Introduction

RANK DISPLAY SYSTEM

INTRODUCTION

There are so many games where the winner is the one who takes the least time in successfully completing the task given. Take for instance the ‘fastest finger first’ in KBC quiz show on TV or the ‘fastest crossing first’ in any type of race. In these competitions, sometimes there may be two or more players who appear to complete the task in equal time. In such cases, it becomes difficult for the judge to announce the winner, though there may be time difference of a few milliseconds between the individuals in accomplishing the task.

Here is a circuit based on Atmel microcontroller AT89C51 that can resolve the time-difference ambiguity and indicate correct ranking of all the participants on a liquid-crystal display (LCD) module. It has been designed for a maximum of eight participants playing at a time, denoted by alphabets 'A' through 'H,' and can be used both for a 'fastest finger first' quiz and 'fastest crossing first' race.

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RANK DISPLAY SYSTEM

CIRCUIT DESCRIPTION

Fig. shows the circuit of the microcontroller- based rank display system. It comprises microcontroller AT89S51, transistor array IC ULN2803, LCD module (16x2), regulator IC 7805 and a few discrete components.

IC AT89C51 is a low-power, high performance, 8-bit microcomputer with 4 KB of Flash programmable and erasable read-only memory (PEROM), 128B of RAM, 32 input/output (I/O ) lines, two 16- bit timers/counters, a five-vector two-level interrupt architecture, a full-duplex serial port, on-chip oscillator and clock circuitry.

Port-0 pins of the microcontroller (IC1) are pulled high via 4.7-kilo-ohm resistor network RNW1 and interfaced with switches S1 through S8 (corresponding to players 'A' through 'H'), respectively.

Port-0 pins P0.0 through P0.7 are also connected to pins 11 through 18 of ULN2803.

Port-2 pins P2.0 through P2.7 are connected to inputs 1 through 8 of IC2.

Each time a switch is pressed, a feedback is sent from port 2 through port 0 via ULN2803 (IC2). The purpose of this feedback is to make a given pin of port-0 'low', independent of the condition of the corresponding switch (S1 through 58) just after it has been pressed once.

One more input switch S11 is provided to reset the circuit for starting the next round. Switch S11 is connected to P3.0 pin 10 of the microcontroller. Pressing of switch S11 starts the next round of questions. Thus, it acts as a latch. R1 through R8 are current-limiting resistors.

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Port-l pins Pl.0 through P1.7 and port-3 pins P3.1 through P3.3 of the microcontroller are interfaced with data line pins 7 through 14 and pins 4 through 6 of the LCD module for displaying the various rankings. Contrast pin 3 of the LCD module can be controlled using preset VR1.

Pin 3.4 of the microcontroller is used to control piezobuzzer PZ1. When P3.4 goes low, piezobuzzer PZ1 sounds. Pin 3.6 of IC1 is connected to slide switch S9 for selection between race and quiz.

Switch S10 is used to manually reset the microcontroller, while the power-on reset signal for the microcontroller is derived from the combination of capacitor C5 and resistor R10.

A 11.0592MHz crystal generates the basic clock frequency for the microcontroller.

230V AC mains is stepped down by transformer X1 to deliver the secondary output of 12V, 500mA. The transformer output is rectified by a full-wave bridge rectifier comprising diodes D1 through D4, filtered by capacitor C3 and then regulated by IC 7805 (IC3). Capacitors C4 and C9 bypass any ripple present in the regulated power supply.

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WORKING

First of all, select the mode by using switch S9.For example, when you slide switch S9 towards 'quiz' option, the given circuit, can be used as 'fastest finger first' quiz system.

At the resumption of power, a message "Welcome to all the players" is displayed on the LCD. After some time, it displays players' names 'A' through 'H' in the first line and the message 'First Question' in the second line.

Now the quizmaster can ask the first question. The monitor program continuously checks the status of port 0. If any input switch S1 through S8 is found low (by the controller program), it means that the corresponding switch has been pressed.

As soon as any of competitors 'A' through 'H' presses his switch first, his rank is stored as ‘1’immediately in the rank table at the corresponding RAM location. The buzzer sounds a beep and the timer starts recording.

The status of the rank table is updated repeatedly at intervals into the rank table and this status is maintained (due to latching at port 0, offered by feedback from IC2) until the next key is pressed.

Now the second case arises:1. If the remaining seven players press their switches within 30

seconds, the LCD displays the message "Done in Time" and the buzzer sounds a beep. Thereafter, the LCD displays the ranks ('1' through'8') of all players below their names.

