PRÁCTICA 1: CONTADOR BINARIO DE 4 BITS
Author
Eliana Diaz
License
Creative Commons CC BY 4.0
Abstract
In this practice, the student will implement a four-bit counter using the 74LS193 Integrated circuit (IC), and the NE555 IC as clock signal.
In this practice, the student will implement a four-bit counter using the 74LS193 Integrated circuit (IC), and the NE555 IC as clock signal.
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\title{PRÁCTICA 1: CONTADOR BINARIO DE 4 BITS}
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\author{Departamento de Ingeniería Eléctrica, Electrónica y Computación \\
Universidad Nacional De Colombia - Sede Manizales\\
Docente: Jaime Enrique Arango\\
Monitor: Carlos Andres Serna Anduquia\\
Integrantes: Laura Natalia Arias Castaño,~\IEEEmembership{ 211003}\\
Eliana Mrcela Diaz Amaya,~\IEEEmembership{214566}\\
Carlos Arturo Zamora Urueña,~\IEEEmembership{806556}% <-this % stops a space
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\markboth{Journal of \LaTeX\ Class Files,~Vol.~13, No.~9, September~2014}%
{Shell \MakeLowercase{\textit{et al.}}: Bare Demo of IEEEtran.cls for Journals}
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\begin{abstract}
—In this practice, the student will implement a
four-bit counter using the 74LS193 Integrated circuit (IC),
and the NE555 IC as clock signal.
\end{abstract}
% Note that keywords are not normally used for peerreview papers.
\begin{IEEEkeywords}
Senal de reloj, Contador, Carry, Borrow, Ascendente, Descentente.
\end{IEEEkeywords}
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\section{INTRODUCCIÓN}
% The very first letter is a 2 line initial drop letter followed
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\IEEEPARstart {S}in duda, los contadores son los bloques digitales más utilizados, están presentes en la mayor parte de los sistemas digitales, y cuentan con un gran número de aplicaciones.\\\\
En primer lugar, el conteo de unidades que, además de la información sobre número de objetos, personas o sucesos, permite el control de dichas variables; por ejemplo controlar el número de objetos a insertar en un envase, el número máximo de personas presentes en un recinto, etc.\\\\
La cuenta directa de unidades (pulsos, objetos, sucesos) encuentra aplicación en muchos procesos, por ejemplo un sencillo control de número de unidades: una cinta transportadora mueve pequeños objetos de uno en uno; al final de ella, un operario coloca una caja de embalaje, al presionar un pedal, deben caer 100 objetos en la caja.\\\\
En esta práctica se muestra el funcionamiento básico de los contadores, tomando como patrón un contador binario de 4 bits.
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%\caption{Simulation results for the network.}
%\label{fig_sim}
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%\caption{Simulation results for the network.}
%\label{fig_sim}
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\section{ OBJETIVOS}
\begin{itemize}
\item Comprender el concepto de señal de reloj para sistemas síncronos.\\
\item Identificar el funcionamiento y utilidad del circuito
integrado NE555 o LM555.\\
\item Implementar y verificar en el laboratorio un
circuito contador binario de 4 bits.
\end{itemize}
% if have a single appendix:
%\appendix[Proof of the Zonklar Equations]
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%\appendix % for no appendix heading
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% is possibly needed
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% \subsection or using \label (\appendices by itself
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\section{ MARCO TEÓRICO}
\subsection{Contador Binario:}
En electrónica digital, un contador es un circuito
secuencial construido a partir de flip-flops y compuertas
lógicas, capaz de realizar el cómputo de los impulsos
que recibe en la entrada destinada para tal efecto,
almacenar datos o actuar como divisor de frecuencia.
Habitualmente, el cómputo se realiza en código binario,
que con frecuencia será el binario natural o el BCD
natural.\\\\
Según la forma en que conmutan los flip-flops, podemos hablar de contadores síncronos (todos los flip--flops reciben en el mismo instante la señal de reloj) o asíncronos ( los flip-flops del contador no cambian de estado exactamente al mismo tiempo, dado que no comparten el mismo impulso de reloj).
\subsection{Contador Binario 74LS193:}
El CI 74LS193, mostrado en la figura 1, es un contador binario de 4 bits que puede contar en ambos 2 sentidos: ascendente y descendente. El sentido de conteo del circuito depende a la entrada donde se apliquen los pulsos: Up o Down.\\
\begin{figure}[htb]
\centering
\includegraphics[width=0.3\textwidth]{fig_1.jpg}
\caption{\ Símbolo del circuito integrado 74LS193
}
\end{figure}
Igualmente tiene una entrada asincronica CLR, la cual al activarse con un “1” borra al contador y una entrada asincronica LOAD la cual al activarse con un “0” almacena el numero presente en las entradas DCBA del contador.\\\\
Tiene dos salidas que sirven para conectar circuitos en cascada si se necesita implementar un contador de un mayor número de bits: la salida de acarreo (carry) para el conteo creciente y la salida de prestamo (borrow) para conteo decreciente. Estas señales se muestran en la figura 2. En la misma se puede observar que si el contador se encuentra contando en sentido ascendente, en el pulso 16 pasa a 0 (0000).\\
\begin{figure}[htb]
\centering
\includegraphics[width=0.3\textwidth]{figura_2.jpg}
\caption{\ Señales en el contador
}
\end{figure}
Sin embargo, la salida de acarreo se puede aplicar a la entrada Up de otro circuito haciendo que el mismo pase a 0001, y así tendríamos un contador de 8 bits con el número 00010000 es decir 16 en decimal.
