different to any other LEDs but it saves a huge amount of soldering as all the wiring has been done for you..Or you could wire it up yourself if you can't get hold of the module. Still only need 10 control wires (just wire you leds the same as shown in the module diagram). Your eye reacts slowly to changes in light intensity so that if a light is turned on and...
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