2. If the remaining seven players don't press their switches within30 seconds, at the end of this period the LCD displays the message "Time Out" and the buzzer sounds a beep. After that, the ranks of those who have pressed their switches

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within time are displayed below their names, while '-' is displayed below the names of the remaining players.

The display stays in this position and the monitoring program checks the status of pin P3.0. If P3.0 (pin 10) of IC1 goes low on pressing switch S11 for about 2 ms, all the things are initialized for the next question and the LCD shows the message 'Next Question' ('Next Round' for race).

For race competitions, the circuit works in a similar manner but you need to replace switch S11 with a foot switch or LDR-laser light combination. The message "Welcome to all the players" is replaced with "Welcome to all the racers." 'Next Question' is replaced with 'Next Round'. "Done in Time" is replaced with "Covered in Time".

In actual application, where contestants are seated in different locations, you can extend input switches S1 through S8 to the players. For this, connect a pair of wires to the connecting terminals of each of these switches on the PCB to extend these to players. In this case, tactile switches S1 through S8 are not required on the PCB.

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PICTURES OF PROJECT

fig.1 LCD displaying message ‘FIRST QUESTION’

fig.2 LCD displaying ranks of the players

HARDWARE DETAILS6

RANK DISPLAY SYSTEM

1. 8051 MICROCONTROLLER

fig.3 AT89S51microcontroller

1.1 INTRODUCTIONThe 8051 microcontroller belongs to the MCS-5 (c) family. Its features are summarized below:

Internal ROM and RAM Input & output ports with programmable pins. Timer and Counter Serial Data Communication.

8051 architecture consists of these specific features: 8-bit CPU with Register A and B. 16-bit program Counter (PC) and Data Pointer (DPTR) 8 bit Program Status Word (PSW) Internal ROM of 4KB Internal RAM of 128B 4 register banks, each consisting 8 registers 16 bytes which may be addressed at bit level 8 bytes of general-purpose data memory 32- input/output pins arranged as 4-8 bit ports PO-P3 Two 16 bit timer/counters (TO-TI)

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Fully duplexed serial data receiver/transmitter (SBUF) Control register TMOD,TCON,SCOM,PCON,IP and IE Oscillator and Clock circuit.

1.2 PIN DIAGRAM AND ARCHITECTURE

fig.4 PIN DIAGRAM AND ARCHITECTURE of 8051

1.3 PIN CONFIGURATIONPin Name Description Type

1 P1.0 or T2 Port 1 Bit 0 or Timer 2 External Input Input/Output

2 P1.1 or T2CAPPort 1 Bit 1 or Timer 2 External

Reload/CaptureInput/Output

3 P1.2 Port 1 Bit 2 Input/Output




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9 Reset System Reset Input

10 P3.0 or RXD Port 3 Bit 0 or Serial Receive Input/Output

11 P3.1 or TXD Port 3 Bit 1 or Serial Transmit Input/Output

12 P3.2 or INT0 Port 3 Bit 2 or External Interrupt 0 Input/Output

13 P3.3 or INT1 Port 3 Bit 3 or External Interrupt 1 Input/Output



16 P3.6 or WR Port 3 Bit 6 or Write Strobe Input/Output

17 P3.7 or RD Port 3 Bit 7 or Read Strobe Input/Output

18 XTAL1 Crystal Input Input

19 XTAL2 Crystal Output Output

20 VSS Circuit Ground Input

21 P2.0 or Addr8 Port 2 Bit 0 or Address bit 8 Input/Output


23P2.2 or

Add10Port 2 Bit 2 or Address bit 10 Input/Output




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29 PSEN

Signal of this pin is used for reading

from external program memory

(ROM).

Output

30 ALE

This pin emits an impulse sequence with

a frequency equal to 1/6 of the frequency

generated by the main oscillator. If

external memory is used, signal from this

pin controls the additional register for

temporary storage of the lower address

byte (A0 - A7). This pin also serves as a

control input during the writing of

program to MCU.

