BCD to Seven Segments
Decoder
DB15
Operating Manual
Ver.1.1
An ISO 9001 : 2000 company
94-101, Electronic Complex Pardesipura,
Indore- 452010, India
Tel : 91-731- 2570301/02, 4211100
Fax: 91- 731- 2555643
e mail : info@scientech.bz
Website : www.scientech.bz
Toll free : 1800-103-5050
DB14
Scientech Technologies Pvt. Ltd.
2
DB14
BCD to Seven Segment Decoder
DB15
Table of Contents
1.
Introduction
4
2.
Theory
5
3.
Experiment
Study of BCD to 7 segment Decoder Using IC 74LS47
7
4.
Data Sheet
10
5.
Truth Table
11
6.
Warranty
12
7.
List of Accessories
12
RoHS Compliance
Scientech Products are RoHS Complied.
RoHS Directive concerns with the restrictive use of Hazardous substances (Pb,
Cd, Cr, Hg, Br compounds) in electric and electronic equipments.
Scientech products are “Lead Free” and “Environment Friendly”.
It is mandatory that service engineers use lead free solder wire and use the
soldering irons upto (25 W) that reach a temperature of 450°C at the tip as the
melting temperature of the unleaded solder is higher than the leaded solder.
Scientech Technologies Pvt. Ltd.
3
DB14
Introduction
DB15 is a compact, ready to use BCD to 7 Segment Decoder experiment board. This
experiment board has been designed to study BCD to 7 Segment decoder using
IC74LS47. The Experiment board has inbuilt common anode display to study
functionality of 74LS47. It can be used as stand alone unit with external Power
Supply or can be used with Scientech Digital Lab ST2611 which has built in Power
Supply, pulse generator, pulser switches, 8 bits data switches, logic probe, digital
display, 8 bits LED display.
List of boards :
Model
Name
DB01
Logic Gates
DB02
Universal Gate- NAND/NOR
DB03
EX-OR Gate Implementation
DB04
Demorgan's Theorem
DB05
EX-OR Gate Application
DB06
Code Conversion (Binary to Gray & Gray to Binary)
DB07
Code Conversion (BCD to Excess-3 code)
DB08
Binary Adder -Subtractor
DB09
Encoder – Decoder
DB10
Multiplexer – Demultiplexer
DB11
Flip-Flops (R-S, D, J-K, T)
DB12
Shift Register (4 bit SIPO)
DB13
4 Bit Synchronous Binary Counter
DB16
Digital to Analog Converter (R-2R ladder)
DB17
3 Digit Event Counter
DB21
Fiber Optic Digital Link
DB22
Analog to digital converter (Counter Type)
DB27
Digital to Analog Converter (R-2R ladder)
DB28
Monostable Multivibrator
DB29
CMOS and Crystal Oscillator
DB30
Adder/ Subtracter (4-Bit/8-Bit)
DB31
Decoder/Demultiplexer
DB32
Modulo-N programmable counter
DB35
4 BIT Shift Register
………and many more
Scientech Technologies Pvt. Ltd.
4
DB14
Theory
The availability of a large variety of codes for the same discrete elements of
information results in the use of different codes by different digital system. It is
sometimes necessary to use the output of one system as the input to another. A
conversion circuit must be inserted between the two systems if each uses different
code for the same information. Thus, a code converter is a circuit that makes the two
systems compatible even though each uses a different code.
BCD is an abbreviation for binary-coded decimal. Binary codes for decimal digits
require a minimum of four bits. The BCD code expresses each digit in a decimal
number by its nibble equivalent. Weights are assigned to binary bits according to their
positions. The weights in the BCD codes are 8, 4, 2, 1. For example, the bit
assignment 0110 can be interpreted by the weights to represent the decimal digit 6
because 0 × 8 + 1 × 4 + 1 × 2 + 0 × 1 = 6
A seven segment decoder /driver is an IC decoder that can be used to drive a seven
segment indicator. There are two types of decoder/drivers, corresponding to common
anode and common cathode indicators. Each decoder driver has 4 BCD inputs and 7
output pins (a to g segment).
The 74LS47 is a seven segment decoder for common anode display. There are two
important types of 7-segment LED display. In a common cathode display, the
cathodes of all the LEDs are joined together and the individual segments are
illuminated by HIGH voltages. In a common anode display, the anodes of all the
LEDs are joined together and the individual segments are illuminated by connecting
to a Low voltage. The figure 1, figure 2 shows the two displays.
