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How to make a 12 hour clock

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IlordrossI

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I am trying to build a digital clock using
( 6 ) 7492 Binary Counters
( 6 ) 7447 BCD to 7-Segment Decoder/Driver
( 6 ) 150 Ohm Resister Packs
( 6 ) 7 Segment Displays

I have figured out how to make the seconds and minute’s sections of the clock. But I am unable to make the 12-hour section. I just can't figure out the right way to connect the 7492 counters to the 7447 BCD Decoders. Anyone who might know please help me out. I will be forever great full.
 
You've managed to take a 7492's output of 0-1-2-3-4-5-8-9-A-B-C-D and correct it to 0-1-2-3-4-5-6-7-8-9-reset, yet you can't make a simple one digit correction built onto that for the 12 hour? :shock: I'm assuming that instead, you used a 7490 to get 0-9 for the ones digit, and then a 7492 to get 0-5 for the tens digit. If so that makes a lot more sense, as there would be no correction logic necessary at this point.

Anyway, on to correcting a 7492's output to result in 12-01-02-03-04-05-06-07-08-09-10-11. Use a truth table and Karnaugh maps to transfer from your given bit patterns to the desired bit patterns.

Code:
  Given         |  Desired
                |
  Q3 Q2 Q1 Q0   |  Ten-HR   1-HR      D4 D3 D2 D1 D0
----------------+------------------+------------------
0  0  0  0  0   |       1      2   |   1  0  0  1  0
1  0  0  0  1   |       0      1   |   0  0  0  0  1
2  0  0  1  0   |       0      2   |   0  0  0  1  0
3  0  0  1  1   |       0      3   |   0  0  0  1  1
4  0  1  0  0   |       0      4   |   0  0  1  0  0
5  0  1  0  1   |       0      5   |   0  0  1  0  1
8  1  0  0  0   |       0      6   |   0  0  1  1  0
9  1  0  0  1   |       0      7   |   0  0  1  1  1
A  1  0  1  0   |       0      8   |   0  1  0  0  0
B  1  0  1  1   |       0      9   |   0  1  0  0  1
C  1  1  0  0   |       1      0   |   1  0  0  0  0
D  1  1  0  1   |       1      1   |   1  0  0  0  1

You'll feed D3-D0 into the 7447 to get your hours digit output. As for the ten-hours output, it looks kind of funny to have a leading zero, so it's simple. It's either completely off, or it displays a 1. Just connect your D4 line straight to your 7 segment's B and C lines, so when D4 is on, a 1 displays, when D4 is off, nothing displays.

Another possibility is that you use a 7493 chip, which counts up to 16. When it starts out at 0, simply convert that to a 12. All of the rest of its outputs will be correct. Then when it reaches its own 12, have that trigger a reset so it starts the cycle all over again.
 
Here's a quick MS-Paint diagram. I leave it up to you guys to do the table correction. Part of the fun of electronics is coming up with clever solutions to small problems, as opposed to just plugging stuff in and seeing that it works. :) If you're still stuck, I'll fill in more details if needed.
 

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Good call! The /2 input is disconnected (or perhaps grounded would be better), which leaves Q0 output idle. Q1-Q3 are the only active pins feeding into the 7447.
 
i make it its easy but its better to make the counter is 7490 BCD because this counter is -ve edge and u dont have to use 6 150 Ohm Resister i make it u can use ine resistace 1K ohm and i am sure from what i say i make it by my hand if u want to see my desgin send to me mail
 
mahmoud1919 said:
i make it its easy but its better to make the counter is 7490 BCD because this counter is -ve edge and u dont have to use 6 150 Ohm Resister i make it u can use ine resistace 1K ohm and i am sure from what i say i make it by my hand if u want to see my desgin send to me mail

You might perhaps try reading the date on the threads?, this one is over TWO YEARS OLD!.
 
what i mean if he use a -ve edge counter he dont need to check on the 9 to make pulse to the next counter because u will take the LSB and connect it by the clock of the next counter os with u get number 8,9(1000,1001) and u take the LSB and -ve edge so when the LSB get zero(0) so the next counter will take pulse to change the number so u dont need to check on the 9 to make all the counter connect to each other and use of variable resistace is better because he can control the density of ligth of the 7-Segment by put all the 7-segment on one Vcc and before the connection by the Vcc connect the variable resistace of 1K ohm i think this is better than this
 
@mahmoud1919:
Your eagerness to help is admirable, but -

The original poster reported that the problem is solved, more than two years ago.
(He) has not posted on this board since December 2005.
 
As I said, your eagerness is admirable. I just didn't want you to waste a lot of time on an old problem.

regards,
Mike
 
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