black nike shoes roshe cheapnicesports.com
Womens Vans Authentic White, Vans Authentic Pure White vans classic slip on checkerboard true white true white, womens vans classic slip on white, vans classic slip on - boys' preschool black/true white

Decoders

BCD to 7-Segment decoder

To display any digit on 7-segment display the digit needs to be converted from BCD to 7-segment code. This is also must because any single digit BCD can be represented in 4-bits, but to display any single digit on "7-segment display" we need 7 bits. These 7 bits respectively glows 7 LEDs on the display, which together looks like a digit.

For example to display 3 on the display, LEDs a,b,c,d and g should glow and others should be off. Thus the seven bits code will be "1111001". Hence we need some kind of decoder which will convert BCD to appropriate 7 bit code that can be directly fed to the 7-segment-display.

A typical arrangement is shown below....

seven_segment_decoder

Truth table ..

Inputs Outputs
    A         B         C         D    
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
    a         b         c         d         e         f         g    
1 1 1 1 1 1 0
0 1 1 0 0 0 0
1 1 1 1 0 0 1
1 1 1 1 0 0 1
0 1 1 0 0 1 1
1 0 1 1 0 1 1
1 0 1 1 1 1 1
1 1 1 0 0 0 0
1 1 1 1 1 1 1
1 1 1 1 0 1 1
X X X X X X X
X X X X X X X
X X X X X X X
X X X X X X X
X X X X X X X
X X X X X X X


One can very well design this decoder from scratch, but there are already some BCD-to-seven segment decoder ICs (IC 7447) available, and which can reduce lot of efforts. Note that, IC 7447 gives active zero output, so please refer datasheet for using it.