Output

31 EA

When this pin is connected to the ground,

MCU gets program instructions from

external program memory. In case that

internal program memory is used

(common case), this pin should be

connected to the positive supply pole

(VCC). During the loading of program to

internal Flash memory, this pin is at

+12V

Input

32 P0.7/Addr7 Port 0 Bit 7 or Address bit 7/Data bit 7 Input/Output

33 P0.6 or Port 0 Bit 6 or Address bit 6/Data bit 6 Input/Output

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Addr6/Data6

34P0.5 or

Addr5/Data5Port 0 Bit 5 or Address bit 5/Data bit 5 Input/Output

35P0.4 or


36P0.3 or


37P0.2 or


38P0.1 or


39P0.0 or


40 VCC Supply Voltage Input

Table 1.Pin descript ion of 8051

2. LCD

fig.5 A LCD

2.1 INTRODUCTION

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These components are “specialized” for being used with the microcontrollers, which means that they cannot be activated by standard IC circuits. They are used for writing different messages on a miniature LCD.

LCD screen consists of two lines with 16 characters each. Each character consists of 5x8 or 5x11 dot matrix.

It displays all letters of alphabet, greek letters, punctuation marks, mathematical symbols etc. In addition, it is possible to display symbols that user makes up on its own.

Contrast on display depends on the power supply voltage and whether messages are displayed in one or two lines. For that reason, variable voltage 0-Vdd is applied on pin marked as Vee. Trimmer potentiometer is usually used for that purpose.

The LCD Character standard requires 3 control lines as well as either 4 or 8 I/O lines for the data bus.

The user may select whether the LCD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-bit data bus is used the LCD will require a total of 7 data lines (3 control lines plus the 4 lines for the data bus). If an 8-bit data bus is used the LCD will require a total of 11 data lines (3 control lines plus the 8 lines for the data bus). The three control lines are referred to as EN, RS, and R/W.

There are three memory blocks inside the display:

DDRAM Display Data RAM CGRAM Character Generator RAM CGROM Character Generator ROM

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Vcc

1 61 51 41 31 21 11 098

654321

7

1 61 51 41 31 21 11 0

98

654321

7

D7

E

Vcc

D4

ContrastRS

Gnd

R/W

Gnd

D0

D3

D6D5

13

2

D2D1

fig.6 LCD Pin Diagram

2.2 PIN CONFIGURATION

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Table 2.Pin descript ion of LCD

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Pin Name Function

1 VSS Ground voltage

2 VCC +5V

3 VEE Contrast voltage

4 RSRegister Select0 = Instruction Register1 = Data Register

5 R/W

Read/ Write, to choose write or read mode0 = write mode1 = read mode

6 EN

Enable0 = start to latch data to LCD character1= disable

7 DB0 -D0(LSB)

8 DB1 -D1

9 DB2 -D2

10 DB3 -D3

11 DB4 -D4

12 DB5 -D5

13 DB6 -D6

14 DB7 -D7(MSB)

15 BPL Back Plane Light

16 GND Ground voltage

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3. DARLINGTON ARRAY (ULN 2803)

fig.7 Darlington Array

3.1 INTRODUCTION

A ULN2803 is an Integrated Circuit (IC) chip with a High Voltage/High Current Darlington Transistor Array. It allows you to interface TTL signals with higher voltage/current loads. In English, the chip takes low level signals (TLL, CMOS, PMOS, NMOS - which operate at low voltages and low currents) and acts as a relay of sorts itself, switching on or off a higher level signal on the opposite side.

Its features are:

A TTL signal operates from 0-5V, with everything between 0.0 and 0.8V considered "low" or off, and 2.2 to 5.0V being considered "high" or on. The maximum power available on a TTL signal depends on the type, but generally does not exceed 25mW (~5mA @ 5V), so it is not useful for providing power to something like a relay coil. On the output side the ULN2803 is generally rated at 50V/500mA, so it can operate small loads directly.

Alternatively, it is frequently used to power the coil of one or more relays, which in turn allow even higher voltages/currents to be controlled by the low level signal. In electrical terms, the ULN2803 uses the low level (TTL) signal to switch on/turn off the higher voltage/current signal on the output side.

Its features are summarized below:

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Output current (single output) 500mA MAX. High sustaining voltage output 50V MIN. Output clamp diodes. Inputs compatible with various types of logic

3.2 PIN DIAGRAM

fig.8 Pin Diagram of ULN 2803

The ULN2803 comes in an 18-pin IC configuration and includes eight (8) transistors.

Pins 1-8 receive the low level signals, pin 9 is grounded (for the low level signal reference). Pin 10 is the common on the high side and would generally be

connected to the positive of the voltage you are applying to the relay coil.

Pins 11-18 are the outputs (Pin 1 drives Pin 18, Pin 2 drives 17, etc.).

