Author Topic: Peripheral Interface Controller based the Display Unit of Remote Display System  (Read 2945 times)

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Author : May Thwe Oo
International Journal of Scientific & Engineering Research, IJSER - Volume 2, Issue 4, April-2011
ISSN 2229-5518
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Abstract— This paper expresses about how to construct the peripheral interface controller (PIC) based the display unit of the remote display system. The remote display system can be used to display the token number that is to know the people. It is also intended for use in clinic, hospitals, bank, and etc. In this research, the peripheral interface controller based remote display system is used for displaying the number and the character. The remote display system consists of two portions: display unit and console unit. The display unit of remote display system contains the display controller, three seven-segment Light Emitting Diode (LEDs), Diode matrix, Category display LEDs and DSUB9 connector. The display controller is controlled by the microcontroller PIC16F873. It controls to display the token numbers. And then it can control at the diode matrix to display the three kinds of character such as A, B, and C. The three numbers of seven-segment LEDs will display the token number from one to 999. The diode matrix helps to display the category display LEDs. The category display LEDs will display one kind of characters. In the research work, the category display LEDs can be displayed only three kinds of characters. For the display unit, the DSUB9 connector applies the data that is from the console unit of the remote display system. In this research work, the display unit works as the receiver the console unit works as the transmitter in remote display system. This paper explains about the design, construction, testing and result of a remote display system.

Index Terms— Diode Matrix, Display Unit, Light Emitting Diode, Peripheral Interface Controller, Remote Display System. 

THIS display system is very useful in many applications. To advertise, to express the number, the remote display system can be used. Because of the token number can be expressed by using the display system. The token number may be used in banks, financial institutions, clinics and etc. The display unit of the remote display system can be controlled by the microcontroller PIC16F873. The token number is displayed by the large-sized seven- segment Light Emitting Diodes (LEDs). The category display LED can be expressed the three charac-ters. This research consists of two modules; one for the construction of hardware circuit (including interfacing circuit and LED matrix circuit) and other for how to con-trol the process by using peripheral interface controller (PIC). In this research, the hardware controlling program is Assembly programming language. The circuit compo-nents consist of resistors, transistors, Integrated Circuit (ICs), LEDs and other accessories. The remote display system consists of two parts. They are console unit and display unit. The display unit is used to display the numbers. That number is needed to know the people. That numbers may be the token number for using many public places. For examples, the token number may be used in the banks and financial institutions, calling the patients one by one at the clinics, calling the candidates at the interviewing and etc. There are many ways to display the number.

2.1 PC Basted Token Number Display
An increasing number of banks are computerizing their operations. For actual field use, the display with target LED arrays must be replaced. No other hardware is needed, except the displays and the buffers. The absence of any seven segment decoder chip like 7447 is to be no-ticed. Because of all the decoding is done entirely by software. Time division multiplexing is another impor-tant concept. The four numbers of seven-segment dis-plays share a common data bus. The PC places the first digit on the data bus, and enables only the first seven-segment unit. After a delay of one millisecond, the digit is replaced by the next digit, but this time only the second display unit is enabled. After displaying all the four digits in this way, the first unit is enabling again. The cycle repeats itself over and over. Another feature provided by the software is the ability to suppress leading zeros. Number five is displayed as 5, rather than as 0005. This is usually done by the hardware using the so called ‘ripple blanking’ facility of the decoder chips. Finally, the computer emits a musical sound whenever there is a change in the displayed number, to attract attention. A regulated 5-volt power supply is recommended [1].

2.2 Digital Bank Token Number Display
Electronic bank token number display systems are quite popular with bank and financial institutions nowadays. These can be used by general practitioners in their clinics to call the patients one by one, and by interviewing com-mittees to call the candidates.  In most applications, there are two sets of displays, a small one kept inside the cabin of the person controlling it, and a large one kept outside for visitors. There is a keyboard for teller to enter token
numbers. The large size plasma devices and TTL chips are being used in the constructing of bank token display [2]. In digital bank token number display system, the display device circuit is used to control both the common cathode LED and common anode plasma displays. A well regulated transistorized circuit provides power to TTL chips as well as to high voltage plasma displays.

2.3 Improvement of Display Unit
The digit display part of the display unit is made to light up by 1 digit to suppress an electric current. The lighting-up time of one digit becomes 1/3 and the light falls. When little flow of the electric current occurs, the color patches occurs to the displaying. The display data is hold by the latch register (74LS 273). The 74LS273 which is D-type flip-flop (D-FF) as the latch register to hold the display of the LED is used. The eight D-FFs are housed in one piece of IC. One 74LS273 is used to control one seven-segment LED. It inputs the data to D terminal to make hold. First, the data for the 100th is outputted to RB6 from RB0 and it is inputted to all the latch registers. Next, RA0 is made H and only the CK of the latch register (IC five) for the 100th is made H level. By this, a 100th digit is displayed in LED1.

3.1 Receiver Operation in Display Unit
The display unit of the remote display system is based on the PIC16F873. And it uses the asynchronous commu-nication of PIC16F873. In asynchronous communication, there are two operations: Transmitter operation, Receiver operation. Fig. 1 showed the schematic diagram of receiver operation of PIC16F873 in the display unit.

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