Common Cathode
Figure 1
Common Anode
Figure 2
Scientech Technologies Pvt. Ltd.
5
DB14
IC Description :
Figure 3
A3 – A0 : These are BCD inputs. A3 is MSB.
a−g
: These are active low outputs to drive common anode display. Outputs are
connected through 330 Ω resistors to common anode display to limit the current
through the LEDs of display.
BI/RBO (Blanking Input/Ripple Blanking Output) : When this pin is at low logic
level all segment outputs are off regardless of the level of any other input. It must be
at high logic or open to get functions for 0000 to 1111.
BI / RBO Ripple Blanking Input : The ripple blanking input must be open or high if
blanking of a decimal zero is not desired. If it is low it will blink decimal zero.
LT (Lamp Test) : When blanking input/ripple blanking output BI / RBO is open or
held high and a low is applied to this input, all segment outputs are ON.
Note : When ripple blanking input RBI and BCD inputs are at a low level with the
lamp test input high, all segment outputs go off and the ripple blanking output RBO
goes to low level.
Scientech Technologies Pvt. Ltd.
6
DB14
Experiment
Objective :
Study of BCD to 7 Segment Decoder using IC 74LS47
Equipments Needed :
1. Digital board DB15.
2. DC Power Supply +5V from external source or ST2611 Digital Lab.
3. Digital Multimeter or Digital Lab ST2611.
Logic Diagram & Truth Table :
(Logic 1 = +5V & Logic 0 = Gnd)
74LS47 Logic Diagram
Figure 4
Scientech Technologies Pvt. Ltd.
7
DB14
Truth Table
Figure 5
Scientech Technologies Pvt. Ltd.
8
DB14
Procedure :
•
Connect +5V and ground to their indicated position on DB15 experiment board
from external DC Power Supply or from DC power block of Digital Lab
ST2611.
•
Connect BCD inputs to pins A0, A1, A2 A3 of IC 74LS47 as shown in logic
diagram as per truth table from 8 bits data switches of ST2611 or from external
source.
•
Connect +5V to pin no. 3, 4, 5. of IC 74LS47
1.
Switch on the Power Supply.
2.
Observe decimal output on common anode display given on the experiment
board. Outputs of individual pins can be seen on logic probe or on LED display
of Digital Lab ST2611 or on multi-meter.
3.
Connect different combination of inputs as shown in truth table and prove truth
table.
4.
Connect logic 0 to BI/RBO input, logic 1 to RBI and LT input.
5.
Repeat step 5, 6 and observe the results.
6.
Connect logic 0 to LT input, logic 1 to RBI and BI/RBO input.
7.
Repeat step 5, 6 and observe the results.
8.
Connect logic 0 to RBI input & BCD inputs, logic 1 to LT & BI/RBO input and
observe the results.
Scientech Technologies Pvt. Ltd.
9
DB14
Data Sheet
Pinout Diagram (Pin 16 = Vcc = +5V) :
A, B, C, D
RBI
LT
BI / RBO
a
to g
BCD Inputs
Ripple-Blanking Input or
Lamp-Test Input
Blanking Input or
Ripple-Blanking Output
Outputs
Numerical Designations – Resultant Displays
Scientech Technologies Pvt. Ltd.
10
DB14
Logic diagram of IC :
Truth Table
Scientech Technologies Pvt. Ltd.
11
DB14
1.
2.
Warranty
We guarantee the product against all manufacturing defects for 24 months from
the date of sale by us or through our dealers. Consumables like dry cell etc. are
not covered under warranty.
The guarantee will become void, if
a)
The product is not operated as per the instruction given in the operating
manual.
b)
The agreed payment terms and other conditions of sale are not followed.
c)
The customer resells the instrument to another party.
d)
Any attempt is made to service and modify the instrument.
3.
The non-working of the product is to be communicated to us immediately giving
full details of the complaints and defects noticed specifically mentioning the
type, serial number of the product and date of purchase etc.
4.
The repair work will be carried out, provided the product is dispatched securely
packed and insured. The transportation charges shall be borne by the customer.
For any Technical Problem Please Contact us at service@scientech.bz
List of Accessories
1.
Patch Cord of 1 mm. 16” (Red) ...............................................................1 No.
2.
Patch Cord of 1 mm. 16” (Black).............................................................1 No.
3.
Patch Cords of 1 mm. 16” (Blue)........................................................... 6 Nos.
4.
e-Manual.................................................................................................1 No.
Updated 18-05-2009
Scientech Technologies Pvt. Ltd.
12