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4. RESISTORS

The resistor's function is to reduce the flow of electric current. This symbol is used to indicate a resistor in a circuit diagram, known as a schematic. Resistance value is designated in units called the "Ohm." There are two classes of resistors; fixed resistors and the variable resistors. They are also classified according to the material from which they are made.

Fixed ResistorsA fixed resistor is one in which the value of its resistance cannot change.

Carbon film resistorsThis is the most general purpose, cheap resistor. Usually the tolerance of the resistance value is ±5%. Power ratings of 1/8W, 1/4W and 1/2W are frequently used. Carbon film resistors have a disadvantage; they tend to be electrically noisy. The physical size of different resistors are as follows.

Fig. 9 Carbon film resistors

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Rough size

Rating power(W)

Thickness(mm)

Length(mm)

1/8 2 3

1/4 2 6

1/2 3 9

http://www.interq.or.jp/japan/se-inoue/e_resistor.htm#variable%23variable

http://www.interq.or.jp/japan/se-inoue/e_resistor.htm#variable%23variable

http://www.interq.or.jp/japan/se-inoue/e_resistor.htm#fix%23fix

RANK DISPLAY SYSTEM

From the top of the photograph1/8W1/4W

1/2W

Metal film resistorsMetal film resistors are used when a higher tolerance (more accurate value) is needed. They are much more accurate in value than carbon film resistors. They have about ±0.05% tolerance. They have about ±0.05% tolerance. Ni-Cr (Nichrome) seems to be used for the material of resistor. The metal film resistor is used for bridge circuits, filter circuits, and low-noise analog signal circuits.

Fig. 10 Metal film resistors(From the top of the photograph

1/8W (tolerance ±1%), 1/4W ( tolerance ±1%),

1W (tolerance ±5%) ,

Table 4.Sizes of di f ferent resis tors 2W (tolerance ±5%))

Variable resistorsThere are two general ways in which variable resistors are used.

1. One is the variable resistor which value is easily changed, like the volume adjustment of Radio.

2. The other is semi-fixed resistor that is not meant to be adjusted by anyone but a technician. Semi-fixed resistors are used to

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Rough size

Rating power(W)

Thickness(mm)

Length(mm)

1/8 2 3

1/4 2 6

1 3.5 12

2 5 15

RANK DISPLAY SYSTEM

compensate for the inaccuracies of the resistors, and to fine-tune a circuit

The rotation angle of the variable resistor is usually about 300 degrees. Some variable resistors must be turned many times to use the whole range of resistance they offer.These are called "Potentiometers" or "Trimmer Potentiometers."

In the photograph , the four resistors at the center of the photograph are the semi-fixed type. The two resistors on the left are the trimmer potentiometers.This

symbol is used to represent variable resistor in circuit diagramfig.11 Variable Resistors

Resistor colour codeTable 5.Color Codes of

resis tor

Example 1

(Brown=1),(Black=0),(Orange=3)10 x 103 = 10k ohm

Tolerance(Gold) = ±5%

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Colour Value Multiplier Tolerance

Black 0 0 -

Brown 1 1 ±1

Red 2 2 ±2

Orange 3 3 ±0.05

Yellow 4 4 -

Green 5 5 ±0.5

Blue 6 6 ±0.25

Violet 7 7 ±0.1

Gray 8 8 -

White 9 9 -

Gold - -1 ±5

Silver - -2 ±10

None - - ±20

RANK DISPLAY SYSTEM

Example 2(Yellow=4),(Violet=7),(Black=0),(Red=2)

470 x 102 = 47k ohm

Tolerance(Brown) = ±1%

5. CAPACITORS

The capacitor's function is to store electricity, or electrical energy. The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC).This symbol is used to indicate a capacitor in a circuit diagram.

The capacitor is constructed with two electrode plates facing eachother, but separated by an insulator. When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.

The value of a capacitor (the capacitance), is designated in units called the Farad ( F ). The capacitance of a capacitor is generally very small, so units such as the microfarad ( 10-6F ), nanofarad ( 10-9F ), and picofarad (10-12F ) are used.Sometimes, a three-digit code is used to indicate the value of a capacitor. For example, when the code is [103], it indicates 10 x 103, or 10,000pF = 10 nanofarad( nF ) = 0.01 microfarad( µF ).