\subsection{Multivibrador astable:}
En electrónica, un astable es un multivibrador que no tiene ningún estado estable, lo que significa que posee dos estados cuasi-estables entre los que conmuta, permaneciendo en cada uno de ellos un tiempo determinado. La frecuencia de conmutación depende, en general, de la carga y descarga de condensadores.\\\\
Entre sus múltiples aplicaciones se cuentan la generación de ondas periódicas (generador de reloj) y de trenes de impulsos.\\\\
El astable a usar tendrá la configuración mostrada en la Figura 3\\
\begin{figure}[htb]
\centering
\includegraphics[width=0.3\textwidth]{multivibrador_astable.jpg}
\caption{\ Multivibrador astable LM555
}
\end{figure}
\section{ MATERIALES}
\begin{itemize}
\item Cable para conexiones en la protoboard.
\item Circuitos integrados NE555 y 74LS193.
\item Un potenciometro de 1M $\Omega$.
\item Un capacitor de 1 $\mu$f.
\item Una resistencia de 22k $\Omega$.
\item Seis resistencias de 330 $\Omega$.
\item Seis resistencias de 1k $\Omega$.
\item Dos pulsadores.
\item Una protoboard.
\item Seis diodos Led.
\item Dip swicth Fuente DC de 5v.
\end{itemize}
\section{ PROCEDIMIENTO}
El circuito base para la práctica se muestra en la figura. El montaje de dicho circuito se presenta en la figura 4.\\
\begin{figure}[htb]
\centering
\includegraphics[width=0.3\textwidth]{montaje.jpg}
\caption{\ Montaje del cicuito base para práctica
}
\end{figure}
La etapa de visualización se realizó con diodos led conectados a las salidas del circuito integrado 74LS193 conservando el orden dado que estas salidas representan números, y el diodo derecho corresponde al bit menos significativo.
\section{ CUESTIONARIO}
\begin{itemize}
\item Explique qué utilidad tiene la carga inicial en el circuito integrado 74LS193.\\\\
El circuito integrado 74LS193 es un contador programable de 4 bits con carga de datos paralelo. Dispone de dos salidas de sobre pasamiento para contar en cascada, así como dos entradas de control para contar de manera ascendente o descendente.
Pin de carga: cuando se da un flanco ascendente, la señal de reloj y este pin tiene un nivel lógico bajo se realiza la carga del dato de preselección de las entradas A,B,C,D.\\\\
\item Defina “senal digital”.\\\\
La señal digital es generada por algún tipo de fenómeno electromagnético y en la cual sus signos representan ciertos valores discretos que contienen información codificada. Los sistemas que emplean señales digitales suelen emplear la lógica binaria . Una señal digital pierde poca calidad y puede reconstruirse y amplificarse en un proceso simultáneo. Estas señales, además, pueden procesarse de manera sencilla y son poco susceptibles al ruido ambiental.
Mientras que las señales analógicas son continuas, las señales digitales tienen la capacidad de pasar de un valor a otro sin atravesar los valores intermedios. Esto está vinculado a la lógica binaria mencionada anteriormente: cada señal digital sólo puede tomar dos estados, representados por unos y ceros.\\\\
\item Defina “conexion en cascada”. \\\\
Una conexión en cascada es aquella en la cual la salida de una etapa se conecta a la entrada de la segunda etapa y así sucesivamente. Dos redes de dos puertos están conectadas en cascada, si los terminales de salida de la primera red son los terminales de entrada de la segunda.\\\\
\item Simule un contador de 8 bits ascendente y descendente, usando conexiones en cascada.\\\\
La simulación de este circuito se presenta en el apéndice b. \\\\
\item Mencione aplicaciones de los contadores digitales.\\\\
Algunas aplicaciones de los contadores digitales son: \\
\begin{itemize}
\item Contar objetos y sucesos: es preciso que el fenómeno a contabilizar sea convertido a señal eléctrica empleando, por ejemplo, sensores.
\item Tomar medidas de tiempo: por ejemplo en los relojes digitales
\item Medir frecuencias: por ejemplo midiendo y controlando la velocidad de un motor.
\item Dividir frecuencias y ampliar periodos de tiempo
\item Repartir tiempos (multiplexado temporal).
\end{itemize}
\end{itemize}
\section{ CONCLUSIONES}
Gracias a la implementación de circuitos contadores se pueden controlar procesos en diferentes dispositivos donde se necesite una etapa de conteo, tambien se puede condicionar el conteo de dichos dispositivos al poder caragar datos en el contador.\\
En los sistemas síncronos los tiempos exactos en que alguna salida puede cambiar de estado se determinan por medio de una señal denominada reloj o clock.Las salidas cambian en los flancos de subida o bajada del pulso de reloj.\\
Al momento de realizar el montaje es importante revisar continuidad en cada conexión que se realice.
% you can choose not to have a title for an appendix
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\section{ REFERENCIAS}
\begin{itemize}
\item www.meteo.ieec.uned.es
\item Definición de señal digital - Qué es, Significado y Concepto http://definicion.de/senal-digital/ixzz3mLID381n
\item http://www.virtual.unal.edu.co/cursos/sedes/manizales/
4040015/lecciones/Capitulo1/cascada.html
\item http://diec.cps.unizar.es/~tpollan/libro/Apuntes/dig17.pdf
\end{itemize}
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