seven segment display using 74LS78 IC decoder

BCD TO SEVEN SEGMENT DISPLAY DECODER 1
CHAPTER - 1
INTRODUCTION
1.1 Introduction
In most of our electronic products or projects we need a power supply for converting mains
AC voltage to a regulated DC voltage. For making a power supply designing of each and
every component is essential. Here I’m going to discuss the designing of regulated 5V Power
Supply.
In this project we need fix 5 volt supply for BCD seven segment decoder (IC 74LS47 or IC
74LS48) to control the output and display the output on seven segment display. so first of all
we make 5 volt DC supply by using these component.
List of Component generate fix 5 volt dc supply
1. Step Down Transformer
2. Voltage Regulator IC 7805
3. Capacitors
4. Diodes
5. Registers
6. LED
7. Switch
When we have 5 volt DC supply than we apply as BCD Inputs A, B, C, D on decoder IC
74LS48. We use hear IC 74LS48 because we have cathode seven segment display if we have
anode seven segment display than we use hear IC 74LS48 as a decoder IC. Decoder IC have
4 BCD inputs and seven segment output ( a, b, c, d, e, f, g ).
List of component control display on seven segment display
1. Push Switch
2. Decoder IC 74LS48
3. Register
4. Cathode Seven Segment Display
5. LED

CHAPTER - 2
CIRCUIT DESCRIPTION
2.1 Circuit Connection
The following shows circuit connection of generate 5 volt and decode and display on seven
segment display.
Figure 2.1 Full Circuit diagram of seven segment decoder
2.2 Working Of The Circuit
2.2.1 Step 1 Step - Down Transformer
The most frequently used device in electronic workshops and laboratories is a universal
power supply provides fix DC voltage. As many application we use DC power supply so first
convert AC power supply to DC power supply as a use of DC voltage than we use different
circuit configuration. We required 5 volt supply so we convert AC 230 volt 50 Hz to 5 volt
DC supply. We use at step-down transformer (230 V to 12 Volt and 1 Amp. ) to decrease
voltage and current. These types of step-down transformer decrease 12 volt and 1 Amp.
2.2.2 Step 2 Rectification Process
Rectification process by using diodes (1N4007) . Rectifiers are many types
1. Half wave rectifier

2. Full wave rectifier
3. Bridge rectifier
These rectifiers are rectified the input signal and gave positive side AC wave but for good
efficiency we use bridge rectification configuration. In this process any AC signal are remain
then by pass capacitor pass AC signal to input and gave only 12 volt dc supply .
2.2.3 Step 3 Voltage Regulator
Voltage regulator is electronically IC that use for regulate voltage. As a use of circuit voltage
regulator are many types but in this circuit configuration we use IC 7805 that regulate output
voltage +5 V.
(a) (b)
Figure 2.2 (a) pins of 7805 voltage regulator
(b) Internal circuit configuration of 7805 voltage regulator
2.2.4 Step 4 BCD Inputs Switches
BCD inputs switches are A,B,C,D that are respectively value in decimal are
A = 1 ( 2^0 )
B = 2 ( 2^1 )
C = 4 ( 2^2 )
D = 8 ( 2^3 )
that means when we press A Switch then display 1 and when we press B then display 2 and
etc.
2.2.5 Step 5 BCD To Seven Segment Decoder
Decoder IC are many types but we use in this project is IC 74LS48. This IC particularly use
for common cathode seven segment LED display if we use common anode display than the
decoder IC is 74LD47.
This decoder IC have four BCD Inputs A,B,C,D and outputs a,b,c,d,e,f,g are seven segment
outputs of seven segment display.
As saw seven segment display unit a, b, c, d, e, f, g are LED segment that means if we want
to display 1 then b, c are ON state and a, d, e, f, g are OFF state

Figure 2.3 74LS48 decoder configurations with common cathode seven segment display

CHAPTER - 3
COMPONENT DESCRIPTION
3.1 Components Requirements
S. No Components Description
1. Decoder IC 74LS48 Max volt 5.5
Min. volt 4.5
2. Diode 1N4007
3. LED Red
Blue
4. Capacitor 1000µF
5. Resistors 220 ῼ
10K ῼ
6. Step –Down Transformer 230V AC - 12 V AC
7. Seven Segment Display Common Cathode Display
8. Switches 4 push switch rating 1 amp
Table 3.1 Components Description

CHAPTER - 4
SEVEN SEGMENTAL DISPLAY
4.1 Introduction
This is basically use for numeric display. It consists of seven segment a, b, c, d, e, f and g . A
segmental display forms the digit to be display by illumination proper segments from the
group. It is use to display 0 to 9 digit and Alphabetic display.
Typically 7-segment displays consist of seven individual colored LED’s (called the
segments), within one single display package. In order to produce the required numbers or
HEX characters from 0 to 9 and A to F respectively, on the display the correct combination of
LED segments need to be illuminated and BCD to 7-segment Display Decoders such as the
IC's 74LS48.
Figure 4.1 Seven Segmental LED Display
A standard 7-segment LED display generally has 8 input connections, one for each LED
segment and one that acts as a common terminal or connection for all the internal display
segments. Some single displays have also have an additional input pin to display a decimal
point in their lower right or left hand corner.