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BREAKDOWN VOLTAGEWhen using a capacitor, you must pay attention to the maximum voltage which can be used. This is the "breakdown voltage." The breakdown voltage is the voltage that when exceeded will cause the dielectric (insulator) inside the capacitor to break down and conduct. When this happens, the failure can be catastrophic.

The types of capacitors used in our project are:

Electrolytic Capacitors (Electrochemical type capacitors)

Aluminum is used for the electrodes by using a thin oxidization membrane.

Large values of capacitance can be obtained in comparison with the size of the capacitor, because the dielectric used is very thin.

The most important characteristic of electrolytic capacitors is that they have polarity. They have a positive and a negative electrode.[Polarised]

If the capacitor is subjected to voltage exceeding its working voltage, or if it is connected with incorrect polarity, it may burst.

Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.

Electrolytic capacitors range in value from about 1µF to thousands of µF. Mainly this type of capacitor is used as a ripple filter in a power supply circuit, or as a filter to bypass low frequency signals, etc.

Fig.12 Electrolytic Capacitors

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From the left to right:1µF (50V) [diameter 5 mm, high 12 mm] 47µF (16V) [diameter 6 mm, high 5 mm] 100µF (25V) [diameter 5 mm, high 11 mm] 220µF (25V) [diameter 8 mm, high 12 mm] 1000µF (50V) [diameter 18 mm, high 40 mm]

Ceramic CapacitorsCeramic capacitors are constructed with materials such as titanium acid barium used as the dielectric. Internally, these capacitors are not constructed as a coil, so they can be used in high frequency applications. Typically, they are used in circuits which bypass high frequency signals to ground.These capacitors have the shape of a disk. Their capacitance is

comparatively small.

fig.13 Ceramic Capacitors

The capacitor on the left is a 100pF capacitor with a diameter of about 3 mm.The capacitor on the right side is printed with 103, so 10 x 103pF becomes 0.01 µF. The diameter of the disk is about 6 mm.

Ceramic capacitors have no polarity. Ceramic capacitors should not be used for analog circuits, because they can distort the signal.

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6. DIODES

A diode is a semiconductor device which allows current to flow through it in only one direction. A diode is specifically made to allow current to flow through it in

only one direction.

Some ways in which the diode can be used are listed here.A diode can be used as a rectifier that converts AC to DC for a power

supply device.Diodes can be used to separate the signal from radio frequencies.Diodes can be used as an on/off switch that controls current.

This symbol is used to indicate a diode in a circuit diagram

Rectification / Switching / Regulation Diode

The stripe stamped on one end of the diode shows indicates the polarity of the diode.The stripe shows the cathode side.The devices shown in the picture are diodes used for rectification. They are made to handle

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relatively high currents. The device on top can handle as high as 6A, and the one below it can safely handle up to 1A.However, it is best used at about 70% of its fig.14 Rectifier Diodes rating because this current value is a maximum rating. This diode is typically used to protect the circuit from momentary voltage spikes.

Light Emitting Diode ( LED )

Light emitting diodes must be chosen according to how they will be used, because there are various kinds.The diodes are available in several colors. The most common

colors are red and green, but there are even blue ones.The device on the far right in the photograph combines a red LED and green LED in one package. The fig.15 LED’s

component lead in the middle is common to both LEDs. As for the remaing two leads, one side is for the green, the other for the red LED. When both are turned on simultaneously, it becomes orange.

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(a) Extended State

(c) A. C. Voltage Applied

(b) Shrinked State

Fig. 18 Oscillation System

Electrode Piezoelectric

Element Piezoelectric

Ceramics Piezoelectric Diaphragm

Electrode

Piezoelectric Metal

Ceramics Plate

Fig. 17 Structure of Piezoelectric Diaphragm

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7. PIEZOBUZZER

fig.16 A Piezobuzzer

Basically, the sound source of a piezoelectric sound component is a piezoelectric diaphragm. A piezoelectric diaphragm consists of a piezoelectric ceramic plate which has electrodes on both sides and a metal plate (brass or stainless steel). A piezoelectric ceramic plate is attached to a metal plate with adhesives. Fig. 18 shows the oscillating system of

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a piezoelectric diaphragm. Applying D.C. voltage between electrodes of a piezoelectric diaphragm causes mechanical distortion due to the piezoelectric effect. The piezoelectric diaphragm bends toward the direction shown in Fig.17. The metal plate bonded to the piezoelectric element does not expand. Conversely, when the piezoelectric element shrinks, the piezoelectric diaphragm bends in the direction shown in Fig.18. Thus, when AC voltage is applied across electrodes, the bending shown in Fig.17 and Fig.18 is repeated producing sound waves in air.

