BCD to Seven Segments Decoder DB15

Operating Manual Ver.1.1

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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.

BCD to Seven Segment Decoder DB15

Table of Contents 1. Introduction 4

2. Theory 5 3. Experiment 7

Study of BCD to 7 segment Decoder Using IC 74LS47 4. Data Sheet 10

5. Truth Table 11 6. Warranty 12

7. List of Accessories 12

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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

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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

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IC Description :

Figure 3

A3 – A0 : These are BCD inputs. A3 is MSB.

ga − : 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.

RBOBI / 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 RBOBI / 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.

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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

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Truth Table

Figure 5

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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.

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Data Sheet Pinout Diagram (Pin 16 = Vcc = +5V) :

A, B, C, D BCD Inputs RBI Ripple-Blanking Input or LT Lamp-Test Input RBO/BI Blanking Input or Ripple-Blanking Output a to g Outputs

Numerical Designations – Resultant Displays

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Logic diagram of IC :

Truth Table

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Warranty 1. 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.

2. 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