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Design 2 digit BCD Display using 7 segment display & 7447 decoder IC

Gujarat Technological University

Prepared ByUrvi Parmar(14CSE54)Subhi Katar(14CSE56)

Monika Piprotar(14CSE59)

Internal GuideProf. Ashish MehtaE & C Dept. BHGCET, Rajkot

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Outline

Introduction Components BCD counter Working of IC7490 Working of IC 7447 BCD Counter circuit 2-digit BCD counter Application

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INTRODUCTION12/10/2015

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WHICH COMPONENT ARE REQUIRED???12/10/2015

No Components

1 IC 7447(BCD to 7 segment decoder driver (15-output)

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2 IC 7490(decode counter) 2

3 IC 7408(Quad 2-input AND gate) 1

4 7 Segment LED 2

5 Registers 16

6 Push 2 switch 1

WHAT IS BCD COUNTER?? A BCD counter is a special type of a digital counter which can count to

ten on the application of a clock signal. To make a digital counter which counts from 1 to 10, we need to have

the counter count only the binary numbers 0000 to 1001. That is from 0 to 9 in decimal .

Digital counters count upwards from zero to some pre-determined count value on the application of a clock signal.

Once the count value is reached, resetting them returns the counter back to zero to start again.

A decade counter counts in a sequence of ten and then returns back to zero after the count of nine.

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BCD COUNTER STATE DIAGRAM..12/10/2015

A decade counter has four flip-flops and 16 potential states, of which only 10.The total number of counts that a counter can count too is called its MODULUS. A counter that returns to zero after n counts is called a modulo-n counter.

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BCD COUNTER A counter which resets after ten counts with a divide-by-10 count

sequence from binary 0000 (decimal “0”) through to 1001 (decimal “9”) is called a binary-coded-decimal counter or BCD Counter.

It is called a BCD counter because its ten state sequence is that of a BCD code and does not have a regular pattern.

Example of Decimal to BCD number:

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Decimal no. BCD0 00009 1001

WORKING OF IC7490 The 74LS90 integrated circuit is basically a MOD-10 decade

counter that produces a BCD output code. The 74LS90 consists of four master-slave JK flip-flops

internally connected.

CONTINUE… The 74LS90 has one independent toggle JK flip-flop driven by

the CLK A input and three toggle JK flip-flops that form an asynchronous counter driven by the CLK B input .

PIN WorkCK B,CK A inputR0(1,2) ResetR9(1,2) SetQA,QB, QC,QD

BCD output

Vcc +5vGND Ground

74LS90 DIVIDE-BY-10 COUNTER BCD counters are binary counters that count from 0000 to 1001

and then resets as it has the ability to clear all of its flip-flops after the ninth count.

Connect a pushbutton switch (SW1) to clock input CLKA, each time the pushbutton switch is released the counter will count by one.

If we connected light emitting diodes (LED’s) to the output terminals, QA, QB, QC and QD , view the binary coded decimal count as it takes place.

CONTINUE…

DRIVING A DISPLAY For diving a display a BCD to 7-segment display

Decoder 74LS47 IC is require.PIN WORKA0,A1,A2,A3

input

LT Lamp testRBO Ripple

Blanking Output

RBI Ripple Blanking Input

a,b,c,d,e,f,g

output

GND groundVcc +5v

CONTINUE… The 74LS47 display decoder receives the BCD code and generates

the necessary signals to activate the appropriate LED segments responsible for displaying the number of pulses applied.

74LS47 decoder is designed for driving a common-anode display, a LOW (logic-0) output will illuminate an LED segment while a HIGH (logic-1) output will turn it “OFF”.

For normal operation, the LT (Lamp test), BI/RBO (Blanking Input/Ripple Blanking Output) and RBI (Ripple Blanking Input) must all be open or connected to logic-1 (HIGH).

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74LS47 BCD TO 7-SEGMENT DRIVER12/10/2015

CONTINUE… The 74LS47 binary coded decimal inputs can be connected to the

corresponding outputs of the 74LS90 BCD Counter to display the count sequence on the 7-segment display as shown each time the pushbutton SW1 is pressed.

By changing the position of the pushbutton and 10kΩ resistor, the count can be made to change on the activation or release of the pushbutton switch, SW1

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7-SEGMENT LED A 7-segment display is made of seven individual light emitting

diodes to form the display. The best method of limiting the current through a seven segment

display is to use a current limiting resistor in series with each of the seven LED’s .

But we can do this in two ways :-1 ) Single current limiting resistor2) Multiple current limiting resistor

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FINAL 4-BIT BCD COUNTER CIRCUIT12/10/2015

Simple 0 to 9 digital counter using a 74LS90 BCD Counter and a 74LS47 7-segment display driver.

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2-DIGIT BCD COUNTER FROM 00-9912/10/2015

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CONTINUE A 2-digit BCD counter would count in decimal from 00 to 99

(0000 0000 to 1001 1001) and then reset back to 00. To count above 10 and produce a 2-digit base-ten

counter and display, we would need to cascade two separate divide-by-ten counters together.

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APPLICATIONS OF BCD COUNTER Digital clock Timer

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BCD COUNTER 12/10/2015

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Thank You