BCD to 7 Segment Display Converter

7-segment displays are commonly used in calculators, digital clocks, microwave ovens etc. There are 7 segments (hence the name) arranged in a rectangular pattern. By convention, each segment is identified by a letter from A to G as shown below. Some displays have a decimal point (including the Logic Circuit Display) but we not be using it.

BCD to 7 Segment Display Converter Image 1

Each segment has an input pin for turning that segment on. The problem is the input for the 7-segment display will normally be in Binary Coded Decimal format. In BCD, each digit from 0 to 9 is represented by a unique 4-bit binary number as shown below.

binary

digit

0000

0

0001

1

0010

2

0011

3

0100

4

0101

5

0110

6

0111

7

1000

8

1001

9

The binary numbers from 1010 to 1111 are not used in BCD. Binary Coded Decimal is not directly compatible with the input of the 7-segment display. Your task is to construct a converter that converts BCD to a format that can be used by the 7-segment display.

Each segment will have its own logic. (Recall that we used a Karnaugh map in class to develop a

reduced Boolean expression for segment A.)

The input to the converter will be a 4-bit binary number with digits b3b2b1b0. The converter will have 7 output leads A to G corresponding to the input of the 7-segment display. (However, these output leads should be put through a 7-1 splitter, just to keep your circuit as neat as possible.) The reduced Boolean expression for each output lead is given below.

BCD to 7 Segment Display Converter Image 2

General Construction of a sum of products circuit.

The diagram below shows how a sum of products circuit (like we will be building) is generally constructed. The inputs and negated inputs form a type of bus on the left. All of the AND gates are arranged vertically in a column as shown. The OR gates appear in a column to the right of the AND gates.

BCD to 7 Segment Display Converter Image 3

You should package your converter as a new logical circuit. Call it “BCD to 7”. Place a BCD to 7 circuit on main and connect it to a 7-seg display as shown below. Run your circuit.

You should be able to toggle the buttons on and off to test all of the BCD numbers from 0 to 9.

Save your converter as a circuit project file.

BCD to 7 Segment Display Converter Image 4