8. POWER SUPPLY

The term power supply is more commonly abbreviated to PSU

To provide a useable low voltage the PSU needs to do a number of things:-

Reduce the Mains AC (Alternating current) voltage to a lower level.

Convert this lower voltage from AC to DC (Direct current) Regulate the DC output to compensate for varying load (current

demand) Provide protection against excessive input/output voltages

1. Reduction of AC Mains

This is achieved by using a device known as a Transformer, an electromagnetic device consisting of an ferrous iron core which has a large number of turns of wire wound around it, known as the Primary Winding. The ends of these turns of wire being connected to the input voltage (in this case Mains AC).

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fig.19 A step-down transformer

A second number of turns of wire are wound around the Primary Winding, this set being known as the Secondary Winding.

The difference between the number of turns provides us with a way of reducing (in our case) a high AC voltage to a lower one.

2. Conversion of AC to DC

To convert our now low AC voltage to DC we use a Rectifier Diode connected to the Secondary Winding.

This is a silicon diode, only allows current to flow in one direction)

As our low AC voltage will be working at a frequency of 50Hz (Mains AC frequency) it is desirable to reduce the inherent hum on this to a lower level.

This is achieved by a technique known as Smoothing (“Ironing” out the bumps in the AC).

A simple way to reduce the hum is to use Full Wave Rectification.

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fig.20Rectification of AC

3. Regulation of Output Voltage

In a simple PSU the easiest way to provide regulation to compensate for varying load conditions is to use a pair of relatively high value Electrolytic Capacitors.

Their values in this case being in the region of 470uF to 2000uF .

One of these capacitors is connected across the DC output of the rectifier diode(s) or bridge, this capacitor also providing an extra degree of smoothing the output waveform.

The second capacitor is connected via a low value, medium to high wattage resistor, which assists in limiting the current demand.

fig.21Electrolytic Capacitor

4. Voltage Regulator

Regulator, usually having three legs, converts varying input voltage and produces a constant regulated output voltage. They are available in a variety of outputs. The most common part numbers start with the numbers 78 or 79 and finish with two digits indicating the output voltage. The number 78

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represents positive voltage. The 78XX series of voltage regulators are designed for positive input. The LM78XX series typically has the ability to drive current up to 1A. The component has three legs: Input leg which can hold up to 36VDC Common leg (GND) and an output leg with the regulator's voltage. For maximum voltage regulation, adding a capacitor in parallel between the common leg and the output is usually recommended.

fig.22Voltage Regulator 7805

PCB ETCHING

Etching is the process where the excess copper is removed to leave the individual tracks or traces as they are sometimes called.

Many different chemical solutions can be used to etch circuit boards. Ranging from slow controlled speed etches used for surface preparation to the faster etches used for etching the tracks. Copper etching is normally exothermic. Almost all etching solutions liberate toxic corrosive fumes, extraction is highly recommended. All etchants are corrosive and toxic, mainly due to the high metal content.

Ferric Chloride

It is an old favorite chemical very good at staining fingers, clothing, etc brown. Etch rate can be very high but is dependant on solution movement over the surface of the board and temperature. At 70C using Spray etching, 1oz copper is removed in a little under a minute, normal etching temperature is more likely to be 45C.

When up to 5% of HCL is added, it increases etch rate, helps to stop staining, and reduces the risk of the solution sludging. Ferric especially with extra HCL makes a very good stainless steel etchant.

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The basic etching reaction takes place in 3 stages. First the ferric ion oxidizes copper to cuprous chloride, which is then further oxidized to cupric chloride.

1. FeCl3 + Cu > FeCl2 + CuCl2. FeCl3 + CuCl > FeCl2 + CuCl2

As the cupric chloride builds up at further reaction takes place,

3. CuCl2 + Cu > 2CuCl

The etch rate quickly falls off after about 17oz/gallon (100g/l of copper has been etched for a typical solution containing 5.3lb/gallon (530g/l) of ferric chloride.

SOLDERING

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (800 °F). The filler metal used in the process is called solder.

In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. Soldering is an ancient technique mentioned in the Bible and there is evidence that it was employed up to 5000 years ago in Mesopotamia.