4.2 Types of 7-SegmentLED Digital Display.
4.2.1 The Common Cathode Display (CCD) –
In the common cathode display, all the cathode connections of the LED’s are joined
Together to logic “0” or ground. The individual segments are illuminated by
application of a “HIGH”, logic “1” signal to the individual Anode terminals. Use in
this type display to control IC is 74LS48
4.2.2 The Common Anode Display (CAD) –
In the common anode display, all the anode connections of the LED’s are joined
together to logic “1” and the individual segments are illuminated by connecting the
individual Cathode terminals to a “LOW”, logic “0” signal. Use in this type display to
control IC is 74LS47
Figure 4.2 Common Cathode And Common Anode 7-Segment Display
Electrical connection of the individual diodes for a common cathode display and a
common anode display and by illuminating each light emitting diode individually,
they can be made to display a variety of numbers or characters.

4.3 Seven-SegmentDisplayFormat
Figure 4.3 7-Segments Display Format
So in order to display the number 3 for example, segments a, b, c, d and g would need to be
illuminated. If we wanted to display a different number or letter then a different set of
segments would need to be illuminated. Then for a 7-segment display, we can produce a truth
table giving the segments that need to be illuminated in order to produce the required
character as shown below.
4.4 Truth Table ForA 7-SegmentDisplay
Individual Segments
Display
a b c d e F g
1 1 1 1 1 1 0 0
0 1 1 0 0 0 0 1
1 1 0 1 1 0 1 2
1 1 1 1 0 0 1 3
0 1 1 0 0 1 1 4
1 0 1 1 0 1 1 5
1 0 1 1 1 1 1 6
1 1 1 0 0 0 0 7
1 1 1 1 1 1 1 8
1 1 1 1 0 1 1 9
Table 4.1 Truth Table for a 7-segment display
Figure 4.4 Seven-Segments Display Elements for all Numbers.

CHAPTER - 5
BINARY CODED DECIMAL
5.1 Introduction
Binary Coded Decimal (BCD or “8421” BCD) numbers are made up using just 4 data bits or
more , but unlike hexadecimal numbers that range in full from 0 through to F, BCD numbers
only range from 0 to 9, with the binary number patterns of 1010 through to 1111 (A to F) .
Decimal
Binary Pattern
BCD
8 4 2 1
0 0 0 0 0 0
1 0 0 0 1 1
2 0 0 1 0 2
3 0 0 1 1 3
4 0 1 0 0 4
5 0 1 0 1 5
6 0 1 1 0 6
7 0 1 1 1 7
8 1 0 0 0 8
9 1 0 0 1 9
Table 5.1 Binary To BCD Convert
5.2 BCD To 7-SegmentDecoderOrDriver
The SN54/74LS48 is a BCD to 7-Segment Decoder consisting of NAND gates, input buffers
and seven AND-OR-INVERT gates. Seven NAND gates and one driver are connected in
pairs to make BCD data and its complement available to the seven decoding AND-OR
INVERT gates. The remaining NAND gate and three input buffers provide lamp test,
blanking input/ripple blanking input for the 74LS48.
The circuit accepts 4-bit binary-coded-decimal (BCD) and, depending on the state of the
auxiliary inputs, decodes this data to drive other components. The relative positive logic
output levels, as well as conditions required at the auxiliary inputs, are shown in the truth
tables.
The LS48 circuit incorporates automatic leading and/or trailing edge zero-blanking control
(RBI and RBO). Lamp Test (LT) may be activated any time when the BI/RBO node is HIGH.
Both devices contain an overriding blanking input (BI) which can be used to control the lamp
intensity by varying the frequency and duty cycle of the BI input signal or to inhibit the
outputs.
• Lamp Intensity Modulation Capability (BI/RBO)
• Internal Pull-Ups Eliminate Need for External Resistors
• Input Clamp Diodes Eliminate High-Speed Termination Effects

Figure 5.1 IC's SN54/74LS48 And Pin Description
Where
A , B , C , D = BCD INPUT
RBI = RIPPLE BANKING INPUTS
LT = Lamp-Test Input
BI / RBO = Blanking Input or Ripple-Blanking Output
a , b , c , d , e , f , g = OUTPUT

5.3 Logic Diagram Of IC 74LS48
(a)
(b)
Figure 5.2 (A) Logic Diagram Of IC 74LS48, (B) Block Diagram Of IC 74LS48

5.4 Circuit Of BCD To 7 – Segment Display System
Figure 5.3 block diagram of BCD To 7- Segment Display
Figure 5.4 Circuit Diagram Of BCD To 7- Segment Display

