▷ Programmable timer by hours with PIC 16f628a - Microcode

In this post, we will see how to make a timer that works for hours, using a PIC 16F628A programmed in BASIC language in the MICROCODE program.

MATERIALS:

We will use the following materials for this project:

• 1 PIC 16F628A
• 1 LCD 16x2
• 3 Push buttons
• 3 Resistors of 1k
• 1 Resistor of 220 Ohms
• 1 LED diode
• 1 Potentiometer of 10k

WIRING DIAGRAM:

EXPLANATION OF THE CODE:

  '****************************************************************
  '*  Name    : encXhoras.BAS                                     *
  '*  Author  : Esteban Carrillo - www.edeptec.com                *
  '*  Notice  : Copyright (c) 2022                                *
  '*          : All Rights Reserved                               *
  '*  Date    : 10/02/2021                                        *
  '*  Version : 1.0                                               *
  '*  Notes   :                                                   *
  '*          :                                                   *
  '****************************************************************
  CMCON = 7
  trisa =%011'Declaramos los puertos a0 y a1 como entradas, y el puerto a2 como salida.
  porta = 0
  
  'Nombramos los puertos a0 y a1 como pulsadorSumar y pulsadorIniciar respectivamente, haciendo referencia a los botones.
  pulsadorSumar VAR porta.0
  pulsadorIniciar VAR porta.1
  'Nombramos el puerto a2 como led
  led VAR porta.2
  
  'CREAMOS VARIAS VARIABLES
  ' Tres de tipo BYTE y dos de tipo WORD
  tiempoProgramado VAR BYTE
  tiempoTranscurrido VAR BYTE
  y VAR BYTE
  tiempoActual VAR WORD
  tiempoLimite var WORD
  
  y = 1' Le asignamos a la variable y el valor de 1
  
  ' Declaramos pines de conexión del lcd
  
  DEFINE LCD_DREG PORTB 
  DEFINE LCD_DBIT 4  
  DEFINE LCD_RSREG PORTB 
  DEFINE LCD_RSBIT 2
  DEFINE LCD_EREG PORTB 
  DEFINE LCD_EBIT 3
  
  'Creamos un loop: cicloProgramarTiempo
  cicloProgramarTiempo:
  
  ' Cada vez que presionemos el pulsadorSumar:
  '* Sumaremos la variable tiempoProgramado, esta variable ira de 0 a 24 
  '* Si la variable tiempoProgramado es mayor a 24 entonces tiempoProgramado = 0
  
      IF pulsadorSumar = 1 THEN 
          PAUSE 500
          tiempoProgramado = tiempoProgramado + 1
          
          IF tiempoProgramado > 24 THEN
              tiempoProgramado = 0
          ENDIF  
      ENDIF
  
      
      LCDOUT $fe, 1,$fe, 2, "PROGRAMAR TIEMPO"
      LCDOUT $fe,$C5, DEC tiempoProgramado  'Imprimimos el valor de la variable tiempoProgramado
      LCDOUT $fe,$C8, "HORAS"
      
     
      IF pulsadorIniciar = 1 THEN ' Si pulsamos pulsadorIniciar, nos dirigimos al loop tiempoOn
          GOTO iniciarTemporizador     
      ENDIF
  
  
  PAUSE 50      
   
  GOTO cicloProgramarTiempo' Cerramos el loop cicloProgramarTiempo
  
  iniciarTemporizador:
     
      tiempoLimite = tiempoProgramado * 60 ' *La variable tiempoLimite tomara valores de 60 a 1440. 
      
      LCDOUT $fe, 1, $fe, 2, "TIME ON: ",DEC tiempoProgramado, "Hr"' Imprimimos en el LCD el tiempo programado.   
      LCDOUT $fe,$c0, "ELAPSED T: ",DEC tiempoTranscurrido , "Hr" ' Imprimimos en el LCD el tiempo transcurrido. 
                               
      FOR tiempoActual = 0 TO tiempoLimite ' Creamos un ciclo for que ira de 0 hasta el valor de la variable tiempoLimite, esta es la pausa durante la cual estará encendido el led
      
          HIGH led ' Activamos led 
          PAUSE 60000 ' Establecemos una pausa de 1 minuto  
          
          IF tiempoActual == y * 60 THEN ' Condición para mostrar en el LCD el tiempoLimite transcurrido.
              y = y +  1
              tiempoTranscurrido =(tiempoActual/60)
              LCDOUT  $fe,$c0, "ELAPSED tiempoProgramado: ",DEC tiempoTranscurrido, "Hr" 
          ENDIF 
      NEXT tiempoActual 
  
  ' Una vez que se haya terminado el ciclo for
      
      LOW LED ' Desactivamos led 
      tiempoProgramado = 0 ' Enceramos la variable tiempoProgramado
      LCDOUT $fe, 1 ' limpiamos el LCD
      
  GOTO cicloProgramarTiempo ' Retornamos al loop cicloProgramarTiempo.  

EXPLANATION OF THE FOR LOOP PART (PAUSE FOR HOURS).

The pauses in microcode, according to what I have tested, can be up to 65,500ms (65.5 seconds - 1 minute 10 seconds), as we can see, it does not allow us to make a single pause that lasts for hours; what we can do is successive pauses, for example PAUSE 65500: PAUSE 65500... but doing this takes up a lot of storage space in the microcontroller, for this reason, we will use a for loop.

Within the for loop, we will set a pause of 60,000 ms, which is equal to 1 minute. To make a pause of 1 hour, the for loop would have to repeat 60 times because 60 times 60,000 is equal to 1 hour (60*60000ms = 3,600,000ms which is equal to 1 hour). To determine the number of repetitions according to the programmed time (value of the variable t), we multiply t * 60 and store the value of this multiplication in the variable time.

tiempo = t * 60
FOR X = 0 TOtiempo
  PAUSE 60000    
NEXT  X

I added a condition to show the elapsed hours on the LCD; for this, I did the following:

Within the for loop, we add the following line of codeIF X == y * 60 THEN, as we know the variable "y" was given the value of 1, so when the value of X is equal to 60 (initially), within this condition we have the following.

We add the value of y + 1, with this we will achieve that the next time we enter this condition it will be when the value of X has multiples of 60."60 = 1 hour, 120 = 2 hours, 180 = 3 hours, etc"Each time this occurs, we will divide the value of X by 60; this will give us the number of elapsed hours, and we will store this value in the variable z. Example:

If x = 180, z = 180/60 ==> 180/60 = 3 ==> z = 3, we print this value on the LCD.

IFx == y * 60 THEN
  y = y +  1  
  z =(x/60)
  LCDOUT  $fe,$c0,"ELAPSED T: ",DEC z, "Hr"       
ENDIF

If you want to activate a load of 110 - 220v with this project, I recommend the following post:

DOWNLOAD THE SIMULATION AND CODE HERE: