# Contador bidirecional com 74LS76



## Alberto Cruz (Oct 18, 2009)

Como fazer um contador up/down com CIs 74LS76, que execute, automáticamente, a seguinte sequência:
   0,1,2,3...5,6,7,6,5...2,1,0,1,2,3...5,6,7,6,5... ...
O circuito que usei foi o anexo com um JK só para detectar as passagens por "000" e fixar os períodos ascendentes e descendentes. Mas não consegui porque o circuito fica muito sensível a falsos estados durante as progressões...
Alguma sugestão para ultrapassar esta dificuldade?


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## lubeck (Oct 18, 2009)

Sorry, my friend but, the most people in this forum, only speak spanish, i hope that somebody speak portuges....

I wrote this message in english, because its an universal lenguaje. supoustly...
anyway welcome....


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## Chico3001 (Oct 18, 2009)

necesitas implementarlo con "maquinas de estados" 

Intenta leyendo este tema que te puede ayudar:

https://www.forosdeelectronica.com/f25/hacer-contador-2088/


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## Alberto Cruz (Oct 19, 2009)

OK, thanks for your comments. In fact, I don't know write spanish but I understand some written spanish. 
So, when I post my question in portuguese, I assumed that someone could help me, because there are similarities between the two languages.
If I can get an orientation of a member with practical experience in this type of circuits, I thank you. In fact, I am convinced that my difficulty can be overcome with a synchronous circuit, but I have no experience to develop it, because I'm not very comfortable with the use of Karnaugth maps, as suggested by Chico3001.


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## lubeck (Oct 19, 2009)

Hi! I have a little TTL Simulator, i will try to search it, and upload to this forum, i think it will be helps you... give me a couple of hours...
bye...

i find it..., this simple ttl simulator contains a lot of examples, for almost ttl family, and it is easy to use, i hope you find one explample that show you all you need....
i am an amateur so that's all that i can help you, the most important to me is try to help the users in this forum... and learn too...
 see us...

the examples....


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## Alberto Cruz (Oct 20, 2009)

Thank you Lubeck, for your cooperation. 

I ran the simulator (I'll try it later) but I did not succeed to unzip the file "ejemplosdecircuitos_094.rar" (files were created equal to the attached). 
I used the program RAR version 3.90.


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## lubeck (Oct 20, 2009)

try with this...


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## Alberto Cruz (Oct 20, 2009)

Viva 
I did the unpacking of some files with Unzip140 program and the result was the same ...!!
I'm realy surprised... and I do not understand why this is happen...!


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## lubeck (Oct 20, 2009)

oh, sorry...
try this steps
A.-Download both files:
      simulator digital_094.zip            Program
and ejemplosdecircuitos_094.zip       Examples

1.- unzip both files and run the program (no  instalation need) 
2.-Go to Menu "Archivo"
3.-Select "Abrir" in popup
4.-Select file you need  in "ejemplosdecircuitos_094" directory dialog ,whith only one click and select the command buttom "Abrir" and simulaator load the example.
if you select with double click maybe the example file runs with notepad program...
5.-Click in "on" protoboard option.


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## MrCarlos (Oct 21, 2009)

Hello Alberto Cruz 

You probably already saw the data sheets of 74LS190 integrated circuits, 191, 193. 
If no one has seen them take a look. They are the diagrams of how they built those counters that have forward or backward. 

entrer to this link to see data sheet's
http://www.alldatasheet.com/


Greetings 
your orders


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## Alberto Cruz (Oct 22, 2009)

OK, lubeck; It works! Thank you.

About the Mr Carlos sugestion, I understand that will be less complicated to make a bidirectional counter with the 74190 (synchronous counter with one mode control up/down input).
But the difficulty I have to solve is to make that counter with JK flip-flops, CI 7476.
As I said earlier, I had no success because the circuit operates in a very sensitive mode to false states during the automatic progressions, ascending and descending...


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## lubeck (Oct 22, 2009)

Your Welcome Alberto...

maybe....

  if you  upload your diagram, somebody know what's happenning, don't you think?

greetings...


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## MrCarlos (Oct 22, 2009)

Alberto Cruz dijo:


> OK, lubeck; It works! Thank you.
> 
> About the Mr Carlos sugestion, I understand that will be less complicated to make a bidirectional counter with the 74190 (synchronous counter with one mode control up/down input).
> But the difficulty I have to solve is to make that counter with JK flip-flops, CI 7476.
> As I said earlier, I had no success because the circuit operates in a very sensitive mode to false states during the automatic progressions, ascending and descending...


 

Hello Alberto Cruz 

No, I'm not saying that you use 74LS1xx, I'm saying is you look at the data sheets of these (74LS191, 192) to get an idea of how to do it with the 7476 

greetings 
their orders


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