# How to design circuit count odd numbers with 7 segment decoder 1-3-5-7-9

#### jasmine21

Joined Dec 4, 2014
6
Hello my friends ! Please help...How to design circuit count odd numbers with 7 segment decoder (1-3-5-7-9 ) ?
Thanks for everything..

#### Papabravo

Joined Feb 24, 2006
21,298
What have you done so far to solve this problem?
How about writing the numbers in binary to see if there is a pattern.

#### jasmine21

Joined Dec 4, 2014
6
What have you done so far to solve this problem?
How about writing the numbers in binary to see if there is a pattern.
I made a circuit that counts from zero to nine..but I can't do that....and I want to truth table and karnaugh map of the odd counter...How is designed ?
writing the numbers in binary can be.

#### Papabravo

Joined Feb 24, 2006
21,298
I asked you to write out the numbers in the sequence, one underneath the other, for a reason. Do it and you will see a pattern that suggests an obvious solution. If you don't see the pattern immediately write the boolean equations for each column. It will come to you eventually.

#### jasmine21

Joined Dec 4, 2014
6
I asked you to write out the numbers in the sequence, one underneath the other, for a reason. Do it and you will see a pattern that suggests an obvious solution. If you don't see the pattern immediately write the boolean equations for each column. It will come to you eventually.
okey thanks for the everything

#### Papabravo

Joined Feb 24, 2006
21,298
So, were you able to solve the problem?

#### jasmine21

Joined Dec 4, 2014
6

#### jasmine21

Joined Dec 4, 2014
6

#### Dodgydave

Joined Jun 22, 2012
11,341
you can just detect when the 1 bit in binary is high, if its low its even...

#### Papabravo

Joined Feb 24, 2006
21,298
Did you write out the numbers 1, 3, 5, 7, 9 in binary? If you did that can you show us what it looks like to you?

#### jasmine21

Joined Dec 4, 2014
6
Did you write out the numbers 1, 3, 5, 7, 9 in binary? If you did that can you show us what it looks like to you?
I must see one bit in the seven segment display.

#### Papabravo

Joined Feb 24, 2006
21,298
I must see one bit in the seven segment display.
I don't think so. You have 2 separate problems which you can solve independently.
1. Make a 4-bit counter that goes {0001, 0011, 0111, 1001}+
2. Make a decoder that maps a 4-bit input into segments
The plus after the curly brackets means that the sequence repeats one or more times. There you got me to write the sequence of states for you. Does that help you to solve the problem?

I don't know why you are completely unwilling to do as I have asked you to do. Is it a cultural thing that prevents you from doing it because you think you will lose face? If it is you need to work very hard to overcome that tendency, or success in engineering will be very hard to come by.

In some cultures, the nail that sticks up gets hammered down.
In western engineering environments, the nail that stays down gets ignored, or worse, that nail gets fired.
You have to choose, get ignored or take a risk that you might get hammered down.
The choice is the essence of freedom, and is ever so precious

Last edited:

#### lightingman

Joined Apr 19, 2007
374
A counter 1 to 10, then a flip-flop on the clock input. Have the flip-flop reset at zero count and then use the divide by 2 from the flip-flop to latch the display number into the display driver.

So, a binary counter (4029) into a 7 seg decoder (4511). The counter will count 0,1,2,3,4,5,6,7,8,9, but the flip-flop will only load the new value into the display (LE input) on every other count (1,3,5,7,9). The zero count can be detected by a 4 input NAND gate on the four binary outputs from the counter. When all inputs are low, you will get a high from that to reset the fli-flop (4013) through a monostable (4047) to give a pulse to the LE input on the driver.

Daniel.

#### djsfantasi

Joined Apr 11, 2010
9,185
Excuse me. Forget everything about this problem for a second. Forget 7 segment displays. Forget truth tables. Forget karnaugh maps. Clear your mind…

Cleared?

Now write in a column, the numbers 1,3,5,7,9 in binary.

Take a cleansing breath. Look at the binary numbers. Uh uh, forget 7 segment decoders! Do you see a pattern? Look carefully. There it is! See it!

#### Dodgydave

Joined Jun 22, 2012
11,341
no, just the last bit is always 1

#### lightingman

Joined Apr 19, 2007
374
Yep. 1 is always high. Count 0,1,2,3 into inputs 2,4,8, and there is 1,3,5,9.

#### MrChips

Joined Oct 2, 2009
31,057
Come on guys. This is probably homework. Allow the OP/TS to figure this out on her own.

#### djsfantasi

Joined Apr 11, 2010
9,185
I don't think so, lightingman