The tools that are essential to solder are a

1. Soldering iron : There are several things to consider when choosing a soldering iron.

30

http://en.wikipedia.org/wiki/Wetting

http://en.wikipedia.org/wiki/Capillary_action

http://en.wikipedia.org/wiki/Solder

http://en.wikipedia.org/wiki/Melting_point

http://en.wikipedia.org/wiki/Metal

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Wattage Fig.23 soldering iron adjustable or fixed temperature power source (electric or gas) portable or bench use

2. Solder : Soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the eutectic alloy of 63% tin and 37% lead has been the alloy of choice.

fig.24 solder

Common solder alloys are mixtures of tin and lead:

63/37: melts at 183 °C (361.4 °F) (eutectic: the only mixture that melts at a point, instead of over a range)

60/40: melts between 183–190 °C (361–374 °F) 50/50: melts between 185–215 °C (365–419 °F)

3. Flux: In high-temperature metal joining processes, the primary purpose of flux is to prevent oxidation of the base and filler materials. Flux is a substance which is nearly inert at room temperature, but which becomes strongly reducing at elevated temperatures, preventing the formation of metal oxides. Secondarily, flux acts as a wetting agent in the soldering process, reducing the surface tension of the molten solder and causing it to better wet out the parts to be joined.

31

http://en.wikipedia.org/wiki/Surface_tension

http://en.wikipedia.org/wiki/Wetting_agent

http://en.wikipedia.org/wiki/Reducing

http://en.wikipedia.org/wiki/Flux_(metallurgy)

http://en.wikipedia.org/wiki/Eutectic

http://en.wikipedia.org/wiki/Alloy

RANK DISPLAY SYSTEM

THE SOFTWARE PROGRAM

The software program (rank .asm) is written in assembly language. The assembly-level program can be written using any text editor and saved as ‘rank .asm’. It will generate the Intel hex file (rank.hex) and listing file (rank .1st) when the program is assembled using the asm51 cross assembler from metalink. The hex file is used to program the chip.

RANK.ASM

latch equ p2

keys equ p0

dline equ p1

restart equ p3.0

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RANK DISPLAY SYSTEM

rs equ p3.3

rw equ p3.2

en equ p3.1

buzzer equ p3.4

mode equ p3.6

flag equ p3.5

org 0000h

sjump main

org 000bh

clr tr0

mov tl0, #00h

mov th0, #00h

djnz r5, al

setb buzzer

al : djnz, return

mov r7, #136

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RANK DISPLAY SYSTEM

djnz r6, return

mov r6, #3

mov r5, #20

clr buzzer

mov a, #0c0h

acall command

mov dptr, #timeout

acall read

acall display

setb buzzer

setb flag

return : reti

main : mov ie, #00h

setb ea

setb et0

mov tmod, #0lh

mov tcon, #00h

mov tl0, #00h

mov th0, #00h

mov r7, #136

mov r6, #3

mov r5, #20

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RANK DISPLAY SYSTEM

mov latch, #0

mov keys, #0ffh

acall lcdly

acall lcd_int

mov dptr, #welcome

acall read

mov a, #0c0h

acall command

jnb mode , race1

mov dptr, #welcome1

sjmp fff1

race1 : mov dptr, #welcome2

fff1 : acall read

acall dispdly

mov a, #80h

acall command

mov dptr, #plrname

acall read

mov a, #0c0h

acall command

jnb mode, race2

mov dptr, #firstqtn

sjmp fff2

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RANK DISPLAY SYSTEM

race2 : mov dptr, #firstrnd

fff2 : acall read

here : clr flag

mov latch, #0

mov keys, #0ffh

acall lcdly

mov 04h, #48

blankrank : mov r0, #31h

again : mov @r0, # ' - '

inc r0

cjne r0, #39h, again

chk : mov a, keys

cjne a, #0ffh , first

sjmp chk

first : clr buzzer

next rank : inc 04h

mov r0, #31h

chkl : jb flag , result1

setb tr0

mov a, keys

cpl a

xrl a, latch

cjne a, #0, scan

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RANK DISPLAY SYSTEM

sjmp chk1

scan : jb acc.0, store

inc r0

jb acc.1, store

inc r0

jb acc.2, store

inc r0

jb acc.3 , store

inc r0

jb acc.4 , store

inc r0

jb acc.5 , store

inc r0

jb acc.6, store

inc r0

jb acc.7 , store

store : mov @r0, 04h

orl a, latch

mov latch, a

cjne r4 , #56 , next _ rank

sjmp result

result : clr tr0

mov tl0 , #00h

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RANK DISPLAY SYSTEM

mov th0, #00h

mov r7, #136

mov r6, #3

mov r5, #20

clr buzzer

mov a, #0c0h

acall command

jnb mode, race4

mov dptr, #intime

sjmp fff4

race4 : mov dptr, # intime1

fff4 : acall read

acall dispdly

setb buzzer

result1 : clr tr0

mov r0, #31h

mov a, #0c0h

acall command

show : mov a ,@r0

acall display

mov a, # ‘ ’

