Hex to Seven-Segment Decoder

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by synckewl, Jul 25, 2006.

1. synckewlNew Member

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Dear guys,

I would like to design a HEX to Seven Segment Decoder using K-maps for seven 4-input functions.

eg 0000 produces 0 while 1111 produces F

I use kMap to derive the logic function for a,b,c,d,e,f,g segment

This is what I get
a = BC + A'C + AD' + B'D' + A'BD
b = B'D' + B'C' + A'CD + AC'D + A' C' D'
c = C'D + A'D + AB' + A'B + B'C'
....
g = AC + B'C + AB' + BC'D + A'BD'

As you can notice, if I draw out the logic diagram, it will be complex. eg: Just a alone, I will need 5 AND gates and 5 inputs OR gates.

Are there any ways I can minimize the use of my logic gates?

Thank you

2. OverclockedMember

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Im guessing you have to convert the Hex to Bin and then To BCD. Or since Hex is just another way of expressing Binary in Microprocessors, just convert Binary to BCD. Once you have it in BCD, you can then use any ordinary BCD to 7 Segment Chip.

Atleast thats my guess on it..

3. synckewlNew Member

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sorry, I think I did not make clear in my first post

For eg: If I have input ABCD in Binary, I will get hex as an output

Input - Output
0000 - 0
0001 - 1
0010 - 2
0011 - 3
...
...
1110 - E
1111 - F

the truth table I got is this

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

Last edited: Jul 25, 2006

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5. philbaNew Member

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use an EPROM/EEPROM/...

6. survivingbrainNew Member

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Microcontrollers.. use the ones with lower IO pin count.. in your case you need 4 bits for input and 7/8(if u want to control dot) bits for output. So go for a controller with 12 I/Olines. If you want to have 2 seven segments, u'll need the ones with 24 I/Olines. But, a single chip + crystal+two or three resistors will do. But u'll have to program it.....

here are some of the chips...

PIC 16F628 - 16 I/O lines
PIC 16F54 - 12 I/O lines
PIC 16F84 - 13 I/O lines - try this one!! outdated, but good for ur project

try 89C2051 if you dont want microchip..
there are a lot of other Chips available..

Other options are a PLA, or a PAL.

7. synckewlNew Member

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I need to build up my 7 segment decoder gates by gates using basic gates.

Should I form the following logic using NAND?
My aim is to minimize the propagation delay and gates required.
a = BC + A'C + AD' + B'D' + A'BD
b = B'D' + B'C' + A'CD + AC'D + A' C' D'
c = C'D + A'D + AB' + A'B + B'C'
....
g = AC + B'C + AB' + BC'D + A'BD'

8. philbaNew Member

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what are you doing this for? it's starting to smell like a course assignment.

you've gotten several good suggestions but seem to be ignoring them.

9. Nigel GoodwinSuper ModeratorMost Helpful Member

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It looks EXACTLY! like a course assignment!.

10. survivingbrainNew Member

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If you really want to do it with gates...

Do it with GATES !!!!

However you can always use XOR gates - you can reduce some of your expressions in terms of XOR..

That way you can reduce your number of gates. Also look for common expressions. U need not use separate gates for them...

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Hex to Seven-Segment

Hello,
I want to make hex to 7-segment with Digital gates (Look like and-or-xor and ... )
and know I want to make I know how can make output is there any program that give me output?
This is my truth table:

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

How can I find output with out drawing karnaugh maps?
if anyone give me gates of this system I will become pleased.

12. shokjokMember

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You have many suggestions posted here. We are assisting you with ideas, not work practices.

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a = BC + A'C + AD' + B'D' + A'BD
b = B'D' + B'C' + A'CD + AC'D + A' C' D'
c = C'D + A'D + AB' + A'B + B'C'
....
g = AC + B'C + AB' + BC'D + A'BD'

This is what I need can anyone make d,e,f for me?

14. Hurra TuxNew Member

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I can do d :

Can you tell what '+' mean and what " ' " mean in your equation ?

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I did it thanks

16. Hurra TuxNew Member

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I've got an idea to do it whith less gates :
You can draw the karnaugh map, and make a circuit to do make a 1 when there should be a 0, and then put a NOT gate at the end (Or change the OR/AND gate to make a NOR/NAND).
So :

a = BC + A'C + AD' + B'D' + A'BD = A'B''C''D'' + A''B''C'
So you reduce to two AND gate (and two Or inputs)

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How to make a hex to octal converter circuit?
our teacher ask to do this. can some one help me?

Input: 1-digit Hexadecimal Number represented by 16 input points
Output: 2-digit Octal Number represented by 8 output points

Logic Function

The circuit will convert the hexadecimal input into its octal equivalent. Both the input and output must be displayed using a seven-segment display. Note: For the number 6 the 'a' LED with light and for the number 9 the 'd' LED will light.
12 hours ago - 3 days left to answer.
can you please provide me the circuits diagram? we are required to do it in a breadboard. and i'm really bad at it.
1 hour ago

18. abell118New Member

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I believe the code for "C" should be 1 1 0 0 1 0 0 1 1 1 0 for the 7 segments ...

19. abell118New Member

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I think "9" also has the "d" segment on as well ...

20. kubeekWell-Known Member

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And I think you are almost four years too late

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Welcome to ETO.

You realise that you are picking over a 9 year old thread.

I think that "9" can be drawn with the "d" segment on or off.
It all depends on personal preference.

The table in post #9 is confusing in several ways.
1, the input bits A,B,C,D are run together with the output bits as though it were all one big word.
2, the input bits A,B,C,D conventionally have weightings of 1, 2, 4, 8 respectively.
The way that the table is written shows the weighting as 8, 4, 2, 1.

JimB