CHAPTER - 6
COMPONENTS DESCRIPTION
6.1 TRANSFORMER
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductors — the transformer's coils or "windings". Transformer is used
here to step down the supply voltage to a level suitable for the low voltage components. The
transformer used here is a 230 / (12V-0-12V) step down transformer.
Figure 6.1 Step-Down Transformer
6.2 RESISTOR
A resistor is a two-terminal electronic component designed to oppose an electric current by
producing a voltage drop between its terminals in proportion to the current, that is, in
accordance with Ohm's law: V = IR. The resistance R is equal to the voltage drop V across
the resistor divided by the current I through the resistor. A resistor is a passive two-terminal
electrical component that implements electrical resistance as a circuit element. The current
through a resistor is in direct proportion to the voltage across the resistor's terminals.
Practical resistors have a series inductance and a small parallel capacitance; these
specifications can be important in high-frequency applications. In a low-noise amplifier or
pre-amp, the noise characteristics of a resistor may be an issue. The unwanted inductance,
excess noise, and temperature coefficient are mainly dependent on the technology used in
manufacturing the resistor. They are not normally specified individually for a particular
family of resistors manufactured using a particular technology. A family of discrete resistors
is also characterized according to its form factor, that is, the size of the device and the
position of its leads (or terminals) which is relevant in the practical manufacturing of circuits
using them.

(a) (b)
Figure 6.2 (a) Fix Carbon Resistor (b) Variable Resistor
6.3 LED (Light Emitting Diode)
A light-emitting-diode (LED) is a semiconductor diode that emits light when an electric
current is applied in the forward direction of the device, as in the simple LED circuit. The
effect is a form of electroluminescence where incoherent and narrow-spectrum light is
emitted from the p-n junction.
Figure 6.3 Blue , Red and Green LED
6.4 CAPACITOR
A capacitor (originally known as condenser) is a passive two-terminal electrical component
used to store energy in an electric field. The forms of practical capacitors vary widely, but all
contain at least two electrical conductors separated by a dielectric (insulator), for example,
one common construction consists of metal foils separated by a thin layer of insulating film.

Capacitors are widely used as parts of electrical circuits in many common electrical devices.
When there is a potential difference (voltage) across the conductors, a static electric
field develops across the dielectric, causing positive charge to collect on one plate and
negative charge on the other plate. Energy is stored in the electrostatic field. An ideal
capacitor is characterized by a single constant value, capacitance, measured in farads. This is
the ratio of the electric charge on each conductor to the potential difference between them.
Figure 6.4 Capacitor
Capacitors are widely used in electronic circuits for blocking direct current while allowing
alternating current to pass, in filter networks, for smoothing the output of power supplies, in
the resonant circuits that tune radios to particular frequencies, in electric power transmission
systems for stabilizing voltage and power flow, and for many other purposes.
6.5 SEMI – CONDUCTOR DIODE
A diode is a two-terminal electronic component with asymmetric transfer characteristic, with
low (ideally zero) resistance to current flow in one direction, and high (ideally infinite)
resistance in the other. A semiconductor diode, the most common type today, is a crystalline
piece of semiconductor material with a p-n junction connected to two electrical terminals.
A vacuum tube diode, now rarely used except in some high-power technologies and by
enthusiasts, is a vacuum tube with two electrodes, a plate (anode) and cathode. The most
common function of a diode is to allow an electric current to pass in one direction (called the
diode's forward direction), while blocking current in the opposite direction (the reverse
direction). Thus, the diode can be thought of as an electronic version of a check valve. This
unidirectional behavior is called rectification, and is used to convert alternating current to
direct current, including extraction of modulation from radio signals in radio receivers—these
diodes are forms of complicated behavior than this simple on conducting electricity until a c

state in which the diode is said to be biased diode varies only a little with the current, and is a
function of temperature; this effect can be used as a temperature sensor Semiconductor
diodes' nonlinear current varying the semiconductor materials
These are exploited in special purpose diodes that perform many example, diodes are used to
regulate voltage ( voltage surges (avalanche diodes ), to generate radio frequency diodes),
and to produce light ( resistance, which makes them useful in some types of circuits. Diodes
were the first semiconductor electronic devices abilities was made by German physicist
diodes, called cat's whisker diodes such as galena. Today most diodes are made of
germanium are sometimes use
Figure 6.5 Semi-Conductor Diode

CONCLUSIONS
In this project we have developed display BCD and tested 5 volt supply. This can output to a
seven segment display. We used various methods to display decimal number on seven
segment display and various application of display decimal number. A for-generate loop was
also used to create a 4-bit adder / subtracted. Two interchangeable methods were developed
for correcting for invalid BCD numbers. By coupling together two one digit BCD adder
subtracters with a correction factor for negative numbers, a fully functional BCD
adder/subtracter was created. Addition and subtraction of number is also application of seven
segment display

BIBLIOGRAPHY
www.wikipedia.com/LEDdisplay.
www.wikipedia.com/semi-conductordiode.
www.wikipedia.com/capacitor
www.wikipedia.com/resistor.
www.wikipedia.com/sevensegmentdisplay.
www.wikipedia.com/BCDdecoder
www.electonicsproject.com/bcdtosevensegmentdisplay
Motorola ICs 74LS48.pdf

seven segment display using 74LS78 IC decoder

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Destaque

Destaque (20)

Semelhante a seven segment display using 74LS78 IC decoder

Semelhante a seven segment display using 74LS78 IC decoder (20)

Último

Último (20)

seven segment display using 74LS78 IC decoder