acall display

inc r0

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RANK DISPLAY SYSTEM

cjne r0, #39h, show

stay : jb restart, stay

mov r1, #4

s1 : mov r2, #200

djnz r2, $

djnz r1, s1

jb restart , stay

nxt_ Ques : mov a, #0c0h

acall command

jnb mode, race3

mov dptr, #nxtqtn

sjmp fff3

race3 : mov dptr , #nxtrnd

fff3 : acall read

jmp here

read : c1r a

movc a, @a+dptr

jz down

acall display

inc dptr

sjmp read

down : ret

lcd_int : mov a, #38h

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RANK DISPLAY SYSTEM

acall command

mov a, #0ch

acall command

mov a,#01h

acall command

mov a, #06h

acall command

ret

command : mov dline , a

clr rs

nop

nop

c1r rw

nop

nop

setb en

acall lcdly1

clr en

acall lcdly1

ret

display : mov dline , a

setb rs

nop

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RANK DISPLAY SYSTEM

nop

clr rw

nop

nop

setb en

acall lcdly

clr en

acall lcdly

ret

lcdly : mov r1 , # 0ah

lp1 : mov r2 , # 0ffh

djnz r2 , $

djnz r1 , lp1

ret

lcdly1 : mov r1 , #3fh

lp2 : mov r2 , #0ffh

djnz r2 , $

djnz r1 , lp2

ret

dispdly : mov r1, #255

d1 : mov r2, #255

d2 : mov r3, # 30

djnz r3, $

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RANK DISPLAY SYSTEM

djnz r2, d2

djnz r1 ,d1

ret

;Look up table starts from here

plrname : db ‘A’, ‘ ’,‘B’, ‘ ’,‘C’, ‘ ’,‘D’, ‘ ’,‘E’, ‘ ’,‘F’, ‘ ’,‘G’, ‘ ’,

‘H’, 0

welcome : db ‘WELCOME To ALL’, 0

welcome1 : db ‘THE PLAYERS’, 0

welcome2 : db ‘THE RACERS’, 0

firstqtn : db ‘FIRST QUESTION’, 0

firstrnd : db ‘FIRST ROUND’, 0

nxtqtn : db ‘NEXT QUESTTON’, 0

nxtrnd : db ‘NEXT ROUND’, 0

intime : db ‘DONE IN TIME’, 0

intime1 : db ‘COVERED IN TIME’, 0

timeout : db ‘TIME OUT’, 0

end

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RANK DISPLAY SYSTEM

PROBLEMS FACED

1. We faced problem in determining the correct values of the

components.

2. Incorrect connection due to confined space on the pcb and shorting of

various connections close to each other.

3. Burning of transistors and capacitors.

4. Burning of PCB tracks.

5. Voltage fluctuations.

6. Fault in PCB layouts.

7. Writing code for working of the circuit.

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RANK DISPLAY SYSTEM

FUTURE SCOPE

In actual application, where contestants are seated in different locations, you can extend input switches S1 through S8 to the players. For this, connect a pair of wires to the connecting terminals of each of these switches on the PCB to extend these to players. In this case, tactile switches S1 through S8 are not required on the PCB.

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RANK DISPLAY SYSTEM

REFERENCES

1. Kenneth J Ayala, “The 8051 Microcontroller: Architecture,

Programming and Applications”, Penram International,

Mumbai.

2. Muhammad Ali Mazidi and Janice Gillispie Mazidi, “The 8051

Microcontroller and Embedded Systems”, Pearson Education,

New Delhi.

3. “Electronics For You”, Magazine, June 2008.

4. www.alldatasheets.com

5. www.en.wikipedia.org

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http://www.en.wikipedia.org/

http://www.alldatasheets.com/

RANK DISPLAY SYSTEM

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Introduction

Documents

rank display system

y switch s10

switch s9

y ic at89c51

status of port

rank table

message time

corresponding switch